Multi‐factor synergistic effects on summer precipitation in the Meiyu region of China.

Summer precipitation in the Meiyu region of China arises from the synergy of multiple factors such as the East Asian summer monsoon (EASM), Western Pacific subtropical high (WPSH), the sea surface temperature (SST), etc. Based on an analysis of the key influencing factors of summer precipitation in the Meiyu region of China from 1961 to 2019, we selected five key factors: the EASM index (EXSMI), Western Pacific subtropical high area index and ridge line index (WPSH‐AI and WPSH‐RLI), Westerly Index (WI), and NAO index. These five indexes were then used to construct a multi‐factor synergy index (MFSI) by the weighted least‐square method. The results show that the MFSI was able to describe the characteristics of EASMI, WPSH, NAO, and the westerly circulation. It showed a good correlation with the temporal and spatial distribution of summer precipitation in the Meiyu region. In the strong (weak) MFSI years, the NAO index was low (high), the North Atlantic region presented a "+ − +" ("− + −") three‐pole structure from south to north, the WI was low (high), the Siberian high pressure was weak (strong), the middle and high latitude Eurasia Mainland upper trough and ridge meridional decreased (increased). On the contrary, the precipitation increased (reduced). This index has a good indication of summer precipitation in the Meiyu region, which has important scientific significance and practical value for the prediction and prediction of precipitation in the Meiyu region of China. [ABSTRACT FROM AUTHOR]