The Climate of Japan: Present and Past 9819951577, 9789819951574

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Advances in Global Change Research 77

Takehiko Mikami

The Climate of Japan Present and Past

Advances in Global Change Research Volume 77

Series Editor Markus Stoffel, Institute of Geological Sciences, University of Geneva, Geneva, Switzerland Advisory Editors Wolfgang Cramer, IMEP, Bâtiment Villemin, Europole de l’Arbois, Aix-en-Provence, France Urs Luterbacher, University of Geneva, Geneva, Switzerland F. Toth, International Institute for Applied Systems Analysis (IIASA), Laxanburg, Austria

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Takehiko Mikami

The Climate of Japan Present and Past

Takehiko Mikami Department of Geography Tokyo Metropolitan University Hachioji, Tokyo, Japan

ISSN 1574-0919 ISSN 2215-1621 (electronic) Advances in Global Change Research ISBN 978-981-99-5157-4 ISBN 978-981-99-5158-1 (eBook) https://doi.org/10.1007/978-981-99-5158-1 © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 This work is subject to copyright. All rights are solely and exclusively licensed by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors, and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Singapore Pte Ltd. The registered company address is: 152 Beach Road, #21-01/04 Gateway East, Singapore 189721, Singapore

Preface

I have been interested in climate and weather since I was a child. I was fascinated by the shapes of clouds and how they changed from moment to moment. On the other hand, I realized that climate changes over long periods of time as I experienced heavy snowfalls in winter, unbearable summer heat, and, in contrast, unusually cold summer weather. As a climate scientist, I began to read books and papers on global climate change, and my interest in past climate change has increased. I became interested in the climate more than 100 years ago, when meteorological observation data were not available, and I became convinced that daily weather information recorded in the Domain Diaries of the Edo period since the seventeenth century would be useful for long-term climate reconstructions in Japan. Unfortunately, very few climate researchers are interested in qualitative documentary records, such as diary weather records, and it has been extremely difficult to systematically and efficiently collect and compile a huge amount of weather data into a database. Fortunately, with the help of a small number of researchers who are cooperating in the collection of weather records from diaries stored in libraries and museums across Japan, the research on climate reconstruction in the historical period is progressing. Minoru Yoshimura has constructed his own historical weather database (HWDB: Historical Weather Database) by coding qualitative weather information provided by many researchers and disseminating the information through his website. Yoshimi Fukuma contributed to the development of historical climate research by digitizing and publishing daily weather information for Hirosaki and Edo (Tokyo) in the Hirosaki Domain Diary of northern Japan, which continued for about 200 years from the seventeenth century to the late nineteenth century. These databases have greatly contributed to the development of historical climatology in Japan. I would like to express my gratitude here. In parallel with my research on climate change and historical climatology, I have also been collecting and analyzing a large number of meteorological observation data on urban climates, especially urban heat islands in Tokyo, to elucidate the reality of urban warming in mega-city Tokyo. In this book, I have also described the urban climate of Tokyo.

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I stayed at Climatic Research Unit (CRU), University of East Anglia, UK, as a visiting scientist for six months in 1989. I was fortunate to share the office of Dr. Hubert Lamb, a well-known eminent historical climatologist, who was retired at that time, and to have the opportunity to talk with him occasionally. I also participated in a number of international conferences and symposia, where I presented my research and discussed with many scientists, and this has contributed greatly to the development of collaboration with overseas researchers and the writing of this book. I would like to thank the following colleagues for their contributions to my research activities: Phil Jones, Keith Briffa, John Kington, Astrid Ogilvie, Rudolf Brazdil, Gunther Können, Fons Baede, Gaston Demaree, Patrick Beillevaire, Ray Bradley, Jun Matsumoto, Hideo Takahashi, Togo Tsukahara, Yoshio Tagami, Hisayuki Kubota, Naoko Hasegawa, Hiroaki Yamato, Yoshimi Fukuma, Mika Ichino and many other researchers. Also, I would like to thank my colleagues for their cooperation in preparing the manuscript of this book. Masumi Zaiki, Junpei Hirano, and Rena Nagata, who used to belong to my laboratory and are still engaged in research collaboration on climate change and historical climatology, reviewed parts of the draft of this book. In particular, Bruce Batten, a researcher of environmental history, reviewed a draft of this book in detail and gave me appropriate advice on every detail. I would like to express my sincere gratitude to him for his many pertinent comments on the content of the text, not to mention the English language. Finally, I am grateful to my family, especially to my wife Michiko, for supporting me throughout my life. Saitama, Japan April 2023

Takehiko Mikami

Contents

1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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2 Climate and Weather in Japan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1 Japan’s Climate with Large Regional Differences . . . . . . . . . . . . . . . 2.1.1 Japan’s Climate from a Global Perspective . . . . . . . . . . . . . . . 2.1.2 Major Air Masses Affecting the Climate of Japan . . . . . . . . . 2.1.3 Mean Annual Temperature, Precipitation and Sunshine Duration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1.4 Annual Variations in Mean Monthly Temperature and Precipitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 Seasonal Variations in the Climate of Japan . . . . . . . . . . . . . . . . . . . . 2.2.1 Main Seasons and Temperature and Precipitation Distributions in Japan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.2 Winter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.3 Spring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.4 Rainy Season in Early Summer . . . . . . . . . . . . . . . . . . . . . . . . 2.2.5 Midsummer Season . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.6 Autumn Rainy Season . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.7 Late Autumn . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3 Extreme Weather and Teleconnection Patterns . . . . . . . . . . . . . . . . . . 2.3.1 Cold and Warm Winters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3.2 Cool and Hot Summers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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3 Climate Change in Japan Since the 20th Century . . . . . . . . . . . . . . . . . . 3.1 Official Meteorological Observation System in Japan . . . . . . . . . . . . 3.1.1 Relocation of JMA Tokyo Meteorological Observatory and Its Effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 Climate Variations in Japan Since the 20th Century . . . . . . . . . . . . . . 3.2.1 Temperature Variations Since the 20th Century . . . . . . . . . . . 3.2.2 Precipitation Variations Since the 20th Century . . . . . . . . . . . 3.2.3 Flood Disasters and Climate Change . . . . . . . . . . . . . . . . . . . .

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3.3 Climate Change in the Mega-City Tokyo . . . . . . . . . . . . . . . . . . . . . . . 3.3.1 Temperature Variations Since the 20th Century . . . . . . . . . . . 3.3.2 Precipitation Variations Since the 20th Century . . . . . . . . . . . 3.3.3 Aridification of Tokyo Due to Urbanization . . . . . . . . . . . . . . 3.4 Urban Heat Islands in Tokyo Metropolis . . . . . . . . . . . . . . . . . . . . . . . 3.4.1 High-Resolution Temperature Observation System in Tokyo Metropolis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4.2 Summer Temperature Distributions in Tokyo . . . . . . . . . . . . . 3.4.3 Anthropogenic Energy Consumption in Tokyo . . . . . . . . . . . 3.4.4 Artificial Urban Surfaces in Tokyo . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Climate Information from Pre-Nineteenth Century Data and Documents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1 Early Meteorological Observations in the Nineteenth Century . . . . . 4.1.1 Early Meteorological Observations in Nagasaki . . . . . . . . . . 4.1.2 Early Meteorological Observations in Tokyo and Yokohama . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1.3 Early Meteorological Observations at the Russian Consulate in Hakodate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1.4 Mid-Nineteenth Century Temperature Observations by a Merchant of the Mito Domain . . . . . . . . . . . . . . . . . . . . . 4.1.5 Meteorological Observations in Naha (Okinawa) in the Mid-Nineteenth Century . . . . . . . . . . . . . . . . . . . . . . . . . 4.1.6 Lighthouse Meteorological Observations in Japan . . . . . . . . 4.2 Diary Weather Records Since the Seventeenth Century . . . . . . . . . . . 4.2.1 Location and Duration of Diary Weather Records . . . . . . . . . 4.2.2 Weather Records of the Two-Century Hirosaki Doman Diary and Their Databasing . . . . . . . . . . . . . . . . . . . . . 4.2.3 Historical Weather Database (HWDB) . . . . . . . . . . . . . . . . . . 4.3 Long-Term Records of Lake Ice Freeze-Up/Break-Up Dates . . . . . . 4.3.1 Records of Freeze-Up and Ice Pressure Ridge at Lake Suwa Since 1444 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3.2 Records of Ice Freeze-Up/Break-Up at Lake Jusan During 1705–1860 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Climate Reconstructions for Historical Periods . . . . . . . . . . . . . . . . . . . . 5.1 Attempts to Reconstruct Typhoon Tracks and Intensity from Early Weather Records . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1.1 Reconstruction of the 1882 Typhoon Weather Map Using Lighthouse Observation Data . . . . . . . . . . . . . . . . . . . . 5.1.2 Reconstruction of the Intensity and Track of the 1828 Siebold Typhoon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1.3 Variability of Typhoons that Hit Japan After the Mid-Nineteenth Century . . . . . . . . . . . . . . . . . . . . . . . . . . .

55 56 57 58 59 59 64 74 76 82 85 86 89 99 114 118 119 121 126 128 132 139 141 141 147 153 157 157 159 162 167

Contents

5.2 Climate Reconstructions from Diary Weather Records Since the Eighteenth Century . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2.1 Winter Temperature Reconstruction Based on the Snowfall Ratio Obtained from Diary Weather Records . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2.2 Winter Monsoon Climate Reconstructions from the 1840s-1850s Based on Early Meteorological Data and Historical Documentary Records . . . . . . . . . . . . . . . 5.2.3 Summer Temperature Variations Reconstructed from Precipitation Frequency: The Case Studies of Tokyo and Hiroshima . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2.4 Meteorological Disasters from the Seventh to Nineteenth Century . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2.5 Great Famines and Climate Change in the 1780s . . . . . . . . . . 5.3 Climate Reconstruction from Records of Full-Flowering Dates for Cherry Trees Over the Past 1200 Years . . . . . . . . . . . . . . . . 5.4 Climate Reconstructions from Pollen in the Highland Moors in Central Japan Over the Past 7600 Years . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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6 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209

Chapter 1

Introduction

Abstract Japan is a relatively small island country with a total area of less than 380,000 square kilometers, but very large regional and seasonal differences characterize its climate. From a global perspective, the Japanese archipelago is located on the eastern edge of the huge Eurasian continent. It thus has a climate that differs greatly from that of Europe, which is located on the continent’s western edge. In addition, because it is surrounded by oceans, it is generally considered to have a temperate climate. Still, in reality, it is characterized by large annual variations in temperature and regional and seasonal differences in precipitation distribution. On the other hand, climatic changes from the past to the present are not uniform, and long-term climate variability and interannual climate anomalies do not necessarily coincide with those of other regions. This book describes the characteristics of Japan’s climate on both spatial and temporal scales and discusses why such regional differences and temporal variations occur. Keywords Japanese archipelago · Temperate climate · Climatic change

Japan is a relatively small island country with a total area of less than 380,000 square kilometers, but its climate is characterized by very large regional and seasonal differences. From a global perspective, the Japanese archipelago is located on the eastern edge of the large Eurasian continent, and thus has a climate greatly different from that of Europe, which is located on the western edge of the continent. In addition, because it is surrounded by oceans, it is generally considered to have a temperate climate, but in reality, it is characterized by large annual variations in temperature and regional and seasonal differences in precipitation distribution. On the other hand, climatic changes from the past to the present are not uniform, and long-term climate variability and interannual climate anomalies do not necessarily coincide with those of other regions of the world. For example, the climate variability on a time scale of several thousand years from about 10,000 years ago, when the last glacial period ended, to the present is almost the same as the global average. However, on a time scale of a few hundred years to a few decades, there are considerable regional difference.

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 T. Mikami, The Climate of Japan, Advances in Global Change Research 77, https://doi.org/10.1007/978-981-99-5158-1_1

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This book describes the characteristics of Japan’s climate on both spatial and temporal scales, and discusses why such regional differences and temporal variations occur. Chapter 2 describes the current climatic characteristics of Japan, focusing on seasonal changes. The actual state of the distinct seasonal changes is explained in an easy-to-understand manner using the latest meteorological data and illustrations. Extreme weather, which is characterized by large deviations from the normal, is described based on several examples and its relationship to global teleconnection patterns is discussed. Chapter 3 describes the actual state of climate change in Japan based on meteorological observation data since the twentieth century. Graphs are used to show how the average temperature and precipitation in Japan have changed since the twentieth century, and the characteristics of these changes are described. In addition to longterm climate change, natural disasters, especially flood disasters that occur every year, have had a great impact on people’s lives in Japan. Through case studies of past flood disasters, the mechanisms that cause heavy rainfall will be explained. Chapters 4 and 5 discuss data and analytical methods for elucidating the evolution of climate change and meteorological disasters in the nineteenth century, before the official meteorological observation by the Japan Meteorological Agency started in Japan. Chapter 4, which is entitled “Climate Information from Pre-19th Century Data and Documents”, presents the research results of the authors’ team on the discovery and collection of nineteenth-century meteorological observation records in various parts of Japan from the early nineteenth century through the twentieth century. The author and his team’s research results on the discovery and collection of meteorological observation records in various parts of Japan from the early 19th to the twentieth century are presented. In addition to the nineteenth-century meteorological observation records, a huge amount of Domain Diaries, which were recorded nationwide from the 17th to the late nineteenth century, have been found in Japan, and the daily weather records in these diaries are very useful for the study of climate change. In addition, a database of lake ice records, which have been continuously recorded for nearly 600 years since the fifteenth century, is being compiled, and is expected to be used effectively for estimating winter climate change. In the last section, Chapter 5, I will explain the methods of climate reconstruction based on the various meteorological data of historical periods described in Chapter 4. In the last two sections of this chapter, the climate reconstructions of Japan for the past 1200 years based on the Records of Full-Flowering Dates of cherry trees and for the past 7600 years based on the Pollen in the Highland Moor in Central Japan are presented, extending the temporal scale of this chapter further.

Chapter 2

Climate and Weather in Japan

Abstract An understanding of the current climate of Japan from a global perspective with regard to its geographical characteristics is provided. First, the major air masses that influence Japan’s climate are described, together with the characteristics of temperature, precipitation, and sunshine duration in Japan, which vary widely from region to region. Next, the “distinct seasonal changes” that characterize Japan’s climate are described focusing on the transition of natural seasons, and the characteristics of each season are explained using weather maps and meteorological satellite images. As is well known, the climate fluctuates from year to year, with extreme weather events sometimes deviating from normal conditions and causing severe natural disasters. In any case, to understand the climate of Japan, it is important to know the reality of the normal climate and to consider the meteorological factors (mechanisms) that bring it about. The normal values shown in the illustrations in this chapter are the average values for the period 1991–2020 unless otherwise stated. Keywords Airmass · Air temperature · Precipitation · Seasonal variation · Winter monsoon · Early summer rainy season

This chapter aims to provide an understanding of the current climate of Japan from a global perspective with regard to its geographical characteristics. First, the major air masses that influence Japan’s climate are described, together with the characteristics of temperature, precipitation, and sunshine duration in Japan, which vary widely from region to region. Next, the “distinct seasonal changes” that characterize Japan’s climate are described focusing on the transition of natural seasons, and the characteristics of each season are explained using weather maps and meteorological satellite images. As is well known, the climate fluctuates from year to year, with extreme weather events sometimes deviating from normal conditions and causing severe natural disasters. In any case, in order to understand the climate of Japan, it is important to know the reality of the normal climate and to consider the meteorological factors (mechanisms) that bring it about. The normal values shown in the illustrations in this chapter are the average values for the period 1991–2020, unless otherwise stated.

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 T. Mikami, The Climate of Japan, Advances in Global Change Research 77, https://doi.org/10.1007/978-981-99-5158-1_2

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The climate of Japan has the following characteristics. 1. Seasonal changes are distinct, especially in winter and summer when the prevailing winds are reversed, dominated by the monsoon climate. 2. Because it is located on the eastern edge of the Eurasian continent, the annual range of temperature is larger, and precipitation is relatively greater, than in Europe on the western edge of the continent. 3. The Himalayas and the Tibetan Plateau, which reach 8,000 m in altitude, block the jet stream of the prevailing westerly winds at high altitudes, which frequently causes it easy to meander downwind of the Japanese islands. 4. The Japanese archipelago is surrounded by the ocean, which has an oceanic climate and is susceptible to ocean currents and SST (Sea Surface Temperature) variations. 5. The northward and southward movement of the Polar Frontal Zone associated with seasonal changes in solar altitude causes a shift in the main air masses that dominate the Japanese islands, and thus makes the weather and climate susceptible to change. For example, the Siberian High in winter and the North Pacific High in summer are centers of action that have a significant influence on weather and climate variations in Japan. 6. Especially in summer, typhoons and tropical cyclones approach or make landfall on the Japanese islands, often causing natural disasters due to storms and heavy rainfall. 7. In winter, the region facing to the Sea of Japan has extremely heavy snowfall and snow depth compared to other places in the world at the same latitudes, while the Pacific side region has dry and sunny days. 8. Due to the continuous precipitation caused by stagnant fronts and typhoons, changeable weather is relatively rare, unlike the case of Europe on the western edge of the continent. 9. The large annual variations in temperature and abundant total annual precipitation compared to other areas at the same latitudes in the Northern Hemisphere explain why flood disasters are frequent, but droughts are rare.

2.1 Japan’s Climate with Large Regional Differences Japan is an island country located on the eastern edge of the Eurasian continent. Its total land area is 378,000 km2 , which is not large, but it is highly elongated from north to south, stretching from 45.55°N to 20.43°N. As a result, the climates of the northern and southern parts of the Japanese archipelago differ markedly, with a range of climates emerging from the subarctic climate (Dfa, Dfb) of Hokkaido in the north to the tropical rainforest climate (Af) of Ishigaki-jima (Okinawa) in the south, as shown in Fig. 2.1. In winter, the Sea of Japan side of the archipelago receives a large amount of precipitation, much of it snowfall, due to the influence of mountain ranges running north–south through the middle of the archipelago, resulting in an area of snowfall

2.1 Japan’s Climate with Large Regional Differences

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Fig. 2.1 World map of Köppen-Geiger climate classification. Source Peel et al. (2007). The map has been modified to be centered on Japan

so heavy that it has few counterparts elsewhere in the world. On the Pacific Ocean side, on the other hand, sunny days are predominant except during the rainy season in summer and autumn.

2.1.1 Japan’s Climate from a Global Perspective Figure 2.2 shows the annual mean distribution of temperature and precipitation over land areas of the world (1981–2010). The top chart shows the world distribution of annual mean temperature, with red–orange areas having higher temperatures and blue-green areas having lower temperatures. In the Northern Hemisphere, if we look at mid- and high latitudes north of 40°N, the eastern edge of Eurasia, where Japan is located, is cooler than the western edge at the same latitude. This is a result of the obliquely tilted distribution of temperatures over Eurasia from Europe in the west edge to East Asia in the east. The bottom chart shows the global distribution of annual precipitation. Areas with annual precipitation of 1000 mm or more extend from southern China to the Japanese islands. High precipitation areas with annual precipitation of 2000 mm or more are found in Africa, South-Southeast Asia, and the equatorial regions of South America. On the other hand, areas with less than 250 mm, which is indicative of a

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Fig. 2.2 Annual mean temperature (top) and Annual precipitation (bottom) in the world. Source NOAA/NCEP GHCN reanalysis dataset and GPCC precipitation dataset

desert climate, reach from the Sahara Desert in Africa through Central Asia to inland China.

2.1.2 Major Air Masses Affecting the Climate of Japan Figure 2.3 shows major air masses affecting the climate of Japan. An air mass is a huge volume of air whose temperature and moisture are almost homogeneous horizontally. The extent of such masses ranges from several hundred to a thousand

2.1 Japan’s Climate with Large Regional Differences

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Fig. 2.3 Major Air Masses affecting Japan’s climate

kilometers horizontally. Air masses are divided into four major types: continental Polar (cP), maritime Polar (mP), continental Tropical (cT), and maritime Tropical (mT). In addition to these four air masses, there is also a very wet and hot Equatorial Air mass that forms near the equator. Air masses are formed in anticyclonic regions, and the main air masses affecting Japan can be classified by their source region and moisture. 1. Siberian Air Mass: Continental Polar (cP) Air Mass that appears over the Siberian Continent from late autumn to winter and early spring, and is extremely stable due to the inversion of air temperature from the ground to an altitude of around 3000 m when the Siberian Continent is cooled by radiative cooling during the winter. In response to the Siberian High in winter, the source region brings cold and clear weather, but as it moves southeastward to the warm Sea of Japan, it rapidly changes and becomes unstable due to the supply of heat and water vapor from the sea surface. As described below, in the Japanese archipelago, this air mass brings snowfall to the Sea of Japan side of the country and dry, clear skies to the Pacific side area in winter. 2. Okhotsk Air Mass: Maritime Polar (mP) Air Mass that develops around the Sea of Okhotsk in early summer and autumn and is cool and moist, corresponding to the Okhotsk High (Blocking High) of the baiu rainy season (see Sect. 2.2.4). Northeasterly winds blowing from there often bring gloomy weather to the northeast coast of Japan. 3. Ogasawara Air Mass: This is a Maritime Tropical (mT) Air Mass corresponding to the North Pacific High (Ogasawara High) that extends south of the Japanese

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archipelago in summer. It is hot and humid but stable and brings clear skies. It is prone to cumulus clouds, and when solar radiation is strong, cumulonimbus clouds develop, often resulting in thunderstorms. 4. Yangtze Air Mass: Continental Tropical (cT) Air Mass that develops over the Yangtze River area in southern China in spring and autumn, corresponding to a mobile anticyclone that moves eastward over the Japanese islands. Within this air mass, it is warm and there are some cumulus clouds, but it is relatively dry and tends to be sunny. 5. Equatorial Air Mass: Maritime Equatorial (mE) Air Mass with the equatorial region as its source region that brings hot and moist southwesterly winds to the Japanese islands in the late baiu season, sometimes bringing torrential rainfall to western Japan.

2.1.3 Mean Annual Temperature, Precipitation and Sunshine Duration In this section, the rough characteristics of Japan’s climate are illustrated using distribution maps of annual mean temperature, annual precipitation, and annual sunshine duration. Each figure was created using GMT (General Mapping Tool) based on mesh normal data (1991–2020) provided by the Japan Meteorological Agency (JMA). As shown in Fig. 2.4, the annual mean temperature increases from Hokkaido in the north to the Okinawa islands in the south, but is lower in the mountainous areas of central Honshu. Among AMeDAS (Automated Meteorological Data Acquisition System: see Sect. 3.1) meteorological stations nationwide, the lowest temperature is −5.9 °C at the summit of Mt. Fuji and the highest temperature is 25.8 °C at MinamiTorishima. The annual mean temperature in the capital city of Tokyo is 15.8 °C, which is slightly higher than that in the suburbs due to urbanization (see Sect. 3.4). The distribution pattern of annual mean precipitation is characterized by the contrast between the Sea of Japan side and the Pacific Ocean side as well as the difference in precipitation between the north and south (Fig. 2.5). Overall, annual precipitation is less than 1600 mm on the Pacific Ocean side from Hokkaido to the Tohoku and Kanto regions, while the Sea of Japan side from Tohoku to western Japan and the Pacific Ocean side from central to western Japan have the location of high precipitation areas of more than 2000 mm. AMeDAS show the lowest precipitation at Tokoro station in Hokkaido, northern Japan (711 mm) and the highest precipitation at Yakushima island, Kyushu (4652 mm). Tokyo has an annual precipitation of 1598 mm, which is less than the average precipitation in Japan (about 1700 mm), but about 1.8 times the world’s average annual precipitation (about 900 mm). The distribution of annual mean sunshine duration is characterized by a clear contrast between the Sea of Japan side, where it is less than 1500 h, and the Pacific side, where it is more than 2000 h (Fig. 2.6). It is interesting to note that the Sea of Japan side has high precipitation and a lack of sunshine, while the western part of

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Fig. 2.4 Annual mean temperature (1991–2020). Data source Japan Meteorological Agency

the Pacific side has around 2000 h of sunshine duration, despite its high precipitation (Fig. 2.5). The east–west contrast between the Sea of Japan side and the Pacific Ocean side observed in the annual precipitation and annual sunshine duration is largely due to the mountain ranges running through the central part of Honshu, the main island.

2.1.4 Annual Variations in Mean Monthly Temperature and Precipitation 1. Seasonal changes in temperature (Fig. 2.7): Annual changes in temperature is similar for each station, with the coldest month being January and the warmest being August, although the annual temperature range is smaller at Naha, Okinawa, where the temperature is highest in July. In January, the coldest month, temperatures fall below freezing in Sapporo, Hokkaido, but are below 10 °C at

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Fig. 2.5 Annual mean precipitation (1991–2020). Data source Japan Meteorological Agency

all other locations except Naha, Okinawa. On the other hand, temperatures in the warmest month vary relatively little between regions, with temperatures ranging from 25 °C to 30 °C except in Sapporo. 2. Seasonal changes in precipitation (Fig. 2.7): There are large regional differences in the pattern of seasonal changes in precipitation. Sapporo and Niigata, where precipitation is heavy in winter, are located on the Sea of Japan side, while Tokyo, on the Pacific side, experiences a peak in precipitation in September/ October. On the other hand, in Kyoto and Nagasaki in western Japan, precipitation is heaviest in June and July. The highest precipitation throughout the year is in Naha, Okinawa, where precipitation is heaviest in May/June and September/ October. These monthly differences in precipitation are closely related to the seasonal changes that are influenced by the winter monsoon and summer rainy season, which will be discussed later.

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Fig. 2.6 Annual mean sunshine duration (1991–2020). Data source Japan Meteorological Agency

2.2 Seasonal Variations in the Climate of Japan As described in Sect. 2.1.3, the Japanese archipelago is long from north to south and there is a mountain range in Honshu that separates the east from the west, so there are marked differences in the distribution of temperature and precipitation not only from north to south but also from east to west. Furthermore, the distribution of temperature and precipitation is influenced by the major air masses and their arrival periods and is therefore characterized by large seasonal variations. This section focuses on seasonal variations, describing the distributions of temperature and precipitation for each of the main seasons specific to Japan, and explaining the factors that cause these distributions using weather maps and meteorological satellite cloud images.

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Fig. 2.7 Climograph for 6 sites in Japan (1991–2020). Data source Japan Meteorological Agency

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2.2.1 Main Seasons and Temperature and Precipitation Distributions in Japan In Japan, which is located in the temperate zone, the four seasons are distinct. However, summer is divided into two phases, the early summer rainy season and midsummer. Autumn is also divided into two phases, the autumn rainy season and late autumn. Using the JMA-AMeDAS normals (1991–2020), the distribution of monthly mean temperature and monthly precipitation is plotted for each season, and the characteristics of their distribution are examined. As space is limited, islands south of 30°N are omitted. 1. Winter (Fig. 2.8): Hokkaido, the northernmost island of Japan, is colder than Honshu and areas southward, with monthly mean temperatures below freezing almost everywhere. The north–south difference in temperature is larger in January and February than in December. The geographical characteristics of the precipitation distribution show that the Sea of Japan side has more precipitation, while the Pacific Ocean side has less precipitation and is drier. 2. Spring (Fig. 2.9): The temperature distribution shows an increase from March to May from Kyushu in the southwest to Hokkaido in the northeast. Particularly, in May, a wide area of western Japan enjoys a mild climate with temperatures exceeding 20 °C. In terms of precipitation distribution, the heavy precipitation area on the Sea of Japan side that was seen in winter is obscured, and precipitation increases on the Pacific Ocean side in western Japan in May. 3. Summer (Fig. 2.10): The characteristic feature of the summer temperature distribution map is that the temperatures in July and August are almost the same, whereas temperatures in June are slightly lower than 25 °C nationwide, especially in the eastern part of Hokkaido. In August, overall precipitation decreases, but is higher in areas facing the Pacific Ocean in western Japan. 4. Autumn (Fig. 2.11): According to the calendar, autumn begins in September, but the temperature distribution map in that month is similar to that of June, indicating that the summer climate still remains. In areas south of Hokkaido, average temperatures are higher than 20 °C. However, from October to November, temperatures fall countrywide, and in November the average temperature falls below 10 °C almost everywhere, indicating a change to an early winter climate. A characteristic feature of the precipitation distribution is that the area of heavy precipitation on the Pacific Ocean side seen in September almost disappears in November, while precipitation increases on the Sea of Japan side in the Tohoku region. In the next section, the mechanism that characterizes the seasons in Japan from a climatological perspective will be explained using weather maps and meteorological satellite images for the six seasons, including both the summer and autumn rainy seasons.

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Fig. 2.8 Temperature and precipitation map in winter. Data source Japan Meteorological Agency

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Fig. 2.9 Temperature and precipitation map in spring. Data source Japan Meteorological Agency

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Fig. 2.10 Temperature and precipitation map in summer. Data source Japan Meteorological Agency

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Fig. 2.11 Temperature and precipitation map in autumn. Data source Japan Meteorological Agency

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2.2.2 Winter Figure 2.12 shows a typical weather map (top) and meteorological satellite image (bottom) of Japan and its surroundings in winter. The weather maps and meteorological satellite images for each season used in the following sections were selected from the JMA archive to show typical days representative of each season. The day shown in Fig. 2.12 is 1 January 2021, with high pressure (H) over the continent to the west of the weather map (top) and low pressure (L) over the North

Fig. 2.12 A typical weather map (top) and meteorological satellite image (bottom) in the winter season. Source Japan Meteorological Agency

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Pacific to the east, with several isobars vertically aligned over Japan. This type of winter pressure pattern is called “high in the west and low in the east.” In the cloud image (bottom) taken from a meteorological satellite on the same day, a streaky cloud line running from northwest to southeast is clearly visible over the Sea of Japan. In fact, what appears to be white is not strictly speaking a cloud, but rather a thermal image showing the infrared radiation energy emitted from the clouds and the sea surface in shades of grey, with the tops of the taller clouds being white due to their lower temperature, and the lower cloud tops and sea surface being blue due to their higher temperature. However, in effect, the white areas in the IR image can be treated as clouds, and they are referred to as such in the following description. Figure 2.13 schematically shows the atmospheric flow over Japan and surrounding areas in winter. The northwesterly winds blowing from the Siberian Continent flow over the Sea of Japan towards the Aleutian Low in the North Pacific. The Siberian High is a low height anticyclone system below 2000 m in altitude that forms in winter when cold air is deposited on the Eurasian continental land surface by radiative cooling. To the south of the Siberian High are the Himalayan Mountains and the Tibetan Plateau, which are more than 5000 m above sea level. On the other hand, the stagnant Aleutian Low, which covers the northern North Pacific Ocean from the Sea of Okhotsk to the coast of Alaska with the Aleutian Islands as its center of action, plays an important role in the winter climate along with the Icelandic Low in the North Atlantic. On the other hand, the Polar Jet Stream around 40°N and the Subtropical Jet Stream around 30°N flow from west to east at around 8 km to 13 km above the

Fig. 2.13 Atmospheric circulation model in winter

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Fig. 2.14 A schematic diagram showing snowfall on the Sea of Japan side in winter

ground surface, with the Siberian High near the ridge of the meandering Polar Jet Stream and the Aleutian Low near the upper-level trough. Secondly, as shown in Fig. 2.8, precipitation is heavy on the Sea of Japan side in winter, but most of the precipitation is snowfall. The mechanism of snowfall on the Sea of Japan side in winter will be explained based on Fig. 2.14. As already mentioned, in winter, the dry northwesterly monsoon from Siberia blows over the Japanese islands, being greatly modified by the heat and moisture supplied from the sea surface as it passes over the Sea of Japan, and becomes more unstable as it reaches the coast of the Japanese islands, forming convective clouds. The air then

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Fig. 2.15 Heavy snowfall in winter at Kakunodate, Akita prefecture in the Sea of Japan region. Photograph taken by T. Mikami

descends down the slopes of the mountain ranges and dries out on the leeward side, resulting in cold northerly winds on the Pacific side, but with clear skies. Figure 2.15 shows a typical landscape of heavy snowfall in the Sea of Japan side area in winter.

2.2.3 Spring As the Siberian High weakens, the winter season ends, and the warm spring season arrives in Japan. When a part of the Yangtze air mass becomes an anticyclone and is influenced by the prevailing westerly winds above, it becomes a moving anticyclone and brings clear skies when it arrives in the Japanese archipelago but causes bad weather when a low-pressure system following it approaches. Figure 2.16 shows a typical spring weather map and meteorological satellite image for 8 May 2020. As the weather map clearly shows, a moving high-pressure system covers a wide area of the Japanese archipelago, and the meteorological satellite image also shows that there is almost no cloud cover within the high-pressure system. However, because high and low pressure alternates in cycles of three to four days, temperature changes are also significant and are referred to as “three cold and four warm days”(sankan shion in Japanese).

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Fig. 2.16 A typical weather map (upper) and meteorological satellite image (lower) in the spring season. Source Japan Meteorological Agency

2.2.4 Rainy Season in Early Summer In June, the early summer rainy season, known as baiu (or tsuyu), arrives. The Baiu Front, which is stagnant along the southern coast of Japan, brings rainfall and cloudy weather over a wide area, mainly over the Pacific side of Japan, as described below. As shown in Fig. 2.17, the weather map shows that the North Pacific High (Ogasawara air

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mass) extends to the south of the front from the east, while an anticyclone (Okhotsk Sea air mass) can be seen near the Sea of Okhotsk to the north of the front (Fig. 2.17). Figure 2.18 shows the atmospheric flow patterns in the early summer rainy season. The subtropical jet stream located south of the Himalayas and the Tibetan Plateau in winter diverges north and south of the mountain range, with the northern flow moving to around 40°N and stagnating, just north of the Baiu Front near the Japanese Islands. The higher Polar Jet Stream meanders along 60°N and forms a blocking anticyclone near the Kamchatka Peninsula, where it often stagnates. Within the blocking high,

Fig. 2.17 A typical weather map (top) and meteorological satellite image (bottom) in the early summer rainy season. Source Japan Meteorological Agency

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Fig. 2.18 Atmospheric circulation model in the early summer rainy season

the air settles and thus forms a low-temperature, moist Okhotsk Sea air mass below a height of about 1000 m, that is called the Okhotsk High. From the Okhotsk High, cool northeasterly winds called yamase flow into the Pacific region of northeastern Japan and often cause rice crop failures (see Sect. 5.2.5). The baiu rainy season period varies from year to year and its duration varies from region to region (Fig. 2.19), with the start and end of baiu occurring earlier in Okinawa, located to the south, and later in Northern Tohoku, which corresponds to the seasonal progression of the Baiu Front. The Baiu Front usually moves northwards to northern Tohoku in the second half of July and then weakens, but if it moves further northwards to Hokkaido and then stagnates, the Baiu Front will move northwards to the northern Tohoku region and then weaken. When the Baiu Front reaches Hokkaido and stagnates, a short rainy season called “Ezo Tsuyu” may also appear in the northernmost islands. The Kanto-Koshinetsu (D) region, which includes Tokyo, was used as an example to examine the variation in the onset and end of the rainy season since 1951: the earliest onset-date was around 6 May (in 1963), and the latest around 22 June (in 1967 and 2007). On the other hand, the earliest and latest end dates were 4 July (in 1978) and 4 August (in 1982). With regard to the duration of the rainy season, the shortest was 27 days (in 1955, 1959 and 2013) and the longest was 80 days (in 1963). However, the length of the rainy season does not necessarily correspond to the total precipitation during the period. For example, in 1963, the longest rainy season, the total precipitation for 80 days was 114% of normal, while in 1985 the

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Fig. 2.19 List of baiu rainy season periods by region (A–L) A: Northern Tohoku, B: Southern Tohoku, C: Hokuriku, D: Kanto-Kohshinetsu, E: Tokai, F: Kinki, G: Chugoku, H: Shikoku, I: Northern Kyushu J: Southern Kyushu, K: Amami Islands L: Okinawa Islands. Data source Japan Meteorological Agency

rainy season was shorter than normal at 38 days, but the total precipitation during the period reached 157% of normal. In fact, the rainy season does not mean that precipitation occurs every day, and the total precipitation decreases when the rainy season includes a “mid-rainy season break”. On the other hand, even if the rainy season is short, total precipitation increases when torrential rains occur. In particular, the large inflow of warm moist air from the southwest towards the Baiu Front in western Japan at the end of the

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rainy season brings large amounts of rainfall and causes large-scale natural disasters such as floods and landslides. The source of the warm moist air that brings such heavy rainfall is the Equatorial Air mass described in Sect. 2.1.2, and typhoons that approach and make landfall on Japan from summer to autumn often appear near the equator.

