Influence of South China Sea SST and the ENSO on Winter Rainfall over South China

The present study investigates the influence of South China Sea (SCS) SSTand ENSO on winter (January--February--March; JFM) rainfall over South Chinaand its dynamic processes by using station observations for the period1951--2003, Met Office Hadley Center SST data for the period 1900--2008, andERA-40 reanalysis data for the period 1958--2002. It is found that JFMrainfall over South China has a significant correlation with Nino-3 andSCS SST. Analyses show that in El Nino or positive SCS SST anomalyyears, southwesterly anomalies at 700 hPa dominate over the South China Sea,which in turn transports more moisture into South China and favors increasedrainfall. A partial regression analysis indicates that the independent ENSOinfluence on winter rainfall occurs mainly over South China,whereas SCS SST has a larger independent influence on winter rainfall innorthern part of South China. The temperature over South China shows an obvious decrease at300 hPa and an increase near the surface, with the former induced byNino-3 and the latter SCS SST anomalies. This enhances the convectiveinstability and weakens the potential vorticity (PV), which explains thestrengthening of ascending motion and the increase of JFM rainfall overSouth China.