Influence of South China Sea SST and the ENSO on winter rainfall over South China

Abstract

The present study investigates the influence of South China Sea (SCS) SST and ENSO on winter (January–February–March; JFM) rainfall over South China and its dynamic processes by using station observations for the period 1951–2003, Met Office Hadley Center SST data for the period 1900–2008, and ERA-40 reanalysis data for the period 1958–2002. It is found that JFM rainfall over South China has a significant correlation with Nino-3 and SCS SST. Analyses show that in El Nino or positive SCS SST anomaly years, southwesterly anomalies at 700 hPa dominate over the South China Sea, which in turn transports more moisture into South China and favors increased rainfall. A partial regression analysis indicates that the independent ENSO influence on winter rainfall occurs mainly over South China, whereas SCS SST has a larger independent influence on winter rainfall in northern part of South China. The temperature over South China shows an obvious decrease at 300 hPa and an increase near the surface, with the former induced by Nino-3 and the latter SCS SST anomalies. This enhances the convective instability and weakens the potential vorticity (PV), which explains the strengthening of ascending motion and the increase of JFM rainfall over South China.