2.2.5 Midsummer Season On Honshu, the main island, when the baiu season ends in mid-July, the hot and sunny midsummer season begins, as shown in Fig. 2.20, which shows the weather map and meteorological satellite image for 6 August 2020. To the south of the front, the North Pacific High extends from the east, broadly covering the area from Japan to southern China. In the meteorological satellite cloud images, clear areas extend to the south of the Baiu Front’s cloud bands, which can be understood to correspond to the North Pacific High.

2.2.6 Autumn Rainy Season In late August, the North Pacific High weakens and retreats to the east of the Japanese archipelago, ending the midsummer season. When the front near Hokkaido starts to move southward again and stagnates on the southern coast of Japan, bad weather similar to that in the baiu season appears mainly in eastern Japan. Figure 2.21 shows the weather map and meteorological satellite image of 10 October 2019; the Japanese archipelago is covered by a moving high-pressure system and the sky is clear, but there is a strong typhoon over the southern ocean, which is moving northwards. This typhoon made landfall in Japan two days later, bringing heavy rain to the southern part of Kanto region. The clear sky spot (Eye) at the center of the typhoon is clearly visible in meteorological satellite images. Figure 2.22 shows an overlapped map of typhoon tracks in September for the 20-year period 2001–2020. It can be seen that typhoons originating in the tropics at 10°N–20°N often move northward along the western margin of the North Pacific High, then turn NE-ENE around 25°N–30°N and approach and often make landfall on Japan.

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Fig. 2.20 A typical weather map (top) and meteorological satellite image (bottom) in the midsummer season. Source Japan Meteorological Agency

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Fig. 2.21 A typical weather map (upper) and meteorological satellite image (lower) in the autumn rainy season. Source Japan Meteorological Agency

2.2.7 Late Autumn As in the spring season, a migratory anticyclone moves eastwards from the western continent, and the Japanese archipelago becomes dry and sunny. Figure 2.23 shows the weather map and meteorological satellite image of 15 November 2020; as can be seen, Japan and a wide region surrounding it exhibit high pressure and clear skies. As the season progresses further, the winter season with a northwesterly monsoon will arrive again.

2.3 Extreme Weather and Teleconnection Patterns

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Fig. 2.22 Typhoon Tracks in September (2001–2020). Source Japan-Asia Climate Data Program: https://jcdp.jp/japan/

2.3 Extreme Weather and Teleconnection Patterns In the previous sections, seasonal changes specific to Japan and their meteorological and climatological mechanisms have been explained mainly using climate maps of normal years. However, climate and weather fluctuate from year to year and the same weather conditions do not always appear. We know empirically that unusual weather conditions that are far from normal may appear even in the same season. Such weather and climate events that differ significantly from the normal year are called extreme weather events. In particular, it has been pointed out that the frequency of extreme weather events is likely to increase in the future due to global climate change, or global warming (e.g. IPCC, 2013). Such extreme weather events have occurred in the past, and there have been many studies on anomalies in the global weather distribution and their mechanisms. In this section, the relationship between the teleconnection patterns caused by changes in global atmospheric circulation and the weather in Japan is described, focusing on the winter and summer seasons, with examples of extreme weather events seen on a global scale. Regarding the various teleconnections that influence climate change in Japan, Yamakawa (2005) explains them in terms of seasonal to multi-decadal scale climate variability.

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Fig. 2.23 A typical weather map (top) and meteorological satellite image (bottom) in the late autumn season. Source Japan Meteorological Agency

2.3.1 Cold and Warm Winters In this section, extraordinarily cold and extraordinarily warm winters in Japan are discussed in relation to atmospheric circulation on a global scale and specific teleconnection patterns. Before that, we will describe the normal patterns of the upper atmospheric circulation and sea-level pressure fields in the Northern Hemisphere, centered on Japan. Figure 2.24 shows the 500-hPa geopotential height (top) and SLP (Sea Level Pressure) field (bottom) in the Northern Hemisphere in January (normal year). The

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500 hPa height map of the middle troposphere shows large-scale atmospheric flow, with the center of low pressure, i.e. the center of cold air, in the northern part of Canada in the Arctic region, around which westerly winds flow as waves (Rossby waves) along the contours (effectively, isobars). The main troughs of westerly wind waves are found on the east coast of the Eurasian continent and the eastern part of the North American continent. On the other hand, in the SLP field (bottom), as explained in Sect. 2.2.2, the Siberian High over Eurasia and the Aleutian Low in the northern North Pacific are present, while the Icelandic Low is observed in the northern North Atlantic. What, then, are the atmospheric circulation patterns in the Northern Hemisphere during cold and warm winter years in Japan? Let us examine the relationship between the Northern Hemisphere surface temperature anomaly distribution and the 500 hPa height field. Incidentally, in the winter of 1981, heavy snowfall occurred in the regions Fig. 2.24 500 hPa Height (top) and Sea Level Pressure fields (bottom) for January in the Northern Hemisphere (1991–2020 normal). Data Source https://psl.noaa.gov/ data/atmoswrit/map/ Image provided by the NOAA-ESSR Physical Science Laboratory, Boulder Colorado from the Web site at https://psl.noaa.gov/

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Fig. 2.25 Heavy snowfall in Fukui City on the Sea of Japan coast in January 1981. Photo THE MAINICHI NEWSPAPERS

on the Sea of Japan side, burying main roads under snow cover and causing traffic disruption, which had a major impact on social life (Fig. 2.25). Looking at Fig. 2.26 (top), the center of the low-pressure system in the 500hPa height map is almost at the North Pole, but another center of low pressure that split from it also exists near the Kamchatka Peninsula north of Japan, and cold air from the North Pole flowed out near Japan, causing extremely cold winter (negative surface temperature anomalies) in Japan. The winter of that year (1981) was also exceptionally cold in Europe and eastern North America. On the other hand, areas of unusually high temperatures (positive surface temperature anomalies) were observed over northern Siberia and northwestern North America, but focusing on the 500hPa height field, it can be seen that most of the warmer areas corresponded to the westerly wave ridge, indicating that warm air from the south was likely to flow in. Such an atmospheric circulation pattern is also called the Eurasian Teleconnection (EU) Pattern, and corresponds to the meandering of the jet stream over Europe (negative anomalies = low pressure anomalies), through northern Siberia (positive anomalies = high pressure anomalies) to near Japan (negative anomalies = low pressure anomalies) in the 500 hPa surface height field. There are also several other teleconnection pattern indices for the Northern Hemisphere atmospheric circulation field in winter. For example, the index of the strength of the Pacific North American (PNA) pattern, in which a trough develops to the east of

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Fig. 2.26 Patterns of January temperature anomalies and 500 hPa geopotential height fields in the Northern Hemisphere for 1981 (top) and 1989 (bottom). Data source NCEP/NCAER Reanalysis

the ridge in the west of North America, is +2.46, a large positive anomaly, although Arctic Oscillation Index (AOI) for January 1981 was weak (-0.116) indicating that they are not closely linked. The Arctic Oscillation (AO), which is a seesaw pattern of pressure fluctuations between the Arctic and mid-latitudes, is usually strongly associated with the occurrence of extreme weather events in Europe in winter. Other teleconnection pattern indices are also known, such as the Western Pacific (WP) Pattern, which is closely related to the winter monsoon in East Asia, and the Southern Oscillation Index (SOI), which is said to be related to warm/cold winters in Japan. It

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is reasonable to assume that the amplitude and phase of westerly wind waves (Rossby waves) are controlled by a mixture of several atmospheric circulation types. On the other hand, Fig. 2.26 (bottom) shows that in January 1989, in contrast to January 1981, Japan experienced a warm winter, and temperatures were also high in northern Europe and eastern North America. The westerly wind wave pattern was dominated by zonal flows without much meandering, the Arctic Oscillation Index (AOI) for January 1989 was +3.1, and the temperature anomaly map shows that the cold air was confined in the Arctic and the outflow to the mid and high latitudes was weak, as indicated by negative anomalies in the Arctic region. Also, the SOI was + 2.5, indicating a rather strong La Niña state.

2.3.2 Cool and Hot Summers The summer weather in Japan is mainly determined by two major anticyclones that emerge over Eurasia and the North Pacific Ocean. As shown in Fig. 2.27, the 100-hPa geopotential height map (top) features the Tibetan High, which extends east–west across the southern part of Eurasia to the North Pacific Ocean. The Tibetan High is a large-scale anticyclone that develops over the Tibetan Plateau due to a combination of continental heating and Asian monsoon heating. Its influence on the summer weather in Japan varies depending on its latitudinal position and its spread to the east. On the other hand, the geopotential height map (bottom) at 500 hPa shows a large-scale North Pacific High that covers the North Pacific Ocean from the sea surface to a height of more than 10,000 m. The degree of north–south displacement and the westward overhang of the ridge in the east–west direction has a significant influence on summer weather in Japan. Two case studies are presented to illustrate how these variations in hemispheric circulation fields and teleconnection patterns affect summer weather in Japan. One is the case of July 2003, when Japan experienced an unusually cool summer; this is shown as a superimposition of surface temperature anomalies and 500 hPa geopotential height fields as shown in Fig. 2.28 (top). The negative temperature anomaly area in blue extends into the subtropics along the 5800 m geopotential height contour to near the Black Sea, but at the 5880 m contour, which represents the extent of the North Pacific High, the area is both further south and smaller than normal. Whereas, positive temperature anomalies areas are distributed over Europe and northeastern Siberia, corresponding to the westerly wind wave ridge, which appears to be forming a blocking anticyclone. During this summer, Europe experienced record high temperatures due to an extreme heat wave, which killed more than 15,000 people, mainly elderly people, in France. The opposite temperature anomalies of hot and cold summer occurred in the west (Europe) and east (Japan) of Eurasia, and in the 500-hPa height fields, the ridge (anticyclone anomaly) over northern Europe,

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Fig. 2.27 Geopotential Height map of 100 hPa (top) and 500 hPa (bottom) for July in the Northern Hemisphere (1991–2020 normal). Data Source https:// psl.noaa.gov/data/atmoswrit/ map/

the trough (cyclone anomaly) over northern central Siberia, and the ridge (anticyclone) over northeastern Siberia may have brought cool summer to Japan as a kind of teleconnection pattern. Figure 2.28 (bottom) shows the 100 hPa geopotential height fields overlapped with surface temperature anomalies in July 2018, when Japan and Europe experienced a heat wave simultaneously. The Tibetan High is strengthening over southern Eurasia, with its eastern edge extending widely over the Japanese archipelago. Although omitted in the figure, the North Pacific High was also strengthening in the summer of 2018, and the heat was particularly severe in western Japan where the two highpressure systems overlapped. The role of strengthening the anticyclone near Japan is thought to have been played by enhanced convective activity near the Philippines,

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Fig. 2.28 Patterns of July temperature anomalies and 500 hPa (top) and 100 hPa (bottom) geopotential height fields in the Northern Hemisphere for 2003 (top) and 2018 (bottom). Data source NCEP/NCAER Reanalysis

which caused the rising air to sink down near Japan and strengthened the downward flow of the anticyclone. Such atmospheric flows are closely related to summer weather in Japan via a teleconnection known as the PJ (Pacific Japan) pattern (e.g., Nitta, 1987). Another teleconnection known to be associated with summer weather in Japan is the Silk Road pattern (e.g., Stephan et al., 2019; Zhou et al., 2019). As mentioned above, when continental heating, which is a factor in the formation of the Tibetan High, causes the subtropical jet stream in the upper troposphere to meander in the north-western region of the high (near the Caspian Sea), the wave propagates eastwards and low-pressure, high-pressure and low-pressure anomalies appear alternately, with high-pressure anomalies near Japan strengthening the North Pacific

References

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High. The PJ pattern and the Silk Road pattern have different causes, but the combination of both effects can be said to strengthen the anticyclone near Japan, resulting in a heat wave. In any case, the mechanisms that bring about Japanese summer weather, especially extreme weather, are complicated and not yet fully clarified.

References IPCC. (2013). Climate change 2013: The physical science basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (T. F. Stocker, D. Qin, G.-K. Plattner, M. Tignor, S. K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex, & P. M. Midgley, Eds.). Cambridge University Press. Nitta, T. (1987). Convective activities in the tropical western Pacific and their impact on the Northern Hemisphere summer circulation. Journal of the Meteorological Society of Japan, 65, 373–390. Peel, M. C., Finlayson, B. L., & McMahon, T. A. (2007). Updated world map of the Köppen-Geiger climate classification. Hydrology and Earth System Sciences, 11, 1633–1644. Stephan, C. C., Klingaman, N. P., & Turner, A. G. (2019). A mechanism for the recent interdecadal variability of the Silk Road pattern. Journal of Climate, 32, 717–736. Yamakawa, S. (2005). Climate variations from the viewpoint of seasonal to multi-decadal scale. Journal of Geography (chigaku Zasshi), 114, 460–484 (in Japanese with English abstract). Zhou, F., Zhang, R., & Han, J. (2019). Relationship between the circumglobal teleconnection and Silk Road pattern over Eurasian continent. Science Bulletin, 64, 374–376.

Chapter 3

Climate Change in Japan Since the 20th Century

Abstract Local meteorological observations in Japan started in Hakodate in 1872, and the Japan Meteorological Agency started official meteorological observations in Tokyo in 1875. Therefore, this chapter clarifies the climatic changes in Japan as compared with global climate change since the twentieth century, when continuous meteorological observation data became available throughout Japan. The actual conditions and mechanisms of flood disasters caused by heavy summer rains, frequently occurring in Japan, will also be described. Urban Heat Island is also discussed using Tokyo as a case study. Temporal and spatial variations in Tokyo metropolitan area are clarified based on our unique urban temperature observations system. Keywords Meteorological observation · Japan Meteorological Agency · Flood disaster · Urban heat islands · Tokyo

Chapter 2 describes the climatic characteristics of Japan, mainly based on normal values. In Sects. 2.3.1 and 2.3.2, under the theme of extreme weather, the mechanisms of extreme weather events in summer and winter in Japan were discussed based on specific case analyses. In this section, we discuss climate change in Japan over the past 120 years, focusing on the period since the twentieth century, when meteorological observation records are available.

3.1 Official Meteorological Observation System in Japan Official meteorological observation in Japan began on August 26, 1872, when Hakodate Climatic Survey Station was established by the Hokkaid¯o Development Commission. However, the meteorological observatory leading to the present Japan Meteorological Agency (JMA) is the Tokyo Meteorological Observatory established by the Home Ministry on June 1, 1875, which is regarded as the official beginning of meteorological observation in Japan (Koinuma, 1969).

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 T. Mikami, The Climate of Japan, Advances in Global Change Research 77, https://doi.org/10.1007/978-981-99-5158-1_3

39

40

3 Climate Change in Japan Since the 20th Century

This chapter will not discuss the history of meteorological observation in Japan; however, we will discuss the early nineteenth-century meteorological observations and their records in Sect. 4.1. The JMA routinely conducts a variety of meteorological observations, and the meteorological observation data are transmitted to the JMA Main Office in real time for effective use in basic data for meteorological analysis and numerical forecasting, disaster prevention work, and weather forecasting. Figure 3.1 shows the JMA’s meteorological observation system. The JMA uses various types of observation equipment to conduct weather observations. AMeDAS (Automated Meteorological Data Acquisition System), which is placed at about 1,300 locations throughout Japan, provides meteorological data on precipitation, temperature, wind direction/velocity, sunshine duration, and snow depth (in some cases), which are automatically observed (Figs. 3.2 and 3.3). In addition, six District Meteorological Observatories and about 50 Local Meteorological Observatories and Meteorological Stations across the country conduct automatic observations of atmospheric pressure, humidity, solar radiation, and snow depth (in some cases).

Fig. 3.1 JMA meteorological observation system in Japan. Source Japan Meteorological Agency

3.1 Official Meteorological Observation System in Japan

41

Fig. 3.2 Location of JMA—AMeDAS stations

3.1.1 Relocation of JMA Tokyo Meteorological Observatory and Its Effect As described in Sect. 3.1, the JMA Tokyo Meteorological Observatory began its meteorological observations on June 1, 1875, at Tameike-Aoicho (present-day Toranomon) in central Tokyo. This location is near the current JMA main office. (see No. 1 in Fig. 3.4). In 1923, the Tokyo Meteorological Observatory became the Central Weather Bureau and moved to Otemachi, outside the Imperial Palace (see Nos. 3 in Fig. 3.4). In 1964, it moved to an adjacent site across the street, where it continued to conduct meteorological observations for about 90 years until November 2014. However, due to the redevelopment project of the Otemachi area, the observation site was moved to Kitanomaru, the green area of the Imperial Palace, in December 2014, independently from the JMA main office (see No. 5 in Fig. 3.4).

42

3 Climate Change in Japan Since the 20th Century

Fig. 3.3 An example of AMeDAS Regional Weather Stations. (A) Anemometer, (B) Sunshine meter, (C) Electric ventilation thermometer, (D) Rain gauge

Fig. 3.4 Relocation of JMA Tokyo Observatories during 1875–Present. Modified from JMA https:// www.jma.go.jp/jma/kishou/minkan/koushu141114/shiryou1.pdf

3.1 Official Meteorological Observation System in Japan

43

Fig. 3.5 Aerial view showing the location of Otemachi (former observation point) and Kitanomaru (current observation point). Photo Skymap Inc.

Figure 3.5 shows the location of Otemachi (the former observation station) and Kitanomaru (the current observation station) as viewed from the sky. Otemachi is located in the built-up area on the northeast side of the Imperial Palace, adjacent to the Metropolitan Expressway with heavy traffic. On the other hand, Kitanomaru is located in a green park on the north side of the Imperial Palace, as shown in Fig. 3.6, and the surrounding area is thickly forested. The JMA conducted parallel observations at both the former and new sites for about three years from 2012, before the relocation of the Tokyo observatory, and published the changes in temperature, relative humidity, precipitation, and snow depth due to the relocation of the observatory. Namely, JMA calculated the changes after the relocation by averaging each meteorological element at the former and new observation sites over two years from April 2012 to March 2014. The results show that the annual mean daily mean temperature, daily maximum temperature, and daily minimum temperature decreased by −0.9 °C, −0.2 °C, and −1.4 °C, respectively, compared to those before the relocation. We compared the diurnal variations of temperatures at Otemachi and Kitanomaru in summer (July and August [2012, 2013]) (Fig. 3.7). As is clear from this graph, the temperature at the Kitanomaru station located in the green-park area is about 0.2–0.4 °C lower than that at Otemachi during the daytime, whereas the difference becomes larger from afternoon to nighttime, reaching as much as 1.4 °C around 5:00 in the early morning. This is because the latent heat is lost by transpiration from the leaves of trees around the forest during the daytime, which suppresses the temperature increase, while radiative cooling from

44

3 Climate Change in Japan Since the 20th Century

Fig. 3.6 Current view of the JMA Kitanomaru observation site. Photo T. Mikami

the grass surface at the observation site is enhanced during the nighttime and early morning. The former observation site, Otemachi, is surrounded by artificial surfaces such as concrete and asphalt, which weaken radiative cooling, especially at night, and the artificial heat emitted from the surrounding buildings also warms the atmosphere, thus suppressing the temperature decrease.

3.2 Climate Variations in Japan Since the 20th Century This section describes the variations in temperature and precipitation in Japan since 1898, using the official JMA meteorological observation data described in Sect. 3.1.1. As explained in Chapter 2, the Japanese archipelago is highly elongated from north to south, resulting in large regional differences in temperature and precipitation. In addition, there are many observation points where temperatures have increased due to urbanization. The JMA calculates average temperature anomalies for Japan using monthly mean temperature data from 15 stations shown in Table 3.1, which are selected from meteorological stations that have continued to observe temperatures since 1898, so that the influence of urbanization is small and not biased to any particular region. The calculation method is as follows:

3.2 Climate Variations in Japan Since the 20th Century

45

Fig. 3.7 Diurnal variations of mean temperatures in Otemachi (former site) and Kitanomaru (current site) in July and August during the parallel observation period. Data source Japan Meteorological Agency Table 3.1 List of 15 JMA meteorological stations used for calculating mean temperature anomalies in Japan

Station name

Latitude

Longitude

Abashiri

44.02

144.28

Nemuro

43.33

145.59

Suttsu

42.8

140.22

Yamagata

38.26

140.35

Ishinomaki

38.43

141.3

Fushiki

36.79

137.06

Iida

35.52

137.82

Choshi

35.74

140.86

Sakai

35.54

133.24

Hamada

34.9

132.07

Hikone

35.28

136.24

Miyazaki

31.94

131.41

Tadotsu

34.28

133.75

Naze

28.38

129.5

Ishigakijima

24.34

124.16

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3 Climate Change in Japan Since the 20th Century

1. For each station in Table 3.1, the monthly mean temperature anomaly (the observed monthly mean temperature minus the 30-year mean for the period 1991–2020) is calculated. 2. The values calculated in 1. are averaged over the year and season for each location. 3. For each month and for the value calculated in 2. above, the average anomaly for 15 locations is calculated. The obtained value is the mean temperature anomaly for that year, season, and month (anomaly based on 1991–2020). On the other hand, precipitation has greater variability from point to point than temperature and more station data is needed to analyze long-term trends in variability. The number of stations used is 51, which is more than that for temperature.

3.2.1 Temperature Variations Since the 20th Century The annual mean temperature variation in Japan during the 124 years (1898–2021) since the end of the nineteenth century will be discussed by comparing it with the variation of the global mean temperature. Figure 3.8 shows a time-series graph averaged over 15 stations selected from JMA meteorological stations throughout Japan, and expressed as anomalies from the 30-year average for the period 1991–2020. The 11-year running mean curve is shown as a thick line to illustrate the long-term trend. The red line shows the global annual mean temperature variations. The amplitude of the mean temperature variability in Japan is far larger than the global mean temperature variability due to the small number of stations used.

Fig. 3.8 Annual mean temperature variations in Japan (black) and Global mean temperature variations (red). Data source Japan Meteorological Agency

3.2 Climate Variations in Japan Since the 20th Century

47

Both Japan’s and the world’s annual mean temperatures show a distinct increasing trend from the 20th to the twenty-first century, although their decadal variations are slightly different. After around 1990, the trends of temperature fluctuations in Japan and the world are almost the same, whereas the trends of temperature fluctuations before the 1990s are different. The global annual mean temperature increased until around 1940 and then stabilized or slightly decreased until around 1980. On the other hand, annual mean temperatures in Japan remained stable until the mid-1940s, rose sharply from the 1950s to the 1960s, and then stabilized until the 1980s. Since then, however, it has increased markedly, and the trend of fluctuation since the twenty-first century is similar to that of the global annual mean temperature. Thus, the annual mean temperature variations in Japan, especially before the twentieth century, show a trend different from that of the rest of the world. Figure 3.9 shows seasonal mean temperature time series based on the meteorological data for the 15 stations shown in Table 3.1. The graphs are divided into winter/spring (top) and summer/autumn (bottom), which have similar trends. In the winter/spring season, there was a clear trend of the rapid increase in mean temperature in the 1940s and the late 1980s. On the other hand, the mean temperature in the summer/autumn season increased at the beginning of the twentieth century and remained stable from about 1920 to 1980. Since 1980, however, an upward trend has continued until the present. Although it is not clear what caused the difference in temperature trends between the cold and warm seasons, previous studies have pointed out that the discontinuity between the 1940s and 1980s observed in winter/spring season temperature fluctuations also occurred throughout the Northern Hemisphere; this has been described as a “regime shift” (e.g., Hare & Mantua, 2000; Kim et al., 2015; Niebauer, 1998; Reid et al., 2016; Song et al., 2019; Urabe & Maeda, 2014). The season and period at which the regime shift appears vary from region to region, but the fact that it appears most clearly in winter and rarely in summer is most likely related to seasonal differences in large-scale atmospheric circulation. Regarding the regime shift in the late 1980s, some studies, such as Reid et al. (2016), suggest that it may have been triggered by rapid warming due to anthropogenic factors and the 1982 El Chichón eruption, although there is no clear evidence to confirm it.

3.2.2 Precipitation Variations Since the 20th Century Since precipitation shows larger regional differences than temperature and analysis of trends requires a larger number of stations, we created time series graphs using data from 51 JMA meteorological stations that have been continuously observed over a long period (Fig. 3.10). As in the case of temperature, annual precipitation at each station is plotted by subtracting the 30-year average value for the period 1991–2020. Annual precipitation variability in Japan is characterized by a periodic change on a scale of several decades, with annual fluctuations repeating from year to year.

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3 Climate Change in Japan Since the 20th Century

Fig. 3.9 Seasonal mean temperature variations in Japan for Winter/Spring (top) and Summer/ Autumn (bottom). Data source Japan Meteorological Agency

3.2 Climate Variations in Japan Since the 20th Century

49

Fig. 3.10 Annual mean precipitation changes in Japan. The black line indicates 11-year running means. Data source Japan Meteorological Agency

In the twenty-first century, precipitation began to increase. It should be noted that precipitation does not show a clear linear trend like temperature, but as noted in the first section, there are large regional differences.

3.2.3 Flood Disasters and Climate Change Extreme weather events such as heat waves, heavy rains, and droughts are expected to increase in the future due to climate change such as global warming. However, since the beginning of the twentieth century, when official meteorological observation records by JMA became available in Japan, meteorological disasters due to heavy rainfall and strong winds have occurred frequently. In this section, we will focus on flood disasters in Japan and discuss their relationship with climate change by means of case studies and case analyses.

3.2.3.1

Flood Disasters in Japan and Their Characteristics

Floods, inundation disasters, and similar events caused by heavy rainfall are collectively referred to as flood disasters. In Japan, such flood disasters are often caused by the approach or landfall of typhoons, increased activity of the Baiu Front (see Sect. 2.2.4), or the rapid development of low-pressure systems. Heavy snowfall and large-scale snowmelt, and avalanches in winter can also cause flooding damage. This section discusses the characteristics of torrential rains that cause flooding in Japan in comparison with the rest of the world. The causes of heavy rainfall differ between cases in which a large amount of rain falls in a short period (10 min to an

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3 Climate Change in Japan Since the 20th Century

Table 3.2 Top 20 causes of heavy rainfall in Japan by units of time Thunderstorm

10 min rainfall

1 h rainfall

3 h rainfall

Daily rainfall

8

2

1

0

Low pressure

5

6.5

3.5

1

Frontal activity

7

8.5

7

4.5

Typhoon

0

3

8.5

14.5

Total

20

20

20

20

hour) and cases in which the total amount of rainfall increases over a day, resulting in heavy rainfall. Table 3.2 classifies the top 20 heavy rainfall events and frequency by cause for rainfall amounts per 10 min to 1 day. In the case of 10-min rainfalls, thunderstorms are the most common cause, followed by frontal activities and low pressures; typhoons are not represented. One-hour rainfall is mostly caused by frontal activities and low pressures, but in the case of 3-h rainfall, typhoons and frontal activities are almost equally numerous, and in the top 20 1-day rainfalls, typhoons are the leading cause. This indicates that frontal activities are a major cause of torrential rainfall concentrated in periods shorter than 3 h in Japan. In the following sections, we will discuss two typical examples of flood disasters and outline the magnitude of the torrential rains and the disasters they caused.

3.2.3.2

Nagasaki Floods (July 1982)

The disaster caused by the 1982 torrential rainfall in Nagasaki can be described as having two aspects: urban flooding in the central part of Nagasaki City and landslides caused by mudslides and other disasters that occurred mainly in suburban areas. The torrential rains were brought about by a large amount of warm moist air that flowed into a frontal zone that moved northward at the end of the rainy season, known as a “wet tongue.” As a result, Nagayo Town and Saigo in Unzen City experienced record-breaking rainfalls of 187 mm per hour and 1109 mm per 24 h, respectively. Figure 3.11 shows the distribution of maximum one-hour precipitation in Nagasaki Prefecture on 23 July 1982, the day of the heavy rainfall event. The area circled in blue has a one-hour precipitation exceeding 121 mm/hour. As mentioned above, Nagayo Town, located to the north of Nagasaki City, experienced the highest recorded precipitation in the history of meteorological observations. Before explaining the characteristics of the disaster, let us look at the characteristics of Nagasaki City’s urban formation. Nagasaki has long prospered as a cosmopolitan city, but its urban area was formed facing a deep inlet surrounded by sloping hills. Because there is little flat land, the city was forced to create reclaimed land and expand its urban area on the slopes surrounding the city. This means that when heavy rains occurred, the reclaimed land drained poorly, making it easy for the urban area to become submerged in water. Ambulances and fire trucks could not

3.2 Climate Variations in Japan Since the 20th Century

51

Fig. 3.11 Distribution of maximum one-hour precipitation in Nagasaki Prefecture on 23 July 1982. Modified from Ninomiya (2022)

easily enter the slopes because the roads were inadequately maintained and narrow. In addition, there were few horizontal escape routes for evacuation in the event of a landslide. Landslides are an important disaster prevention issue for Nagasaki City, which has urbanized by expanding into land use in mountainous areas and valleys. In the torrential rains of July 1982, mudslides, landslides, and cliff collapse reached 4,457 locations in Nagasaki Prefecture. 262 people, which is 88% of the 299 people killed or missing, were victims of landslides. Meanwhile, large-scale flooding damage occurred in the three river basins of the Nakashima, Urakami, and Hachiro Rivers that run through Nagasaki City. A total area of 303 hectares was inundated in the Nakashima and Urakami river basins, with 5,535 houses inundated above floor level and 2,129 houses inundated below floor level. The disaster was magnified by the extremely heavy rainfall in a short period, although another important factor was the topographical characteristics of the rivers, with their steep and short gradients and low water conveyance capacity. In any case, in addition to the rapid outpouring of water from the torrential rains and the failure to take appropriate initial measures against flooding, the specific urban structure of Nagasaki City, with its urban areas spread out on slopes, probably contributed to the increased damage.

52

3.2.3.3

3 Climate Change in Japan Since the 20th Century

West Japan Floods (July 2018)

From late June to early July 2018, 36 years after the Nagasaki floods, a wide area from the Chubu region (central Japan) to Kyushu (southwestern Japan) suffered flood disasters due to typhoons and the Baiu Front. Figure 3.12 shows the total precipitation distribution over western Japan during the 11 days from June 28 to July 8. In particular, Yanase in Kochi Prefecture, facing the Pacific Ocean received a total precipitation of 1852.5 mm during the 11 days. This flood is generally referred to as the “West Japan Flood,” and the JMA has analyzed its characteristics and causes. Figure 3.13 illustrates the meteorological factors that brought record-breaking heavy rainfall over western Japan from 5 to 8 July 2018, with a large amount of moist air flowing along the western edge of the North Pacific High. The Japan Meteorological Agency has identified the following three factors as the cause of the heavy rainfall.

Fig. 3.12 Distribution of total rainfall amount in western Japan from June 28 to July 8, 2018. Source Japan Meteorological Agency

3.2 Climate Variations in Japan Since the 20th Century

53

Fig. 3.13 Schematic diagram showing the meteorological mechanism of the “Western Japan Torrential Rain”. Source Japan Meteorological Agency

1. Continuous merging of two air masses containing large amounts of water vapor near western Japan 2. The formation of persistent upwelling due to the stagnation and strengthening of the Baiu front 3. Formation of local linear precipitation zones (Senjo Kosuitai). The pressure pattern and location of the Baiu front at the time of the West Japan Floods are similar to those in the case of the Nagasaki Flood in 1982, but the temporal and spatial scale of the West Japan Floods was much larger. Not only western Japan but also central Japan was affected, and the disaster was a prolonged one lasting from June 28 to July 8. In addition, record-high temperatures of 35 °C to 40 °C had persisted throughout the country since mid-July. Let us take a look back at the scale of flood damage caused by this torrential rain: as of July 31, 2018, the number of deaths was 220 and 10 people were missing; 13,258 houses were flooded above floor level and 20,942 houses were flooded below floor level, with particularly large numbers of deaths and missing persons in Hiroshima (114 people), Okayama (64 people) and Ehime (27 people) Prefectures, accounting for about 90% of the total. This indicates that while the damage was concentrated in relatively small areas, the area directly affected by the torrential rains covered a wide area.

54

3.2.3.4

3 Climate Change in Japan Since the 20th Century

Long-Term Trends in Heavy Rainfall Disasters

Is flood damage caused by heavy rainfall increasing in Japan? First, as a rough indication of the scale of flooding caused by meteorological factors, we will examine long-term trends in the number of houses inundated above and below floor level. Although the large-scale flooding damage caused by the 2011 Great East Japan Earthquake and Tsunami should not be ignored, we exclude flooding damage caused by tsunamis from our analysis and focus on typhoons, frontal activities, developing low-pressure systems, and heavy snowfall as the main causes of flooding damage. Table 3.3 shows the change in the scale of torrential rainfall and flood damage by decade since the 1950s. Note, however, that only cases where the number of dead or missing persons per disaster was 50 or more and inundation damage occurred were taken into account in the study. Regarding number of disasters by decade, in the 1950s there were 31, in the 1960s there were 17, in the 1970s there were 9, and since the 1980s there has been a sharp decline to less than 5 per decade. Looking at the factors that brought about heavy rainfall disasters, typhoon disasters accounted for more than half of all disasters from the 1950s to the 1970s, but since the 1980s, frontal activity and typhoons have been conspicuous in causing damage. The number of people killed or missing due to torrential rains and floods was the highest in the 1950s, at about 16,000, and has been declining rapidly ever since. The number of houses flooded above and below floor level has also shown a clear downward trend, although the number of flooded houses per disaster (Flooded Houses/ Total Number) exceeded 100,000 until the 1970s. However, since the 1980s, the number of inundated houses per disaster has been rapidly decreasing to less than 30,000. This indicates that not only the number of heavy rain floods but also the area damaged per disaster has been decreasing in recent years. This trend could be attributed to factors such as improved forecast accuracy for typhoon tracks and Table 3.3 Change in the size of meteorological disasters by period (only those with 50 or more dead and missing persons per disaster) Period

1950–1959

Dead and missing

Flooded houses

Total number

typhoon

Major disaster factors Frontal activity

Low pressure

16,167

3,579,820

31

18

8

5 2

Heavy snow

1960–1969

2,655

2,048,157

17

8

6

1970–1979

1,560

1,050,548

9

7

1

1

1980–1989

756

189,276

5

1

2

2

1

1990–1999

131

44,952

2

1

2000–2009

301

56,169

3

1

2010–2019

526

103,832

4

2

1 2

Source Japan Chronological Scientific Tables: Rika Nenpyo (2021)

1

1

3.3 Climate Change in the Mega-City Tokyo

55

frontal activity, a shift in housing types from low-rise wooden houses to mediumrise concrete buildings, and an increase in disaster preparation awareness among the residents. On the other hand, since the 1990s, the number of fatalities and missing people, as well as the number of houses flooded above and below floor level, have been on the increase again. The increase since the 1990s may be closely related to the effects of climate change.

3.3 Climate Change in the Mega-City Tokyo The Greater Tokyo Area (Tokyo Metropolis plus surrounding cities) has a population of about 38 million, accounting for 30% of Japan’s total population of 125 million, making it the largest city in the world. This section describes climate change in the megacity Tokyo based on meteorological observation data. Annual mean temperature variations in Tokyo are compared with those in the world as a whole and in New York (Fig. 3.14). As discussed in Sect. 3.1.1, the temperatures after 2015 in Tokyo (marked with ▲) are corrected for the temperature decrease caused by the relocation of the observation site from urban Otemachi to forested Kitanomaru. The figure shows that the annual mean temperatures of the world’s major cities, such as Tokyo and New York, have increased at a greater rate than the global mean temperature since the end of the nineteenth century. In particular, the mean temperature in Tokyo has continued to increase at a rate far exceeding that of global warming. We, therefore, divided the entire period from 1876 to 2020 into three time periods: 1876–2020, 1921–2020, and 1971–2020, and calculated the rate of temperature increase per 100 years for each time period (Table 3.4). This table shows that the global means and the two mega-cities show the long-term temperature increase after 1876, with Tokyo having an increased rate of 2.55 °C/100 years, and New York with 1.55 °C/100 years. The increase rate in global means is relatively low at 0.77 °C/ 100 years. However, after 1921, the rate of temperature increase rose to 3.28 °C/100 years in Tokyo, which is more than three times higher than the global mean of 1 °C/100 years. Furthermore, for the 50 years after 1971, the temperature increase rate of 1.99 °C/100 years in the Global means was remarkable, while the temperature increase rate of Tokyo was about twice as high as the global means, reaching 3.86 °C/100 years. However, the rate of temperature increase in New York since 1971 was 1.75 °C/100 years, which is lower than the rate of global means. Although it is not clear what causes the difference in the recent temperature increase rates between New York and Tokyo, it is likely that the urbanization of Tokyo has been marked since the 1970s, as represented by the increase in high-rise buildings, while in New York, the urban structure such as skyscrapers in Manhattan has hardly changed since the early twentieth century, and thus the temperature increase rate in New York may have been lower than that in Tokyo.

