Large-scale Circulation Anomalies Associated with Interannual Variation in Monthly Rainfall over South China from May to August

Interannual variation in summer rainfall over South China (SC) was investigated on the monthly timescale. It was found that monthly rainfall from May to August exhibits different features of variation, and the amounts are basically independent of each other. There is a significant negative correlation, however, between May and July SC rainfall, which is partially related to the developing phases of ENSO events. It was also found that stronger (weaker) lower-tropospheric winds over SC and the upstream parts are responsible for more (less) SC rainfall in every month from May to August. Despite this monthly consistent enhancement of horizontal winds, the wind anomalies exhibit distinct differences between May-June and July-August, due to the remarkable change in climatological winds between these two periods. More SC rainfall is associated with a lower-tropospheric anticyclonic anomaly over the SCS and the Philippine Sea in May and June, but with a cyclonic anomaly centered over SC in July and August.