Junpei Hirano and Takehiko Mikami

1. Reconstruction of summer temperature variations in Kawanishi town,Northern Japan based on historical weather documents Junpei Hirano and Takehiko Mikami National Research Institute for Earth Science and Disaster Prevention

2. Recently, much attention has been focused on prediction of future climate • changes in relation to global warming. For the accurate prediction, • knowledge of past climate variations is important. • In Japan, modern meteorological observation by JMA started in the 1870s. • Before the 1870s, a few old instrumental pressure and temperature data • are available (Konnen et al.,2003; Zaiki et al.,2006) • Zaiki et al (2006) analyzed long-term temperature variations in western • Japan since the mid-19th century based on old instrumental data. Background

3. Background (Continued ) Pre 1900 availability of meteorological data in Japan ( Zaiki et al 2006) • Lack of long-term meteorological data before the1830s is a problem.

4. Background (Continued ) Significance for reconstructing long-term summer temperature variations since the 1830s • In the 1830s,a severe famine“Tempo famine”occurred due probably to cool summer climate（Yaji and Misawa1981; Kondo 1985） • Reconstructing long-term summer temperature variations after the 1830s is important for understanding the relation between climate variations and occurrence of meteorological disaster(such as severe famine). ☑Problem: Long-term temperature data back to the 1830s is not available.

5. Background (Continued ) Climatic reconstruction based on historical weather documents • Historical climatologist have been attempted to reconstruct climate variations in the 18th and the 19th centuries based on historical daily weather documents in old diaries. ✔Summer/winter temperature variations 　（Mizukoshi,1993；Mikami1996;Mikami et al2000) ✔Typhoon landfall frequency 　（Mizukoshi1993；Grossman and Zaiki,2011) ✔Length of (Baiu) early summer rainy season （Mizukoshi1993；Murata1988) Problem ☑Most of the historical weather documents stopped in the 1860s due to political turmoil ☑Connecting between reconstructed data(before the1860s) and modern meteorological data(after the 1870s)is difficult. Date Weather description

6. Purpose ☑We newly obtained a historical weather documents “Takeda Genemon’s Diary” at Kawanishi in northern Japan. ☑“Takeda Genemon’s Diary” has almost complete daily weather description from 1830 to 1980 without any gaps. ☑Weatherdocuments in “Takeda Genemon’s Diary” is one potentially useful form of proxy data for reconstructing summer temperature variations after the 1830s. Purpose: Reconstruct long-term summer(July) temperature variations since the 1830s based on historical weather documents of the “Takeda Genemon’s Diary”. Location of Kawanishi Town

7. Data Weather documents in “Takeda Genemon’s Diary” Overlapping period 1889－1980 Instrumentaltemperature data at Yamagata observatory 1830188919802011 Year

8. Methods • We investigated relationship between temperature at Yamagata and occurrence number of “fine”, “cloudy”, “rain” days, documented in “Takeda Genemon’s Diary”, for their overlapping period(1889-1980). Correlation coefficients between July temperature and occurrence number of each weather day in July ☑The highest correlation is found between July maximum temperature and occurrence number of “fine” weather day in July. ☑We attempted to estimate July maximum temperature based on number of “fine” days documented in “Takeda Genemon’s Diary”.

9. Methods(Continued ) Relationship between July maximum temperature and number of “fine” days. • July maximum temperature is highly correlated with number of “fine” days. • We obtained a simple linear regression equation, representing relationship between number of “fine” days, and July maximum temperature. • Y=0.3317X+22.071 • Y: July maximum temperature. • X： Number of “fine” weather days in July.

10. Results Variation of July maximum temperature in Kawanishi from 1830 to 2011 • Cool periods are found out in the 1830s, 1900s, and the period from1980s to the early 1990s. • The 1830s and the 1900s are in accordance with periods of severe famines. • Warm periods are found in the 1850s, 1880s, and the early 1920s . • Warm episodes in the late 19th century are in accordance with the results of Zaiki et al(2006), based on old instrumental temperature data in western Japan.

11. Conclusion • We reconstructed July maximum temperature variations after the 1830s in Kawanishi town based on the historical weather documents of the “Takeda Genemon’s Diary”. • We found out cool periods in the 1830s, the early 1900s and the period from the 1980s to the early 1990s. • Cool episodes in the 1830s and 1900s are in accordance with poor rice harvests and severe famines in Japan. • Warm periods are found out in the late 19th century (the 1850s and the 1880s)