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3 Climate Change in Japan Since the 20th Century

Fig. 3.14 Annual mean temperature variations in Tokyo as compared with those in the world as a whole and in New York. The global mean temperature was calculated assuming a base temperature for the period 1961–1990 as 14 °C with an uncertainty of several tenths of a degree. Thick lines indicate 11-year running means. The triangle marks in Tokyo indicate the corrected values due to the relocation of the observation site (see Sect. 3.1.1). Data source Japan Meteorological Agency for Tokyo; Climatic Research Unit, UEA for Global; NOAA National Weather Service for New York/Central Park

Table 3.4 100-year temperature increasing rates calculated for different periods (Linear regression equation slope)

Global

Tokyo

New York

1876–2020

0.77

2.55

1.55

1921–2020

1

3.28

1.35

1971–2020

1.99

3.86

1.75

3.3.1 Temperature Variations Since the 20th Century In Sect. 3.2.1, we discussed average temperature variations across Japan since the twentieth century. In this section, we focus on temperature fluctuations in Tokyo, where 30% of Japan’s population resides, and discuss them based on observed data. Figure 3.15 shows annual mean temperatures in Tokyo, divided into daily maximum temperatures, daily mean temperatures, and daily minimum temperatures (data after 2015 have been corrected for relocation). Eleven-year running mean curves (thick lines) are also included to make it easier to see the long-term trends. The upward

3.3 Climate Change in the Mega-City Tokyo

57

Fig. 3.15 Annual mean temperature variations in Tokyo since 1876. Thick lines indicate 11year running means. The triangle marks indicate the corrected values due to the relocation of the observation site (see Sect. 3.1.1). Data source Japan Meteorological Agency

trend of daily minimum temperatures is the most prominent: these have increased significantly since the 1950s. The annual mean of daily maximum temperature, on the other hand, shows an increase from the 1920s to around 1960, followed by a slight decrease until the 1980s, and then an increase again from 1990 onward. It has been suggested that this may be due to a reduction in the amount of solar radiation that the land surface receives, causing global dimming (Wild et al., 2007).

3.3.2 Precipitation Variations Since the 20th Century Figure 3.16 shows the long-term variability of annual precipitation in Tokyo. As in Fig. 3.15, an 11-year running mean curve is added, but no significant increase or decrease in precipitation is observed, such as that seen with air temperature. In the case of precipitation, the year-to-year variability is remarkable. The average annual precipitation for the entire period is 1530 mm, although there is a difference of more than 2.5 times between the highest year (1938) with 2230 mm and the lowest year (1984) with 880 mm. In terms of decadal averages, there is a difference of more than 350 mm between the relatively high rainfall of the 1910s (1712 mm) and the low

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3 Climate Change in Japan Since the 20th Century

Fig. 3.16 Annual precipitation variations in Tokyo since 1876. The thick line indicates 11-year running means. Data source Japan Meteorological Agency

rainfall of the 1960s (1345 mm). The long-term trend was a decrease in rainfall from the beginning of the twentieth century to the 1980s, followed by an increase from the end of the twentieth century to the twenty-first century.

3.3.3 Aridification of Tokyo Due to Urbanization As mentioned above, annual precipitation has been slightly increasing in recent years; however, this does not necessarily mean that the climate is becoming wetter everywhere. Instead, large cities such as Tokyo are likely becoming drier, as expressed by the popular expression “Tokyo Desert.” Figure 3.17 shows the long-term trend of relative humidity in Tokyo divided into the annual average, January (winter) average, and July (summer) average. In particular, the relative humidity in January, which was nearly 70% at the end of the nineteenth century, has fallen to the 40% range in recent years. This is mainly due to the increase in saturated water vapor pressure caused by the rise in temperature, while the amount of water vapor in the atmosphere itself has not changed significantly. This aridification is thought to be due to the increase in ground surfaces covered with concrete and asphalt owing to urbanization and to the decrease in water bodies and green areas in central Tokyo. The reason why the relative humidity has turned to increase despite the rise in temperature since the 2010s may be due to the increase in evapotranspiration from plants after the observation site was moved to a forested green area at the end of 2014 (see Sect. 3.1.1).

3.4 Urban Heat Islands in Tokyo Metropolis

59

Fig. 3.17 Daily mean relative humidity variations in Tokyo since 1876. Thick lines indicate 11year running means. The triangle marks indicate the corrected values due to the relocation of the observation site (see Sect. 3.1.1)

3.4 Urban Heat Islands in Tokyo Metropolis Urban Heat Island, which is named after the fact that the temperature in urban areas is higher than that in the surrounding rural areas and looks like an island, is clearly observed in the megacity of Tokyo. In this section, we focus on the urban heat islands in Tokyo and discuss their actual conditions and mechanisms.

3.4.1 High-Resolution Temperature Observation System in Tokyo Metropolis In Europe, the first observations of urban heat islands were made in Vienna (Austria) in the early morning hours of May 1927, when mobile observations of temperatures were made by motor vehicles (Schmidt, 1927; Stewart, 2019). In Japan, Fukui and Wada (1941) conducted mobile observations of air temperatures at 103 locations using nine automobiles in the former city of Tokyo (roughly equivalent to today’s 23 wards) at midnight on March 6, 1939. The resulting isotherms clearly showed that the temperature difference between the city center (urban center) and suburban areas reached 5 °C (Fig. 3.18). The population of Tokyo at that time was about 6.7 million,

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Fig. 3.18 Temperature distribution in the former Tokyo City area on 6 March 1939. Modified from Fukui and Wada (1941)

and this was the first case study in the world in which a clear heat island effect was observed in one of the world’s largest cities. To quantitatively elucidate the temporal and spatial variability of the urban heat island in a large city like Tokyo, it is not sufficient to make mobile observations at a single date and time by car; instead, simultaneous observations at many fixed points are essential. Since the spatial structure of the urban heat island varies with the season and time of day, it is necessary to acquire as much high-density temperature observation data as possible over a long period. However, AMeDAS, the existing meteorological observation system operated by the Japan Meteorological Agency, has a low density of stations in the Tokyo metropolitan area, and thus cannot accurately represent the spatiotemporal variations of the heat islands surrounding central Tokyo. Therefore, the author’s research team installed temperature data loggers in the Stevenson screen (Fig. 3.19 left) of public primary schools in approximately 200 locations (currently approximately 120 locations) in the greater Tokyo metropolitan area within a radius of 60 km around the central area of Tokyo. The temperature sensor (HIOKI-LR9601) is connected to the HIOKI-LR5011 data logger and the temperature is automatically observed every 10 min (Fig. 3.19 right). This unique observation system, called E-METROS (Extended Metropolitan Environmental Temperature and Rainfall Observation System), began making observations in 2006. The number of AMeDAS stations in the same area is 28, as shown in Fig. 3.20 (right), which is insufficient to elucidate the detailed actual conditions of the urban heat island. As explained above, a logger with sensor is attached to the interior space of the Stevenson screen to measure the air temperature under natural ventilation. Although the effect of

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solar radiation and radiation from the ground surface (infrared radiation and reflection of solar radiation) can be removed, the response to the external temperature, which changes within a short period, tends to be delayed. On the other hand, the JMA’s AMeDAS uses a cylindrical motorized ventilated thermometer (the forced draft thermometer) to measure air temperature, which is forced ventilated and thus responds more quickly to changes in outdoor air temperature than natural ventilation, although it is easily affected by the surrounding environment in the vicinity. In the case of the Stevenson screen, it is suitable for measuring air temperatures that are averaged to some extent over time and space. However, as pointed out by Yamato and Hamada (2019), the Stevenson screen itself is slightly warmer during the daytime when there is solar radiation, so the internal air temperature is likely to be higher than that observed with a forced draft thermometer, especially during the summer daytime. On the other hand, during clear nights, the temperature is likely to be lower than that observed by a forced draft thermister due to the radiative cooling of the Stevenson screen itself. It is not appropriate to directly compare our E-METROS observations of natural ventilation and AMeDAS observations of motorized forced ventilation or to draw isotherms by mixing both types of data. However, the same instrument (the temperature logger manufactured by HIOKI as mentioned above) and the same time interval (every 10 min) are employed for all 120 to 200 locations set in the Stevenson screen, and hence the E-METROS system is highly homogeneous and representative in time and space, making it suitable for analyzing temperature contours. Using all of the data (instrumentally corrected) for the two-year period from August 2006 to July 2008, a seasonal mean temperature distribution map was prepared to clarify the characteristics of temperature distribution in the greater Tokyo metropolitan area throughout the year. Figures 3.21 and 3.22 show isotherms of the

Fig. 3.19 A Stevenson screen in primary schools (left) and a logger with a temperature sensor (right)

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Fig. 3.20 Temperature observation map of the Tokyo Metropolitan Area: (a) Extended-METROS stations, (b) JMA AMeDAS stations. The shaded area includes DID (population density >4000/ km2 ). From Mikami and Yamato (2011)

average daily minimum and maximum temperature distributions in winter (December to February) and summer (June to August), respectively. For comparison, isotherms based only on JMA-AMeDAS stations are also plotted (left figures). First, we describe the characteristics of the winter mean daily minimum temperature distribution (Fig. 3.21). In the isotherms (left) based on AMeDAS observations, the highest temperatures are observed in the area bounded by the 4 °C isotherms from central Tokyo to the bay area, and temperatures tend to decrease in a northwesterly direction toward the inland areas. Overall, temperatures appear to decrease in direct proportion to the distance from the coast to the interior. On the other hand, Fig. 3.21 (right) shows the isotherms of the mean daily minimum temperature distribution for the same period using the E-METROS observation data. The figure clearly shows the formation of a well-defined heat island centered in the central part of Tokyo. The highest temperature peak, exceeding 5 °C, is located near the center of the city. Furthermore, concentric circular isotherms appear around the city center, and almost all of the 23 wards of Tokyo, except the northwestern part, have temperatures of 3 °C or higher, extending from Yokohama to the southern coastal area in Kanagawa Prefecture. The relatively higher-temperature area extends in a northwesterly direction toward Saitama City to Kumagaya City (northwest of Saiatama) to the north of Tokyo. This temperature distribution pattern is not evident in the AMeDAS temperature distribution map (Fig. 3.21 left).

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Fig. 3.21 Mean minimum temperature distribution in winter (December–February in 2007 and 2008). Data source (left) JMA AMeDAS, (right) Extended-METROS (Unit: Degrees C). From Mikami and Yamato (2011)

Figure 3.22 shows the distribution map of mean daily maximum temperatures in summer, which, as in Fig. 3.21, shows the isothermal map based on AMeDAS data only (left) and the detailed isothermal map based on E-METROS data (right) in parallel. In the AMeDAS isotherms, the low-temperature region below 28 °C extends from Chiba (east of Tokyo) to the coastal areas of Tokyo and Kanagawa (south of Tokyo), and the temperature tends to gradually increase towards the inland areas. In the E-METROS isotherms shown in Fig. 3.22 (right), the center of the hightemperature region above 30 °C is located in south-central Saitama Prefecture (north of Tokyo) and the high-temperature area over 29 °C extends in a southeastward direction toward Tokyo. The relatively lower-temperature area below 28 °C extends over the coastal area in southern Kanagawa Prefecture and is also seen in parts of eastern Tokyo and western Chiba Prefecture. In these bayside areas, the invasion of sea breezes from the south during the daytime in summer is thought to suppress the temperature increase and result in relatively low daily maximum temperatures compared to the central and inland areas of Tokyo. Based on analyses using data obtained from such large-scale observation networks in the Tokyo metropolitan area, significant progress has been made in elucidating the actual conditions and causing factors of the summer heat island phenomenon, especially in Tokyo (e.g. Mikami & Yamato, 2011; Yamato et al., 2011, 2017, etc.).

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Fig. 3.22 Mean maximum temperature distribution in summer (August in 2006, June–August in 2007, and June–July in 2008). Data source (left) JMA AMeDAS, (right) Extended-METROS (Unit: Degrees C). From Mikami and Yamato (2011)

3.4.2 Summer Temperature Distributions in Tokyo In Tokyo and other large cities in Japan, rising summer temperatures cause cumulonimbus clouds to develop and localized torrential rains to occur more frequently. The number of cases of heat stroke due to the hot weather is also increasing. In the Kanto region centering on Tokyo, the temperature distribution during the summer daytime differs from that during the nighttime, and maximum summer temperatures reaching nearly 40 °C are not unusual in the inland northern part of Kanto. This section discusses the summer temperature distribution in the Tokyo metropolitan area based on meteorological observation data.

3.4.2.1

High-Density Temperature Observation System in Tokyo Metropolitan Area

E-METROS analysis reveals that the temperature distribution in the Tokyo metropolitan area fluctuates from time to time, never showing the same distribution. In addition to seasonal variations, daytime and nighttime temperatures show different distributions within a single day. The spatial temperature distribution also varies greatly depending on the weather conditions at any given time. Various factors were found to affect the temperature distribution within the Tokyo metropolitan area,

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such as the difference between sunny and cloudy/rainy days, differences in prevailing wind direction and wind speed, and so on. As an example, here we discuss the daily variations in temperature distributions during a typical summer season (July and August) by producing eight average temperature distribution maps every three hours from 2:00 at night (Figs. 3.23–3.27) based on observation data for two months in July and August 2010, which was a typical hot summer season. The isotherms shown in each figure are drawn at intervals of 0.2 °C; the red areas are relatively hotter and the blue areas are relatively cooler. In areas where the isotherms are crowded, temperatures change abruptly and spatial variations are larger. Figure 3.23 shows the temperature distribution at 2:00 and 5:00 during the night and early morning. The winds are light during these hours, and especially at 5:00, when the daily minimum temperature appears, a concentric heat island centered in the central part of the city is observed. This temperature distribution is similar to the anthropogenic heat distribution in the Tokyo metropolitan area (discussed later), suggesting that anthropogenic heat is one of the major factors in the formation of heat islands during the nighttime. In the suburban to rural areas surrounding Tokyo, the temperature is more than 2 °C lower than in central Tokyo. However, in the morning, from 8:00 to 11:00 a.m., a couple of hours after sunrise, the heat island around the city center begins to lose its shape, as shown in Fig. 3.24. By 11:00 a.m., just before noon, the warmer area expands to the northern inland area, while the coastal area facing the Bay of Tokyo is 2 °C cooler than the hotter inland area due to the suppression of the temperature increase. This is because cool sea breezes from the Bay of Tokyo and the Pacific Ocean prevent the temperature from rising in coastal areas, as described later in this chapter. In the afternoon, the temperature distribution at 14:00, when the daily maximum temperature occurs, shows a widely extended high-temperature area from northern Tokyo to inland Saitama Prefecture, as shown in Fig. 3.25. Although the heat island centered in the central part of Tokyo that appears from nighttime to early morning is not observed, the temperature difference from the bayside area, which is relatively cooler during the daytime due to the intrusion of sea breezes, forms a cliff-like zone. In other words, the intrusion of cool sea breezes may be obstructed by the dome of hot air in the city center. Figure 3.26 shows a bird’s-eye view of the relationship between the temperature distribution and the sea breeze in the greater Tokyo metropolitan area at 14:00. The temperature distribution at 14:00 remains almost unchanged at 17:00. As shown in Fig. 3.25, the center of the high-temperature region that extended inland during the daytime moves southward to the Tokyo metropolitan area at 20:00, and the relatively low-temperature region along the coastal area almost disappears. At 23:00, a typical heat island shape centered over the central part of the city emerges, and the concentric circle temperature distribution continues until the early morning of the next day.

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Fig. 3.23 Distribution of mean temperatures over the extended Tokyo metropolitan area at 2:00 (top) and 5:00 (bottom) in July and August 2010

Such detailed spatiotemporal variations of temperature in the Tokyo metropolitan area were demonstrated for the first time by high-density observations such as EMETROS. It is not clear whether similar temporal and spatial variations in temperature are observed in other seaside cities. Since not only Tokyo but also other major cities in Japan are located facing the sea, the effect of sea breezes on urban heat islands, especially during the daytime in summer, is of particular interest.

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Fig. 3.24 Distribution of mean temperatures over the extended Tokyo metropolitan area at 8:00 (top) and 11:00 (bottom) in July and August 2010

3.4.2.2

Effects of Sea Breeze on Summer Temperature Patterns in Tokyo

Yamato et al. (2017) analyzed in detail the effect of sea breezes on the summer temperature distribution in the greater Tokyo area by adding existing wind speed and direction data to E-METROS temperature observation data (Figs. 3.28–3.30). In the Kanto Plain, including Tokyo, land-sea wind circulation caused by the land-sea temperature difference between daytime and nighttime often develops on clear days

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Fig. 3.25 Distribution of mean temperatures over the extended Tokyo metropolitan area at 14:00 (top) and 17:00 (bottom) in July and August 2010

when the North Pacific High covers the area in summer and the pressure gradient is small. Therefore, a comprehensive case study was conducted on 4 August 2006, a day when a typical land-sea wind circulation appeared, to investigate the influence of sea breezes on temperature distribution in the Tokyo metropolitan area. The data used were mainly AMeDAS data from JMA and our E-METROS data. Figure 3.28 shows the daily variation of temperature and wind on the day in question using AMeDAS data. Sea breezes entered from the coastal areas around 9:00 a.m., and valley breezes began to blow inland at noon. In the Bay of Tokyo and Sagami Bay, sea breezes blowing at right angles to the coastline were observed.

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Fig. 3.26 Same as Fig. 3.25 (top), except for overviewing image with sea breezes from the Bay of Tokyo and Sagami Bay

In the Kanto Plain, sea breezes and valley winds remained separated until noon, while southerly winds were observed over the entire Kanto Plain at around 15:00. The temperature difference between the coastal and inland areas was small around 9:00, but by noon the isotherms were concentrated over the coastal areas and the temperature difference with the inland areas increased. At 15:00, temperatures in the northwestern Kanto Plain and inland basins also reached maximum temperatures of 38 °C or higher for the day, and by 18:00, only the northwestern Kanto Plain remained hot.

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Fig. 3.27 Distribution of mean temperatures over the extended Tokyo metropolitan area at 20:00 (top) and 23:00 (bottom) in July and August 2010

To analyze the influence of sea breezes on the temperature distribution in the Tokyo metropolitan area, the location of the sea breeze front (SBF) was estimated. In previous studies, it has been observed that when the SBF passes an inland station, air temperature decreases, and the dew point temperature increases rapidly along with a change in wind direction (Chiba et al., 1990). Therefore, we investigated the relationship between the movement of sea-breeze fronts and temperature distribution in the Tokyo metropolitan area for each period from 12:00 to 18:00 on the case analysis day (4 August 2006) using a similar method (Fig. 3.29). During the period studied, temperatures tended to be higher on the inland side of the SBF and lower on the seaward side; on the inland side of the SBF, temperatures were higher the closer to the front and lower the farther away from the front. In particular, temperatures tended to be higher on the leeward side of the SBF from central Tokyo. In other words, when a sea breeze front passed through the area, temperatures decreased at that location. The center of the high-temperature area from 14:00 to 15:00 was located near Kawagoe City in central Saitama Prefecture, which is adjacent to the northern part of Tokyo, and the SBF moved northward at a slower speed just south of the center of the area. The SBF is located around the south side of this high-temperature area and is connected to the convergence line (CL) extending northeastward from the Bay of Tokyo. Figure 3.30 shows the movement of the SBF hourly from 11:00 to 16:00, indicating that the SBF reduced its speed as it moved downwind of central Tokyo and that there was a time lag of about 2 h before the highest temperature was observed near Kawagoe

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Fig. 3.28 Distributions of temperature and wind recorded by AMeDAS on 4 August 2006. The light/dark shaded areas represent areas higher than 200/800 m above the mean sea level. Revised from Yamato et al. (2017)

City. Around 14:00, the SBF curved significantly northwest of central Tokyo as it entered downwind of Tokyo, and the speed of the front decreased. The SBF then accelerated again, and the front eventually moved out of the area shown in the figure. Temperatures near the dotted line (CL) in Fig. 3.29 were slightly higher than those around the SBF from 12:00 to 18:00. This convergence line (CL), which indicates the meeting point of sea breezes from the Bay of Tokyo and Sagami Bay, moved northeastward and reached central Tokyo around 16:00, and then ceased. The duration of the high temperature near Kawagoe City is uncertain, but temperatures in the inland area northwest of the Kanto Plain remained unusually high until after 16:00.

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Fig. 3.29 Temperature and surface wind distribution in Tokyo Metropolitan Area observed on 4 August 2006. The sea breeze front (SBF) is shown by the dashed line. The convergence line (CL) is shown by the dotted line. Modified from Yamato et al. (2017)

Relatively high-temperature zones were also detected north of central Tokyo, where sea breezes from the Bay of Tokyo and Sagami Bay converge. By the way, it is known that a band of cumulus clouds called Kanpachi Street Cloud (Fig. 3.31) often appears on summer afternoons over the western area of central Tokyo. Kanpachi is the Japanese name for Loop Route 8, which runs west

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Fig. 3.30 Positions of the sea breeze front recorded on 4 August 2006. Areas with population densities exceeding 4000 people km2 are shown in grey. The curved lines indicate the sea breeze front. From Yamato et al. (2017)

of the center of Tokyo, and is roughly equivalent to the location of the CL shown in Fig. 3.29. Kai et al. (1995) conducted a case study to clarify the mechanism of the occurrence of the Kanpachi Street Cloud on the afternoon of 21 August 1989, by analyzing the temperature, wind direction and speed, and weather map of that day. As shown in Fig. 3.32, the Kanpachi Street Cloud occurred along Loop Route 8 during the daytime in summer due to the convergence of two sea breezes with different directions of flow and the enhanced convective activity caused by the heat island circulation in Tokyo. The cloud sequences were found to be generated by the convergence of two sea breezes with different wind systems during the summer daytime along Loop Route 8. The results of Yamato et al. (2017) are noteworthy because they demonstrated the relationship between the convergence line by two sea breezes and cloud sequences of cumulus clouds pointed out by Kai et al. (1995), based on the migration of sea breeze fronts and the distribution of high-temperature areas over a wider area.

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Fig. 3.31 A typical example of Kanpachi Street Cloud, a band of cumulus clouds that appears along Loop Route 8, which runs north–south through the western suburbs of Tokyo in summer. Source Photolibrary. https://www.photolibrary.jp

3.4.3 Anthropogenic Energy Consumption in Tokyo Figure 3.33 is a photograph of the Tokyo metropolitan area at night taken from space by an astronaut on the International Space Station. The white lights are various artificial lights emitted by human activities. The small black circular area in the center of the city is the Imperial Garden, the largest green area in central Tokyo. To the east, Tokyo Station, Ginza, and other commercial areas of the city center are brightly illuminated. To the west of the city center, large downtown areas such as Ikebukuro, Shinjuku, and Shibuya emit strong light. Several lines and evenly spaced dots of light emitting from the center of Tokyo are railroad tracks and stations. The main roads also appear as white lines. On the other hand, the orange masses of light emitted from the reclaimed land facing the Bay of Tokyo are artificial lights from the industrial area. Thus, nighttime light observed from space is an accurate indicator of human activity. As represented by the nighttime light, the light and heat from energy consumption by various types of human activities are released in urban areas, heating the atmosphere and causing the temperature to rise. Figure 3.34 shows the heat consumption (W/m2 ) from various energy sources such as factories, offices, houses, automobiles, etc. This is a map of man-made heat exhaustion estimated by a mesh unit. According to a survey by the Tokyo Metropolitan Government, the estimated amount of artificial heat exhaust in the Tokyo area in FY1994 was 24 W/m2 per year on average in

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Fig. 3.32 Sea breezes from the Bay of Tokyo and Sagami Bay converging near Tokyo’s Loop 8 (red line) at 15:00 on 21 August 1989. The gray color indicates the convergence area. Modified from Kai et al. (1995)

the 23 wards. Since the average annual solar radiation received in the Tokyo area is about 130 W/m2 , it implies that the amount of artificial heat released in the Tokyo wards accounts for nearly 20% of the total solar radiation energy. Particularly, in the city center, where commercial activities are especially pronounced, the amount reaches more than 40 W/m2 , and locally it exceeds 100 W/m2 , which is almost equivalent to the amount of solar radiation received in Tokyo. In particular, the demand for cooling in urban centers reaches its peak when high temperatures occur during the summer daytime. Therefore, the exhaust heat from outdoor units of air conditioners and cooling towers installed on the rooftops of high-rise buildings raises the temperature, creating a vicious cycle that further increases the demand for cooling.

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Fig. 3.33 The nighttime photograph of Tokyo Metropolitan Area taken by International Space Station astronaut Dan Tani on February 5, 2008. Image courtesy of the Earth Science and Remote Sensing Unit, NASA Johnson Space Center

3.4.4 Artificial Urban Surfaces in Tokyo This section discusses another contributing factor to the urban heat island, namely, artificial ground surface cover. Figure 3.35 shows an aerial view of Tokyo Station and its surroundings, with a row of high-rise buildings and a dense concentration of low and mid-rise concrete structures in the background. In the left foreground, the water surface of the outer moat of the Imperial Palace Garden can be seen. Urban ground surfaces covered with concrete buildings and asphalt paved roads have significantly different thermal characteristics, such as heat capacity and thermal conductivity, and radiation characteristics, such as evaporation efficiency, reflectance (albedo), and emissivity, as compared to the suburban countryside, where forests, grasslands, fields, and bare land are predominant. For example, concrete and asphalt absorb solar radiation energy during the summer daytime and their surface temperatures often exceed 50 °C (Fig. 3.36). The reason why we feel hot under the blazing sun in summer is because of the heat radiated from the hot concrete surface in addition to the solar radiation. Furthermore, even at night, these surfaces continue to heat the surrounding atmosphere because their surface temperatures are higher than the air temperature. This,

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Fig. 3.34 Anthropogenic heat consumption in the Kanto area (annual means in 1998)

combined with the above-mentioned artificial heat emissions, greatly reduces the nighttime temperature drop in urban areas. The fact that concrete and asphalt are impervious to water also contributes to the high temperatures in cities. As is well known, when water evaporates, it removes vaporization heat to lower the ambient temperature (latent heat effect), but in cities covered with non-permeable concrete and asphalt, this effect is extremely small, resulting in higher temperatures. In recent years, experimental trials of waterretaining pavement and thermal barrier pavement have been conducted in Tokyo. It is expected that surface temperatures can be slightly reduced by modifying the pavement surface of roads, but it would take a great deal of time and cost to completely improve asphalt-covered roads in urban centers. Rather, the installation of roadside trees will provide shading during the summer daytime, which will have the effect of lowering the surface temperature by about 20 °C compared to areas exposed to direct sunshine (Fig. 3.36). Furthermore, the transpiration effect from the leaf surface of the trees removes latent heat, which can suppress the temperature rise in the surrounding area. In Tokyo, there are several parks and green spaces of more than 50 ha, including the Imperial Palace Garden. Figure 3.37 shows an example of the results of large-scale meteorological observations conducted during the summer season in and around Shinjuku Gyoen National Garden, at 58 ha, one of the largest green spaces in Tokyo. The temperature profiles are shown along the main cross-section line inside and outside the green space during

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Fig. 3.35 Aerial view of high-rise buildings around Tokyo Station. The water area in the left foreground is the outer moat of the Imperial Palace Garden. Photograph taken by Skymap Inc.

the afternoon (16:40) and in the early morning (4:50). During the daytime, the temperature difference between the inside and outside of the green space is 1.5 °C, indicating that the cool air inside the green space is flowing out 250 m northward to the city center on the leeward side due to the SSE wind. On the other hand, when the wind decreases from night to early morning, cool air accumulates in the green space due to radiative cooling and seeps out to the surrounding area as gravity flows. Although the velocity of the outflow of cool air is very weak, ranging from 0.1 m/sec to 0.2 m/sec, the temperature of the cool air that flows to the south side of the urban area remains low until 80 m away from the edge of the green area. This phenomenon of cool air generated in the green space flowing out to the surrounding urban area during the night and early morning is called “Park Breeze”(Sugawara et al., 2016). The author’s research team has published numerous research results for several parks and green spaces in Tokyo (e.g., Hamada & Mikami, 1994; Narita et al., 2004; Sugawara et al., 2021). Unfortunately, the total area of parks and green spaces in Tokyo is much smaller than those in large European and North American cities such as London, Paris, and New York. Figure 3.38 shows an aerial view of Meiji Shrine/Yoyogi Park, with the skyscrapers of Shinjuku in the distance on the left. Figure 3.39 is a thermal image of the surface

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Fig. 3.36 Surface temperature on the asphalt road in the summer daytime. A visible image (top) and an infrared thermal image (bottom) in the Shinjuku area. Photograph and thermal image taken by T. MIkami

temperature distribution in the area indicated by Fig. 3.38, captured by helicoptermounted thermography. It shows that the air temperature (A.T.) and surface temperature (S.T.) in this area differ by 3 °C and 10 °C, respectively, between inside and outside the green area. To improve the environment of Tokyo, which has the world’s largest heat island and is becoming hotter and hotter, it is important to preserve large green spaces with abundant trees and to develop roadside trees.

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Fig. 3.37 Temperature profiles along the main cross-section line in and around Shinjuku Gyoen Park on a typical summer day

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Fig. 3.38 Aerial view of Meiji-Shrine/Yoyogi Park in Tokyo. In the distance on the left and right are the skyscrapers of west Shinjuku and Shinjuku Gyoen Park, respectively. Photograph taken by Skymap Inc.

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Fig. 3.39 Aerial photo (left) and thermal image (right) in Shinjuku/Shibuya area. A.T.: Air temperature, S.T.: Surface temperature. Photograph and thermal image taken by Skymap Inc.

References Chiba, O., Ishikawa, A., & Hirota, C. (1990). On the penetration time of the sea breeze front and its width: The sea breeze front observed in the atmospheric surface layer: Part1. Tenki, 37, 415–419 (in Japanese). Fukui, E., & Wada, N. (1941). Horizontal distribution of air temperature in the great cities of Japan. Geographical Review of Japan (Chirigaku Hyoron), 17, 354–372. (in Japanese with English abstract). Hamada, T., & Mikami, T. (1994). Cool island phenomena in urban green spaces: A case study of Meiji Shrine and Yoyogi park. Geographical Review of Japan (Chirigaku Hyoron), 67A, 518–529. (in Japanese with English abstract). Hare, S. R., & Mantua, N. J. (2000). Empirical evidence for North Pacific regime shifts in 1977 and 1989. Progress in Oceanography, 47, 103–145. Kai, K., Ura, K., Kawamura, T., & Ono, H. P. (1995). A case study on the Kanpachi street cloud over Tokyo. Tenki, 42, 417–427. (in Japanese). Kim, Y. H., Kim, M. K., Lau, W. K. M., Kim, K. M., & Cho, C. H. (2015). Possible mechanism of abrupt jump in winter surface air temperature in the late 1980s over the Northern Hemisphere. Journal of Geophysical Research: Atmospheres, 120, 12474–12485. Koinuma, K. (1969). Meteorological observation commenced by Japanese Home Ministry in 1875 and beginning of Japanese name “Kishodai”. Tenki, 16, 105–108. (in Japanese). Mikami, T., & Yamato, H. (2011). High-resolution temperature observations using ExtendedMETROS in the Toyo Metropolitan area and their urban climatological significance. Journal of Geography (Chigaku Zasshi), 120, 317–324. (in Japanese with English abstract)

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Narita, K., Mikami, T., Sugawara, H., Honjo, T., Kimura, K., & Kuwata, N. (2004). Cool-island and cold air seeping phenomena in an urban park, Shinjuku Gyoen, Tokyo. Geographical Review of Japan (Chirigaku Hyoron), 77, 403–420. (in Japanese with English abstract). Niebauer, H. J. (1998). Variability in Bering sea ice cover as affected by a regime shift in the North Pacific in the period 1947–1996. Journal of Geophysical Research, 103, 17717–17737. Ninomiya, K. (2022). Analysis of intense rainfalls over Nagasaki area on 23, July 1982 using precipitation data of Japan Meteorological Agency and other organizations. Tenki, 69, 379– 385.(in Japanese) Reid, P. C., Hari, R. E., Beaugrand, G., Livingstone, D. M., Marty, C., Straile, D., Barichivich, J., Goberville, E., Adrian, R., Aono, Y., Brown, R., Foster, J., Groisman, P., Hélaouët, P., Hsu, H.-H., Kirby, R., Knight, J., Kraberg, A., Li, J., …, Zhu, Z. (2016). Global impacts of the 1980s regime shift. Global Change Biology, 22: 682–703. Schmidt, W. (1927). Die Verteilung der Minimumtemperature in der Frostnacht des 12. Mai 1927 im Gemeindegebiete von Wien. Fortschritte der Landwirtschaft, 2, 681–686. Song, S. Y., Yeh, S. W., & Park, J. H. (2019). Change in relationship between the East Asian winter monsoon and the East Asian jet stream during the 1998–99 regime shift. Journal of Climate, 32, 6163–6175. Stewart, I. D. (2019). Why should urban heat island researchers study history? Urban Climate, 30, 100484. Sugawara, H., Shimizu, S., Takahashi, H., Hagiwara, S., Narita, K., Mikami, T., & Hirano, T. (2016). Thermal influence of a large green space on a hot environment. Journal of Environmental Quality. https://doi.org/10.2134/jeq2015.01.0049 Sugawara, H., Narita, K., & Mikami, T. (2021). Vertical structure of the cool island in a large urban park. Urban Climate, 35, 100744. Urabe, Y., & Meda, S. (2014). The relationship between Japan’s recent temperature and decadal variability. SOLA, 10, 176–179. Wild, M., Ohmura, A., & Makowski, K. (2007). Impact of global dimming and brightening on global warming. Geophysical Research Letters, 34, L04702. Yamato, H., Mikami, T., & Takahashi, H. (2011). Influence of the sea breeze on the daytime urban heat island in summer in the Tokyo Metropolitan area. Journal of Geography (Chigaku Zasshi), 120, 325–340. (in Japanese with English abstract) Yamato, H., Mikami, T., & Takahashi, H. (2017). Impact of sea breeze penetration over urban areas on midsummer temperature distributions in the Tokyo Metropolitan area. International Journal of Climatology, 37, 5154–5169.

Chapter 4

Climate Information from Pre-Nineteenth Century Data and Documents

Abstract Official instrumental meteorological observations by the Japan Meteorological Agency began in Hakodate (1872), followed by Tokyo (1875). Also, lighthouses made meteorological observations since the 1870s, and the total number of lighthouse meteorological observations was larger than those of JMA observations before the nineteenth century. On the other hand, temperature and pressure observations were made and recorded by foreigners residing in Japan and by the observatory staff of the Japanese shogunate from the 1820s. While, in Japan, a huge amount of weather information has been recorded in old historical documents, such as diaries, since the seventeenth century. Most of these diary weather records have been digitized and used for reconstructing climate changes during the historical period. Keywords Early meteorological observation · Nagasaki · Lighthouse meteorological observation · Diary weather record · Lake-freezing record

Official instrumental meteorological observations by the Japan Meteorological Agency began in Hakodate (1872), followed by Tokyo (1875) as described in Sect. 3.1. Prior to that, were there no meteorological observations in Japan? Actually, temperature and pressure observations were made and recorded by foreigners residing in Japan and by the observatory staff of the Japanese shogunate from the 1820s. The earliest meteorological observations in Japan were probably made by Swedish naturalist C. P. Thunberg in 1775–1777 (Demaree & Mikami, 2000), although the only continuous observations made at a single location and recorded in meteorological records are probably those made by Dutch medical doctors at Dejima, Nagasaki, from 1819 onward. What can we learn about climate change in Japan before 1820, when there were no continuous meteorological observations? In global climate change studies during the historical period, dendroclimatology, which uses the growth width and isotopic ratios of tree-rings, is often used as a tool for climate reconstruction. However, we must be cautious in reconstructing long-term climate change from tree-ring data because we need to remove the effects of tree species, growing environment, and tree age effects (changes in annual-ring width due to physiological effects). In addition, climate

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 T. Mikami, The Climate of Japan, Advances in Global Change Research 77, https://doi.org/10.1007/978-981-99-5158-1_4

85

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reconstructions using tree-rings are mainly available for summer temperatures, and there are few case studies of winter climate reconstructions (e.g., Yonenobu, 2006). Recently, some attempts have been made to reconstruct climate changes using oxygen isotope ratios of cellulose contained in annual rings (e.g., Nagavciuc et al., 2020; Sternberg, 2009; Nakatsuka et al., 2020). A unique climate reconstruction using natural proxies other than tree-ring analysis is a work that elucidated climate changes over the past 7600 years by analyzing pollen of Japanese pine on peatlands in a high moorland (Sect. 5.4). There are also studies attempting phenological climate reconstructions on a scale of several hundred to a thousand years based on historical documents that record seasonal natural phenomena such as the dates of lake freezing (Sect. 4.3) and the full flowering of cherry trees (Sect. 5.3). The most notable climate reconstructions in Japan are the daily weather data recorded in diaries kept in various parts of the country from the seventeenth to nineteenth centuries (Sects. 4.2 and 5.2), from which a database of the vast number of weather records has been compiled (Sect. 4.2.3). Among various proxy data, diary weather records have the highest temporal resolution and are one of the best proxies for detecting the past frequency of extreme weather events such as heavy rainfall, which has attracted much attention in recent years.

