华南夏季极端降水时空变异及其与西北部太平洋海气异常关联性初探

Primarily Analyses on Variations of Summer Extreme Precipitation in South China and Its Relation to the Sea-Air Anomaly in Northwestern Pacific Ocean

基于长时间序列的观测和再分析数据,分析了1958-2008年间华南夏季极端降水的时空变异特征及其与西北部太平洋海域的海表温度、潜热通量以及水汽输送异常的联系。华南地区夏季极端降水异常变化的主要模态显示,华南绝大部分地区夏季极端降水异常呈同相变化,并以2～5年的年际变化最为显著。特别是近50年来该地区夏季极端降水趋势变化在20世纪80年代末存在明显转折,即在1989年之前华南绝大部分地区夏季极端降水频次呈减少趋势,之后表现为增多趋势。结果表明,西北部太平洋同期海气异常与我国华南地区夏季极端降水显著关联的关键区主要位于南海海域及其邻近的西太平洋暖池区。该海域的海表温度、潜热通量的异常变化可能是影响华南夏季极端降水的重要因素,而南海北部水汽经向输送的异常变化可能是引起华南夏季极端降水变异的关键因素之一。这可为我国华南地区夏季极端降水变异规律、机理及模拟预测研究提供一定的参考依据。

Based on the long time observation and reanalysis data, the spatio-temporal variations of summer extreme precipitation event （SEPE） anomaly in South China during 1958--2008 were investigated and their possible relationship with the anomalies of sea surface temperature （SST）, latent heat flux and water vapor transport in the northwestern Pacific ocean were primarily discussed. The dominate mode of the SEPE anomaly in South China indicates that, for most part of South China, the SEPE anomaly gener- ally varies in phase with striking interannual variation of 2-5 years. In the recent 50 years, there is a sig nificant shifting in the trend of the SEPE around the end of 1980s, that is, the trend is decreasing before 1989 while increasing subsequently. The analyses suggest that, the South China Sea （SCS） and its adia- cent region of western Pacific warm pool is the key sea area of the northwestern Pacific ocean, where the air-sea anomalies are significantly associated with the SEPE anomaly in South China. The anomalies of SST and latent heat flux in the key sea area can be considered as important factors to impact the SEPE, and the anomalous meridional water vapor transport over the north of SCS is very likely one of key proces- ses to induce the SEPE anomaly in South China. The results above would provide the essential reference for the further research of rules, mechanisms and forecasts of the SEPE in South China.