Junpei Hirano(NIED), Masumi Zaiki(Seikei Univ), Takehiko Mikami(Teikyo Univ)

Background of documentary-based climate reconstruction in Japan ・ Knowledge of centennial-scale climate variations is essential to evaluate potential impact of climate variations on human history and environmental changes. ・ “Poor coverage of instrumental data outside Europe in the 18th and early 19th centuries(Lamb,1995)”prevent us to understand accurate picture of centennial-scale variations. ・ Foundation of Japan Met Agency (JMA) in Pre-1875: No meteorological data are available except for some early instrumental records (Zaiki et al.,2006).

Pre 1900 availability of meteorological data in Japan ( by Zaiki et al., 2006) JMA period Pre-JMA period Background of documentary-based climate reconstruction in Japan(Continued )

✔ Summer/winter temperature (Mizukoshi,1993 ； Mikami,1996; Hirano et al., 2012) ✔ Typhoon frequency (Mizukoshi,1993 ； Grosman and Zaiki,2011) ✔ Rainfall in Baiu season （ Mizukoshi,1993 ； Murata,1988) Large number of daily weather documents in old diaries during the 18 th and the 19 th centuries are available. Documents have been used as useful proxy for reconstructing centennial-scale climate variations. Background of documentary-based climate reconstruction in Japan (continued ) Date Weather

Summer temperature reconstruction based on historical weather documents Relationship between number of rainy days in July and July mean temperature in Tokyo (Mikami,1996) ☑ July temperature in Tokyo is negatively correlated with number of rainy days. Number of rainy days July mean temperature

Summer temperature reconstruction based on historical weather documents (continued) Reconstructed July mean temperature in Tokyo for (after Mikami,1996)

Winter temperature reconstruction based on historical weather documents ☑ Snowfall rate (number of snowfall /number of precipitation ) in Yagamata is negatively correlated with winter mean temperature (Hirano et al.,2012). ●

Winter temperature reconstruction based on historical weather documents (continued) ☑ Cold winters frequently appeared during the early 19th century (Hirano et al.,2012)

Variation in summertime rainfall frequency in central Japan from 1700 to 1890 ☑ Wet period in the early 18th and the mid-19th centuries were detected in central Japan. Wet

Comparison of summertime rainfall frequency with tree-ring based reconstruction. ☑ Wet summer in the 18th and the mid 19th centuries was detected from both documentary records and tree-ring data. Wet Tree-ring data Number of rainy days

Historical Weather Database(HWDB). ✓ Study group of historical climatologists have created Historical Weather Database(HWDB). ✓ Monthly based data are available on the NOAA's National Climatic Data Center (NCDC) website.

(Continued ) Historical Weather Database(HWDB) (Continued ) T1: Fine T2: Partly Cloudy T3: Cloudy T4: Shower T5: Thunderstorm T6: Heavy Thunderstorm T7: Little Rain T8: Rain T9: Heavy Rain TA: Hail, etc TB: Snow Shower TC: Little Snow TD: Snow ✓ Daily weather description in each diary was categorized into 13 categories. YEAR MN LOCATION T1 T2 T3 T4 T5 T6 T7 T8 T9 TA TB TC TD Z S IKEDA IKEDA IKEDA IKEDA ✓ The database contains number of days for each 13 weather type per month. Contents of database

Future issues ✓ Most of the documentary-based climate reconstruction in Japan have been focused on climate variation within Japan. ✓ Further efforts are necessary to compare reconstructed results in Japan those with the other East Asian region. ✔ These efforts could lead us to better understanding of centennial scale climate variations over East Asia.