Impacts of Different Onset Time El Nino Events on Winter Precipitation over South China

Winter precipitation over South China tended to be much higher than normal for the spring El Nino events during 1979-2016. For the spring El Nino events, the meridional and zonal circulations served as a bridge, linking the warmer sea surface temperature (SST) in the eastern equatorial Pacific (EEP) and South China winter precipitation. This possible physical process can be described as follows: During boreal winter, a positive SST anomaly in the EEP was concurrent with strong anomalous convection activity over South China via anomalous Walker circulation, an anomalous Hadley Cell along 110 degrees-130 degrees E, and a zonal westward teleconnection wave train pattern at 700 hPa in the Northern Hemisphere. In addition, an anomalous pumping effect at 200 hPa contributed to the convective activity. Meanwhile, the western Pacific subtropical high moved southwards and strengthened at 500 hPa, and abnormal southwesterly winds brought plentiful water vapor to South China at 850 hPa. All these factors favored an increase in precipitation over South China. For the summer El Nino events, the aforementioned anomalies were weaker, which resulted in a precipitation close to normal over South China.