Influences of three oceans on record-breaking rainfall over the Yangtze River Valley in June 2020

Abstract

The rainfall over the Yangtze River Valley (YRV) in June 2020 broke the record since 1979. Here we show that all three oceans of the Pacific, Indian and Atlantic Oceans contribute to the YRV rainfall in June 2020, but the Atlantic plays a dominant role. The sea surface temperature (SST) anomalies in three oceans are associated with the two vorticity anomalies: negative 200-hPa relative vorticity anomalies over North China (NC) and negative 850-hPa relative vorticity anomalies in the South China Sea (SCS). The rainfall anomalies in the YRV are mainly controlled by atmospheric process associated with the NC vorticity. The positive SST anomalies in May over the western North Atlantic induce positive geopotential height anomalies in June over the mid-latitude North Atlantic, which affect the rainfall anomalies in the YRV by changing the NC vorticity via Atlantic-induced atmospheric wave train across Europe. The Indian Ocean and tropical North Atlantic, as capacitors of Pacific El Nino events in the preceding winter, affect the SCS vorticity associated with the anomalous anticyclone over the SCS and also facilitate the YRV rainfall by providing favorable moisture conditions. This study suggests that the May SST over the western North Atlantic is a good predictor of June rainfall anomalies in the YRV and highlights the important impacts of three-ocean SSTs on extreme weather and climate events in China.