Distinct impacts of two types of South Asian highs on East Asian summer rainfall.

This paper analyses the different relationships between the two types of South Asian highs (SAH)—the southern mode of the SAH (SSAH) and the traditional SAH in its entirety (ESAH)—with respect to the variations in summer rainfall over East Asia. The ESAH is closely related to summer rainfall over northeastern China, whereas the SSAH is closely linked to summer rainfall over the Yangtze River valley, northern China, and Japan. Above‐normal rainfall tends to occur over northeastern China in strong ESAH years, whereas strong SSAH years tend to yield above‐normal rainfall over the Yangtze River valley and Japan together with below‐normal rainfall over northern China. The westerly jet and the western Pacific subtropical high (WPSH) shifts northward associated with a strengthened ESAH. The related anomalous southwesterly winds to the northwestern side of the WPSH transports abundant water vapour to northeastern China and leads to above‐normal rainfall there. In contrast, the westerly jet shifts southward and WPSH shifts southwestward to the South China Sea associated with a strengthened and southeastward‐shifted SSAH. Accordingly, a cyclonic anomaly appears over Northeast Asia and mid‐latitude western northern Pacific and an anticyclonic anomaly occurs over subtropical western North Pacific. The associated southwesterly wind anomalies over the Yangtze River valley and Japan contributes to above‐normal rainfall over these regions via transporting sufficient amount of water vapour. In addition, the anomalous northerly winds to the western flank of the cyclonic anomaly results in below‐normal rainfall over northern China via carrying drier air southward. Furthermore, the preceding winter ENSO events may play a more important role in the SSAH variation via modulating India Ocean SST. [ABSTRACT FROM AUTHOR]