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

Background of documentary-based climate reconstruction in Japan

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Knowledge of centennial-scale climate variations is essential to evaluate potential impact of climate variations on human history and environmental changes.

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“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.

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Foundation of Japan Met Agency (JMA) in 1875.

Pre-1875: No meteorological data are available except for some early instrumental records (Zaiki et al.,2006).

Background of documentary-based climate reconstruction in Japan(Continued

) Pre-JMA period JMA period Pre 1900 availability of meteorological data in Japan ( by Zaiki et al., 2006)

Background of documentary-based climate reconstruction in Japan (continued

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Large number of daily weather documents in old diaries during the 18 th and the 19 th centuries are available.

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Documents have been used as useful proxy for reconstructing centennial-scale climate variations.

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Summer/winter temperature (Mizukoshi,1993

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Mikami,1996; Hirano et al., 2012)

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Typhoon frequency (Mizukoshi,1993

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Grosman and Zaiki,2011)

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Rainfall in Baiu season

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Mizukoshi,1993

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Murata,1988) Date Weather

Summer temperature reconstruction based on historical weather documents

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July temperature in Tokyo is negatively correlated with number of rainy days.

Number of rainy days Relationship between number of rainy days in July and July mean temperature in Tokyo (Mikami,1996)

Summer temperature reconstruction based on historical weather documents (continued) Reconstructed July mean temperature in Tokyo for 1721-2010(after Mikami,1996)

Winter temperature reconstruction based on historical weather documents

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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)

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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 Wet Wet Wet

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Wet period in the early 18th and the mid-19th centuries were detected in central Japan.

Comparison of summertime rainfall frequency with tree-ring based reconstruction.

Tree-ring data Wet Wet Number of rainy days

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Wet summer in the 18th and the mid 19th centuries was detected from both documentary records and tree-ring data.

Historical Weather Database(HWDB).

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Study group of historical climatologists have created Historical Weather Database(HWDB).

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Monthly based data are available on the NOAA's National Climatic Data Center (NCDC) website.

https://www.ncdc.noaa.gov/paleo/study/5412

Historical Weather Database(HWDB)

(Continued

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Daily weather description in each diary was categorized into 13 categories.

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

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The database contains number of days for each 13 weather type per month.

Contents of database

YEAR MN LOCATION T1 T2 T3 T4 T5 T6 T7 T8 T9 TA TB TC TD Z S4 1715 01 IKEDA 17 0 0 0 0 0 1 10 0 0 0 0 3 0 31 1716 01 IKEDA 28 0 0 0 0 0 1 2 0 0 0 0 0 0 31 1717 01 IKEDA 25 0 0 1 0 0 0 2 0 1 0 2 0 0 31 1718 01 IKEDA 21 0 1 0 0 0 2 6 0 0 0 0 1 0 31

Future issues

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Most of the documentary-based climate reconstruction in Japan have been focused on climate variation within Japan.

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Further efforts are necessary to compare reconstructed results in Japan those with the other East Asian region.

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These efforts could lead us to better understanding of centennial scale climate variations over East Asia.