INTERANNUAL VARIABILITY OF WINTER AND SPRING PRECIPITATION IN SOUTH CHINA AND ITS RELATION TO MOISTURE TRANSPORT

The interannual variability of winter and spring precipitation in South China (SC) and its relation to moisture transport are investigated by using the monthly precipitation data of NMIC, NCEP reanalysis datasets and NOAA ERSST analysis datasets from 1960 to 2008. The results show that winter and spring precipitation in SC is less than normal from the 1960s to the start of the 1970s and from the end of the 1990s to the present. Most of rainfall anomalies on the whole regional scale of SC is well in phase during winter and spring, and the frequency of persistent drought is higher than that of persistent flood. Seasonal variations of moisture transport differences of SC between persistent drought and flood events are observed: the differences in winter are characterized by moisture transport from Bay of Bangle (BOB) and South China Sea (SCS), while differences in spring are characterized by that from SCS and North China (NC). There are two types of Niño3.4 sea surface temperature anomaly (SSTA) related to persistent winter and spring drought (flood) events in SC, which are positive SSTA next to Niño4 (Niño3) and negative SSTA next to Niño3 (Niño4). Moreover, the variations of moisture transport from BOB and SC have important effects on persistent drought/flood in SC when the Niño3.4 index is in the positive phase, while those from western North Pacific (WNP)-SC in winter and those from Philippine Sea (PHS)-SC and NC in spring primarily contribute to persistent drought/flood events in SC when the Niño3.4 index is in the negative phase, and these stronger (weaker) moisture transports are observed in persistent flood (drought) during winter and spring regardless of the Niño3.4 index. In conclusion, with the correlation between variations and distributions of Niño3.4 SSTA and persistent drought/flood events in SC, moisture transport is responsible for the formation of precipitation anomalies. In addition, the moisture transport from SCS is most significantly correlated with persistent drought/flood events during winter and spring.