4.1 Early Meteorological Observations in the Nineteenth Century As already mentioned, the official meteorological observation in Japan began in 1872, when the Hakodate Climatic Survey Station, the predecessor of the current JMA Hakodate Local Meteorological Observatory, was established (see Sect. 3.1). However, official meteorological observations managed by the JMA are regarded to have started in June 1875 as a responsibility of the Meteorological Department of the Ministry of Home Affairs at that time (Japan Meteorological Agency, 1975). In any case, official meteorological observation began in Japan later than in Western countries. Table 4.1 shows the location (latitude and longitude) and altitude (above sea level) of JMA meteorological stations, which started observations in the nineteenth century. There are 59 stations in total, of which only 7, including Hakodate, started observations in the 1870s. Hishikari (2017), in his book “A History of Thermometer in Japan: 1660–1910”, investigates the history of thermometers in Japan going back to the seventeenth century. Although it is unclear when the thermometer was first brought to Japan, Andriaen van der Burgh, the head of the Dutch trading post in Nagasaki, wrote in his diary on May 24, 1652, when he returned to Nagasaki after he visited Edo, a list of orders for “various valuable articles” to be presented to the Edo shogunate in 1653. Among them were several “indoor thermometers” (to determine the temperature of the air). Interestingly, two years later, Gabriel Happart, the head of the trading house,

4.1 Early Meteorological Observations in the Nineteenth Century

87

Table 4.1 List of JMA meteorological stations that started in the nineteenth century Station name

Lat.

Lon.

Hakodate

41.8167

140.7533

Altitude (m.ASL) 35

Start of obs. Aug.1872

Tokyo

35.6917

139.7517

25

Jun.1875

Sapporo

43.0600

141.3283

17

Sep.1876

Nagasaki

32.7333

129.8667

27

Jul.1878

Hiroshima

34.3983

132.4617

4

Jan.1879

Nemuro

43.3300

145.5850

25

Jul.1879

Wakayama

34.2283

135.1633

14

Jul.1879

Kyoto

35.0117

135.7350

41

Oct.1880

Niigata

37.9117

139.0467

4

Apr.1881

Aomori

40.8217

140.7683

3

Jan.1882

Kanazawa

36.5883

136.6333

6

Jan.1882

Kochi

33.5667

133.5483

1

Mar.1882

Osaka

34.6850

135.5267

23

Jul.1882

Akita

39.7167

140.0983

6

Oct.1882

Hamamatsu

34.7083

137.7183

46

Dec.1882

Sakai

35.5433

133.2350

2

Jan.1883

Shimonoseki

33.9567

130.9383

3

Jan.1883

Kagoshima

31.5533

130.5467

4

Jan.1883

Tanegashima

31.5533

130.5467

25

Jan.1883

Gifu

35.4000

136.7617

13

Feb.1883

Suttsu

42.7950

140.2233

33

Jun.1884

Fushiki

36.7917

137.0550

12

Feb.1885

Miyazaki

31.9383

131.4133

9

Jan.1886

Izuhara

34.1967

129.2917

4

Sep.1886

Choshi

35.7383

140.8567

20

Jan.1887

Oita

33.2350

131.6183

5

Jan.1887

Ishinomaki

38.4267

141.2983

43

Sep.1887

Asahikawa

43.7567

142.3717

120

Jul.1888

Nagano

36.6617

138.1917

418

Jan.1889

Fukushima

37.7583

140.4700

67

May.1889

Yamagata

38.4267

141.2983

153

Jul.1889

Tsu

34.7333

136.5183

3

Jul.1889

Abashiri

44.0167

144.2783

38

Aug.1889

Kushiro

42.9850

144.3767

5

Dec.1889

Matsuyama

33.8417

132.7800

32

Jan.1890

Fukuoka

33.5817

130.3767

3

Jan.1890 (continued)

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4 Climate Information from Pre-Nineteenth Century Data and Documents

Table 4.1 (continued) Station name

Lat.

Lon.

Kumamoto

32.8133

130.7067

Altitude (m.ASL) 38

Start of obs. Feb.1890

Nagoya

35.1667

136.9650

51

Jul.1890

Naha

26.2067

127.6867

28

Jul.1890

Saga

33.2650

130.3050

6

Aug.1890

Utsunomiya

36.5483

139.8683

119

Sep.1890

Okayama

34.6600

133.9167

5

Jan.1891

Tokushima

34.0667

134.5733

2

May.1891

Obihiro

42.9217

143.2117

38

Feb.1892

Tadotsu

34.2750

133.7517

4

Jul.1892

Hamada

34.8967

132.0700

19

Jan.1893

Hikone

35.2750

136.2433

87

Oct.1893

Kure

34.2400

132.5500

4

May.1894

Koufu

35.6667

138.5533

273

Aug.1894

Yokohama

35.4383

139.6517

39

Aug.1896

Maebashi

36.4050

139.0600

112

Dec.1896

Kumagaya

36.1500

139.3800

30

Dec.1896

Kobe

34.6817

135.2200

5

Dec.1896

Mito

36.3800

140.4667

29

Jan.1897

Fukui

36.0550

136.2217

9

Jan.1897

Tsuruga

35.6533

136.0617

2

Oct.1897

Iida

35.5233

137.8217

516

Nov.1897

Matsumoto

36.2450

137.9700

610

Jan.1898

Takayama

36.1550

137.2533

560

Jun.1899

Latitude and longitude indicate the present location

wrote in his diary that he had ordered “two barometers” as a present to the Edo shogunate around the same time as the thermometer (Hishikari, 2017). However, even if thermometers and barometers were presented to the Edo shogunate in the mid-seventeenth century, they were not used for continuous meteorological observation. The first full-scale meteorological observation in Japan was made by Carl Peter Thunberg, who came to Japan in 1775 to serve as a doctor at the Dutch trading post in Nagasaki. Although Thunberg’s meteorological observations were of short duration (14 months), as will be discussed in Sect. 4.1.1, in the nineteenth century, continuous meteorological observations were made in various parts of Japan (Fig. 4.1).

4.1 Early Meteorological Observations in the Nineteenth Century

89

Fig. 4.1 Availability of nineteenth century instrumental meteorological (temperature or pressure) data in Japan. From Zaiki et al. (2018)

4.1.1 Early Meteorological Observations in Nagasaki Full-scale meteorological observations in Japan began at Dejima (small artificial island), Nagasaki in 1775 and continued intermittently until the 1870s. This section describes the meteorological observations started by Thunberg and thereafter carried out by the doctors of the trading post at Dejima.

4.1.1.1

Japan’s Earliest Meteorological Observations in the Eighteenth Century

The earliest meteorological observations in Japan were made by Carl Peter Thunberg, a botanist and physician from Sweden, for about 14 months from 1775 to 1776, mainly in Nagasaki (Demaree et al., 2013). Thunberg was posted as a doctor for the Dutch merchants at Dejima, and began his meteorological observations on September 1, 1775. He made temperature observations four times a day (6:00 [?] in the morning, 12:00 noon, 15:00 in the afternoon, and 18:00 in the evening) and also recorded

90

4 Climate Information from Pre-Nineteenth Century Data and Documents

the weather and wind of the day (Fig. 4.2). The thermometer was placed on a wellventilated wooden post outside the north-facing window of his room. He did not bring a barometer with him, so he left no records of atmospheric pressure. During his stay in Japan, Thunberg was away from Nagasaki for about four months, from March 4 to June 28, 1776, to accompany the chief of the trading post to Edo (present-day Tokyo), and he continued to observe the weather with his thermometer during his trip. Therefore, although the period of fixed-point weather observation in Nagasaki was only about 10 months, it is valuable as the only record of daily temperature observation by a thermometer for which data were still available in the eighteenth century. At Dejima, a record of monthly temperature observations was also kept from January to November 1779 by another observer, but unfortunately, no record of daily observations has been found for that period.

Fig. 4.2 An example of sub-daily weather observations by C. P. Thunberg. From Thunberg, C. P. 1796: Travels in Europe, Africa, and Asia, performed between the years 1770 and 1779. In Four Volumes. Vol. III. Containing a Voyage to Japan, and Travels in Different Parts of that Empire in the years 1775 and 176. By Charles Peter Thunberg. The Third Edition. London, Printed for F. and C. Rivington. (ULBonn N 61)

4.1 Early Meteorological Observations in the Nineteenth Century

4.1.1.2

91

Meteorological Observations by Dutch Medical Doctors in the Nineteenth Century

No stationary observations were made at Dejima (Nagasaki) for some time after the temperature observations by Thunberg, et al. However, Tsukahara (1998) revealed that records of meteorological observations made in Nagasaki by the German physician and botanist Philipp Franz von Siebold and others between 1819 and 1828 were stored at the Ruhr University Bochum. In addition, it was found that the original meteorological observation records and statistics made by Dutch Trade Factory staff and Dutch medical doctors at Dejima from 1845 to 1883 are in the collection of the Royal Netherlands Meteorological Institute (KNMI) (Können et al., 2003). In other words, meteorological observations by Dutch medical doctors at Dejima began 50 years before the JMA Nagasaki Observatory was established and began official meteorological observations in July 1878; the Dutch data are expected to provide valuable data for the study of climate change. Therefore, the author’s research team, led by Dr. Masumi Zaiki and Dr. Gunther Können, has digitized the meteorological observation records from Dejima and homogenized the data. The location of the observation sites from 1819 to the present is shown in Fig. 4.3. The monthly data are available on the website of JapanAsia Climate Data Program (https://jcdp.jp/) and from the website of Climatic Research Unit, University of East Anglia, UK (https://crudata.uea.ac.uk/cru/data/ japan/). Figure 4.4 shows a picture of Nagasaki Port and Dejima taken around 1820. Sources for and descriptions of Dejima-Nagasaki meteorological data are explained below.

Fig. 4.3 Location of the observation sites 1819–present in Nagasaki. From Können et al. (2003)

92

4 Climate Information from Pre-Nineteenth Century Data and Documents

Fig. 4.4 Illustration of Nagasaki Port and Dejima around the 1820s. From Collection of Nagasaki Museum of History and Culture

(1) 1819–1828 Blomhoff/von Siebold Series at Dejima This data is a record of observations made by J. Cock Blomhoff, who was a director (1817–1823) of the Dutch Trading Post at Dejima, and the Dutch (actually German) physician P. F. von Siebold (Fig. 4.5). Siebold’s role in the dissemination of modern medicine to Japan is particularly well known, but his activities at Dejima also included natural scientific and ethnographic investigations and research. The data include a blank period (November 1823–December 1824) between the observations by Blomhoff and those by von Siebold. For the sake of convenience, we will refer to the records made by Blomhoff before the blank period as Blomhoff Data (1819–1823) and those made by von Siebold after the blank period as von Siebold Data (1825–1828). The Blomhoff Data only contains temperature data; observations were made indoors until June 1819, then outdoors, and finally from January 1821, both indoors and outdoors. The von Siebold Data also includes a blank period from November 1825 to November 1826; before the blank period, only air temperature was recorded; after the blank period, air pressure and humidity were measured in addition to air temperature. As shown in Fig. 4.5, the original Blomhoff/von Siebold Data is handwritten;

4.1 Early Meteorological Observations in the Nineteenth Century

93

Fig. 4.5 An example of handwritten meteorological observation records by von Siebold in January 1828. Source The Siebold Archive, Faculty of East Asian Studies, Ruhr University Bochum, Germany; shelfmark 1.142.002

the documents are now stored in the von Siebold collection at the Ruhr University Library in Bochum, Germany, with numbers assigned by the Siebold Catalog (Schmidt, 1989). In the von Siebold Data, there is a record of simultaneous observations in Jedo (Edo, present-day Tokyo) and Nagasaki for a year in 1825. Furthermore, von Siebold also made meteorological observations while traveling from Nagasaki to Edo between March and July 1826. Siebold is thought to have traveled to Edo with the instruments he used at Dejima; therefore, no observations were made at the Dutch trading post at Dejima during this period, and no record was left. As for the Blomhoff Data, Blomhoff’s official diary as Director of the Dutch Trading Post states: “It snowed and rained heavily last night and today as well. I saw heavy snow, rain, hail, and icing last night as well as today. So last evening and this morning the thermometer showed 32 °F. The temperature gauge showed 32 °F last evening and this morning.” This very same description is found for January 12–20, 1820, and January 20–23, 1823. From this, it can be inferred that the thermometer functioned approximately normally with respect to the temperature in the Blomhoff

94

4 Climate Information from Pre-Nineteenth Century Data and Documents

Data. It is not clear whether von Siebold used the same thermometer used by Blomhoff or replaced it with a new one. Only the von Siebold Data contains observations of atmospheric pressure; the diary of the Director of the Dutch Trading Post (Cock Blomhoff 1820, 1823), Blomhoff also often recorded atmospheric pressure, but the Blomhoff Data records do not include these observations. Von Siebold’s barometric pressure records are recorded from November 1, 1826 to September 29, 1828 in French inches, and after September 23, 1827 in English inches. After September 23, 1827, when the barometer was changed, there was a decrease of about 7 hPa in the value of atmospheric pressure. This trend continues until the end of von Siebold’s observations on September 29, 1828. The cause of the drop in atmospheric pressure is still unknown. Siebold also observed humidity. The hygrometer was made by Siebold himself and is described as being “manufactured from a hair of a Japanese beauty which was scalded in soda and then in pure water.” Observations were made at Morgen, Mittag, and Abend, i.e., three times a day in the morning, noon, and evening, but there is no clear description of the precise time of the observations. However, some of the records contain hourly observations of temperature and pressure for two consecutive days (e.g., February 19 and 20, and August 25 and 26, 1828), apart from the daily observation records. As a result of comparing these records with the daily observation records, the actual observation times were found to be 6:00, 12:00, and 22:00 Nagasaki local time (Local Time, hereafter referred to as L.T.). The Dutch who resided in various parts of the world at that time used the local time calculated from longitude; the L.T. in Nagasaki is the present Japanese Standard Time (JST) +0:20. During the period from November 1826 to September 1827, observations were made six times a day, and no precise observation time was given. Therefore, we compared the current daily variation of air temperature and atmospheric pressure in Nagasaki with that seen in the von Siebold Data for each of the six observation times using the JMA-AMeDAS data for air temperature and air pressure. As a result, it was determined that the times of observation were 6:00, 9:00, 12:00, 15:00, 18:00, and 22:00 L.T. (2) 1845–1858: Dejima Data Series The Blomhoff/von Siebold series of observations seem to have been made out of a personal spirit of inquiry and research, while the Dejima Data are official observations made at the request of the Dutch government (Fig. 4.6). The first observers were O. G. J. Mohnicke (1845–1851) and Mohnicke’s assistants, J. A. G. A. L. Bassle (1845– 1848) and F. C. Lucas (1848–1852). Mohnicke also participated in meteorological observations in the Dutch East Indies (present-day Indonesia). Later, J. K. van den Broek (1854–1857), J. L. C. Pompe van Meerdervoort (1857–1862) and others took over the observation. The items recorded were temperature, pressure, humidity, precipitation, wind speed, wind direction, and cloud cover, far more than in the Blomhoff/von Siebold series described in (1). The observation times are given as 6:00, 9:00, 15:30, and 22:00 L.T. (for barometric pressure and cloud cover only). For the data from January 1845

4.1 Early Meteorological Observations in the Nineteenth Century

95

Fig. 4.6 An example of the Dejima Data Series for November 1848. Stored in the KNMI Library, the Netherlands

to September 1848, only 10-day averages are recorded for temperature, barometric pressure, humidity, precipitation, and cloud cover. For the period from October 1849 to September 1851, the observations were made at 15:00 L.T. instead of 15:30 L.T. From October 1849 to September 1855, daily hourly temperature, pressure, humidity, wind speed, and cloud cover were recorded (Fig. 4.7). From November 1855 to July 1856, only monthly averages of temperature and pressure are available. According to Stamkart (1851), the thermometer and barometer were located at a height of 1 m on the north exterior wall of the building. Although the thermometers seem to have been moved from outdoors to indoors at the beginning of Pompe’s observations, there is no clear information in the original description as to when the thermometers were moved indoors or whether the average values of three thermometers were recorded at all times. In addition, it is said that the freezing point on the thermometers was tested twice during snowfall. The first test, on January 17, 1848, showed that the thermometer value was correct (Stamkart, 1851), while the second one, on February 4, 1852, revealed that the thermometer reading was 0.8 °C higher than it should have been (KNMI Yearbook, 1856); the difference was taken into account in the observations recorded in the original description (KNMI Yearbook, 1855, 1856). The barometer was a mercury column barometer sent from von Siebold in the Netherlands (KNMI Yearbook, 1855), and then a HEVEL barometer of the same type was used from October 1848 to October 1851 (Stamkart, 1851). During this

96

4 Climate Information from Pre-Nineteenth Century Data and Documents

Fig. 4.7 An example of the Dejima Data Series for July 1853. Stored in the KNMI Library, the Netherlands

4.1 Early Meteorological Observations in the Nineteenth Century

97

period, only the highest and lowest values were recorded due to a malfunction of the barometer. Then again, after 1851, the first barometer was used and tested (KNMI Yearbook, 1856). At that time, it was common for published barometric data to be corrected for temperature but not for gravity. Therefore, we assume that the published observation records are corrected for temperature and that the pressure data read from other original source records should be corrected for temperature. Precipitation was constantly observed, but the published records are from 1852 onward. In addition, Pompe’s precipitation records are daily reports of the total amount of precipitation since the beginning of the month or the total amount of precipitation for a single rainfall. In this case, it is easy to calculate the daily precipitation, but if this fact is not noticed, there are many unrealistic daily precipitation values in the records. It is known that the last observer, Pompe, stayed in Japan until 1862 and also continued to make observations (Geerts, 1875). (3) 1852–1853: Dejima Documents Data Series This record is the missing part of the Dejima Data Series published by KNMI. The records are handwritten and include precipitation data as in the Dejima Data Series (Fig. 4.8). The atmospheric pressure data are not corrected for temperature. However, since the attached thermometer values are reported, temperature correction is possible.

Fig. 4.8 An example of the Dejima Documents Data Series for July 1853. Stored in the KNMI Library, the Netherlands

98

4 Climate Information from Pre-Nineteenth Century Data and Documents

(4) 1871–1878: Nagasaki Hospital Data Nagasaki Hospital was established on September 20, 1861 by a physician, Pompe van Meerdervoort, on a hill about 500 m southeast of Dejima (present Nitasako Elementary School, 37 m above sea level). Pompe left Japan in November 1862. After that, it is thought that observations were not made until 1871. Observations were resumed by pharmacist A. J. C. Geerts in November 1871, and then taken over by physician W. K. M. van Leeuwen van Duivenbode in November 1874. Three daily observation records (Fig. 4.9) from November 1871 to December 1877 are reported in the KNMI Yearbook. For the year 1878, only the values of monthly mean temperature and atmospheric pressure are reported. In addition, the accumulated monthly mean values of temperature and pressure for 1879–1880 and the monthly mean values for 1881 and 1882 are also recorded, but when compared with the data of Nagasaki Marine Observatory, which started observations in July 1878, the values are exactly the same and therefore must have been measured at the Nagasaki Hospital. Therefore, the data recorded after 1879 are considered to be the same as those of the JMA Nagasaki Observatory.

Fig. 4.9 An example of the Nagasaki Hospital Data Series for January 1872. Stored in the KNMI Library, the Netherlands

4.1 Early Meteorological Observations in the Nineteenth Century

99

4.1.2 Early Meteorological Observations in Tokyo and Yokohama Although the nineteenth-century meteorological observations described in the previous chapters were made mainly by Dutch and other foreigners in Nagasaki, research has revealed that sub-daily meteorological observations were made by Japanese scientists in several locations in Japan, especially in Edo (now Tokyo) and Osaka (Amano, 1952, 1953). These Japanese meteorological observations are linked to the development of astronomical research by so-called Japanese “Dutch scholars” together with the modernization of Japan and the introduction of modern Western instruments. As a follow-up to the work of evaluating and homogenizing the early nineteenthcentury Japanese observation data from Dejima (Können et al., 2003), here we present a summary and monthly data from the nineteenth-century instrumental data found at Tokyo, Yokohama, Osaka, and Kobe. A detailed description of the data sources at each location is given in Zaiki et al. (2006). The first official meteorological observation in Japan started in Hakodate in 1872. In 1975, the official Meteorological Observatory was established in Tokyo under the direct control of the current JMA. In this section, data from Tokyo, Yokohama, Osaka, and Kobe are presented and compared with current JMA observation records. The collection period for each data series is shown in Fig. 4.1 in the previous section. Figure 4.10 displays the relevant geographical locations. Two types of observation records for Tokyo have been found: the Tokyo Palace series (1825–1828) and the Tokyo Calendar series (1839–1855). There are also records of observations by E. Knipping for the period 1872–1878, but they are not discussed here because the location of observation shifted and the records also

Fig. 4.10 Location of the pre-1872 observation sites in Japan. The Tokyo/Yokohama area is indicated by a dashed line in Map (a), and enlarged in Map (b), showing the relative distance between Tokyo, Yokohama, and Yokosuka. From Zaiki et al. (2006)

100

4 Climate Information from Pre-Nineteenth Century Data and Documents

overlap with those from JMA, which started in June 1875. As pointed out by Zaiki et al. (2006), the temperature and pressure values obtained for the Tokyo Palace series are uncertain and unreliable. Digitized monthly data are available from our website JCDP (https://jcdp.jp/instrumental-meteorological-data/).

4.1.2.1

Early Meteorological Observations in Tokyo

There are two types of nineteenth-century unofficial weather observation records for Tokyo. (a) Tokyo Palace Series: 1825–1828 Location: 35.69N, 139.77E, 4.0 m above MSL (mean sea level) The meteorological observations were probably made at the “Nagasakiya” hotel,” which was a special hotel for foreign visitors. This hotel was located near the Shogun’s residence in Edo. The temperature data observed during this period, especially in winter, are unusually high and unreliable. The atmospheric pressure is uncertain, although no anomalous values were observed. (b) Tokyo Calendar Series (Table 4.2): 1839–1855 (Reiken K¯obo Collection) Location: 35.71N, 139.74E, 20.0 m above MSL before April 1, 1842 Location: 35.69N, 139.75E, 6.5 m above MSL after April 2, 1842 These observations were made by the Tokugawa Shogunate’s Edo Bakufu Astronomical Office. Meteorological observations consisting of temperature, pressure, and weather were made from December 17, 1838 to February 16, 1855. There is a blank period following April 1, 1842 due to a fire. Meteorological observations resumed on August 1, 1842, but temperatures were not recorded until March 21, 1844. Observations of atmospheric pressure began even later, on December 30, 1844. This suggests that the meteorological instruments were severely damaged. No documentation of the meteorological instruments or their location within the observatory has been preserved. Figure 4.11 shows an example of meteorological records in Reiken K¯obo. The temperatures are probably reliable since no anomalous values were detected. However, the original data on atmospheric pressure for the period May 1845 to September 1848 is highly uncertain. Also, the original data of the atmospheric pressure for the period from May 1845 to September 1848 is too high, clearly showing anomalous variations (Fig. 4.12: top chart). After appropriate correction, a reasonable variation graph was obtained as shown in Fig. 4.12: bottom chart (Zaiki et al., 2006). No reliable observational record for Tokyo survives for the approximately 20year period from 1856 to 1875. However, there is a record of unofficial weather observations made in Tokyo by E. Knipping et al. from September 1872 to December 1878, although the reliability of the data is low due to the relocation of observation sites and problems with the data.

2.0

3.0

2.0

1873

1874

1875

1872

6.1

7.0

5.0

1854

1855

1.8

4.1

2.3

6.6

4.3

4.5

1853

5.0

4.1

5.9

5.0

5.4

1851

4.6

1850

6.9

6.1

5.1

5.0

5.6

3.3

1852

4.8

5.5

1848

5.2

1847

1849

6.3

4.5

1845

1846

1844

1.2

0.7

1841

1842

1.3

3.3

3.2

2.8

2.3

1839

1840

FEB

JAN

Tokyo

(a)

8.7

7.0

5.7

8.9

8.9

6.8

8.2

10.2

9.5

10.2

8.3

7.9

9.4

7.6

6.1

6.1

6.3

MAR

11.8

12.0

13.3

13.7

15.1

12.8

13.9

14.6

15.0

15.6

14.0

14.0

12.8

14.0

12.4

APR

16.7

16.2

17.6

18.4

18.0

18.5

17.5

19.8

18.2

19.0

18.5

17.6

18.6

18.3

17.0

18.0

18.1

MAY

20.6

21.7

19.3

22.2

22.1

22.5

22.0

22.0

21.7

21.1

20.5

22.2

21.7

20.8

20.0

20.9

21.3

JUN

25.4

23.6

25.0

26.9

27.1

25.2

25.8

26.0

24.8

27.1

25.8

24.9

25.6

25.2

26.6

23.5

27.6

JUL

24.7

25.7

26.3

27.0

28.6

27.9

28.0

25.6

26.2

28.2

26.3

26.5

23.5

27.3

24.8

25.4

27.1

AUG

Table 4.2 Early meteorological data in Tokyo: (a) monthly mean temperature, (b) monthly mean SLP

21.0

20.8

21.6

20.6

23.0

24.7

22.4

24.4

25.7

25.3

24.6

22.9

25.7

21.5

22.6

21.0

22.5

22.5

SEP

14.6

14.3

15.3

15.9

18.6

17.5

18.0

16.9

18.1

18.2

17.8

17.2

18.4

16.9

17.1

15.7

16.1

16.2

OCT

8.7

8.6

8.4

9.9

12.4

12.5

12.2

11.6

12.6

11.6

11.9

12.9

10.4

11.2

12.7

9.5

12.6

10.6

NOV

(continued)

3.8

5.1

5.3

5.3

7.2

6.6

6.1

6.9

7.1

9.4

8.3

8.6

7.6

4.7

8.1

3.4

4.8

5.3

DEC

4.1 Early Meteorological Observations in the Nineteenth Century 101

1019.8

1017.1

1016.6

1018.9

1016.8

1019.4

1020.1

1020.9

1020.6

1015.1

1016.4

1016.5

1014.7

1011.1

1015.9

1014.8

1016.4

1020.0

1012.7

1841

1842

1845

1846

1847

1848

1849

1850

1851

1852

1853

1854

1855

1018.7

1019.3

1015.0

1874

1875

Revised from Zaiki et al. (2006)

1015.2

1015.9

1017.0

1017.7

1015.5

1019.6

1016.5

1016.4

1017.3

1021.1

1873

1872

1019.9

1018.9

1839

1840

1019.7

FEB

JAN

Tokyo

(b)

Table 4.2 (continued)

1017.1

1018.4

1014.9

1018.9

1016.0

1016.8

1016.8

1012.0

1017.0

1012.3

1016.8

1016.9

1015.0

1018.3

1020.1

1019.2

1015.6

MAR

1013.3

1014.6

1017.6

1013.7

1015.8

1015.0

1015.8

1017.6

1014.5

1012.3

1012.5

1014.6

1013.9

1017.8

1016.9

1015.4

APR

1015.0

1014.2

1013.8

1015.3

1013.6

1012.8

1014.1

1015.0

1012.4

1015.4

1015.6

1011.3

1014.1

1014.9

1013.5

1014.5

MAY

1010.6

1013.0

1012.2

1011.9

1011.5

1010.7

1010.7

1009.3

1009.0

1012.9

1015.5

1007.8

1020.4

1010.8

1011.3

1011.3

JUN

1004.2

1011.9

1011.6

1011.1

1012.4

1010.9

1010.9

1010.6

1008.9

1006.5

1010.8

1006.4

1009.8

1007.6

1010.1

1006.7

JUL

1009.1

1012.5

1013.4

1010.8

1014.0

1011.9

1011.5

1010.6

1010.0

1005.1

1010.4

1023.1

1011.9

1007.7

1008.6

1007.0

AUG

1008.9

1014.1

1013.3

1014.3

1014.9

1013.0

1012.7

1014.3

1013.3

1010.2

1016.9

1011.3

1020.8

1011.5

1011.8

1010.0

1013.4

SEP

1013.1

1017.7

1017.8

1016.5

1018.5

1016.8

1017.0

1015.1

1016.4

1015.7

1016.3

1016.3

1018.5

1015.7

1015.9

1015.9

1016.1

OCT

1013.8

1017.2

1018.0

1018.8

1018.8

1017.5

1015.2

1017.4

1015.7

1017.9

1013.5

1016.6

1018.0

1018.9

1017.8

1016.6

1019.4

NOV

1011.9

1017.3

1019.0

1019.1

1016.1

1017.4

1014.9

1017.3

1016.3

1015.9

1018.2

1016.5

1016.5

1018.9

1018.4

1018.5

1019.1

DEC

102 4 Climate Information from Pre-Nineteenth Century Data and Documents

4.1 Early Meteorological Observations in the Nineteenth Century

103

Fig. 4.11 An example of meteorological records in “Reiken-koubo”. Stored in the National Archives of Japan

Fig. 4.12 Time series of daily pressure taken at the calendar observatory in Tokyo 1839–1852: a raw data (converted from inches to hectopascals); b corrected for biases and, in the period 1845–1848, for changes in scales and floating zero points of the scales. From Zaiki et al. (2006)

104

4 Climate Information from Pre-Nineteenth Century Data and Documents

Fig. 4.13 Seasonal variations in monthly mean temperatures in Tokyo for the period 1839–1854 (Reiken Kobo), 1883–1822 and 1981–2010 (JMA meteorological observation)

Table 4.2 shows (a) monthly mean temperatures and (b) monthly mean sea level pressures in Tokyo. Comparison with modern monthly mean JMA observational temperature data (1883–1922 and 1981–2010) indicates reasonable seasonal variations of early meteorological data for 1839–1854 (Fig. 4.13).

4.1.2.2

Early Meteorological Observations in Yokohama and Yokosuka

Yokohama is located 28 km south-southwest of Tokyo. According to Zaiki et al. (2006), meteorological observations in the Yokohama and Yokosuka area were made at five different locations during the period 1860–1874, with some overlaps. Since the observers, observation locations, and observation times were different, it is difficult to evaluate them as the same meteorological observation record. Table 4.3 shows the corrected and homogenized monthly air temperature and atmospheric pressure. Furthermore, the continuous meteorological observation records by Dr. J. C. Hepburn from November 1859 to December 1869 are highly homogeneous. Dr. Hepburn was a member of the American Meteorological Society and came to Japan on October 17, 1859, under commission from Columbia University, bringing with him his observation equipment. From the following month, November 1859, he made meteorological observations three times a day (at sunrise, 2 p.m., and 9 p.m.), and in the first and second issues of The Japan Herald, a weekly English-language newspaper published in 1861, monthly observation data for the year from November 1859 to October 1860 and November 1860 to October 1861, respectively, were published (Fig. 4.14). The daily data from November 1861 onward were published weekly in The Japan Herald. Hepburn presented his research entitled “Meteorological Tables: From observations made in Yokohama from 1863 to 1869 inclusive” at The Asiatic Society of Japan on June 17, 1874, and published tables of average monthly temperature, average monthly maximum and minimum temperature (°F), monthly precipitation (in English inches), and the monthly number of precipitation days (Fig. 4.15). What is

11.5

10.4

NOV

DEC

1867

1866

1865

1864

Yokohama

1015.3

JAN

1016.1

FEB

3.0

2.0

1874

(b)

5.3

4.8

1873

3.2

5.3

3.7

4.8

4.4

1871

2.9

1870

7.2

4.9

3.9

3.4

1872

5.5

5.6

1868

5.5

1867

1869

4.4

4.0

1865

1866

1019.0

MAR

6.3

9.2

9.2

7.5

9.0

7.7

7.2

9.4

8.6

7.7

5.9

1014.4

APR

11.5

14.2

14.2

14.2

13.4

11.5

13.6

13.0

12.0

14.2

13.7

1013.5

MAY

16.5

18.6

18.6

18.6

16.8

17.0

18.1

17.4

15.8

17.9

17.4

1009.7

JUN

21.8

21.3

21.3

21.3

20.9

20.2

20.3

21.0

18.2

20.9

20.1

1006.4

JUL

24.0

25.4

25.4

25.4

21.4

21.4

24.5

24.0

22.9

22.0

24.6

1010.8

AUG

25.8

26.8

26.8

26.8

25.4

23.7

23.6

26.4

24.8

26.4

26.3

1015.1

SEP

20.3

22.5

22.5

22.5

23.8

22.5

21.0

21.6

19.8

21.9

20.8

1015.0

OCT

13.2

18.2

18.2

18.2

17.8

16.6

15.6

17.3

16.2

15.3

16.8

1018.5

NOV

7.0

13.0

13.0

13.0

11.8

10.5

11.6

10.6

10.1

10.1

10.8

(continued)

1022.6

DEC

3.1

7.9

7.9

7.3

5.5

7.0

7.4

5.5

6.8

6.2

6.5

15.3

17.1

OCT

3.0

20.2

23.9

SEP

2.2

27.3

26.6

AUG

1864

26.2

25.3

JUL

5.6 21.8

21.5

JUN

6.6

17.3

17.0

MAY

4.3

12.4

13.2

APR

1862

9.2

7.2

MAR

1863

4.8

3.9

3.2

1860

1861

FEB

JAN

Yokohama

(a)

Table 4.3 Early meteorological data in Yokohama: (a) monthly mean temperature, (b) monthly mean SLP

4.1 Early Meteorological Observations in the Nineteenth Century 105

1008.3

JUL

1007.8

AUG

1011.9

SEP

1015.3

OCT

1020.6

NOV

DEC

1016.3

1015.5

Revised from Zaiki et al. (2006)

1874

1873

1872

1014.5

1014.9

1017.2

1014.2

1012.2

1011.9

1010.5

1011.5

1011.9

1014.6

1016.6

1013.3

1013.1

1009.9

JUN

1014.6

1013.6

MAY

1014.0

1014.8

APR

1870

1014.7

MAR

1871

1016.4

FEB

1016.4

JAN

1869

1868

Yokohama

(b)

Table 4.3 (continued)

106 4 Climate Information from Pre-Nineteenth Century Data and Documents

4.1 Early Meteorological Observations in the Nineteenth Century

107

Fig. 4.14 Table of monthly mean observations (Nov.1860–Oct.1861) at Yokohama published in “The Japan Herald”

interesting in this table is the unusually high precipitation in the summer of 1868 and the extremely low precipitation in the summer of 1867. Hirano et al. (2018) examined the secular changes in precipitation in the second half of the nineteenth century based on Hepburn’s precipitation data. Figure 4.16 shows the change in precipitation for each season from 1863 to 1869. The year-to-year variations in summer (JJA: June, July, and August) show a marked peak in 1868; the precipitation in 1868 was 1500 mm, while that in 1867 was 258 mm. Such excessive precipitation was not seen in other seasons, so the high summer precipitation in 1868 must have been extremely unusual. A comparison of the Hepburn precipitation observations with the official meteorological data (1896– 2015) from the Yokohama JMA Meteorological Observatory shows that the summer (JJA) precipitation in 1868 was extremely high, far exceeding the 1197 mm of 1941. This suggests that the year-to-year variations in precipitation were unusually high. Incidentally, an examination of historical meteorological records from various regions of Japan at that time shows that heavy rainfall and flood disasters occurred nationwide in 1868. On the other hand, in 1867, drought was recorded over a wide area of the Japanese islands.

