华南夏季降水的变化特征及其与热带太平洋海温异常的关系

根据1958-2008年华南48站降水资料、NOAA全球逐月海温格点资料、NCEP/NCAR再分析资料，采用EOF分解、相关、合成等统计方法，分析了华南夏季降水的变化特征及其与冬季热带太平洋海温的关系。结果表明，华南夏季降水变化特征主要表现为，空间分布以全区一致型为主，其次是南北反相对称型和东西反相对称型，且这3种分布模态都表现出显著的年际和年代际特征。全区一致型降水异常与热带太平洋海温显著相关，二者的相关性也具有年代际变化特征，其对应的热带太平洋海温具有沿赤道太平洋呈“负-正-负”的纬向分布型，类似于中部型El Nino。全区降水偏多时期，西南季风偏强，西太平洋副热带高压偏强、脊点位置偏西，南亚高压偏强、脊点位置偏东，总体的环流形势有利于华南地区的水汽输送和上升运动；降水偏少时期，情况相反。

The Variation of Summer Precipitation in South China and Its Relationship with SST Anomalies in the Tropical Pacific

Based on the precipitation data of 48 selected stations in South China, the NCEP/NCAR analysis data during 1958-2008 and the NOAA monthly sea surface temperature (SST) data for the period 1957-2008, The variation features of summer precipitation in South China and its relationship with the SST in the tropical Pacific in winter have been studied using EOF decomposition, correlation, synthesis and other statistical methods. The results indicate that the first mode show consistent anomalous signs in the whole South China region, the Second mode is out-of-phase at the north and south of South China and the third mode is out-of-phase at the east and west of South China. These three modes show obvious interannual and decadal variation. The tropical Pacific SSTA, which corresponds to the first mode rainfall anomaly, has a “-+-”zonal three-pole type pattern along the equatorial Pacific, similar to El Nino-Modoki. The significant positive correlation between SST index and rainfall index also has decadal characteristic. In the period with more precipitation, the southwest summer monsoon and the west Pacific subtropical high (WPSH) are stronger. The ridge position of the WPSH extends westward. The ridge of South Asian high extends eastward and its strength is stronger. All of them are in favor of water vapor transport and convective motion in South China, leading to increased precipitation in South China. Conversely, there will be less precipitation in South China.