New evidences on the climatic causes of the formation of the spring persistent rains over southeastern China

The spring persistent rains (SPR) over southeastern China (SEC) are a unique synoptic and climatic phenomenon in East Asia. A former study has found that the southwesterly flow which lies on the southeastern flank of the Tibetan Plateau (TP) is one of the deflected westerly flows of the TP, and it is suggested to be the direct climatic cause of SPR. This study found that the southwesterly flow is also highly correlated with the sensible heating of the southeastern TP in interannual variability, in addition to having a high correlation in seasonal variability. These facts suggest that the thermal forcing of the TP is another important climatic cause of SPR. Numerical sensitivity experiments further prove that the mechanical and thermal forcings of the TP are the climatic causes of the formation of the SPR. On the other hand, the Nanling Mountains and Wuyi Mountains (NWM) over southeastern China not only increase the SPR precipitation amount evidently, but also make the SPR rain belt move to the south by blocking the strong southwesterly flow.