4.1.2.3

Early Meteorological Observations in Osaka and Kobe

In Osaka and Kobe, two major cities in western Japan, early unofficial intermittent meteorological observation data date back to the 1820s. Since JMA started its official

108

4 Climate Information from Pre-Nineteenth Century Data and Documents

Fig. 4.15 Table of monthly mean meteorological observations (Jan.1863–Dec.1869) at Yokohama by Hepburn

4.1 Early Meteorological Observations in the Nineteenth Century

109

Fig. 4.16 Year-to-year variations of seasonal and monthly precipitation at Yokohama for the period 1863–1869. From Hirano et al. (2018)

meteorological observations in 1883 for Osaka and at the end of 1896 for Kobe, nineteenth-century meteorological observation data before the start of JMA’s official meteorological observations may be valuable even if they are not continuous. Zaiki et al. (2006) described the early nineteenth-century meteorological observations in Osaka and Kobe, including observers, observation periods, and observation items, and suggested some issues. The following is information on temperature and pressure observations in Osaka and Kobe. Osaka: Japanese scientist Shigeyoshi Hazama made temperature and pressure observations at his home from 1828 to 1833; however, the reliability of the observation records is low due to the problems with the location of the thermometer and the unit of reading for the pressure.

110

4 Climate Information from Pre-Nineteenth Century Data and Documents

Fig. 4.17 An example of Osaka (Gratama series) data for September 1869. Stored in the KNMI Library, the Netherlands

Temperature and pressure data observed by the Dutch medical doctor K. W. Gratama are available, although the observation period was only 18 months, from August 1869 to January 1871 (Fig. 4.17). Table 4.4 shows the observed monthly temperature and pressure data for Osaka. Kobe: In Kobe, located about 30 km west of Osaka, there are meteorological observation records from October 1869 to December 1871 and from January 1876 to November 1888 (Table 4.5). The observer of the former is unknown, and the atmospheric pressure observation data are unreliable due to substantial bias. The observers of the latter were Kobe Marine harbor masters J. Marshall and J. J. Mahlmann.

4.1.2.4

Reconstruction of Long-Term Temperature Series (1820–2000) for West Japan

In the previous section, we introduced the nineteenth-century meteorological observation data found at Dejima (Nagasaki) and other locations in Japan. However, these data are not long-term enough to be included in the official nineteenth-century meteorological observation data of JMA, making it difficult to discuss climate change in Japan over a 200-year period from the nineteenth century to the present. In Europe, on the other hand, instrumental meteorological observations began in the late seventeenth century, and long-term temperature and pressure series have been published,

22.4

25.7

1008.0

1007.6

Revised from Zaiki et al. (2006) The years with asterisk ‘*’ include unreliable values

1017.9

1012.1

1871

1014.3

1010.0

1015.8

1011.9

1018.7

1017.9

1870

1020.6

1023.4

1025.7

1869

1012.2

1013.4

1017.3

1833*

1012.9

SEP

1012.3

1010.6

1007.8

1009.0

AUG

1020.2

1007.6

JUL

1022.8

1009.4

JUN

1832* 1014.3

MAY

1016.5

1015.4

APR

1015.1

1019.9

MAR

1011.5

FEB

1831*

JAN

24.2

22.9

1830*

1829*

1828*

Osaka

(b)

4.1

17.2

1871

13.6

26.9

9.5

24.8

6.5

4.1

8.8

1870

5.7

1869

24.1

5.3

SEP

1833*

26.9

26.6

27.2

AUG

28.8

22.6

25.9

JUL

6.4

20.9

JUN

1832* 18.8

MAY

25.1

14.9

APR

22.0

8.9

MAR

26.6

6.9

FEB

1831*

JAN

1830*

1829*

1828*

Osaka

(a)

Table 4.4 Early meteorological data in Osaka: (a) monthly mean temperature, (b) monthly mean SLP

1015.5

1015.1

1018.5

1021.1

OCT

18.9

17.8

18.8

19.0

OCT

1020.5

1019.6

1022.5

1022.9

1020.3

NOV

13.5

12.1

13.3

12.5

10.3

NOV

1017.9

1017.9

1021.9

1024.7

1024.7

DEC

7.9

7.9

10.4

7.3

5.4

DEC

4.1 Early Meteorological Observations in the Nineteenth Century 111

6.9

4.6

1871

1876

1020.5

1022.6

1020.5

1019.1

1870*

1871*

1869

Kobe

(b)

FEB

5.3

1887

JAN

2.3

3.1

1886

1888

3.4

3.5

2.4

1884

1885

1021.1

1017.8

MAR

7.1

8.1

5.7

6.3

6.5

12.8

1013.7

1015.6

APR

14.2

13.5

13.3

12.2

12.1

4.1

6.2

12.7

3.5

3.4

8.4

12.9

13.7

12.9

15.0

14.3

APR

1883

1.0

1881

7.2

8.2

7.6

8.2

9.8

8.7

MAR

12.9

3.7

1880

6.5

4.0

5.5

5.5

4.4

FEB

1882

3.8

5.2

1878

1879

1877

4.1

JAN

1870

1869

Kobe

(a)

1011.8

1014.8

MAY

17.4

17.3

16.8

16.5

16.7

17.4

18.6

18.0

19.2

18.1

18.5

18.6

16.6

MAY

1010.1

1010.4

JUN

21.6

22.0

21.4

21.7

22.2

20.4

22.8

21.1

22.7

22.6

20.4

24.8

21.5

JUN

1007.7

1009.7

JUL

27.1

26.5

24.7

25.0

26.7

25.2

26.2

26.5

27.3

26.1

27.4

26.5

27.4

26.4

JUL

1007.6

1008.4

AUG

28.1

27.1

27.3

25.4

26.9

25.5

28.0

26.4

29.0

27.6

26.8

28.6

27.4

26.6

AUG

Table 4.5 Early meteorological data in Kobe: (a) monthly mean temperature, (b) monthly mean SLP

1010.2

1014.1

SEP

23.6

24.3

24.1

23.5

24.0

22.2

24.4

23.7

23.6

25.1

23.1

23.5

24.3

23.7

SEP

1017.6

1017.1

1014.3

OCT

17.4

18.8

17.9

16.2

18.2

17.4

17.1

17.4

18.3

16.1

16.8

18.6

12.8

18.3

1020.8

1019.4

1019.3

NOV

13.9

11.9

11.4

8.5

10.7

10.8

10.4

11.7

11.0

10.3

11.2

14.3

NOV

OCT

(continued)

1018.2

1018.0

1022.2

DEC

6.2

6.9

4.2

5.2

4.8

4.7

6.4

7.1

6.6

8.5

10.5

DEC

112 4 Climate Information from Pre-Nineteenth Century Data and Documents

1018.9

1016.2

1019.7

1887

1017.0

1018.1

1013.4

1018.4

1021.1 1013.7

1016.3

1018.5

Revised from Zaiki et al. (2006) The years with asterisk ‘*’ include unreliable values

1888

1019.2

1886

1021.9

1017.7

1023.8

1885

1017.7

1022.7

1884

1018.5

1018.3

1018.7

1022.0

1883

1023.4

1015.5

1014.9

1882

1020.1

1017.6

1006.7

1013.4

1015.4

1012.6

1016.9

1011.6

1013.1

1012.3

1014.6

1010.8

1011.8

1013.6

1014.0

1008.4

1009.3

1011.1

1004.8

1014.3

1012.1

1013.7

1009.5

1010.9

1008.7

1006.3

1007.4

1012.2

1012.0

1010.8

1013.4

1011.2

1009.0

1007.0

1009.1

1009.6

1881

1021.0

1007.6

1012.7

1021.7

1010.6

1008.4

1022.1

1018.7

1011.4

1880

1017.2

1016.3

1010.2

1021.1

1019.4

1022.8

1021.3

1018.5

1879

AUG

1878

1010.3

JUL 1009.0

1012.6

JUN 1012.6

1014.1

MAY 1012.9

1016.9

APR 1011.3

1018.6

1020.3

1876

MAR

1877

FEB

JAN

Kobe

(b)

Table 4.5 (continued)

1008.2

1009.8

1013.1

1013.2

1014.8

1014.7

1011.8

1013.7

1012.0

1010.1

1012.9

1010.5

SEP

1018.4

1017.2

1014.8

1021.4

1018.3

1018.1

1015.2

1016.1

1021.5

1017.5

1015.1

1017.3

OCT

1018.2

1020.1

1017.2

1020.2

1021.8

1023.1

1017.7

1021.0

1019.6

1014.8

NOV

1018.8

1022.0

1022.9

1018.2

1023.5

1019.3

1018.8

1019.6

1020.8

DEC

4.1 Early Meteorological Observations in the Nineteenth Century 113

114

4 Climate Information from Pre-Nineteenth Century Data and Documents

contributing to climate change research. Among those long-term time series, The Central England Temperature (CET) series proposed by Manley (1953, 1974) and succeeded by Parker et al. (1992) provides a 360-year time series from 1659 to the present. In Japan, Zaiki et al. (2006) have also worked to construct a West Japan Temperature (WJT) series for the period 1820–2000, based on data from five sites west of Tokyo (Tokyo, Yokohama, Osaka, Kobe, and Nagasaki) where early nineteenthcentury meteorological observation data were available. Figure 4.18 shows the annual mean and seasonal West Japan Temperatures (WJT) during 1820–2000, which are connected to the temperature time series averaged by 11 JMA meteorological stations that were selected in western Japan. The WJT series shows a temporary warm period in the 1850s and 1860s. It should be noted that this period corresponds to the end of the Little Ice Age in Europe (e.g., Grove, 1988). The WJT and data for Tokyo, Yokohama, Osaka, Kobe, and Nagasaki can be downloaded from the website of the Climatic Research Unit, University of East Anglia, UK (https://crudata.uea.ac.uk/ cru/data/japan/), and the JCDP (Japan-Asia Climate Data Program) website (https:// jcdp.jp/instrumental-meteorological-data/).

4.1.3 Early Meteorological Observations at the Russian Consulate in Hakodate In Hakodate, Hokkaido, Japan’s northernmost prefecture, the first official meteorological observation began in August 1872, as mentioned in Sect. 3.1. However, more than 10 years earlier, from January 1859 to May 1863, modern meteorological observations were conducted at the Russian Consulate, and records of these observations were published (Fig. 4.19) (Zaiki et al., 2014). The Russian meteorological data at Hakodate during 1859–1863 include daily observations of air pressure, temperature, precipitation, and wind directions at 7:00, 14:00, and 21:00. The observations were conducted at the height of 9 m before March 1860 and 45 m after April 1860. The latter location might have been close to the former Russian Consulate near the coast on the northern slope of Mt. Hakodate. Figure 4.20 shows annual variations in the monthly mean temperatures at the Hakodate JMA observatory for a specified period as compared with Russian data averaged for the period 1859–1862. The winter temperatures during 1859–1862 (Russian Observations) were warmer than those in the twentieth century period (JMA Hakodate). On the other hand, Russian observation data in the warm season, particularly in July and August, indicate extremely low temperatures during 1859–1862. Figs. 4.21 and Fig. 4.22 show the January and July temperature variations since 1850 for Hakodate and the Northern Hemisphere. In January, long-term temperature variations show a gradual increasing trend since the end of the nineteenth century in the Northern Hemisphere. In the case of Hakodate,

4.1 Early Meteorological Observations in the Nineteenth Century

115

Fig. 4.18 The west-Japan Temperature (WJT) series by season and year for the period of 1820– 2000. From Zaiki et al. (2006)

the increasing temperature trend seems to start around the 1940s, and temperatures were rather higher from the mid-nineteenth century to the early twentieth century. In any case, the trend toward increased temperatures has been particularly prominent since the late 1970s (Fig. 4.21). In July, temperature variations in the Northern Hemisphere are similar to those in January except for the temporary cooling during the 1940s to 1970s. As for the Hakodate time series, decadal to centennial time scale variations can be detected, which shows rather warm periods in the 1870s, 1920s, and 1970s. However, rapid warming

116

4 Climate Information from Pre-Nineteenth Century Data and Documents

Fig. 4.19 An example of the meteorological observation table at Hakodate. From “Annales de L’Observatoire Physique Central de Russie” Fig. 4.20 Annual variations in the monthly mean temperatures at Hakodate JMA observatory. The black line shows Russian observation data

4.1 Early Meteorological Observations in the Nineteenth Century

117

Fig. 4.21 January mean temperatures at Hakodate and Norther Hemisphere. Data Japan Meteorological Agency and Climatic Research Unit, UEA, UK

Fig. 4.22 July mean temperatures at Hakodate and Norther Hemisphere. Data Japan Meteorological Agency and Climatic Research Unit, UEA, UK

118

4 Climate Information from Pre-Nineteenth Century Data and Documents

trends since the 1980s can be found in both Hakodate and Northern Hemisphere (Fig. 4.22).

4.1.4 Mid-Nineteenth Century Temperature Observations by a Merchant of the Mito Domain In Mito, located about 100 km northeast of Tokyo, a domain merchant, Mr. Otaka, kept a daily diary from September 1852 to February 1869, roughly the last 16 years of the Edo period (1603–1869). The time when the air temperature was measured is noted as “five o’clock” in the irregular time system of the Edo period. Figure 4.23 shows a record of three days from July 25 to 27 (June 3 to 5 in the lunar calendar), 1865, as an example. The red dashed line in the box is an example of the record for July 25, and it reads as follows. Upper part: “July 25th 20 °C (at 6:40), 31.1 °C afternoon.” Lower part: “Morning mist falling. A little cloudy from about 8:00 a.m. Earthquake after 9:00 a.m. The sun shines and it is hot all day. Cloudy in the evening, with an evening shower and a fresh breeze.” In this way, the temperature each morning (and sometimes the temperature in the afternoon) as well as the weather and other phenomena such as earthquakes are recorded The temperature observation data for this period was discovered in

Fig. 4.23 An example of the weather diary in 1865 by Mr. Otaka, a merchant of Mito Domain. The box enclosed by the red dashed line is the record of July 25. Source “Mito Otaka Records No. 13”, Historiographical Institute, The University of Tokyo

4.1 Early Meteorological Observations in the Nineteenth Century

119

Fig. 4.24 Annual variations in average monthly temperatures in Mito during the Edo period (1852–1869) and at present (1991–2000) (1852–1869 data is corrected by M. Zaiki)

Tokyo and Yokohama. It is very valuable in that it was recorded almost continuously. However, in principle, the temperature data was observed only once in the morning, so when comparing it with the temperature data of JMA Mito Meteorological Observatory, it is necessary to calculate the daily average temperature by correcting for the daily variation of the temperature based on the current 24 observation data. Figure 4.24 compares the monthly mean temperature in Mito at the end of the Edo period (1852–1869) and at the present time (1991–2000). The annual average temperatures at the end of the Edo period (13.5 °C) and at present (13.8 °C) are almost the same, while the average temperature in January is 1.1 °C lower in the Edo period than at present. Conversely, the average temperature in July is 1.2 °C higher than the present. In other words, Mito at the end of the Edo period was characterized by hot summers and cold winters. The fact that present-day Mito is less cold in winter can be attributed partly to the increase in man-made energy consumption due to urbanization.

4.1.5 Meteorological Observations in Naha (Okinawa) in the Mid-Nineteenth Century The Ryukyu Kingdom, located to the southwest of Japan, was formally annexed and dissolved by Japan in 1879 to form Okinawa prefecture. Father Louis Theodore Furet, who was a missionary of the Paris Foreign Missions Society, arrived in Naha, Okinawa in 1855, and carried out meteorological observations for a short period from April 2 to May 4 (Beillevaire, 2018; Demaree et al., 2018). Figure 4.25 shows Furet’s first observation sheet in Okinawa. Furet’s continuous meteorological observations were made from December 1856 to September 1858, five times a day (6:00, 10:00,

120

4 Climate Information from Pre-Nineteenth Century Data and Documents

13:00, 16:00, and 22:00 L.T.). Figure 4.26 shows an example of data sheets from February 1857. Furet’s meteorological observation included air pressure, temperature, relative humidity, wind direction and force, cloud amount and shape, and precipitation. These daily meteorological observations were compiled into annual summary sheets (Fig. 4.27). Based on Furet’s meteorological observations, Demaree et al. (2018) created some graphic diagrams of air pressures (Figs. 4.28 and 4.29). It is noteworthy that the corrected air pressure dropped to 721.6 mmHg (962 hPa) on May 18, 1857 (16:00 L.T.) in the pressure time series graph shown in Fig. 4.29. The description of torrential rains on the eighteenth suggests that a strong typhoon passed west of Okinawa. The diary of a merchant in Mito, described in Sect. 4.1.4, also describes strong winds and rainfall that may have been caused by this typhoon as follows: “May 19, it began to rain from midnight last night, and today there was a strong north wind all day long, and the rain continued until tonight.” The fact that northerly winds continued to blow suggests that the typhoon passed near Okinawa, then changed track to the northeast and passed off the southern coast of the Japanese main island. Thus, even before the start of official meteorological observations by JMA, it is possible to reconstruct the intensity and track of a typhoon if several unofficial weather observation records and weather data from diaries are available.

Fig. 4.25 Furet’s first observation sheet on Okinawa, April 1855. From Beillevaire (2018)

4.1 Early Meteorological Observations in the Nineteenth Century

121

Fig. 4.26 An example of monthly tables showing the observations at 6:00 on the first three days of February 1857. From Beillevaire (2018)

4.1.6 Lighthouse Meteorological Observations in Japan The history of lighthouses in modern Japan began in 1866, when the Edo shogunate, upon opening the country to the outside world, concluded the “Treaty of Edo” with the United States, the United Kingdom, France, and the Netherlands, which promised the construction of eight lighthouses in Japan (Nyomura, 2002). In 1868, the new Meiji government invited R. H. Branton from England to guide the construction of lighthouses. In 1872, meteorological observations began at various lighthouses, and the records of these observations were compiled by the British Meteorological Committee. The records of these observations were published as “Contribution to the Meteorology of Japan” by the British Meteorological Committee (Nyomura, 2002). Figure 4.30 shows the oldest stone Mikomotoshima Lighthouse in Japan, located on a small uninhabited lava island 9 km off the southern tip of the Izu Peninsula, about 140 km southwest of Tokyo. The Statistics Office of the Japan Meteorological Agency (JMA) kept microfilm records of meteorological observations at 133 lighthouses throughout Japan. They were turned into image files to prevent deterioration, and the author’s research team digitized some of those image files into data files in EXCEL format (January 1877– December 1884). As of 1877, the first year for observation data was available, there

122

4 Climate Information from Pre-Nineteenth Century Data and Documents

Fig. 4.27 Furet’s annual summary sheet of meteorological observation for the year 1858. From Beillevaire (2018)

were 26 lighthouses in Japan (Fig. 4.31), and the number of daily observations was twice a day from 1877 to 1881, increasing to eight times a day from 1882 to 1887. However, from 1887 to 1917, the number of observations decreased to 6 per day, and after 1918 to 3 per day. This was probably due to the increase in the number of JMA meteorological stations in the twentieth century, which may have reduced the role of meteorological observations at lighthouses. The following is a detailed description of the observation system for each period.

4.1 Early Meteorological Observations in the Nineteenth Century

123

Fig. 4.28 Monthly mean atmospheric pressure at the 5 observation times in Naha. From Demaree et al. (2018)

Fig. 4.29 Atmospheric pressure variations (5 times/day) observed by Furet in Naha from 18 Dec. 1856 to 24 Sep. 1858. From Demaree et al. (2018)

(1) Jan.1877–Dec.1881 (Fig. 4.32, Table 4.6) Recording method: Vertical writing using Chinese numerals. Observation time: Twice a day at 9:00 and 21:00. Observation items: Average wind direction (8 directions), average wind speed (6 levels from no wind to storm), and weather (7 types: clear, cloudy, hazy, foggy, rainy, hail, snow) are recorded, followed by the barometer reading (in English inches) in

124

4 Climate Information from Pre-Nineteenth Century Data and Documents

Fig. 4.30 Mikomotoshima lighthouse, the oldest existing stone lighthouse in Japan, constructed in 1870. Photograph by takeshi noguchi

the lighthouse at 9:00 and 21:00 and thermometer readings (°F) inside/outside the lighthouse at 9:00 and 21:00. In addition, the direction and force of the wind (6 levels), daily precipitation (English inch), and the name of the observer at each time are recorded. (2) Jan.1882–May 1887 (Fig. 4.33, Table 4.7) Recording method: Vertical writing using Chinese numerals. Observation time: 8 times a day at 0:00, 3:00, 6:00, 9:00, 12:00, 15:00, 18:00, and 21:00. Observation items: barometer (in English inches) and attached thermometer (°F) 8 times a day, outdoor thermometer (°F), wind direction (8 directions) and wind force (12-step Beaufort scale), daily precipitation (in English inches), cloud cover, cloud formations, direction and height (top or bottom) of visible clouds. (3) Jun.1887–Dec.1917 (Fig. 4.34) Recording method: Horizontal writing using Arabic numerals. Time of observation: 6 times a day at 2:00, 6:00, 10:00, 14:00, 18:00, and 22:00. Observation items: onsite air pressure and temperature (English inch, °F), sea level pressure (mmHg), temperature (°C), precipitation (mm), weather, cloud formations and cloud cover, wind direction (16 directions) and wind force (scale 0–6), force of waves (scale 0–6), remarks. (4) Jan.1918–Apr.1953 (Fig. 4.35) Recording method: Horizontal writing using Arabic numerals.

4.1 Early Meteorological Observations in the Nineteenth Century

125

Fig. 4.31 Location of the 26 lighthouses where meteorological data were collected in 1877. From Zaiki et al. (2018)

Observation time: 3 times a day at 6:00, 14:00, and 22:00. Observation items: onsite air pressure and temperature (°C), wind direction (16 directions) and wind force (0–6), cloud amount, and precipitation (mm), force of waves (scale 0–6), weather, cloud formations, and cloud amounts, remarks. The history of lighthouse meteorological observations in Japan is as follows. The earliest surviving observation record is from 1877, with data from 26 stations (Fig. 4.31). Subsequently, the number of lighthouse meteorological observation stations increased, reaching 43 in 1886 (Table 4.8). Lighthouse meteorological observations continued until 1953, and the number peaked at 84 in 1899 and then declined. On the other hand, the number of JMA meteorological observatories has shown an increasing trend, but in recent years, due to personnel cost reductions, they have been replaced by automated weather stations with no staff (Fig. 4.36).

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4 Climate Information from Pre-Nineteenth Century Data and Documents

Fig. 4.32 An example of original lighthouse observation data sheets (Shinagawa Lighthouse on January 1877)

4.2 Diary Weather Records Since the Seventeenth Century In 1603, Ieyasu Tokugawa became a national hegemon and established the Edo shogunate (Tokugawa Shogunate) based in Edo (present-day Tokyo). The period of approximately 260 years from then until 1867 is known as the “Edo Period” in Japan. The shogunate was replaced by a new government following the Meiji Restoration of 1868. The Edo shogunate was the supreme governing body of all the samurai, and the feudal lords known as daimyo were assigned to each of 200 + domains throughout Japan. Many domains kept official diaries, and these diaries serve as valuable sources for research into the history of the Edo period (Fig. 4.37). In addition to domain diaries, various other official and personal diaries have been kept in Japan since ancient times, and many of them have been published in modern times. When keeping a diary, most Japanese customarily write the day’s weather after the date, so in theory, it should be possible to reconstruct the daily weather conditions in historical times by collecting diaries from all over Japan. As described in Chap. 1, Japanese people are interested in daily weather because seasonal changes are prominent in Japan, and the weather is often discussed in daily conversation. In addition, since the Japanese are an agriculture-oriented people, it may have been important to record daily weather conditions for purposes related to farming.

4.2 Diary Weather Records Since the Seventeenth Century

127

Table 4.6 An example of digitized data sheets (Shinagawa Lighthouse on January 1877) Shinagawa

139.75

January 1877 Date 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

Hour

35.62 Barometer

Thermometer

Wind

B_Inside

T_Inside

W_Direction

T_Outside

W_Force

9

30.30

45

46

NE

3

21

30.02

47

45

NE

3

9

29.89

42

37

NW

2

21

29.80

42

37

NW

2

9

29.94

33

37

N

3

21

30.10

43

40

SE

2

9

30.20

42

43

N

2

21

30.21

47

40

SW

2

9

30.25

42

37

N

2

21

30.21

33

39

C

0

9

30.20

43

39

NW

2

21

30.05

38

32

SE

2

9

30.00

42

42

W

2

21

30.00

35

29

NE

2

9

30.00

40

37

W

2

21

30.02

45

40

N

3

9

30.18

45

44

NW

3

21

30.30

47

42

NW

3

9

30.45

41

40

NW

2

21

30.40

47

40

N

2

9

30.45

42

40

N

2

21

30.50

45

40

NE

2

9

30.40

42

39

W

2

21

30.20

47

43

N

2

9

30.05

41

38

N

2

21

29.96

46

44

NE

3

9

29.93

40

40

NW

3

21

29.95

41

42

W

3

9

30.23

38

39

NW

2

21

30.32

42

36

SW

2

9

30.32

39

39

NW

2

21

30.32

42

39

E

2

9

30.25

39

39

N

2

21

30.20

35

38

N

2

9

30.25

39

39

N

2 (continued)

128

4 Climate Information from Pre-Nineteenth Century Data and Documents

Table 4.6 (continued) Shinagawa

139.75

January 1877 Date 19 20 21 22 23 24 25 26 27 28 29 30 31

Hour

35.62 Barometer

Thermometer

Wind

B_Inside

T_Inside

W_Direction

T_Outside

W_Force

21

30.35

35

39

SE

2

9

30.35

42

39

N

2

21

30.33

43

41

NE

2

9

30.20

45

45

NW

2

21

29.90

49

47

E

2

9

29.85

50

45

N

3

21

30.02

40

39

NW

4

9

30.20

41

39

NW

3

21

30.30

44

40

NW

3

9

30.43

38

36

NE

3

21

30.50

40

34

E

2

9

30.60

38

37

N

2

21

30.55

42

39

E

2

9

30.41

32

31

N

2

21

30.34

34

29

N

2

9

29.90

39

37

N

2

21

29.90

48

45

S

2

9

29.95

36

34

NW

2

21

30.08

42

40

NW

2

9

30.10

41

40

N

3

21

30.10

45

43

E

2

9

30.10

41

41

W

2

21

30.00

46

44

NE

2

9

29.83

42

39

N

2

21

29.88

45

41

NW

2

9

30.04

41

42

N

2

21

30.20

39

42

N

2

4.2.1 Location and Duration of Diary Weather Records Table 4.9 shows a list of diaries with daily weather records from all over Japan. Although much more weather diaries are thought to exist, this list is limited to diaries that were kept for more than 10 years, as currently identified by the author. The diaries are classified into five types: the name of the diary, the start and end year of the weather entry, the place name and latitude/longitude of the location where the diary was written, and the number of years the diary was kept. Each diary is classified

4.2 Diary Weather Records Since the Seventeenth Century

129

Fig. 4.33 An example of original lighthouse observation data sheets (Iwojima Lighthouse on July 1–6, 1882)

as D = domain diary, F = family diary, P = personal diary, S = shrine diary, and T = temple diary. Twenty-two diaries were kept for more than 100 years, including 5 that were kept for more than 200 years. The earliest diary is the Nanbu Domain Kar¯ozeki Diary from Morioka, which begins in 1644. There are ten diaries that begin in the seventeenth century and are distributed all over Japan from Hirosaki in the north to Miyazaki in the south. The majority of the domain diaries end around 1867, when the Edo Shogunate collapsed. The domain diary is an official document and the weather described is highly reliable. The original domain diaries were written vertically with traditional handwriting on Japanese “Washi” paper, and it is not easy to read the cursive characters. Most of them are kept in local libraries and museums, and some of them have been converted into image files to prevent deterioration and made available to the public on websites. Some of the domain diaries have also been reprinted in text form and published in books. The authors’ research team has collected a huge amount of diary weather records, compiled them into a database, and made them publicly available through a website (see Sect. 4.2.3).

130

4 Climate Information from Pre-Nineteenth Century Data and Documents

Table 4.7 An example of digitized data sheets (Iwojima Lighthouse on July 1–6, 1882) Iwojima

129.75

32.70 Barometer

Thermometer

Wind

Hour

B_Inside

T_Inside

T_Outside

W_ Direction

29.73

73.0

72.0

E

July 1882 Date 1

0

W_Force

Precipitation

2

1

3

29.70

73.0

71.5

E

3

1

6

29.67

70.5

69.0

E

4

1

9

29.68

72.0

70.0

E

−999

1

12

29.87

74.0

78.0

NW

1

1

15

29.67

80.0

85.5

NW

1

1

18

29.67

84.0

86.0

NW

1

1

21

29.69

82.0

81.0

E

1

2

0

29.72

79.1

78.6

SW

1

2

3

29.71

77.0

76.2

SW

1

2

6

29.71

72.0

73.5

E

1

2

9

29.74

78.0

79.8

SW

1

2

12

29.75

81.0

85.0

NW

1

2

15

29.75

82.5

81.0

NW

1

2

18

29.72

78.0

77.8

E

1

2

21

29.72

79.0

76.0

SE

1

3

0

29.79

78.0

76.5

SSE

1

3

3

29.67

77.0

76.2

SE

1

3

6

29.66

75.0

72.5

NE

2

3

9

29.66

74.0

72.0

NE

3

3

12

29.62

78.0

76.5

E

4

3

15

29.61

80.0

79.5

WNW

3

3

18

29.67

80.0

79.3

ESE

1

3

21

29.70

78.0

76.2

E

3

4

0

29.70

78.5

76.5

E

2

4

3

29.70

77.0

73.5

NW

4

4

6

29.72

76.0

74.0

NW

3

4

9

29.75

78.0

78.5

E

2

4

12

29.80

82.0

79.8

W

2

4

15

29.77

86.0

84.5

W

2

4

18

29.79

85.0

86.5

W

1

4

21

29.81

80.0

78.5

SE

1

5

0

29.73

78.0

74.5

SE

1

5

3

29.77

78.0

74.5

S

2

0.15

0.00

2.15

0.00

(continued)

4.2 Diary Weather Records Since the Seventeenth Century

131

Table 4.7 (continued) Iwojima

129.75

32.70 Barometer

Thermometer

Wind

Hour

B_Inside

T_Inside

T_Outside

W_ Direction

29.73

76.0

73.5

W

July 1882 Date 5

6

W_Force

Precipitation

1

5

9

29.78

77.0

74.5

W

1

5

12

29.81

79.0

78.2

NW

1

5

15

29.80

80.0

78.5

SW

2

5

18

29.83

80.0

77.0

S

1

5

21

29.83

79.0

78.5

SE

1

6

0

29.85

78.0

76.8

E

1

6

3

29.80

77.0

75.0

E

2

6

6

29.81

76.0

75.2

NE

1

6

9

29.80

78.0

79.0

NE

2

6

12

29.81

81.0

84.5

SW

1

6

15

29.77

80.0

75.8

E

1

6

18

29.75

78.0

76.2

NE

1

6

21

29.73

76.5

74.5

E

3

0.00

0.08

Fig. 4.34 An example of original lighthouse observation data sheets (Hakodate Lighthouse in June 1887)

132

4 Climate Information from Pre-Nineteenth Century Data and Documents

Fig. 4.35 An example of original lighthouse observation data sheets (Mikomotoshima Lighthouse in February 1918)

4.2.2 Weather Records of the Two-Century Hirosaki Doman Diary and Their Databasing The Hirosaki Domain Diary was kept over a period of 207 years from 1661 to 1867. The Hirosaki City Library has approximately 3,300 volumes of the Hirosaki Domain Diary recorded in Hirosaki City and approximately 1,220 volumes of the Hirosaki Domain Edo Diary recorded at the domanial residence in Edo (Tokyo). Studies focusing on the weather records of these very long-term diaries include Maejima and Tagami (1983) and Mikami (1983). Figure 4.38 shows the Hirosaki Domain Diary of April 1729 (in the Gregorian Calendar) as an example. It is written vertically on traditional Japanese paper with a brush pen, and the date and weather are written in the area surrounded by the red dashed line. This kind of format is also used in personal diaries, in which Japanese people customarily note the daily weather. In this example, the entry reads “12th day of the third month: Cloudy, rain all day” is written. The date is given in the traditional lunar calendar; in the Gregorian Calendar, it corresponds to April 9, 1729. Yoshimi Fukuma, former head of JMA Akita Meteorological Observatory, has been living in Hirosaki City since his retirement and has been visiting the City Library every day for 15 years to input the weather and related information in the

4.2 Diary Weather Records Since the Seventeenth Century

133

Table 4.8 List of lighthouses with meteorological observations as of 1886 Lighthouse

Lon.

Lat.

Start

End

Shinagawa

139.75

35.62

1877

1899

Haneda

139.78

35.52

1877

1899

Honmoku

139.68

35.43

1877

1899

Kannonzaki

139.73

35.25

1877

1899

Kenzaki

139.67

35.13

1877

1899

Mikomotoshima

138.93

34.57

1877

1910

Irouzaki

138.83

34.60

1877

1899

Omaezaki

138.22

34.58

1877

1910

Sugashima

136.90

34.50

1877

1899

Kashinozaki

135.85

33.47

1877

1899

Tomogashima

135.00

34.27

1877

1899

Wadamisaki

135.17

34.65

1877

1899

Esaki

134.98

34.60

1877

1899

Nabeshima

133.82

34.38

1877

1899

Tsurushima

132.62

33.88

1877

1899

Hesaki

131.02

33.95

1877

1899

Mutsureshima

130.85

33.97

1877

1899

Tsunoshima

130.88

34.35

1877

1906

Eboshijima

129.98

33.68

1877

1899

Iwojima

129.75

32.70

1877

1900

Nojimazaki

139.88

34.90

1877

1899

Inubozaki

140.87

35.70

1877

1899

Kinkazan

141.58

38.27

1877

1921

Shiriyazaki

141.45

41.42

1877

1910

Hakodate

140.68

41.78

1877

1899

Mejirushiyama

135.43

34.67

1877

1884

Jogashima

139.60

35.13

1878

1899

Anorisaki

136.90

34.45

1878

1903

Shionomisaki

135.77

33.43

1878

1900

Kobe

135.18

34.68

1878

1888

Shirasu

130.78

33.98

1878

1899

Kagenoojima

129.82

32.70

1882

1900

Ohsezaki

129.60

32.60

1880

1910

Kuchinotsu

130.18

32.60

1880

1899

Satamisaki

130.65

30.98

1878

1953

Kurasaki

131.40

31.50

1885

1899

Kattoshimisaki

140.58

41.73

1886

1938 (continued)

134

4 Climate Information from Pre-Nineteenth Century Data and Documents

Table 4.8 (continued) Lighthouse

Lon.

Lat.

Start

End

Nosappumisaki

145.82

43.37

1878

1906

Bentenjima

145.57

43.33

1878

1899

Hiyoriyama

141.00

43.23

1885

1952

Niigata

139.05

37.93

1883

1899

Rokkousaki

137.32

37.52

1884

1903

Tateishimisaki

135.00

34.75

1882

1899

Fig. 4.36 Changes in the number of lighthouses with meteorological observations and JMA meteorological stations

Fig. 4.37 An example of diary weather records on October 1, 1834 (Lunar Calendar) in the Hirosaki Clan Edo Diary. The weather is described in the red box. Stored in Hirosaki City Library

Hachinohe-Domain Tohyama Diary

Tadotsu-Domain Diary

D

D

1765–1869

1792–1919

1739–1867

1745–1873

Daily Weather Table in Kofu

Hagi-Domain Ohmetsuke Diary etc.

F

D

1726–1870

Sabae-Domain Diary

D

1758–1912 1830–1889

Inatsuka Family Diary

Gen-emon Diary

F

P

1712–1867

Myoko Hozoin Diary

T

1702–1868 1711–1869

Tsuyama-Domain Diary

Fujisawa-san Diary

1700–1872

D

Isahaya-Domain Diary

D

1697–1871

1686–1869

1685–1871

1669–1862

T

Tsushima-Domainn Souke Diary

Tottori-Domain Ohmetsuke Diary etc.

D

D

Shake Gobansho Diary

S

1674–1869

Gokaisho Diary

Sadowara-Domain Shimazu Diary

D

D

1644–1840

Nanbu-Domain Karouzeki Diary

D

1661–1867 1665–1869

Hirosaki-Domain Edo Diary

Hachinohe-Domain Diary

D

D

1663–1872 1661–1867

Nijo-Ke Nainai Gobansho Diary

Hirosaki-Domain Diary

F

D

Period 1720–1941

Name of diary

Ishikawa Family Diary

Type

F

Table 4.9 A list of old diaries with daily weather records Place name

Tadotsu

Hachinohe

Hagi

Kofu

Sabae

Kawanishi

Ikeda

Myoko Sekiyama

Fujisawa

Tsuyama

Isahaya (Nagasaki)

Tottori

Izuhara

Nikko

Miyazaki

Usuki

Morioka

Hachinohe

Tokyo

Hirosaki

Kyoto

Hachioji (Tokyo)

Lat.

