Summer extreme precipitation in eastern China: Mechanisms and impacts

With the highest population density in China, eastern China has an unshakable position in Chinese socioeconomic development. To understand the precipitation changes and the related mechanisms is of great significance for regional management of water resources and agricultural irrigation. In this study, the impacts of western North Pacific subtropical high (WNPSH) on precipitation changes in eastern China and the underlying processes are investigated. The results indicate that the strength and location of WNPSH are in close relations with the changes of summer precipitation in eastern China, and their influences vary across both space and time. In particular, WNPSH exerts remarkable impacts on precipitation in June and July in Jiang-Huai region and precipitation in June in South China such as the Pearl River basin. The interannual variations of WNPSH exhibit significant correlations with water vapor flux in East Asia, and the variations of the location and direction of the west flank of the WNPSH are well corroborated with the influences of the East Asian summer monsoon (EASM) on precipitation in eastern China. The westward extension of WNPSH tends to favor the strong moisture transport to East Asia, intensify the EASM, and thus increase water vapor flux in East Asia, which greatly benefits the occurrence of Meiyu regimes in Jiang-Huai region. Besides, analysis results also show that the westward extension of WNPSH drives tropical cyclones southward so as to increase the occurrence of extreme precipitation in South China. This study helps to bridge the knowledge gap in the relationship between WNPSH, tropical cyclones, and summer precipitation events in eastern China.