Rainy season at Beijing and Shanghai since 1736

Abstract

The rainy season is an important climate feature over Eastern China where anomaly in either its timing or length can lead to adverse economic and social consequences. Here, we illustrate that the records of daily precipitation description at Beijing and Shanghai contained in Memos-to-Emperor during the Qing Dynasty provide a unique source to extend the rainy season information to 1736. The information together with the instrument measurements since 1875 in both cities reveals significant inter-annual and decadal variations of the beginning and ending dates, and length of the rainy season. The analysis further reveals that, on the decadal time scale, the length of the rainy season increased in Shanghai since 1961 with more frequent extreme rainfall events, but decreased in Beijing since 1975 with persistent dry conditions. This pattern of changes was not seen in any other periods of the data, in particular during 1736-1820 when both cities showed an increase in the length of the rainy season. ©2008, Meteorological Society of Japan.