34.27

40.50

34.41

35.65

35.95

38.00

34.83

36.94

35.34

35.07

32.85

35.50

34.25

36.75

32.02

33.12

39.70

40.50

35.69

40.61

35.03

35.66

Lon.

133.76

141.49

131.40

138.57

136.25

140.05

135.43

138.21

139.49

134.01

130.05

134.24

129.30

139.75

131.48

131.81

141.16

141.49

139.75

140.47

135.77

139.32

Start

1765

1792

1739

1745

1726

1830

1758

1712

1711

1702

1700

1697

1686

1685

1669

1674

1644

1665

1661

1661

1663

1720

End

1869

1919

1867

1873

1870

1980

1912

1867

1869

1868

1872

1871

1869

1871

1862

1869

1840

1869

1867

1867

1872

1941

Years

(continued)

105

128

129

129

145

151

155

156

159

167

173

175

184

187

194

196

197

205

207

207

210

222

4.2 Diary Weather Records Since the Seventeenth Century 135

1814–1876 1770–1830

Torii Family Diary

F

1806–1889

1814–1869 1812–1866

Tadokoro Family Documents

F

1714–1760 1825–1871

Igeta Shrine Diary

S

Banshu Tatsuno-Domain Diary

Oba Misa Diary

D

P

1860–1886

1775–1806

1827–1858

1835–1866

Kadoya Youan Diarey

Ohkyo Zakki

P

P

1806–1838

Kakuson Diary

P

1847–1881 1862–1895

Hayami Family Diary

Zoku Kyogetsudo Diary

F

1830–1864

Kokutaiji Nikkan

T

P

1700–1740

Moriya Toneri Diary

Sakakibara-Domain Edo Diary

P

D

1694–1746

Nakamura Heizaemon Diary

Myouhouin Diary

P

T

1815–1870

Nobeoka-Domain Diary

Genba Diary

D

P

1796–1860

Sekiguchi Diary

Kitakouji Family Diary

F

F

1780–1869 1782–1869

Harimaya Nakai Family Diary

Sugiura Family Diary

F

1779–1871

Murakami Kajou Diary

F

Period

Name of diary

Type

F

Table 4.9 (continued)

Setagaya (Tokyo)

Tatsuno (Hyogo)

Himi (Toyama)

Ogachi

Kanazawa

Kashiwazaki (Niigata)

Kyoto

Akkeshi (Hokkaido)

Tokyo

Takayama (Kagoshima)

Ikeda (Osaka)

Kyoto

Kitakyushu

Tanabe

Choshi

Nobeoka

Toyooka

Kyoto

Yokohama

Kyoto

Tokyo

hiroshima

Place name

35.64

34.87

36.85

39.07

36.50

37.36

35.01

43.05

35.69

31.34

34.83

34.99

33.85

33.73

35.72

32.58

35.55

35.06

35.49

35.01

35.69

34.40

Lat.

139.65

134.55

136.99

140.42

136.60

138.56

135.76

144.85

139.76

130.95

135.43

135.78

130.89

135.38

140.82

131.67

134.82

135.75

139.67

135.77

139.77

132.46

Lon.

1860

1775

1827

1835

1806

1862

1847

1830

1700

1825

1714

1694

1812

1814

1815

1770

1814

1796

1806

1782

1780

1779

Start

1886

1806

1858

1866

1838

1895

1881

1864

1740

1871

1760

1746

1866

1869

1870

1830

1876

1860

1889

1869

1869

1871

End

(continued)

27

32

32

32

33

34

35

35

41

47

47

53

55

56

56

61

63

65

84

88

90

93

Years

136 4 Climate Information from Pre-Nineteenth Century Data and Documents

Sakakibara-Domain Diary

Shonai Diary

D

P 1872–1881

1839–1849

1857–1869

1855–1868

[Type] D: Domain; F: Family; P: Personal; S: Shrine; T: Temple

Hirasawa Hosaku Diary

P

1737–1751

Ouoka-Echizennokami Tadasuke Diary

Shinkakuji Temple Diary

P

T

1699–1715

Hodoji Nikkan

T

1787–1805 1872–1889

Sugita-Genpaku Diary

Yorozu Diary

P

F

1868–1894 1805–1828

Nakahara Kazou Diary

Emi Keisaiou Diary

P

1863–1889

Gekuh Korakan Diary

P

Period

Name of diary

Type

S

Table 4.9 (continued)

Tsuruoka

Takada

Oshamanbe (Hokkaido)

Usa (Kochi)

Tokyo

Yamagata

San-nohe

Tokyo

Murakami (Niigata)

Kitakyushu

Ise

Place name

38.73

37.14

42.52

33.45

35.68

38.25

40.37

35.67

38.13

33.89

34.48

Lat.

139.83

138.24

140.38

133.45

139.76

140.34

141.26

139.78

139.47

130.87

136.70

Lon.

1872

1839

1857

1855

1737

1699

1872

1787

1805

1868

1863

Start

1881

1849

1869

1868

1751

1715

1889

1805

1828

1894

1889

End

10

11

13

14

15

17

18

19

24

27

27

Years

4.2 Diary Weather Records Since the Seventeenth Century 137

138

4 Climate Information from Pre-Nineteenth Century Data and Documents

Fig. 4.38 An example of Hirosaki Domain Diary. The date and weather are written in the area enclosed by the red dashed line. March 12 in Lunar calendar: April 9, 1729 in Gregorian calendar, Cloudy, all-day rain. Stored in Hirosaki City Library

diary into his laptop PC. Figure 4.39 shows a part of the database he created. The database is written only in Japanese, so it is not available in English. PDF version of the database is also accessible at the following website. Japan-Asia Climate Data Program (JCDP) https://jcdp.jp.

Fig. 4.39 An example of Hirosaki Domain Diary Weather Database (Japanese only). The red underlined descriptions correspond to the dates shown in Fig. 4.38. From Fukuma (2018)

4.2 Diary Weather Records Since the Seventeenth Century

139

4.2.3 Historical Weather Database (HWDB) As shown in Table 4.9, a large number of diaries which include daily weather-related information have been kept in local libraries and museums in Japan. Dr. Minoru Yoshimura, with the cooperation of historical climatology researchers throughout Japan, coded the weather in more than 50 diaries throughout the country to construct a unique weather database for the historical period (Yoshimura, 2013). As already mentioned, the weather descriptions in diaries are varied, so it is not easy to reconstruct them in a unified format. In other words, it is necessary to typify and code weather terms in many diaries. Furthermore, the description of daily weather is not simply a single word such as “sunny” or “rainy,” but also includes expressions such as “sunny, rainy after 7:00”, “sunny and cloudy,” and so on. There is also information on temperature, dryness, humidity, wind direction, and wind force. Therefore, he has created a database that encodes these as well. This database is named Historical Weather Database (HWDB) and is available on the following website. Historical Weather Database on the Web (HWDB) http://tk2-202-10627.vs.sakura.ne.jp/ There is also a link to the website from JCDP (https://jcdp.jp). Clicking “Enter” on the above page takes you to the top page of the database (Fig. 4.40).

Fig. 4.40 Top page of HWDB website (http://tk2-202-10627.vs.sakura.ne.jp/index_hw.html)

140

4 Climate Information from Pre-Nineteenth Century Data and Documents

A list of the original diaries of HWDB, in Japanese, can be seen by clicking on number 5 in the menu at the top left. Basically, the contents are almost the same as the list of diaries described in Sect. 4.2.1, so those who are interested should refer to Table 4.9. A unique feature of this website is the availability of daily weather distributions for historical periods. Here, let us reconstruct the weather conditions throughout Japan on January 5–6, 1801. Figure 4.41 shows the weather in the Hirosaki Domain Diary described in Sect. 4.2.2, with a red dashed frame. The weather conditions are described as follows: January 5 (left panel): “Snow continued to fall throughout last night, accumulating to about 9 cm this morning, and snowing occasionally thereafter”; January 6 (right panel): “Snow fell throughout last night, accumulating to about 6 cm by this morning”. Thus, we can see that Hirosaki had snowfall for two consecutive days, but what were the conditions like in the rest of Japan? Let us check the weather distribution for these two days on the HWDB Weather Distribution Map. On the top page, two maps of Japan are shown, and the date selection method is explained in English. In the next box, you can choose either “Better” (◎) or “Worse” (∆)weather conditions for that day. For example, if various types of weather occur in a day, such as “sunny, occasionally cloudy,” “rainy after cloudy,” or “rainy in the morning, cloudy in the afternoon, and sunny at night,” select “Better” if you want the best weather to be displayed with priority, and “Worse” if you want the worst weather to be displayed with priority. The order of priority from good weather to bad weather is, in principle, “Sunny” > “Cloudy” > “Rain” > “Snow”.

Fig. 4.41 Weather records on January 5 (left) and 6 (right), 1801 recorded in the Hirosaki Clan Diary. Sored in Hirosaki City Library

4.3 Long-Term Records of Lake Ice Freeze-Up/Break-Up Dates

141

Fig. 4.42 Typical weather distribution maps for two continuous days: January 5–6 in 1801 (additions to HWDB)

Choosing “1. Weather Distribution (continuous two days)” from the menu on the cover page and specifying “Worse” weather (∆) for January 5 and 6, 1801 results in Fig. 4.42. The weather distribution for these two days shows the typical weather pattern of the winter monsoon season described in Sect. 2.2.2, with snowfall on the Sea of Japan side and sunny weather on the Pacific Ocean side. It can be inferred that locations on the Sea of Japan side, such as Hirosaki, experienced snowfall while the Pacific Ocean side was clear and dry due to the strengthening of the west-high, east-low pressure pattern (see Sect. 2.2.2). In addition to displaying weather distribution on the website, the HWDB database can also display a one-month weather calendar, but unfortunately, it does not support English. The coded data (text file) that is the source of the HWDB will be made accessible to the public through the Japan-Asia Climate Data Program (JCDP) in the near future.

4.3 Long-Term Records of Lake Ice Freeze-Up/Break-Up Dates 4.3.1 Records of Freeze-Up and Ice Pressure Ridge at Lake Suwa Since 1444 Continuous records of lake freezing and the formation of ice pressure ridges at Lake Suwa in Central Japan have been kept for nearly 600 years from the fifteenth century to the present, and it has long been known that these records can be used for winter climate reconstructions. It was probably the meteorologist Dr. Sakuhei Fujiwhara (Fujiwhara, 1921) who first drew attention to the relationship between the long-term ice freezing records of Lake Suwa and climate change.

142

4 Climate Information from Pre-Nineteenth Century Data and Documents

Dr. Hidetoshi Arakawa, also a meteorologist, continued Fujiwhara’s legacy by compiling the ice records for Lake Suwa. In 1954, he published a paper entitled “Fujiwhara on Five Centuries of Freezing Dates of Lake Suwa in the Central Japan” in an English-language journal (Arakawa, 1954). In this paper, he revised Fujiwhara’s data and compiled a chronology of lake-ice freezing and Omiwatari (ice-pressure ridge) occurrence dates in Lake Suwa for about 500 years from 1443/44 to 1953/54. Omiwatari occurred at Lake Suwa for about 500 years from 1443/44 to 1953/54, and the changing dates of occurrence attracted attention as proxy data for understanding long-term climate change. Omiwatari means “Deity crossing.” Since ancient times, when Lake Suwa is frozen over for a few days in winter, a crack appears in the lake ice and protrudes in a linear pattern as the ice contracts and expands due to fluctuating temperatures, connecting the two shores of the lake. The ice cracks are believed to be the path taken by the Male God of the Suwa Upper Shrine (south of the lake) to the residence of the Female God of the Lower Shrine (north of the lake) on the opposite shore, and ceremonies are held to celebrate the occurrence of Omiwatari. Figure 4.43 is a map showing three Omiwatri routes that appeared on Lake Suwa in January 2003, and is recorded in “Miwatari Chushinroku,” which is continuously documented at Yatsurugi Shrine in Suwa City. Such route maps are not recorded every year, but usually, give the place names of the start (south of the lake) and end (north of the lake) points of Omiwatri. The case of Lake Suwa is not unique, as ice-pressure ridges may occur not only in lake ice but also in sea ice; however, the existence of a 600-year record of such is without parallel elsewhere in the world. Perhaps the fact that the phenomenon was associated with the religious beliefs of the local people is the reason why it was continuously recorded for such a long period of time. Figure 4.44 shows a photograph taken on February 10, 2018, which was 10 days after Omiwatari occurred. The protrusion of the ice was smaller than in the past, and the ice around it was also thinner. The reason why the freezing records of Lake Suwa attracted attention is that in years when the freezing date of the lake is early, the lake tends to become colder due to the early onset of winter, but when winter temperatures are high, the freezing date is delayed. Therefore freezing dates have been used to reconstruct past long-term winter temperature fluctuations. For example, Gray (1974) estimated the mean winter (DJF) temperature in Tokyo from 1444 to 1953 using the freezing date chronology of Arakawa (1954). There is a significant correlation (r = 0.65) between the freezing date of Lake Suwa and the mean temperature during the winter season from 1898 to 1953, when the JMA Tokyo records overlap with reliable freezing dates for Lake Suwa. Hence, the mean winter temperature of Tokyo was calculated from the Lake Suwa freezing date data for the period 1444–1953 using linear regression. Using a similar method, Mikami and Ishiguro (1998) reconstructed the mean temperature variation at Suwa since 1444 based on the high correlation between the Lake Suwa freezing dates and the December/January mean temperatures during the observation period (Figs. 4.45 and 4.46). As discussed below, there are blank periods due to data heterogeneity and missing measurements. Although the reconstructed

4.3 Long-Term Records of Lake Ice Freeze-Up/Break-Up Dates

143

Fig. 4.43 An example of a typical Omiwatari route map from the “Miwatari Chushinroku” continuously recorded at Yatsurugi Shrine in Suwa city. In the 2002/2003 winter, the three Omiwatari routes pointed out by the blue arrows were confirmed

temperatures are characterized by large interannual variations, no clear trend of change (e.g., warming) is observed over the entire period. This suggests the need to reexamine the long-term lake freezing and Omiwatari dates records based on the original documentary records. Sharma et al. (2016) attempted to verify long-term warming using the ice freeze dates of Lake Suwa (1443–2014) and the breakup dates of the Torne River in Finland (1693–2013). Regarding Lake Suwa, they judged that the reliability of the records was low, and they excluded 1683–1923 from the analysis, so they were not able to utilize the ice freeze-up date data for nearly 600 years. Our research team is currently verifying all original records of long-term freezing and Omiwatari, which have been preserved at museums and shrines in Suwa city. In fact, there are some problems with the freezing and Omiwatari date records for Lake Suwa. Figure 4.47 shows the freezing dates and Omiwatari dates for four stages: 1444–1682 (Stage 1), 1683–1871 (Stage 2), 1898–1923 (Stage 3), and 1924– 1953 (Stage 4). The observers (e.g., shrines) and format of the records of the freezing dates and Omiwatari dates are not the same (Ishiguro, 2001). For example, in stage 1, Omiwatari always occurs 2 or 3 days after the freezing date, but in stage 2 and later, Omiwatari occurs from 1 to 10 days after the freezing date, or in some cases 28 days after the freezing date of lake-ice. The number of days between freezing and the occurrence of Omiwatari varied greatly. This fact means that, in general, the temperature fluctuation pattern after lake-ice freezing varies from year to year. In

144

4 Climate Information from Pre-Nineteenth Century Data and Documents

Fig. 4.44 Omiwatari (Ice pressure ridge) at Lake Suwa in Central Japan. Photograph taken by T. Mikami on 10 February 2018 Fig. 4.45 Relationship between the freeze-up dates of Lake Suwa and the December/January mean temperatures at JMA Suwa Observatory (1945–1990). From Mikami and Ishiguro (1998)

4.3 Long-Term Records of Lake Ice Freeze-Up/Break-Up Dates

145

Fig. 4.46 December/January mean temperature variations at Suwa since 1444 reconstructed from the freeze-up dates of Lake Suwa. Time-series from 1898 are plotted using observation data. From Mikam and Ishiguro (1998)

other words, the mechanism by which Omiwatari always occurs two or three days after the freezing date, as seen during Stage 1, is meteorologically unnatural and difficult to explain.

Fig. 4.47 Freezing and Omiwatari dates based on the database of Arakawa (1954). From Ishiguro (2001)

146

4 Climate Information from Pre-Nineteenth Century Data and Documents

The recording style during Stage 1, for example, in the case of 1486 is as follows: “Lake-ice froze during the night of 10 January, and Omiwatari occurred at around 9 o’clock in the morning of 12 January.” The format of the description, in which the lake-ice froze during the night of a certain day and Omiwatari occurred two or three days later in the morning, remained virtually unchanged for about 240 years from 1444 to 1682. However, from 1683 to 1923 (Stages 2 and 3), the recording format was not consistent, partly due to changes in observers (shrines, etc.), with only Omiwatari dates being recorded without the freezing date, or only Omiwatari Haikan Ceremony dates being recorded (Fig. 4.48). Therefore, even in studies of climate change using these long-term freezing date records of Lake Suwa, some studies exclude the records from 1683 to 1923 from the analysis because they are not reliable (Sharma et al., 2016). However, Omiwatari was likely an important phenomenon for shrines and local inhabitants for a long time, although the lake ice freezing itself may not have been a concern. Therefore, I believe that the lake-ice freezing dates for Stage 1 (1444– 1682) may have been formally estimated at a later date. (The expression “complete freezing” is not used in the old records.) Furthermore, our research team found that the chronology of Arakawa (1954) contains a considerable number of data errors and deficiencies. A research team led by Dr. Naoko Ishiguro-Hasegawa is currently examining all the freezing and Omiwatari dates records of Lake Suwa based on the original historical documents and plans to publish soon a complete revision and updating of the database (Arakawa, 1954) compiled by Fujiwhara and Arakawa.

Fig. 4.48 Scenes from the Omiwatari viewing ceremony held on the ice of Lake Suwa on January 13, 2006. The lake ice was frozen up on 30 December 2005, and Omiwatari occurred on 7 January 2006. (Courtesy of Kiyoshi Miyasaka at Yatsurugi shrine)

4.3 Long-Term Records of Lake Ice Freeze-Up/Break-Up Dates

147

Fig. 4.49 Location of Lake Jusan in northern Japan. Source Geospatial Information Authority of Japan map

4.3.2 Records of Ice Freeze-Up/Break-Up at Lake Jusan During 1705–1860 Lake Jusan is a brackish lake located in Aomori Prefecture, northern Japan, facing the Sea of Japan (Fig. 4.49). As described in Sect. 4.2.2, Yoshimi Fukuma, former director of the JMA Akita Meteorological Observatory, succeeded in compiling a database of all weather-related records in the Hirosaki Domain Diary, which has continued for over 200 years since 1660. In this diary, Fukuma noted that Lake Jusan north of Hirosaki was frozen up every year in early winter and broken up the following spring and that the dates of the freezing and thawing were described in detail. Since the records of ice freeze-up/break-up dates were almost continuous for more than 150 years from the early 1700s to 1860, those dates were extracted and entered into the data file. Unfortunately, there are no records of ice freeze-up/break-up at Lake Jusan after 1860. Since Yoshimi Fukuma provided us with this valuable data file, this section presents in Table 4.10 the data on the occurrence dates of ice freezeup/break-up of Lake Jusan. We would like to take this opportunity to express our gratitude to Yoshimi Fukuma.

148

4 Climate Information from Pre-Nineteenth Century Data and Documents

Table 4.10 Ice freeze-up/break-up dates and ice duration of Lake Jusan Break-up date

Freeze-up date Year

Month.Day

DOY-NOV

Year

1701

1702

1702

1703

1703

1704

Month.Day

Duration DOY-NOV

Days

1704

1705

3.29

149

1705

1706

4.17

168

1707

3.26

146

111 94

1706

12.05

35

1707

12.16

46

1708 1709

12.32

62

1708

3.19

140

1709

4.04

155

1710

3.20

140

78

3.25

145

86

3.29

149

103

1710

12.29

59

1711

1711

12.35

65

1712

1712

12.16

46

1713 1714

3.27

147

1714

12.26

56

1715

3.28

148

92

1715

12.26

56

1716

4.08

160

104 104

1713

1716

12.11

41

1717

3.25

145

1717

12.26

56

1718

3.08

128

72

1718

12.23

53

1719

4.04

155

102 116

1719

12.11

41

1720

4.05

157

1720

12.35

65

1721

3.21

141

76

1721

12.22

52

1722

3.26

146

94

1722

12.17

47

1723

3.31

151

104

1723

12.07

37

1724

3.19

140

103

1724

12.27

57

1725

1.30

91

1725

12.26

56

1726

1726

12.08

38

1727

3.22

142

104

1727

12.23

53

1728

3.23

144

91

1729

4.07

158

1729

12.27

57

1730

3.30

150

93

1730

12.07

37

1731

3.30

150

113

1728

1731

12.21

51

1732

3.31

152

101

1732

12.13

43

1733

3.28

148

105

1733

12.05

35

1734

3.26

146

111

1734

12.12

42

1735

3.17

137

95

1735

12.18

48

1736

3.12

133

85

1736

12.04

34

1737

3.27

147

113 (continued)

4.3 Long-Term Records of Lake Ice Freeze-Up/Break-Up Dates

149

Table 4.10 (continued) Break-up date

Freeze-up date Year

Month.Day

DOY-NOV

Year

Month.Day

Duration DOY-NOV

Days

1737

12.10

40

1738

2.22

114

74

1738

11.29

29

1739

3.31

151

122

1739

12.30

60

1740

4.06

158

98 116

1740

11.28

28

1741

3.24

144

1741

12.32

62

1742

3.28

148

86

1742

12.15

45

1743

4.02

153

108

1743

12.18

48

1744

2.29

121

73

1744

12.12

42

1745

4.03

154

112

1745

12.25

55

1746

3.27

147

92

1747

3.14

134

1747

12.24

54

1748

3.08

129

75

1748

12.12

42

1749

3.25

145

103

1746

1749

12.24

54

1750

3.10

130

76

1750

12.23

53

1751

3.28

148

95

1751

12.08

38

1752

3.22

143

105 102

1752

12.16

46

1753

3.28

148

1753

12.20

50

1754

2.28

120

70

1754

12.01

31

1755

4.09

160

129

1755

12.05

35

1756

4.10

162

127

3.21

141

1756

1757

1757

1758

1758

12.24

54

1759

1759

12.28

58

1760

2.28

120

1761

3.22

142

1760

62

1761

12.07

37

1762

4.08

159

122

1762

12.04

34

1763

3.25

145

111

1763

12.18

48

1764

3.23

144

96

1764

12.17

47

1765

3.18

138

91

1765

12.22

52

1766

4.06

157

105

1766

12.31

61

1767

3.30

150

89

1767

12.08

38

1768

3.02

123

85

1768

12.16

46

1769

3.17

137

91

1770

3.18

138

1769 1770 1771

12.15

45

1771

3.22

142

1772

3.25

146

101 (continued)

150

4 Climate Information from Pre-Nineteenth Century Data and Documents

Table 4.10 (continued) Break-up date

Freeze-up date Year

Month.Day

DOY-NOV

Year

Month.Day

Duration DOY-NOV

Days

1772

12.11

41

1773

3.19

139

98

1773

12.08

38

1774

4.03

154

116

1774

12.20

50

1775

4.07

158

108

1776

3.26

147

1776

12.28

58

1777

3.30

150

92

1777

12.10

40

1778

3.27

147

107

1775

1778

12.60

90

1779

3.09

129

39

1779

12.11

41

1780

3.30

151

110

1780

12.08

38

1781 110

1781

12.18

48

1782

4.07

158

1782

12.24

54

1783

3.20

140

86

1783

12.28

58

1784

4.04

156

98

1784

12.12

42

1785

3.17

137

95

1785

12.17

47

1786

3.30

150

103

1786

12.25

55

1787

1787

12.19

49

1788

3.24

145

96

1788

12.23

53

1789

4.06

157

104

1789

12.15

45

1790

3.20

140

95 102

1790

12.14

44

1791

3.26

146

1791

12.28

58

1792

3.17

138

80

1792

12.39

69

1793

3.24

144

75

1793

12.41

71

1794

3.28

148

77

1794

12.28

58

1795

4.02

153

95

1795

12.15

45

1796

3.24

145

100

1796

12.14

44

1797

3.28

148

104

1797

12.21

51

1798

4.02

153

102

1799

4.11

162

1798 1799

12.39

69

1800

3.25

146

77

1800

12.19

49

1801

3.28

148

99

1801

12.35

65

1802

3.14

134

69

1802

12.26

56

1803

3.26

146

90

1803

12.41

71

1804

4.13

165

94

1804

12.23

53

1805

1805

12.38

68

1806

1806

3.10

130

62

1807

4.04

155

155 (continued)

4.3 Long-Term Records of Lake Ice Freeze-Up/Break-Up Dates

151

Table 4.10 (continued) Break-up date

Freeze-up date Year

Month.Day

DOY-NOV

Year

Month.Day

Duration DOY-NOV

Days

1807

12.26

56

1808

3.23

144

88

1808

12.26

56

1809

3.23

143

87

1809

12.11

41

1810

1810

12.31

61

1811

4.02

153

92

1811

12.02

32

1812

3.26

147

115

1812

12.17

47

1813

4.02

153

106

1813

12.07

37

1814

4.12

163

126

1814

12.20

50

1815

4.04

155

105

1815

12.18

48

1816

3.31

152

104

1816

12.38

68

1817

3.17

137

69

1817

12.33

63

1818

4.01

152

89

1818

12.41

71

1819

3.30

150

79

1819

12.30

60

1820

3.11

132

72

1820

12.32

62

1821

3.14

134

72

1821

12.24

54

1822

3.24

144

90 109

1822

12.17

47

1823

4.05

156

1823

12.21

51

1824

3.08

129

78

1824

12.20

50

1825

4.05

156

106

1825

12.32

62

1826

4.10

161

99

1826

12.35

65

1827

3.16

136

71

1827

12.28

58

1828

4.03

155

97

1828

12.42

72

1829

4.10

161

89

1829

12.43

73

1830

3.22

142

69

1830

12.21

51

1831

4.05

156

105

1831

12.30

60

1832

4.08

160

100

1832

12.13

43

1833

4.15

166

123

1833

12.20

50

1834

3.27

147

97

1834

12.28

58

1835

4.10

161

103

1835

12.22

52

1836

4.01

153

101

1836

12.17

47

1837

4.09

160

113

4.10

162

108

1837

12.07

37

1838

1838

12.39

69

1839

1839

12.24

54

1840

1840

12.35

65

1841

4.10

161

96

1841

12.18

48

1842

3.29

149

101 (continued)

152

4 Climate Information from Pre-Nineteenth Century Data and Documents

Table 4.10 (continued) Break-up date

Freeze-up date Year

Month.Day

DOY-NOV

Year

Month.Day

Duration DOY-NOV

Days

1842

12.10

40

1843

3.08

128

88

1843

12.31

61

1844

3.25

146

85

1844

12.22

52

1845

3.22

142

90 110

1845

12.13

43

1846

4.02

153

1846

12.24

54

1847

3.29

149

95

1847

12.28

58

1848

3.26

147

89

1848

12.23

53

1849

3.16

136

83

1849

12.12

42

1850

3.26

146

104

1850

12.20

50

1851

4.01

152

102 135

1851

12.04

34

1852

4.18

169

1852

12.24

54

1853

4.02

153

99

1853

12.15

45

1854

3.09

129

84

1854

12.29

59

1855

3.11

131

72

1855

12.32

62

1856

4.09

161

99

1856

12.27

57

1857

4.07

158

101 104

1857

12.19

49

1858

4.02

153

1858

12.19

49

1859

3.27

147

98

1859

12.17

47

1860

4.08

160

113

1860

12.25

55

1861

Data Courtesy of Yoshimi Fukuma

As mentioned above, Lake Jusan is a brackish lake connected to the Sea of Japan. During the Edo period (1600–1868), people loaded rice and other agricultural products harvested in the Hirosaki Plain onto boats passing along the Iwaki River and transported them through Lake Jusan to consumption areas in western Japan from the Sea of Japan. Therefore, it would have been important to record the freezing and thawing of Lake Jusan every year. Preliminary analysis for the 155-year time series of the freeze-up and break-up dates since 1705 shows large year-to-year variations and long-term trends (Fig. 4.50). Regarding the freeze-up dates, it was the earliest around 1740, and the latest around 1820s. As for the break-up dates, it was the earliest around 1720, and gradually became late until the 1830s. The ice freezing duration of Lake Jusan shows no clear trend for 155 years.

References

153

Fig. 4.50 Ice freeze-up/ break-up dates and freezing duration of Lake Jusan

References Amano, R. (1952). The meteorological observation in Osaka in the years around 1830. Journal of the University of Mercantile Marine Ser, A3, 137–157. (in Japanese). Amano, R. (1953). Meteorological observations in Tokyo during the period 1838–1855. Journal of the University of Mercantile Marine Ser, A4, 167–194. (in Japanese). Arakawa, H. (1954). Fujiwhara on five centuries of freezing dates of Lake Suwa in the central Japan. Arch Meteorol Geophys Und Bioklimatologie, B6, 152–166. Beillevaire, P. (2018). Father Louis Furet, missionary of the Paris Foreign Missions Society: His life and scientific observations on Okinawa (1855–1862). Journal of Geography (Chigaku Zasshi), 127, 483–501. (in English). Demaree, G. R., & Mikami, T. (2000). Some 17th and 18th century Dutch meteorological observations at Deshima, Nagasaki(Japan), seen as a complement to Japanese climatological historical documents. Proceedings of the international conference on climate change and variability, 107–113. Demaree, G., Mikami, T., Tsukahara, T., & Zaiki, M. (2013). The meteorological Observations of the “Vereenigde Oost-Indische Compagnie (VOC)”—What can be learned from them? Historical Geography of Japan (Rekishi Chirigaku), 55–5, 99–106. (in English). Demaree, G. R., Mailier, P., Beillevaire, P., Mikami, T., Zaiki, M., Tsukahara, T., Tagami, Y., & Hirano, J. (2018). The atmospheric oressure observations 1856–1858 by Father Louis Furet, at Naha, Japan. Journal of Geography (Chigaku Zasshi), 127, 503–511. (in English). Fujiwhara, S. (1921). Notes on the climatic variations concluded from the dates of the firest complete freezing of Lake Suwa in Japan. Geografiska Annaler, 3, 358–361. Fukuma, Y. (2018). Making the database of Hirosaki Clan Agency diary and its significance. Journal of Geography (Chigaku Zasshi), 127, 565–568. (in Japanese with English abstract). Geerts, A. J. C. (1875). Observations on the climate at Nagasaki during the year 1872. Trans. Asian Soc. Japan, 3, 63–71. Gray, B. M. (1974). Early Japanese winter temperatures. Weather, 29, 103–107. Grove, J. M. (1988). The Little Ice Age. Methuen. Hirano, J., Mikami, T., Zaiki, M., & Nishina, J. (2018). Analysis of precipitation data at Yokohama, Japan, from 1863 to 1869 observed by J.C. Hepburn. Journal of Geography (Chigaku Zasshi), 127, 531–541. (in English). Hishikari, I. (2017). A history of thermometer in Japan 1660–1910. Chuo Koron Business Publicaion.

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Ishiguro, N. (2001). Homogeneity of the Omiwatari records of lake Suwa as the database for winter temperature estimation. Geographical Review of Japan, 74A, 415–423. (in Japanese with English abstract). Japan Meteorological Agency. (1975). A centennial history of meteorology in Japan (Kishou Hyakunennsi). Meteorological Society of Japan (in Japanese). KNMI Yearbook. (1855). Nederlandsch Meteorologisch Jaarboek 1855. KNMI, 209–286, 290–291. KNMI Yearbook. (1856). Nederlandsch Meteorologisch Jaarboek 1856. KNMI, 293–324. Können, G. P., Zaiki, M., Baede, A. P. M., Mikami, T., Jones, P. D., & Tsukahara, T. (2003). Pre1872 extension of the Japanese instrumental meteorological observation series back to 1819. Journal of Climate, 16, 118–131. Maejima, I., & Tagami, Y. (1983). Climate of Little Ice Age in Japan. Geographical Reports of Tokyo Metropolitan University, 18, 91–111. (in English). Manley, G. (1953). The mean temperature of Central England, 1698 to 1952. Quarterly Journal of the Royal Meteorological Society, 79, 242–261. Manley, G. (1974). Central England temperatures, monthly means 1659 to 1973. Quarterly Journal of the Royal Meteorological Society, 100, 389–405. Mikami, T. (1983). Classification of natural seasons in Japan for summer half years 1783–90 based on the seasonal march of weather. Journal of Geography (Chigaku Zasshi), 92, 105–115. (in Japanese with English abstract). Mikami, T., & Ishiguro, N. (1998). Climate change in the past 550 years reconstructed from freezing records of Lake Suwa. Meteorology Research Note (Kisho Kenkyu Note), 191, 73–83 (in Japanese). Nagavciuc, V., Kern, Z., Ionita, M., Hartl, C., Konter, O., Esper, J., & Popa, I. (2020). Climate signals in carbon and oxygen isotope ratios of Pinus cembra tree-ring cellulose from the Calimani Mountains, Romania. International Journal of Climatology, 40, 2539–2556. Nakatsuka, T., Sano, M., Li, Z., Xu, C., Tsushima, A., Shigeoka, Y., Sho, K., Ohnishi, K., Sakamoto, M., Ozaki, H., Higami, N., Yokoyama, M., & Mitsutani, T. (2020). A 2600-year summer climate reconstruction in central Japan by integrating tree-ring stable oxygen and hydrogen isotopes. Climate of the Past, 16, 2153–2172. Nyomura, Y. (2002). Meteorological observations at lighthouses in Japan. Kisho, 46–3, 36–42. (in Japanese). Parker, D. E., Legg, T. P., & Folland, C. K. (1992). A new daily Central England temperatures series, 1772–1991. Int J Climat, 12, 317–342. Sharma, S., Magnuson, J. J., et al. (2016). Direct observations of ice seasonality reveal changes in climate over the past 320–570 years. Scientific Reports, 6, 25061. Schmidt, V. (1989). Die Sieboldiana Sammlung der Ruhr-Universita¨t Bochum. Acta Sieboldiana III. Harrossowitz Wiesbaden, 461 pp. Stamkart, F. J. (1851). Meteorologische waarnemingen, gedaan op het eiland Decima, bij de stad Nangasaki, op Japan. Breedte5328 459N., Lengte51298 529 beoosten Greenwich. Verhandelingen Der Eerste Klasse Van Het Koninklijk Nederlandsch Instituut Van Wetenschappen, Letterkunde En Schoone Kunsten Te Amsterdam, Third Series, 4, 215–234. Sternberg, L. (2009). Oxygen stable isotope ratios of tree-ring cellulose: The next phase of understanding. New Phytologist, 181, 553–562. Tsukahara, T. (1998). Scientific analysis and research of the meteorological data in Japan during 1827–1828 observed by von Siebold. Annual Report of Fukutake Science and Culture Foundation, 1998, 63–73. (in Japanese). Yonenobu, H., & Eckstein, D. (2006). Reconstruction of early spring temperature for central Japan from the tree-ring widths of Hinoki cypress and its verification by other proxy records. Geophysical Research Letters, 33, L10701. Yoshimura, M. (2013). Making the database of weather record in old diaries and its significance. The Historical Geography (Rekishi Chirigaku), 55–5, 53–68. (in Japanese with English abstract).

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Zaiki, M., Konnen, G. P., Tsukahara, T., Jones, P. D., Mikami, T., & Matsumoto, K. (2006). Recovery of the nineteenth-century Tokyo/Osaka Meteorological data in Japan. International Journal of Climatology, 26, 399–423. Zaiki, M., Kimura, K., Tomatsuri, Y., & Tsukahara, T. (2014). Temperature variability in Hakodate based on the 19th century meteorological records taken at the Russian consulate and the data from Japan Meteorological Agency. Geographical Studies (Chirigaku Ronshu), 89–1, 20–25. (in Japanese). Zaiki, M., Mikami, T., Hirano, J., Grossman, M., Kubota, H., & Tsukahara, T. (2018). Climate characteristics in the south-eastern Kanto region of Japan derived from mid to late 19th century meteorological records. Journal of Geography (Chigaku Zasshi), 127, 447–455. (in Japanese with English abstract).

