The rainy season in the Northwestern part of the East Asian Summer Monsoon in the 18th and 19th centuries

Abstract: The Yu-Xue-Fen-Cun (YXFC) is one of the government archives of the Qing Dynasty (1644–1911) in China. It records the beginning/ending dates, duration and rainfall infiltration depths into soil and snowfall accumulation for individual precipitation event. By comparing YXFC with instrumental data, a set of criteria used to identify the rainy season was established. This set of criteria was used to reconstruct the initial/final dates and length of rainy season during 1736–1900 and 1955–2000 at three sites (including Taiyuan, Datong and Yulin) based on both YXFC records and instrumental data. The results show that there is evident inter-decadal variation in rainy season length, with periodicity of 16–20a, 30–40a and 50–60a. The length of the rainy season gradually increases before the mid-19th century and decreases afterward, and the length of rainy season in 1736–1840 is statistically significantly longer than that in 1955–2000. These findings suggest that the intensity of the East Asian Summer Monsoon (EASM) became weaker from the mid-19th century, reaching the weakest condition in 1955–2000 during the context of the past 260 years. [Copyright &y& Elsevier]