Variation Characteristics of Rainfall in the Pre-Flood Season of South China and Its Correlation with Sea Surface Temperature of Pacific

The characteristics of rainfall variation in the pre-flood season of South China (PFSSC) and its correlation with the sea surface temperature (SST) of the Pacific are studied in this paper. The results show that in the last 50 years, rainfall in PFSSC clearly has interannual and interdecadal oscillations, primarily in the 4a and 8a cycles. Interannual correlation analysis indicate that the rainfall in PFSSC displays a significantly negative correlation with the SST of the warm pool region in January–March and April–June. The interdecadal correlation analysis reveals that the rainfall in PFSSC is negatively correlated to the SST of the warm pool region, but has a significant positive interdecadal correlation with the Middle Eastern Pacific Ocean. For NINO1 + 2 and NINO3 regions, when the background ocean temperature is warm, the SST is significantly positively correlated to the rainfall in PFSSC; however, when the background ocean temperature is cold, there is no significant correlation between the two, even the correlation coefficients are negative. For the warm pool region, the SST demonstrates a significantly negative correlation to the rainfall in PFSSC, which is not dependent on the background SST. It is a remarkable fact that under the different SST backgrounds, the interannual variation of SST will bring different atmospheric response, and it is the reason that under the warm SST background, the correlation is more significant between the SST in tropical Pacific and the rainfall in PFSSC. Under the background of global warming, more attention should be given to study the rainfall in PFSSC and its correlation with the SST in the eastern tropical Pacific.