Chapter 5

Climate Reconstructions for Historical Periods

Abstract This chapter presents case studies of climate reconstructions for historical periods based on the climate information from pre-nineteenth century data and the documents described in the previous chapter. The first part presents examples of studies that reconstruct typhoon tracks and intensity from early meteorological observation records and diary weather records. The second part presents studies that reconstruct summer and winter temperature fluctuations mainly from diary weather records. Finally, unique climate reconstructions from full-flowering date record for cherry trees in Kyoto over the past 1200 years and pollen analysis in the highland moors in central Japan over the past 6000 years are demonstrated, Keywords Climate reconstruction · Typhoon tracks and intensity · Meteorological disaster · Great famines · Full-flowering date records

This section presents case studies of climate reconstruction for historical periods based on the climate information from pre-nineteenth century data and the documents described in Chap. 4. In the first part, examples of studies that reconstruct typhoon tracks and intensity from early meteorological observation records and diary weather records are presented, and in the second part, studies that reconstruct summer and winter temperature variations mainly from diary weather records are presented.

5.1 Attempts to Reconstruct Typhoon Tracks and Intensity from Early Weather Records JMA (Japan Meteorological Agency) has published tracks of all typhoons that have occurred since 1951. For example, Fig. 5.1 shows the track of Typhoon No. 15 which made landfall in Japan in mid-October 1951. RSMC Tokyo—Typhoon Center provides text data of all typhoon locations (latitude and longitude), which is downloadable from https://www.jma.go.jp/jma/jma-eng/jma-center/rsmc-hp-pub-eg/bes ttrack.html. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 T. Mikami, The Climate of Japan, Advances in Global Change Research 77, https://doi.org/10.1007/978-981-99-5158-1_5

157

158

5 Climate Reconstructions for Historical Periods

Fig. 5.1 An example of Typhoon tracks: A case of Typhoon No. 15 in mid-October, 1951. From the JMA website for tropical cyclone tracks

However, there was no official track map for typhoons before 1950. In Japan, the first official weather map by the Japan Meteorological Agency was published on March 1, 1883, as shown in Fig. 5.2, and no official weather maps exist before that date. However, as described in Sect. 4.1.6, meteorological observation began in Japan in 1877 at more than 20 lighthouses across the country, and daily barometric observation records are available. By combining these atmospheric pressure observation data with weather records in diaries, it is possible to reconstruct weather maps prior to 1883. In particular, when a typhoon makes landfall in Japan, the pressure gradient near the center of the typhoon increases, making it possible to accurately estimate and reconstruct the typhoon track. Furthermore, even before the start of lighthouse meteorological observation, if a typhoon passed near a point where initial meteorological observation records were kept, the typhoon track might be estimated based on the rapid decrease in atmospheric pressure. Therefore, this section introduces an attempt to reconstruct typhoon tracks and typhoon weather maps by focusing on the case of a notable typhoon that made landfall in Japan before the start of official JMA meteorological observations.

5.1 Attempts to Reconstruct Typhoon Tracks and Intensity from Early …

159

Fig. 5.2 The first official weather map by JMA at 6:00 on March 1, 1883. Source Japan Meteorological Agency

5.1.1 Reconstruction of the 1882 Typhoon Weather Map Using Lighthouse Observation Data As mentioned above, in 1883, when the first weather map was published in Japan, there were only 20 meteorological observatories under the supervision of JMA in the whole country, while lighthouse meteorological observations were conducted at 40

160

5 Climate Reconstructions for Historical Periods

observatories in 1883, twice as many as those of JMA observatories (see Fig. 4.36). Therefore, we attempted to reconstruct the weather map for August 5, 1882, when a typhoon hit Japan and caused severe damage; this was at the time when lighthouses made meteorological observations eight times a day. The Japan Weather Archives (Nihon Kisho Shiryo) contains detailed descriptions of the chronology of storms from the seventh century to the end of the nineteenth century based on various historical documents. Among them, we noted a description of a storm and flood disaster in western Japan on August 5, 1882. According to the report, Tokushima, on Shikoku Island, one of the four main islands of Japan, suffered flooding on that day, with water levels reaching approximately 2.4 m in the city’s main streets due to a heavy rainstorm. In Kobe City, the storm began in the afternoon, and the tidal surge reached a height of more than 4.5 m at sea, damaging more than 50 houses. It is also reported that in Osaka, the water level of the Yodo River, a major river, rose more than 3.6 m, causing two levees to break. We, therefore, created sea level pressure distribution maps for 15:00 and 18:00 on August 5, 1882, when the typhoon is estimated to have made landfall (Fig. 5.3). The data used were the meteorological observation records of 40 lighthouses and the observation records of JMA’s Kochi Meteorological Observatory. Kochi Meteorological Observatory had just been established in March 1882, and we were able to obtain the meteorological observation records for August. At the lighthouse, eight observations per day were made from 1882, and the pressure data at 15:00 and 18:00, when the typhoon was estimated to have made landfall, were used to perform barometric sea level correction. The isobaric lines were automatically drawn using the contour plotting software “Surfer.” The center of the typhoon was located near Kochi at 15:00 and near Nabeshima in the Seto Inland Sea at 18:00. Thus the speed of the typhoon is estimated to have been 32 km per hour, assuming that it passed through these two points in 3 h (Fig. 5.4).

Fig. 5.3 Sea level pressure distribution maps at 15:00 (left) and 18:00 (right) on August 5, 1882. Isobaric contours were created from 40 lighthouse meteorological data and JMA Kochi observation data

5.1 Attempts to Reconstruct Typhoon Tracks and Intensity from Early …

161

Although the center of the typhoon is estimated to have passed near these two points, information on the change in wind direction would be useful for reconstructing an accurate track. Therefore, we examined changes in wind direction at Kochi and Nabeshima on August 5. The wind direction at the JMA Kochi weather station was NW at 15:30 and changed to S at 21:30, indicating that the center of the typhoon passed east of Kochi. On the other hand, the wind direction at Nabeshima Lighthouse changed from NE at 15:00 to N at 18:00 and WSW at 21:00. Thus, the center of the typhoon is estimated to have passed just east of Nabeshima. Figure 5.5 shows the weather distribution over Japan on August 5, when the typhoon made landfall, and on the following day, August 6, using HWDB (see Sect. 4.2.3). The rainfall from the 5th to the 6th was observed over a wide area from western Japan to eastern Japan. Therefore, we inferred that the typhoon passed along the track indicated by the red dashed line. By combining the lighthouse weather observation records and the HWDB weather distribution map, we can reconstruct typhoon tracks in the nineteenth century before the start of JMA official weather observation.

Fig. 5.4 Expanded SLP contour map at 18:00 on August 5, 1882. Red circles indicate the location of lighthouses

162

5 Climate Reconstructions for Historical Periods

Fig. 5.5 The weather distribution over Japan on August 5 (left), when the typhoon made landfall, and on the following day, August 6 (right). Source Historical Weather Database

5.1.2 Reconstruction of the Intensity and Track of the 1828 Siebold Typhoon Until the discovery of nineteenth-century meteorological observation data from Dejima, Nagasaki, the track and intensity of the Siebold Typhoon, which made landfall in Nagasaki in southwestern Japan in the 1820s and is believed to have caused the largest damage in history, were not quantitatively evaluated. This section describes a methodology for reconstructing typhoons in historical times through the analysis of a case study of Typhoon Siebold, which made landfall in 1828.

5.1.2.1

Siebold Incident

From the evening of September 17, 1828 to the following morning, northwestern Kyushu in southwestern Japan was hit by a severe storm and high tide. As a result, the Dutch ship Cornelius Houtman, which was anchored in Nagasaki Port at the time, ran aground on the opposite shore, and a large number of Japanese maps and other items prohibited from leaving the country were found on board, leading to the “von Siebold Incident” in which Siebold and others who owned these items were captured and severely punished. Various historical documents and observations record that a powerful typhoon (later called the Siebold Typhoon) that made landfall near Nagasaki Port at midnight that day was the main cause of the strong winds that stranded ships at anchor. Here we will analyze and discuss the Siebold Typhoon, which is estimated to have been the most powerful typhoon in the past 300 years (Takahashi, 1962), including the reality of the severe disaster it brought, estimation of its size and typhoon track, and comparison with similar typhoons in recent years. Konishi (2010) provides a detailed analysis of the damage caused by the Siebold Typhoon and, based on historical documents from the Saga Domain, estimates the death toll in northern Kyushu around 13,000 to 19,000 people. In terms of the number of victims, it was a far more severe disaster than the Ise Bay Typhoon, which made

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landfall on the Kii Peninsula in late September 1959, causing storm surge damage and leaving 5098 people dead or missing. The force (strength) of a typhoon can be estimated from the atmospheric pressure and wind speed near its center. Today, we can accurately determine the central pressure, wind speed, typhoon track, etc., based on detailed meteorological observations at meteorological stations around the country and high-resolution meteorological satellite data. However, the strength of the Siebold Typhoon was difficult to estimate accurately because there was no official meteorological data from JMA observatories when this typhoon hit Kyushu in 1828. Therefore, our research team attempted to estimate the strength of the Siebold Typhoon based on an analysis of meteorological observation data at Dejima, Nagasaki in collaboration with Dutch meteorological researchers. Takahashi (1962) estimated that the Siebold Typhoon was the strongest in the past 300 years, with a central pressure of 900 hPa and maximum wind speed of 50 m/ sec, based on the damage (number of deaths, total destruction, etc.). The strongest typhoon during the period for which JMA observation records are available was the Muroto Typhoon that made landfall near Cape Muroto in Kochi Prefecture on September 21, 1934, with a minimum pressure of 911.6 hPa and a maximum wind speed of 60 m/sec near the center at the time of landfall. If the pressure and wind speed at landfall of Siebold Typhoon exceeded those of Muroto Typhoon, it may have been the strongest typhoon in history.

5.1.2.2

Meteorological Observation by Von Siebold

Actually, the atmospheric pressure data at the time of the typhoon attack was described in detail by Siebold in a letter he sent to his mother in 1829, including the intensity of the storm at the time and the barometer readings (Nagayama, 1954). According to the letter, there was a danger of the house collapsing due to the strong winds, so the meteorological observation instruments on the second floor of the building were moved to a safer location downstairs, and the barometer reading observed just before the collapse was 28.1 inches (951.6 hPa). As described in Sect. 4.1.1.2, meteorological observations by Dutch doctors, including von Siebold, had been conducted almost continuously since 1819 at Dejima, Nagasaki, and data on atmospheric pressure and wind at the time of typhoon hits were recorded by von Siebold in detail. Among them, a record from September 1828, including the date for the typhoon hit, is worth noting (Fig. 5.6). The red dashed box in Fig. 5.6 shows the records for September 17 and 18, when the typhoon made landfall. Observations include barometric pressure (in inches), temperature (in Fahrenheit), humidity (%), wind direction/force, and precipitation, with a note column at the end. Observations were made three times a day and are only indicated as morning, noon, and evening. Previous investigations by our research team have shown that morning corresponds to 6:20, noon to 12:20, and evening to 22:20 by JST (see Sect. 4.1.1.2). Here, we will focus on atmospheric pressure as an indicator of typhoon force and clarify its temporal variation.

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Fig. 5.6 A handwritten meteorological observation record by von Siebold in September 1828. Source The Siebold Archive, Faculty of East Asian Studies, Ruhr University Bochum, Germany; shelfmark 1.142.002

However, since the unit of observed atmospheric pressure is inches (scale of mercury columns), it is necessary to convert it to hPa, which is currently used. In addition, there was a systematic error in the atmospheric pressure data during this period making readings 7 hPa lower than they should have been, and this was also corrected (see Sect. 4.1.1.2). Furthermore, a note in German at the end of the observation record for the 17th was deciphered: “In the evening, storm from SE, around 12 o’clock typhoon, after 12 o’clock barometer 28.4 [inches].” Correcting for 28.4 inches and converting to the proper units yields 964.84 hPa, for around midnight.

5.1.2.3

Changes in the Air Pressure Before and After the Typhoon Landfall

The above-mentioned factors are illustrated in Fig. 5.7, which shows the atmospheric pressure changes before and after Typhoon Siebold made landfall in Nagasaki on September 18, 1828. For comparison, the pressure changes in Nagasaki before and

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after Typhoon No. 9119, which made landfall in Nagasaki Prefecture on September 27, 1991 are indicated to overlap with Siebold Typhoon. Typhoon No. 9119 caused strong wind damage in the Chugoku region (Southwestern Japan) before moving out over the Sea of Japan, and also caused devastating damage to pre-harvest apples in Aomori Prefecture (Northern Japan) which afterward made landfall again in southern Hokkaido. The atmospheric pressure in Nagasaki began to decrease gradually in the afternoon of September 17, but rapidly dropped after 10:00 p.m. in the evening. At midnight, just before Siebold moved the barometer downstairs, it reached 964.84 hPa, the lowest pressure ever recorded. The subsequent observation record was 1002.6 hPa at 6:00 a.m. on the 18th, and there was no record at the nearest approach of the typhoon after midnight. Therefore, assuming that the two-hour pressure reduction from 10:00 p.m. to midnight continued, we can estimate that the pressure dropped to 930 hPa at 2:00 a.m., when the typhoon made its closest approach to Nagasaki. If the time of the closest approach was 1:30 a.m., the minimum pressure would have been 940 hPa. This pressure is lower than that of Typhoon No. 9119 in 1991 and is comparable to that of the Ise Bay Typhoon that made landfall on the Kii Peninsula on September 15, 1959, killing over 5,000 people, and to that of the Muroto Typhoon that made landfall on Kochi Prefecture on September 21, 1934. Konishi (2010) estimated the maximum wind speed near the center of the Siebold Typhoon at landfall to be 55 m/ sec. In any case, the landfall and approach of Typhoon Siebold caused the atmospheric pressure to drop to 930 to 940 hPa in Nagasaki, and the storm and storm surge caused

Fig. 5.7 Variations in air pressures at Nagasaki before and after the landfall of Siebold Typhoon (Sep.1828) as compared with Typhoon No. 9119 (Sep.1991)

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the collapse of houses and capsizing of ships, resulting in unprecedented damage in Kitakyushu, with more than 10,000 deaths. Based on the pressure distribution of typhoons observed in recent years, Konishi (2010) estimates that the central pressure of Typhoon Siebold, which made landfall in western Kyushu, about 30 km from Nagasaki, was between 910 and 940 hPa, with an estimated minimum pressure of 950 hPa at landfall in Nagasaki at 2:00 am. The central pressure of Typhoon Siebold is estimated to have been between 910 and 940 hPa.

5.1.2.4

Reconstruction of the Siebold Typhoon Track

The author’s research team has been collecting daily weather records from diaries kept in various parts of Japan during the Edo period (1600s–1860s) and using them to reconstruct the climate of historical periods when meteorological observation records were not available (Sects. 4.2 and 5.2). In addition, an attempt has been made to code the collected daily weather conditions and display them as weather symbols on a map of Japan (Sect. 4.2.3). By mapping and tracking these daily nationwide weather conditions, the movement of clear and rainy areas can be visualized, and the movement of fronts, low-pressure systems, typhoons, etc. that bring rainfall can be estimated. The weather distribution across Japan after Typhoon Siebold made landfall is shown on the map, and the typhoon track can be estimated by tracking its movement. On September 17 in Kitakyushu, wind and rain began to intensify around noon, and the wind increased in the night, becoming a storm after 23:00. The Siebold observation record at around midnight, when the date changes, states that a SE storm blew. The next day, the 18th, the weather was rainy nationwide, but in the Kinki region, there were occasional wind and rain showers from mid-morning to early afternoon, while the wind subsided in the evening and the sky became clear. However, strong winds temporarily blew at Kanazawa on the Sea of Japan side in Hokuriku around 13:00. On the other hand, in Aomori Prefecture (Hirosaki), where Typhoon No. 9119 in 1991 caused strong wind damage, there are no records of strong winds from Typhoon Siebold, only those of occasional rain showers. The typhoon then moved in the ENE direction, and the Hirosaki Domain Edo Diary written in Edo (Tokyo) states that at around 22:00, Edo was hit by torrential rain and strong wind from the South, whereas the next morning, the 19th, was clear and hot. Therefore, it is presumed that Edo was enveloped in the tropical hot air brought by the typhoon as it passed over the city. Based on the above-mentioned process, we estimate the track of Siebold Typhoon as indicated by the yellow dashed arrows in Fig. 5.8. The landfall point of Siebold Typhoon at Kitakyushu was almost the same as that of Typhoon No. 9119 in 1991, although Siebold Typhoon did not pass over the Sea of Japan, instead moved in the ENE direction over Honshu, passed north of Edo (Tokyo), and then moved into the Pacific Ocean.

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Fig. 5.8 The Siebold Typhoon track (broken yellow line) reconstructed from several weather records in local diaries. The black line shows Typhoon No. 9119 track in September 1991. The white arrows indicate wind direction

5.1.3 Variability of Typhoons that Hit Japan After the Mid-Nineteenth Century Typhoons are defined as tropical cyclones that develop in the northwestern Pacific Ocean. Kubota et al. (2021) collected nineteenth-century meteorological observation records in Japan and the Philippines and ship logbooks of meteorological observations by European and American vessels in the ocean around the middle of the nineteenth century, all predating the first official typhoon records by the Japan Meteorological Agency (JMA). As station data for Japan, they used the official JMA meteorological observation data since 1873 and the lighthouse meteorological observation data since 1877 as described in Sect. 4.1.6. In addition, although not fixed points, they also used meteorological observation data from ship logbooks recorded by European and American navy ships that came to Japanese ports in the 1850s and 1860s. Figure 5.9a shows the variation in the number of typhoons that made landfall in Japan during the 143-year period from 1877 to 2019, and Fig. 5.9b shows the variation in the APDI index, which indicates the annual average of the strength of typhoons that made landfall in Japan. On average, three typhoons made landfall in Japan each year, and in some years, such as 1950, ten typhoons made landfall, while in other years, such as 1973, 1984, and 2000, no typhoons made landfall.

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Fig. 5.9 a Annual Typhoon (Tropical Cyclone) landfall numbers in Japan from 1877 to 2019. b Annual power dissipation index (APDI) for Typhoon landfall in Japan from 1877 to 2019. From Kubota et al. (2021)

On the other hand, a clear periodicity in typhoon intensity (APDI) is observed: the frequency of strong typhoons increases around 1900, in the 1910s, from the 1930s to the 1960s, and after the 1990s. In particular, it is of interest to note that there is a marked tendency for stronger typhoons to make landfall between 1977 and 2019, which may be related to global warming. Data on all typhoons that made landfall in Japan between 1877 and 2019 (landfall location, minimum pressure, wind speed, etc.) are available on the JCDP (Japan-Asia Climate Data Program) web page (https:// jcdp.jp/reconstructed-typhoon-data/). Figure 5.10 shows the location of the closest meteorological observation points to typhoons that made landfall in Japan during the period 1877–2019, by longitude (a) and latitude (b). From Fig. 5.10a, we can see that the landfall location of typhoons has moved eastward since the late nineteenth century. On the other hand, as shown in Fig. 5.10b, the landfall location of typhoons tends to move northward from the 1910s to 1930s and after the 2000s, and southward in the 1970s. Focusing on the period from 1977 to 2019, typhoon landfalls clearly tend to move northward and eastward. This indicates that typhoons making landfall in Japan in recent years tend to be displaced in a northeasterly direction. This displacement trend of typhoon landfalls is likely to be caused by atmospheric circulation changes in the northwestern Pacific Ocean. Recent studies have indicated that the peak intensity of typhoons (tropical cyclones) increases in the Northwest Pacific Ocean after 1980 (Kossin et al., 2014; Sun et al., 2019). In addition, summer typhoons (tropical cyclones) are known to move along the western edge of the Northwest Pacific High (WNP); Nagata and Mikami

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Fig. 5.10 Longitude (a) and latitude (b) of the nearest station during Typhoon landfall in Japan. From Kubota et al. (2021)

(2017) found that the WNP subtropical high was displaced northwestward in the first half of the twentieth century (1900–1950), and southwestward in the second half of the twentieth century (1950–2000), supporting the findings of Kubota et al. (2021) of a northwesterly shift in typhoon landfall locations in the early twentieth century and a southwesterly shift in the late twentieth century.

5.2 Climate Reconstructions from Diary Weather Records Since the Eighteenth Century An attempt to reconstruct the long-term climate variations in historical periods from daily weather records in diaries is a research method unique to Japan and not found anywhere else in the world (e.g., Mikami et al., 2015). As mentioned in the previous section, since ancient times, Japanese people, both public and private, have customarily recorded daily weather conditions in diaries, and some diaries have been kept for as long as 100 to 200 years by local domains and families (see Sect. 4.2). In addition, the high resolution of the daily time scale makes it possible to determine the frequency and rate of occurrence of specific weather conditions on a monthly and seasonal basis. Based on these data, many attempts have been made to reconstruct monthly and seasonal mean temperatures and precipitation in Japan (e.g., Hirano & Mikami, 2008, 2015; Hirano et al., 2012, 2013, 2022; Maejima & Tagami, 1983;

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Mikami, 1983, 1987, 1988, 1992a, 1992b, 1993, 1996, 1999, 2002, 2008, 2012; Mizukoshi, 1993; Yamamoto, 1970; Zaiki et al., 2012).

5.2.1 Winter Temperature Reconstruction Based on the Snowfall Ratio Obtained from Diary Weather Records The earliest study to use snowfall ratios calculated from diary weather records for long-term climate reconstructions for winter in Japan was probably done by Yamamoto (1967). He focused on the daily weather records in the Kanmon Gyoki, a fifteenth century (1416–1444) imperial diary kept in Kyoto, and found a statistically significant correlation between the snowfall ratio (the ratio of the number of snowfall days divided by the number of precipitation days) and the date of full bloom of cherry trees during the five-month period from November to March. Since the date of the full bloom is closely related to winter temperature fluctuations, the snowfall ratio was found to be an accurate indicator of winter climate change. Yamamoto (1967) also used several different diaries to extend the period of climate reconstruction by snowfall ratio. However, when combining them to discuss longterm climate changes, attention should be paid to the accuracy (reliability) of weather descriptions by diaries. There have been many attempts to reconstruct climate variations from diaries since the seventeenth century and later. Daily weather records in old diaries are suitable for long-term winter climate reconstructions using snowfall ratios. As an example, we present here a study by Hirano et al. (2012) of winter temperature reconstruction since the 1830s using diaries in northeastern Japan. The study area, Kawanishi, is geographically located in the transition zone between the Sea of Japan and Pacific Ocean climates in northeast Japan and is a suitable site for studying winter climate variability in Japan because the number of snowfall days in winter tends to increase during cold winters and decrease during warm winters (Fig. 5.11). The daily weather data used in this study were extracted from the Takeda Gen’emon Diary recorded from Kawanishi Town, Yamagata Prefecture, which is a valuable source of data written by several generations of the Takeda family for 151 years from 1830 to 1980. In addition, the diary is continuous from 1830, when no official weather data were available, to 1980, when JMA official weather records were available, and the weather records in the diary and the JMA official weather records overlap for a long period of 91 years (1889/90–1979/80). Therefore, the temperature variation estimated from the diary snowfall ratio can be verified by comparing it with the JMA observed temperature. Figure 5.12 shows the relationship between the snowfall ratio (%) calculated from the Takeda Gen’emon Diary weather records and the average winter (Dec.-Feb.) temperature at the JMA Yamagata Meteorological Observatory. It reveals that the

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Fig. 5.11 Location of Kawanishi town where the diary weather records (1830–1980) were documented. From Hirano et al. (2012)

higher the snowfall ratio, the lower the average winter temperature. The correlation coefficient between the two is −0.75 (p < 0.01), indicating a statistically significant relationship. Therefore, linear regression was used to estimate the average winter temperature at Kawanishi since 1830/31 by substituting the snowfall ratio obtained from the weather records of the diaries. In addition, for the purpose of understanding the regional representativeness of the estimated winter mean temperatures, a correlation coefficient distribution chart (abbreviated) between the estimated winter mean temperatures at Kawanishi and the winter mean temperatures in various regions of Japan was created, which revealed that the correlation was higher in the central to western regions of Japan. Fig. 5.12 Relationship between the mean winter temperature in Yamagata and the snowfall ratio computed from the diary weather records. From Hirano et al. (2012)

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Fig. 5.13 Relationship between estimated winter temperature in Kawanishi and the WJT temperature (Zaiki et al., 2006) during 1830/31–1979/80. From Hirano et al. (2012)

To confirm this result, we examined the relationship between the winter (DJF) mean temperature of the West Japan Temperature (WJT) series shown in Fig. 4.18 (Zaiki et al., 2006) and the estimated winter temperature at Kawanishi for the 130 years when both sets of data are available (Fig. 5.13). The results showed that the correlation coefficient between the two was 0.72 (p < 0.01), indicating a high positive correlation. This suggests that both the Kawanishi and WJT temperature estimates are accurate. As shown in Fig. 5.14, the average winter temperatures estimated from snowfall ratios using the Kawanishi diaries show a long-term trend of increasing temperatures since 1830. However, a temporary short warm period can be found in the reconstruction from the middle of the nineteenth century. The warm years from the late 1841s to the early 1850s are consistent with the analysis by Zaiki et al. (2006), which discussed the variation of West Japan Temperature based on early nineteenth-century meteorological observation data. This section has demonstrated methods for reconstructing the winter climate of historical periods from snowfall ratios described in diaries and discussed the characteristics of the estimated temperature time series. In recent years, climate change characterized by global warming has attracted worldwide attention, and studies have been conducted in various parts of the world to discuss the variation of snowfall ratio in terms of winter climate change during the period when meteorological observation data are available (e.g., Feng & Hu, 2007; Jennings et al., 2018; Knowles et al., 2006; Serquet et al., 2011). However, a research method such as the one described in this section, which calculates snowfall ratios from weather records in diaries of historical periods and statistically estimates average winter temperatures to clarify long-term variations, is original and unique to Japan.

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Fig. 5.14 Variations in mean winter temperatures in Kawanishi reconstructed from diary weather records (1830/31–1979/80) combined with JMA observation data (1889/90–2008/09). From Hirano et al. (2012)

5.2.2 Winter Monsoon Climate Reconstructions from the 1840s-1850s Based on Early Meteorological Data and Historical Documentary Records In Sect. 5.2.1, a case study of reconstructing average winter temperatures from snowfall ratios based on diary weather records at a single location was presented. This section will introduce a study by Hirano et al. (2022), who reconstructed the winter monsoon climate around Japan in the middle of the nineteenth century by combining multiple diary weather records and early meteorological observations in relation to the variation of the atmospheric circulation field on a pan-East Asian scale. This study is unique in that it uses winter monsoon outbreak days (WMDs) as an indicator of the intensity of the winter monsoon around Japan. The idea of this study is based on the winter pressure pattern of “high in the west and low in the east,” as described in Sect. 2.2.2. In winter, the Japanese archipelago is wedged between the Siberian High in Eurasia to the west and the Aleutian Low to the east, with isobars aligned vertically, and a northwesterly monsoon over the Sea of Japan bringing snowfall to areas on the windward side of the mountain (see Figs. 2.12 through 2.15). In other words, winter monsoon outbreak days (WMDs) are defined as days when the weather as recorded in dairies at the two locations on the Sea of Japan side (Hirosaki and Kawanishi) shown in Fig. 5.15 is snowy and the temperature in Tokyo (then Edo) on the Pacific side is below normal values (colder).

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Fig. 5.15 Location of the daily weather records, Lake Suwa, and the temperature records used in this study. From Hirano et al. (2022). Blue text and arrows are additions by Mikami)

First, the relationship between the winter precipitation distribution over the Japanese archipelago corresponding to the WMDs and the SLP and 850-hPa atmospheric circulation field in the Northern Hemisphere was clarified for the period when meteorological observation data were available (1968/69–1979/80). Then, WMDs for the mid-nineteenth century, when meteorological observation data were not available, were obtained from diary transcription records and early temperature data. As shown in Figs. 5.16 and 5.17, the WMDs for the years, when the winter monsoon was strong (e.g., 1839/40, 1840/41, 1841/42) and those when the winter monsoon was weak and the winter was mild (e.g., 1844/45, 1847/48, 1853/54), were estimated. Daily scale analysis allows us to determine intra-seasonal variations in monsoon intensity during winter (December-February). For example, the frequency of WMDs in 1853/54 was unusual, being high during December but rarely occurring after January. Also during this winter, Lake Suwa was recorded as an open lake without freezing, indicating that the winter monsoon outbreak was weak in the latter half of the winter and it was warm. As an indicator of the strength of the winter pressure pattern of “high in the west and low in the east,” the pressure difference between Beijing in the west and Tokyo in the east was obtained from early meteorological observation records, and intra-seasonal variations during the winter months of December to February were

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Fig. 5.16 Interannual variations in the frequency of winter monsoon outbreak days (WMDs) for the years 1839/40–1853/54. Blue dots indicate Lake Suwa’s open-lake years. From Hirano et al. (2022)

Fig. 5.17 Winter monsoon outbreak days (WMDs) for the years 1839/40–1853/54. The blue dots indicate WMDs, the red dots indicate non-WMDs, and the black dots indicate days with no data. From Hirano et al. (2022)

examined for the 1850s (Figs. 5.18 and 5.19). The results show that in the abovementioned winter of 1853/54, the pressure difference between Beijing and Tokyo and the daily variations were large and the winter monsoon break was active in December, but after mid-January, the pressure difference between Beijing and Tokyo became less variable and the daily amplitude became smaller, indicating that the monsoon activity weakened. Thus, by analyzing diary weather records together with early meteorological observation data, it is possible to evaluate more objectively the actual state of winter climate change in the historical period.

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Fig. 5.18 Location of the early instrumental SLP records used in this study. From Hirano et al. (2022. Blue text and arrows are additions by Mikami)

Fig. 5.19 Temporal variations in surface pressure differences between Beijing and Tokyo (∆SLP B-T) and winter monsoon outbreak days (WMDs) for a 1850/51, b 1851/52, c 1852/53, and d 1853/ 54. From Hirano et al. (2022)

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5.2.3 Summer Temperature Variations Reconstructed from Precipitation Frequency: The Case Studies of Tokyo and Hiroshima In the previous section, we described an attempt to estimate average winter temperatures and to reconstruct long-term climate reconstructions for historical periods by obtaining monthly and seasonal snowfall ratios computed from snowfall records described in diaries. In this section, we focus on rainy weather recorded in diaries and estimate average temperatures based on summer rainfall frequencies. As case studies, we introduce attempts to reconstruct the mean July temperature in Tokyo from 1721 to 2020 and the mean July and August temperatures in Hiroshima from 1779 to 2015. Estimation of summer temperatures from rainfall frequency basically relies on the assumption that days with rainfall have lower average temperatures than those without rainfall (that is, sunny and cloudy days). If the weather changes rapidly from sunny to rainy in a single day, the correlation with the average temperature would not be high. Therefore, when reconstructing summer temperatures from rainfall frequencies, it is essential to select regions and seasons where the correlation between the two is high.

5.2.3.1

A Case Study of Tokyo: 1721–2020

A number of historical documents suggest that the climate of Japan during the eighteenth and nineteenth centuries, which corresponds to the latter half of the Little Ice Age, may have been cooler and wetter, especially in summer, than current climatic conditions. For example, in the eighteenth and nineteenth centuries, famines were frequent from the Tohoku region (northeast Japan) to the central and southwestern regions of the country. Most of the great famines in Japan were caused by rice crop failures due to cool summers and wet weather conditions (e.g., Kondo, 1985; Mikami, 1987, 1988, 1999; Yaji & Misawa, 1981). Therefore, quantitative assessment of climate variability and its change during the Little Ice Age is important for predicting future climate change. Statistical analysis combining meteorological data and proxy records is necessary to clarify long-term variations in temperature and precipitation from decadal to centennial scales. For example, meteorological data from Tokyo have only been available for approximately 150 years since the JMA Tokyo Meteorological Observatory was established in 1875. Prior to that date, the continuous instrumental and meteorological data needed to discuss decadal climate change and variability in Japan was largely lacking. Therefore, reconstructing long-term temperature series in an objective and quantitative manner based on historical proxy records would be important. Among the many historical data to reconstruct climate changes in Japan during the Little Ice Age, continuous weather records described in old diaries would be most

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useful (e.g., Maejima & Tagami, 1983, 1986; Mikami, 1987, 1988, 1992a, 1992b). In this section, I have updated Mikami (1996) to clarify the decadal variation of summer temperatures in Tokyo from 1721 to 2020 by combining the observation data and weather records in old diaries. Also analyzed are the long-term trends and variability that appear in the temperature time series. Figure 5.20 shows variations in summer temperatures for Tokyo from June to August. The black line shows the secular change of the monthly mean temperature for each month, and the red line shows the 11-year running means. The most striking feature of these temperature trends is probably the low-temperature period at the beginning of the twentieth century and the subsequent upward trend. The temperatures in July show larger interannual variations (standard deviations) than those in June and August, and the upward trend of temperatures in June and July has become smaller since 2000, which may have been caused by the relocation of the observation site in December 2014 (see Sect. 3.1.1). Fig. 5.20 Summer temperature variations in Tokyo from 1876 to 2020. The red line shows 11-year running means

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The slightly different trends among the three-month summer temperature time series may be due to the different mechanisms of the relationship between temperature and atmospheric circulation in each month. From a climatological point of view, the main characteristics of synoptic fields in the summer months are the strength of the Okhotsk High (blocking high) in June and July, the displacement and activity of the polar frontal zone in July, and the northwestward expansion of the North Pacific High (subtropical anticyclone) in July and August. In considering temperature trends in Tokyo since the 1940s, attention should be paid to the effects of the urban heat island effect in addition to recent anthropogenic greenhouse effect-induced global warming (see Sect. 3.4). The above-mentioned meteorological data for the past 145 years is not sufficient to discuss decadal to centennial variations in summer temperatures in Tokyo. Therefore, we attempted to reconstruct Tokyo summer temperatures from early diary weather records. The data used in this study are the daily weather records in the diary of the Ishikawa family in the western suburbs of Tokyo, which has been kept for generations since 1721. The Ishikawa family was a farming household in Hachioji city, located in the western suburbs of Tokyo, but they were also samurai warriors, half of whom were on defense duty under the orders of the Tokugawa Shogunate during the Edo period. Figure 5.21 shows a sample of the Ishikawa Diaries, in which the area enclosed by the red dashed line corresponds to the period from October 25 to November 5, 1739 (Lunar calendar converted to Gregorian calendar). The diary is written vertically in kanji (Chinese characters) in the Japanese style, from right to left, and each line describes the weather and farming activities of the day. The original records of the diaries are preserved in the Hachioji Historical Museum, and the diaries from 1720 to 1912 have been typeset and published. Based on this weather data, Yoshida (1987) symbolized the daily weather from 1721 to 1941 and compiled it as a weather diagram (Fig. 5.22). Mikami (1996) attempted to estimate summer temperatures in Tokyo since 1721 using this weather diagram. Actually, Taguchi (1951), having noted this valuable record, transcribed daily weather records for 222 years from 1721 to 1941 from the original records of the Ishikawa Diary and stored them in the library of the Japan Meteorological Agency (Tokyo). In general, hot summers in Japan are characterized by high temperatures and dry, sunny weather due to a strong subtropical anticyclone. On the other hand, cool summers are usually cloudy and rainy due to the influence of a stagnant polar front or a passing extratropical cyclone. This suggests a high correlation between the number of rainy days and average summer temperatures. Fortunately, the Ishikawa Diaries and the JMA Tokyo meteorological observation data overlap for 65 years from 1876 to 1940, allowing us to compare the two data during this period. We therefore first compared the number of rainfall days in the Ishikawa Diaries and the JMA data. In the JMA data, a rainfall day is defined as one in which the daily precipitation exceeds 1 mm. The average number of rainy days in June, July, and August in the Ishikawa Diaries for the overlapping period (1876–1940) was 9.2, 8.4, and 7.7, respectively, while that in the JMA data for the same months was 10.8, 8.7,

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Fig. 5.21 An example of Ishikawa Diary in Tokyo. From Hachioji Historical Museum 1991

and 7.1. Although the number of rainy days in June is underestimated in the Ishikawa Diaries, for rainfall in July and August there is good agreement between the Ishikawa Diaries and the JMA data. To confirm the relationship between temperature and the number of rainy days, correlation coefficients between the number of rainy days and the average summer temperature for the overlapping period were calculated using the JMA data; the correlation coefficients for June, July, and August were −0.41, − 0.70 and −0.45, respectively. Since the average temperature in July has the highest correlation with the number of rainy days in that month, it would be possible to reconstruct July temperatures in Tokyo from 1721 to 1940 based on the weather records in the Ishikawa Diary. The higher correlation coefficient in July can be explained by the fact that the average rainy season in July is from mid-June to mid-July as described in Sect. 2.2.4. As shown in Fig. 2.19, the average rainy season (baiu) in early summer in the Tokyo area is from mid-June to mid-July, which means that in years when the rainy season ends early, the area is covered by the North Pacific High that moves northward during the subsequent midsummer season. On the other hand, if the Baiu Front remains stagnant along the southern coast of Japan in July, the average temperature

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Fig. 5.22 An example of weather diagrams in Tokyo based on Ishikawa Diary (July 1770–1819). From Yoshida (1987)

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will decrease under the influence of the cool Okhotsk High. For June and August in Tokyo, other weather information, such as the number of sunny and cloudy days as an indicator of solar radiation, may be useful for estimating the average temperature for the historical period (Ichino et al., 2018). In this study, we will focus on the July temperature reconstruction, because July temperature variations can represent almost a 100-year period of summer temperature variations as shown in Fig. 5.20. We performed a simple least-squares regression analysis on the average July temperature and the number of rainy days in Tokyo (JMA data) for the period 1876– 1940 (Fig. 5.23). Here, x (predictor) is the number of rainy days, and y (predictant) is the average monthly temperature in July, yielding the linear regression equation y = −0.25x + 26.83. The coefficient of determination R2 was 0.51. The dashed line indicates the 95% estimation band. Based on this regression equation, July temperatures in Tokyo were estimated for each year from 1721 to 1940 for which both proxy (historical) and observed (meteorological) data were available from 1876 to 1940. By linking the reconstructed time series of temperatures for 1721–1940 with the observed temperatures from the JMA data for 1876–2020, the long-term variation of July temperatures over the 300-year period 1721–2020 is revealed as shown in Fig. 5.24. The 95% error band is shown in gray. The estimated temperature trends show that there were periods of lower and higher temperatures: from 1721 to 1790, temperatures are estimated to have been about 1.5 °C to 2.0 °C lower than today’s levels. July temperatures during this reconstructed period show large interannual variations, with average temperatures estimated to have been lower than 22.5 °C in 1721, 1728, 1736, 1738, 1742, 1743, 1744, 1755, 1758, 1780, 1783, 1784, 1786, 1869; 1730–1740 and 1780. The temperatures in the 1780s were often extremely low and varied widely from year to year, and these years are known to have been marked by major famines: in the summer of 1783, the Fig. 5.23 Relationship between the number of rain days with more than 1 mm/ day in July and the mean July temperatures in Tokyo for 1876–1940

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Fig. 5.24 The long-term variation of July temperatures in Tokyo during the 300-year period 1721– 2020. The blue line and the red line indicate reconstructed and observed temperatures respectively. The 95% error band is displayed in gray

extremely cool and wet weather caused a major rice crop failure, and this extreme weather brought a historic famine to Japan (Mikami, 1987, 1992a, 1992b). Even in the observation period, 1895, 1901, 1902, 1908, 1931, 1945, 1988, and 1993 were characterized by extremely cool summers with average July temperatures below 22.5 °C. On the other hand, the nineteenth century was rather warm, especially from the 1810s to the early 1850s, with high values above 26.5 °C in 1811, 1817, 1821, 1851, 1852, and 1853. The 1830s was a period of relatively low temperatures, and the 1830s saw a recurrence of great famine similar to the 1780s. The lowest July temperatures in the observation period occurred around 1900 when the average temperature was similar to that in 1740. The reliability of the reconstructed temperature time series can be confirmed by comparing reconstructed temperatures based on weather records and observed temperatures from the period 1876–1940, when both are available. As indicated in Fig. 5.24, there is a good fit between the two time-series during the period of overlap. In addition, the observed temperatures show the lowest temperature around 1900, which is also clearly shown in the reconstructed temperatures.

