Seasonal Evolution of Anomalous Rainband over East China Regulated by Sea Surface Temperature Anomalies in the Northern Hemisphere

A seasonal evolution of rainbands over East China is evident and shows remarkable year-to-year variations. The present study identifies two dominant interannual modes of the seasonal evolution of rainbands over East China from 1981 to 2018: 1) the sudden change pattern, in which the anomalous rainfall changes abruptly from boreal spring to summer, especially over South China; and 2) the northward migration pattern, which shows a gradual poleward migration of the anomalous rainband over East China with the East Asian summer monsoon (EASM). Both of them are regulated by the sea surface temperature anomalies (SSTAs) in the Northern Hemisphere from spring to summer. In the sudden change pattern, the SSTAs in the Pacific modulate spring rainfall over South China via the ENSO–EASM teleconnection. By contrast, the North Atlantic SSTAs change the midlatitude wave train and modify summer rainfall over South and North China, in conjunction with the anomalous tropical circulation due to the Indian Ocean SSTAs. In the northward migration pattern, the North Pacific SSTAs alter spring rainfall over South China by varying the low-level western North Pacific subtropical high and the zonal land–sea thermal contrast over East Asia. Afterward, the ENSO-like SSTAs induce a Pacific–Japan teleconnection and shift the anomalous rainband northward to the Yangtze–Huai River and North China in summer. The seasonal switch of the SSTAs regulating these two modes is physically linked from boreal spring to summer. This mechanism provides potential seasonal predictability of the seasonal evolution of the anomalous rainband over East China.