5.2.3.2

A Case Study of Hiroshima: 1779–2015

Hirano et al. (2018) attempted to reconstruct summer temperatures since the late eighteenth century from old diaries in Hiroshima, which is located about 680 km west-southwest of Tokyo. The reconstruction of summer temperatures since the eighteenth century in Tokyo described in the previous section was based on statistically significant correlations between the number of rainfall days in July and average temperatures for the period when the diary weather records and the JMA official

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weather observation records overlapped. However, it has not been established that the significant correlation between the number of days of summer rainfall and temperature seen in Tokyo is valid everywhere in Japan. To this end, Hirano et al. (2018) created correlation distribution maps for the number of rainfall days and monthly mean temperatures (maximum, minimum, and mean) for each month of summer (June, July, and August) based on data from 37 JMA meteorological stations across Japan during 1901–1950 in order to establish where the correlation between the two was highest. Figure 5.25 shows the correlation distribution of the number of rainy days and monthly mean temperature for July, with high negative correlations (R = −0.6 or higher) observed in the Tokyo and Hiroshima areas. Statistically significant correlations of −0.5 or higher are distributed over a wide area from central Japan to southwestern Japan, from the Kanto region to Kyushu. On the other hand, the correlation is lower from Hokkaido to northeastern Japan, indicating that this area is not suitable for estimating summer temperatures from the number of rainfall days. This may be caused by the fact that in northern Japan, when a dry cold air mass from the Arctic covers the region during the summer, temperatures are often lower even on clear days. Hirano et al. (2018) used the Murakami Kaj¯o Diary from 1779 to 1871 for the reconstruction of summer temperatures in Hiroshima. This period does not overlap with data from the JMA Hiroshima Meteorological Observatory, which started observations in 1879. However, by applying appropriate corrections, the reconstructed and observed temperatures can be connected. Figure 5.26 shows a time series of mean daily maximum temperature in July (blue line) reconstructed from a significant correlation (R2 = 0.50) between the number of rainfall days in July and the Fig. 5.25 The correlation distribution of the number of rainy days and monthly mean temperature for July. From Hirano et al. (2018)

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Fig. 5.26 Variations in daily mean maximum temperature in July for Hiroshima during 1779–2015. The blue line and the red line indicate reconstructed and observed temperatures

monthly mean daily maximum temperature. As for the reconstructed period of 1779– 1871, the 1780s and 1830s show a low-temperature trend, which is consistent with the reconstructed July mean temperature in Tokyo shown in Fig. 5.24, corresponding to great famines during the Edo period. On the other hand, the 1820s shows a hightemperature maximum in Hiroshima but a low-temperature minimum in Tokyo, indicating that the two reconstructed temperature time series do not coincide. It is known that a “cool in the north and hot in the west” pattern sometimes appears in the distribution pattern of summer temperature anomalies in Japan. In particular, when the polar frontal zone stagnates in central Japan, the cold air mass from the north tends to cause a cool summer north of the Kanto region, while western Japan experiences clear skies and high temperatures under the North Pacific High. In the period of instrumental observation, the “cool in the north and hot in the west” pattern often appeared around the 1970s, suggesting that such temperature anomaly patterns may have appeared repeatedly over a hundred-year period.

5.2.4 Meteorological Disasters from the Seventh to Nineteenth Century With regard to extreme weather events and weather disasters since the twentieth century, when meteorological observations were available, the data reveal an increase in temperature and precipitation extremes as a result of global warming, as explained in Sect. 3.2. It is possible to obtain qualitative information about climate change and meteorological disasters in the Edo period before the nineteenth century, when no official meteorological observations were made, from historical documents and paintings. For example, Fig. 5.27 shows a painting depicting the flood disaster that occurred in Edo Bay (Tokyo Bay at present) in September 1856, in which many houses and people were swept away by a severe storm surge, and thousands of people were said to have been killed. But what about quantitative information? How frequently did such meteorological disasters occur in the Edo period from the 17th to the 19th century? In this section, a quantitative analysis of the occurrence

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Fig. 5.27 Flood disaster caused by storm surge in Edo (Tokyo) Bay in September 1856. From National Archives of Japan Digital Archive

of meteorological disasters during the Edo period is attempted based on historical documents.

5.2.4.1

Storm Disasters and Great Famines in Summer

The descriptions of heavy rain and strong winds from the Hirosaki Domain Edo (Tokyo) Diary described in Sect. 4.2.2 were tabulated chronologically to analyze the long-term fluctuation trend of weather disasters in the Edo period and to examine the relationship with periods of famine. The Hirosaki Domain Diary Weather Database (Fukuma, 2018) introduced in Sect. 4.2.2 was used for the tabulation. First, the number of days with heavy rain and strong winds per decade was compiled over the warm season (May–October) for about 200 years (1671–1860) during the Edo period and displayed in a graph (Fig. 5.28). Although rainfall-related expressions vary from day to day, only descriptions such as “heavy rain,” “intense rainfall,” “rainstorm,” and “all-day rain” are tabulated. As for the wind, only descriptions of strong winds, such as “gale”, “severe wind,” and “windstorm,” which are assumed to indicate strong winds, were included in the total.

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Fig. 5.28 Decadal changes in the frequency (days) of heavy rains (blue) and gales (brown)

The graph in Fig. 5.28 identifies the following characteristics of the occurrence of heavy rain and strong winds during the Edo period. 1. The frequency of heavy rain and strong winds tends to increase throughout the Edo period as a whole, although there are variations by period. 2. The frequency of heavy rains and strong winds shows periodic fluctuations over several decades, with peaks corresponding to the three major famines of the Edo period: the Ky¯oh¯o Famine (1720s), the Tenmei Famine (1780s), and the Temp¯o Famine (1830s). 3. In years when heavy rains are more likely to occur, strong winds are also more likely to occur. This is not surprising, suggesting that many of the causes of heavy rainfall and strong winds are thunderstorms, developing low-pressure systems, typhoons, and so on, all of which often produce wind and rain simultaneously. 4. It has generally been believed that the great famines in the Edo period were triggered by poor rice harvests, caused by prolonged low summer temperatures and lack of sunshine as well as the increased frequency of heavy rains and strong winds. So, in what period of the year would heavy rainfalls, which sometimes cause floods, occur more frequently? Also, is the period when the frequency of heavy rainfall increases the same in the Edo period as in the present or has it changed? In this section, the frequency of heavy rainfall events is compared for the Edo period

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(1668–1865) and the present (1876–2021) based on the frequency of heavy rainfall events every five days. For the Edo period, we used the data of heavy rain, etc. shown in Fig. 5.28. However, we cannot use the same method to classify heavy rain for the present day, when there is no diary weather record. Therefore, based on instrumental meteorological data from the JMA Tokyo Observatory, heavy rainfall days were defined as days with daily precipitation of 50 mm or more, and the number of such days was counted every five days. This is an empirical definition, which is qualitatively and quantitatively different from the heavy rainfall days recorded in the diary of the Edo Period, for which meteorological observation data are not available. Here, we attempt to compare the frequency of heavy rainfall occurrences for the Edo Period and the present day based on the total number of such days in a 100year period, because the total duration of the periods being compared is different. Figure 5.29 shows the frequency of heavy rainfall every 5 days during the warm season (May–October) in the Edo Period (upper chart), based on the documentary record, and the present day (lower chart), based on the instrumental meteorological data. The frequency of heavy rainfall events from May to July is similar in the Edo Period and the present day, but the pattern of variation from August onward is quite different. In the Edo Period, heavy rainfall frequency increased from late July to August, reached its peak at the end of August, and then gradually decreased. On the other hand, in the present day, the frequency of heavy rainfall events increases from late July, reaching its peak in early October. In other words, the peak of heavy rainfall frequency in the Edo Period was in late summer (August–September), while in the present day, it is in autumn (late September–early October), indicating that there is a seasonal delay in the occurrence of heavy rainfall. The reason for the seasonal delay in the peak of heavy rainfall is not clear, but it may be related to the fact that the timing of the occurrence of tropical cyclones such as typhoons, and their approach to Japan, has become later than that of the Edo Period due to climate change (global warming). Tagami et al. (2018) focused on the records of storms, floods, and drought in the Japan Weather Archives (Nihon Kisho Shiryo) chronology and created a graph of the time series of their occurrence frequency (Fig. 5.30). The results revealed that the trends in the frequency of storms and floods were similar, but that for the frequency of droughts was reversed. Furthermore, as shown in Fig. 5.30, storms increased during the major famine outbreaks of the Edo Period. Tagami et al. (2018) states that periods of increased storms were coincident with the weakening of the North Pacific High, resulting in a cool summer, which was followed by disastrous typhoons. As shown in Fig. 5.29, this result is reasonable because the frequency of heavy rainfall peaked in the August–September typhoon season during the Edo Period, when famines were frequent.

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Fig. 5.29 Seasonal changes in the frequency of heavy rainfall in Edo Period (top) and modern times (bottom)

Fig. 5.30 Long-term changes in the frequency of storms, floods, and droughts in Japan. Shown by 11-year running means. From Tagami et al. (2018)

5.2.4.2

Heavy Snowfall in Edo (Tokyo)

How was the winter climate in historical times, such as the Edo period? It would be significant from the viewpoint of historical climatology to compare the presentday winter climate, which is currently undergoing climate change (global warming), with that of the Edo Period, corresponding to the latter half of the Little Ice Age. How much heavy snow has fallen in Tokyo in the past? In addition, it appears that the recent mild winters and urban climate have made heavy snowfall less frequent, suggesting that heavy snowfalls may have been more common in the Edo period

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when there was almost no such urban influence on the climate in the city of Edo. In this section, we will discuss past heavy snowfalls in Tokyo based on the available data. The record for the deepest snowfall since the JMA Tokyo Observatory was established in 1875 stands at 46 cm on February 8, 1883. Since this is data from the observation site of the JMA, it is probable that there was more snow in different parts of Tokyo. Incidentally, the Tokyo Daily News Paper (Tokyo Nichinichi Shinbun) for 9 February 1883 contains the following description: “February 6 was clear and windless, and the stars were shining brightly at night, so we expected the weather to be fine again tomorrow. However, it suddenly became cloudy from around 2:00 a.m. on February 7, and it started sleeting from around 4:00 a.m., and snow began to fall in earnest from around 5:00 p.m. By midnight of that day, the snowfall exceeded 30 cm, and the wind had become even more violent, and the snow had piled up so much that not a single person could be seen walking on Ginza Street in front of our newspaper office. Even in places where the snow had been removed from under the eaves, nearly 90 cm of snow had accumulated, and in some places where the wind had blown it down, the snow had accumulated to 1.5–1.8 m in depth.” The 90 cm of snow on the street in front of the newspaper office is nearly double the 46 cm recorded by the meteorological observatory and is clearly an excessive figure. Of course, there are regional differences in snow depth, so even in Tokyo, snow may have accumulated close to 1 m in some places. In Tokyo, how much snowfall is regarded as “heavy snowfall”? As shown in Fig. 5.31, heavy snowfall has been reported in downtown Tokyo in recent years, where urban heat islands are most prominent. Here we define ‘heavy snowfall’ as an accumulation of 20 cm or more. By examining the records for the past 82 years (1940–2021), we find that a total of 25 heavy snowfalls occurred, the period for which records are available. This is almost once every three years. By calendar month, there were 7 heavy snowfalls in January, 16 in February, 2 in March, and no snowfalls of more than 20 cm in April or December. As can be seen, Tokyo is most frequently hit by heavy snowfalls in February. Comparing the number of occurrences for the first 41 years and the second 41 years, with 1980 as the border year, we find that there were 16 occurrences in the first half and 9 in the second half, indicating a clear downward trend. Hence, we went further back and examined the heavy snowfalls in the Edo period (1603–1868). Figure 5.32 is an ukiyoe painting depicting a snowy scene in Tokyo during the Edo period. As mentioned before, the exact depth of snow cover is not given, but it can be inferred to some extent from descriptions in documents and other sources. Let us count the number of snowfalls of 30 cm (1 Japanese foot) or more from the Japan Weather Archives (Nihon Kisho Shiryo). The number of heavy snowfalls in the 243-year period from 1633 to 1876 is 62. This is about once every four years. However, since the Japanese old unit of length, one shaku is approximately 30 cm, a comparison of the past 82 years (1940–2021) using the same criteria shows that snowfall exceeding 30 cm was recorded only 4 times, which means that it occurred

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Fig. 5.31 The main street of Ginza in Tokyo covered with heavy snow. From photolibrary https:// www.photolibrary.jp

Fig. 5.32 Ukiyoe painting depicting the snowy landscape of Edo. From Digital Collection, National Diet Library, Japan

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once every 20 years. Did it snow more frequently in the Edo period, which corresponds to the Little Ice Age, than it does today? Or is the urban climate making heavy snowfalls less likely in Tokyo? Or did people in the Edo period overestimate the depth of snow accumulation? All of these interesting questions must be addressed before drawing any firm conclusions about climate change and snowfall.

5.2.5 Great Famines and Climate Change in the 1780s As discussed in Sect. 5.2.3, summer temperatures in the 1780s are estimated to have been extremely low. What were the climatic conditions around 1783, when a great famine occurred? Of course, since meteorological observations were not yet available at that time, it is impossible to directly compare average temperatures in the 1780s with those today. However, many historical records exist regarding the severe summer weather that caused a poor harvest and crop damage from cold, which was the trigger for the great Tenmei Famine. For example, Fig. 5.33 is a painting from around 1786, showing scenes of severe starvation. The famine is said to have killed about 20,000 people throughout the country. From historical documents, we can learn various aspects of the unusual weather in 1783, since meteorological observations were not yet being made, we cannot obtain precise figures, such as the average temperature in August, for example. In addition, the regional aspects of the weather, such as whether the cool summer occurred on a nationwide scale or on a local scale, have not yet been fully clarified. Furthermore, the meteorological factors that brought about the cool summer, for example, whether it was caused by the development of the Okhotsk High, the stagnation of a front, or the southward shift of cold air from the Arctic, are also not well understood. Concerning the climate in the 1780s, various historical documents have provided us with ideas of when and in which regions chilly weather damage, drought, and long continuous rainfall occurred, although most of these ideas are qualitative and subjective. In particular, sources that were written more than a few decades later than the events themselves often use exaggerated expressions about the climate in order to emphasize the severity of the famine. In addition, there are differences in lifestyle between the present and more than two hundred years ago, so a simple comparison with the present entails the risk of drawing false conclusions. In a previous study, the author attempted to clarify the weather conditions during the warm season (May– October) in the 1780s (1781–1790), including the Tenmei famine years, from both temporal and spatial perspectives (Mikami, 1983). For this purpose, we have collected daily weather records from old diaries kept in various parts of the country. Then, based on these records, we created daily weather distribution maps. Nowadays, as described in Sect. 4.2.3, we can easily display the weather distribution map for any given day using the Historical Weather Database (HWDB). For example, if we create weather distribution maps for the period from July 1 to July 2, 1783 (Fig. 5.34) and put them in sequence by date, we can clearly recognize that the area of rainfall moved from western Japan to eastern Japan. This is probably

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Fig. 5.33 The Great Tenmei Famine Map artwork (circa 1786). About 20 thousand people were starved to death in the whole of Japan. From Fukushima Prefecture Aizumisato Town Board of Education Collection

caused by a low-pressure system that moved eastward from the East China Sea along the south coast of the country. After the passage of the low-pressure system, the weather in western Japan recovered, but in the northern Tohoku region, cloudy and rainy weather continued throughout this period. The weather reports in historical documents at Hachinohe in northern Japan on July 2 and 3 described very cold and easterly winds, suggesting that the development of the Okhotsk High and the cool easterly winds (yamase) blowing from this High

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Fig. 5.34 Weather distribution maps during 1–2 July 1783. Created from HWDB

Fig. 5.35 Weather distribution maps during 10–11 August 1783. Created from HWDB

brought about such unseasonable weather (see Fig. 2.18). After that, the severe weather continued into August. As shown in Fig. 5.35, the weather distribution for August 10 and 11 reveals that rainfall occurred nationwide for two consecutive days. Is it possible to quantitatively express the climatic conditions in historical periods using weather distribution maps? For this purpose, the author classified daily weather distribution maps into seven types by focusing on the distribution of rainfall areas and then calculated the number of days for each type by month and by season. For example, one category of rainfall area could be a type that extends over western Japan, while another could be a type with rainfall areas distributed over central Japan. Table 5.1 shows the occurrence frequency (days) of each weather type in July and August for the 1780s. The sunny weather type tends to appear under the typical summer pressure pattern of the North Pacific High extending over the Japanese archipelago, and years with more days of this type are years with longer sunshine hours and higher temperatures. In terms of the number of sunny weather days throughout the country in the 1780s, both 1783 and 1786 were cool summers with 10 or fewer days or clear sky, while for the years 1781, 1785, and 1790, the number of sunny days exceeded 30. Although it is generally accepted that cool weather continued every year in the 1780s, the results

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Table 5.1 July and August weather types in Japan during the 1780s (from Mikami, 2012) 1781 1782 1783 1784 1785 1786 1787 1788 1789 1790 Nationwide sunny type

33

18

8

22

32

9

15

15

19

33

Nationwide rainy type

2

3

14

3

1

3

2

3

7

5

East Japan rainy type

12

9

17

5

17

8

14

9

9

8

Central Japan rainy type 12

8

6

5

3

12

13

8

13

4

West Japan rainy type

3

Kyushu rainy type Mixed type Others Total

62

8

4

13

3

21

4

17

7

1

12

8

14

2

7

8

7

6

10

2

4

2

1

5

3

1

1

62

62

62

2

1

62

62

62

2

1

1

62

62

62

of the author’s survey clearly show that the 1780s were characterized by a period of climatic instability with large variability in the frequency of cool and hot summers. Let us compare the unusually small number of sunny summers in 1783 and 1786 from the viewpoint of the regional characteristics of cool summers. In the case of 1783, the total number of days with rainfall over the whole country and eastern Japan accounted for about half of the total, or 31 days, while in the case of 1786, the number of days with rainfall distributed over central and western Japan reached 33 days, clearly indicating a shift in the center of the rainfall area between the two years. As for the magnitude of the cool summer, the number of days of the nationwide rainy type in 1783, which reached 14 days, was larger than that in 1786, when there were only 3 days. We will discuss the estimated weather conditions in the 1780s in relation to crop failures and famines. The year 1781 was a typical hot summer, and no one would have predicted a great famine two years later. The subsequent year (1782) was a little cooler, with more rainy days, especially in southwestern Japan, but overall, conditions were not that bad. The following year, 1783, was an extremely cool summer, resulting in a poor harvest, especially in the northeastern part of Japan. As a result, a great famine of unprecedented scale broke out. In the next year, 1784, the summer weather recovered to almost normal levels or even better, especially in eastern Japan, and people were blessed with sunny weather day after day. Figure 5.36 is a weather calendar showing the daily weather conditions from north to south in August 1783, when the great famine occurred, and in August 1784, the following year, showing the recovery of the weather in 1784. However, despite the improved weather, 1784 was another year of famine due to the after-effect of the previous year’s poor harvest. Because, due to the great crop failure of 1783, there was simply an extreme shortage of seed rice to plant the following year, which led to the largest number of deaths from starvation in the northern part of the Tohoku region. The following year, 1785, as already noted, was marked by a remarkably hot summer mainly in western Japan, although the number of rainy days increased in eastern Japan. The people were gradually recovering from

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Fig. 5.36 Weather calendars showing the daily weather conditions from north to south in August 1783 (top) and 1784 (bottom). From HWDB

the pain of the great famine. However, in 1786, the next year, there occurred another cool summer again, in central and western Japan, resulting in a bad harvest. Famine, therefore, struck again, and its effects continued until the following year 1787. Another natural factor that should not be overlooked here is the impact of volcanic eruptions in 1783. In Japan, Mt. Asama erupted in early August 1783, killing many people and damaging crops due to pyroclastic flows and volcanic ash. On the other

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197

hand, the great fissure eruption of Mt. Laki (Lakagígar) in Iceland in early June 1783 produced dry fog causing unusual weather in Europe (Damodaran et al., 2018). In general, when a major volcanic eruption occurs, sulfate aerosols spread over the Earth’s surface, weakening, and reducing the amount of solar radiation reaching the ground, which is assumed to cause a decrease in air temperature due to the parasol effect. In the case of Mt. Asama, the plume from the eruption did not reach the stratosphere, so there was almost no parasol effect. Nevertheless, it is undeniable that a large amount of volcanic ash from Mt. Asama may have directly damaged crops and rice harvests. What about the eruption of Mt. Laki? A large amount of sulfur dioxide was released into the atmosphere. The sulfate aerosol that was injected into the stratosphere may have reached Japan by the prevailing westerly winds over the Northern Hemisphere. Therefore, the combined effect of both volcanic eruptions may have caused an unusual summer climate of Japan in 1783. In any case, the effect of large volcanic eruptions on the global climate is complicated, and difficult to clarify their mechanisms (e.g., Nin et al., 2017; Robock, 2000). It is also reported that a strong El Niño event occurred in 1783 (Quinn, 1992), which may have accelerated the cool summer conditions in Japan.

5.3 Climate Reconstruction from Records of Full-Flowering Dates for Cherry Trees Over the Past 1200 Years In Japan, cherry trees bloom in various regions in spring, usually achieving full bloom from late March to early April. It is customary for the people of Japan to celebrate the arrival of spring by holding a feast under the cherry trees in full bloom. Historical documents, such as diaries and local chronicles, provide us with the dates of the annual feasts. Empirically, cherry blossoms bloom earlier than usual in years when winter and spring temperatures have been higher than normal and later in years when they have been lower. In Europe, long-term climate reconstruction studies based on wine grape harvest dailies and other data are well-known (e.g., Chuine et al., 2004; García de CortázarAtauri et al., 2010; Labbé et al., 2019). However, phenological studies focusing on the date of the full bloom of cherry trees are unique to Japan. It was probably first described by Taguchi (1939) in the Japan Weather Archives (Nihon Kisho Shiryo), a chronological table of the dates of hanami (cherry-blossom viewing) banquets in Kyoto, Tokyo, and other cities during the period 812–1885. Arakawa (1955, 1956), by tabulating the dates of cherry blossom viewing in Taguchi (1939) and other sources by century, found that cherry blossom blooming and full-flowering dates were later from the eleventh to fourteenth centuries and surmised that winters must have been colder in this period. After that, climate reconstructions based on phenological analysis were in decline for a while. However, since the

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1990s, Dr. Yasuyuki Aono and others have been conducting a series of studies on the initial blooming and full flowering of cherry trees and maples in Kyoto and Tokyo using historical data (Aono, 2012, 2015; Aono & Kazui, 2008; Aono & Nishitani, 2022; Aono & Omoto, 1994; Aono & Saito, 2010; Aono & Tani, 2014). In this section, we introduce a study by Aono and Kazui (2008) that reconstructs spring temperature fluctuations in Kyoto since the ninth century using initial blooming dates and full-flowering dates for cherry trees. Aono and Kazui (2008) used historical records from AD 801 to 1880 and observation records from JMA Kyoto Meteorological Observatory from AD 1881 to 2005 to reconstruct spring temperatures in Kyoto. The date of bloom or full flowering of cherry trees varies depending on the species. In most parts of Japan today, Somei-Yoshino (Prunus × yedoensis) is the most popular, while Yamazakura (Prunus jamasakura) was the most common in Kyoto before the nineteenth century. Even today, P. jamasakura is popular among tourists in Arashiyama, a western suburb of Kyoto (Fig. 5.37). Therefore, newspapers publish the date of the full flowering of P. jamasakura in Arashiyama every year, enabling comparison with records of the full flowering of P. jamasakura before the nineteenth century. Figure 5.38 shows the long-term variation of the full-flowering dates of P. jamasakura collected from historical documents and newspapers. For the early centuries, there are many years for which no data is available, but after the fifteenth century, data could be found for almost every year. The earliest full-flowering date was March 27, 1409, and the latest was May 4, 1323; the average full-flowering date

Fig. 5.37 Full-flowering of cherry trees (P. jamasakura) at Arashiyama in Kyoto. From photolibrary https://www.photolibrary.jp

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Fig. 5.38 Inter-annual variations in the full-flowering dates of the cherry tree, P. jamasakura, at Kyoto, acquired from old diaries and chronicles. From Aono and Kazui (2008)

for the entire period under study was April 15. In the thirteenth century, the middle of the fifteenth century, and the latter half of the seventeenth century, the full-flowering date was later. The long-term variation of reconstructed mean March temperature in Kyoto since the ninth century is shown in Fig. 5.39. The estimated temperatures for the period from the ninth to the twelfth century show no clear trend, partly due to the many lacunae in the data. For the seventeenth and eighteenth centuries, a cooling trend was observed from 1600 to 1670, a warming trend from 1700 to 1720, and a cooling trend around 1800. After the eighteenth century, a temporary cooling trend in the 1820s is notable. Subsequently, the temperature tends to increase over the nineteenth and twentieth centuries.

Fig. 5.39 March mean temperature reconstructions in Kyoto since the ninth century. From and Kazui (2008)

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5.4 Climate Reconstructions from Pollen in the Highland Moors in Central Japan Over the Past 7600 Years Ozegahara is a highland moor in central Japan that extends 6 km east to west and 2 km north to south. It is a peatland formed about 10,000 years ago with an average elevation of 1400 m. To the west of Ozegahara is Mt. Shibutsu, with an elevation of 2228 m, and to the east is Mt. Hiuchi with an elevation of 2346 m (Figs. 5.40 and 5.41). Ozegahara has a cool climate, with an annual mean temperature of 4.6 °C, more than 10 °C lower than that of Tokyo, and annual precipitation of 1775 mm, slightly higher than that of Tokyo. In Ozegahara, a peat deposit formed by dead plants gradually accumulates in water-filled depressions, causing the pits to collapse and creating a raised marshland. The peat accumulates at a rate of less than 1 mm per year, reaching 4 to 5 m in the deepest part. Dr. Yutaka Sakaguchi, a former geography professor at the University of Tokyo and a specialist in peatland research, together with his research team, succeeded in cutting a 4.5 m layer of peat from a pit in the Ozegahara moor in the fall of 1973. The peat was sampled from the center of the highland moor, where the sediments had not been washed away by running water and had preserved granular materials such as volcanic ash and pollen that had fallen from the air in that area for a long time. Various types of pollen are preserved in the peat layer, and conventional pollen analysis made it possible to identify the trees represented. Sakaguchi’s idea was to use the types of pollen and their relative abundance for the purpose of climate reconstruction. He took the 4.5-m peat column that had been collected and sliced it at intervals of 2 cm. The peat extraction hand borer used in conventional pollen analysis could not take samples shorter than 5 cm because of disturbance of the sedimentary layers, but in the 1973 survey, the 4.5 m peat layer deposited on top of the clay layer was cut from the side of a deeply dug well. It, therefore, succeeded in obtaining a highly accurate peat sample without disturbing the stratigraphy. Based on the results of the pollen analysis, Sakaguchi noted that the major constituent of pollen in the peat layer was Pinus pumila and decided to conduct long-term climate reconstructions based on variation in the occurrence rate of that species. Sakaguchi next focused on the contemporary P. pumila high pine forest zone on Mt. Shibutsu (Fig. 5.42). He noticed that the lower limit of the zone was around 1700 m, mid-slope on Mt. Shibutsu. In general, shifts in the elevation of vegetational zones in high mountains are greatly influenced by climate change. As temperatures rise and become warmer, zones shift upward, so in the case of Mt. Shibitsu, the P. pumila high pine forest zone moves upward toward the summit and its growing area decreases. What this means is that the amount of pollen being released also decreases. Conversely, when temperatures decrease and become colder, vegetational zones move downward, and in the case of Mr. Shibutsu, the amount of P. pumila pollen consequently increases. An important question is the dispersed direction of pollen released from P. pumila trees on Mt. Shibutsu. It was found that the prevailing wind direction in June, the

5.4 Climate Reconstructions from Pollen in the Highland Moors in Central …

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Fig. 5.40 Location of Ozegahara highland moor and Mt.Shibutsu in central Japan

flowering season of P. pumila, varied from NW to SW based on meteorological observations. Since Mt. Shibutsu is to the west of the location where the peat column was obtained, this means that most of the P. pumila pollen deposited there came from Mt. Shibutsu. It follows that variation in the abundance of P. pumila pollen at various locations within the peat column should be a good proxy for climate change. By the way, there was another problem to be solved here regarding the dating of samples

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Fig. 5.41 Mt. Shibutsu and Ozegahara Highland Moor. From photolibrary https://www.photolibr ary.jp

Fig. 5.42 The summit of Mt. Shibutsu and a group of dwarf stone pines (Pinus pumila). Mt. Hiuchi and Ozegahara highland moor can be seen in the distance on the right. From photolibrary https:// www.photolibrary.jp

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from the column. Sakaguchi (1982, 1983) used the age of tephra layers from a nearby volcanic eruption, which could be dated precisely from historical documents, as well as radiocarbon (14 C) dating, to solve this problem. Figure 5.43 shows Sakaguchi’s graph of climate reconstructions for the past 7600 years (Sakaguchi, 1983). The unit of the abscissa is Pinus pumila content (%), which is the mean value of samples at intervals of 2 cm. The average value for the entire period is 8%. Values after 1806 are not plotted in this graph because the peat surface layer was disturbed, making the top of the column unsuitable for analysis. The black areas indicate warm periods, which were almost continuous prior to 2600 BC (about 4600 years ago). This period corresponds to the Holocene Thermal Maximum (5000–9000 BP), showing that the global warm period and the Japanese warm period occurred almost simultaneously (e.g., Renssen et al., 2012). The period 2000–1300 BC (4000–3300 BP) was relatively warm, while the Latest Jomon period of 900–400 BC (2900–2400 BP) was considerably cooler. The period from AD 700 to 1300 was relatively warm. The period from AD 900 to 1100 was one of average climate with variations in temperature of relatively small amplitude. This period corresponds to the Medieval Warm Period (MWP) or Little Climatic Optimum in Europe (e.g., Lamb, 1977). The argument has been put forward that the MWP did not occur globally at the same time, but that rather only a limited number of regions were marked by warming, and the timing of the warming was staggered (e.g., Bradley et al., 2016; Esper & Frank, 2009; Goosse et al., 2006; Hughes & Diaz, 1994; Zhang et al., 2009). However, despite the small amplitude of variation, it is noteworthy that the analysis of Pinus pumila pollen from the Ozegahara highland moor detected a distinct warm period that was roughly contemporaneous with the MWP. After that, a cold period continued from around AD 1300 to the nineteenth century, which is synchronous with the global Little Ice Age. In this section, I have introduced the climate change during the past 7600 years as revealed by Sakaguchi (1982, 1983) high-precision time-resolved pollen analysis of Pinus pumila pollen in a 4.5-m peat layer collected from the Ozegahara highland moor in Central Japan. The idea of vertical shifts in vegetation zones that Sakaguchi focused on is very unique, and the fact that homogeneous data can be obtained by using continuous sediments from the same location is of tremendous significance.

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Fig. 5.43 Past 7600 year climatic variations in Japan reconstructed from Pinus pumila pollen analysis at Ozegahara highland moor. From Sakaguchi (1982)

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Chapter 6

Conclusions

Abstract How can we discuss climate change in Japan over the past 200 years, getting back to the nineteenth century? Climate reconstructions based on unofficial weather observation data, diary weather records, and official JMA weather observation data are indispensable. This book describes a method for quantitatively and objectively reconstructing the climate in historical periods based on as much detailed data and materials as possible. There remains a huge amount of climate information in old documents and diaries in various parts of Japan. We hope the Data Rescue project to find and collect this data will be developed soon. Keywords Climate change · Climate reconstruction · Data Rescue

The primary purpose of this book is to provide readers, for whom English is the universal language, with as accurate knowledge of the climate of Japan, an island nation in the Far East, as possible, so that they may understand the climate of Japan in the present and past. I hope to offer detailed information on the climate of Japan to people living in other parts of the world and in other countries. The main Japanese archipelago is located between 30 and 40 degrees north latitude, which is in the southern latitude zone of Europe, but in winter the sea of Japan side area sometimes experiences heavy snowfalls of over 5 m. On the other hand, from summer to autumn, developed tropical cyclones, known as “typhoons,” often hit Japan, causing flood disasters due to torrential rains. The unique climatic and meteorological conditions of Japan are not well known overseas. It would be easy for foreign researchers to obtain information on Japan’s climate by reading articles by Japanese meteorologists published in international journals related to meteorology and climatology. However, it is difficult for researchers and the general public who do not specialize in meteorology/climatology to obtain knowledge about the current state of Japan’s climate and long-term climate change. How can we discuss climate change in Japan over the past 200 years, going back to the nineteenth century? Climate reconstructions based on unofficial weather observation data and diary weather records, in addition to official JMA weather observation data, are indispensable. This book describes a method for quantitatively © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 T. Mikami, The Climate of Japan, Advances in Global Change Research 77, https://doi.org/10.1007/978-981-99-5158-1_6

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and objectively reconstructing the climate in historical periods based on as much detailed data and materials as possible. There remains a huge amount of climate information in old documents and diaries in various parts of Japan, and we hope that the Data Rescue project to find and collect these data will be developed in the near future.