影响华南汛期持续性强降水年际变化的大气环流和海温异常

ATMOSPHERIC CIRCULATION AND SEA SURFACE TEMPERATURE ANOMALIES ASSOCIATED WITH THE INTERANNUAL VARIATION OF PERSISTENT HEAVY PRECIPITATION IN FLOOD SEASON OF SOUTH CHINA

利用1961—2017年中国地面观测站日降水资料、全球大气多要素和海表温度月资料,分析华南区域持续性强降水过程的气候特征,诊断并比较与华南前汛期、后汛期区域持续性强降水年际变化相关的大气环流和海表温度异常特征。结果表明,3—12月华南都可能出现持续性强降水过程,其中汛期4—9月的占了94.4%。伴随着区域持续性强降水的年际变化,华南本地垂直上升运动显著异常是前汛期和后汛期的共同点,但前汛期、后汛期在华南及周边环流异常、水汽输送来源以及海温异常分布等方面都存在一定差异。在前汛期华南区域持续性强降水偏重年,赤道西太平洋区域海温偏低,由于大气罗斯贝波响应使西太平洋副热带高压偏强,热带西太平洋向华南区域水汽输送加强,从而有利于区域持续性强降水偏重。后汛期华南区域持续性强降水偏重年的海温异常分布是赤道中东太平洋区域正异常、东印度洋至西太平洋暖池区负异常,海温异常通过西北太平洋副热带高压、南海热带季风强度、水汽输送和垂直环流等多方面,导致后汛期区域持续性强降水偏重。

Using the daily precipitation data from surface observation stations in China,the global atmospheric multi-factor and SST monthly analysis data from 1961 to 2017,the present study analyzed the climatic characteristics of the persistent heavy precipitation processes in South China and diagnosed and compared the characteristics of atmospheric circulation and sea surface temperature(SST)anomalies related to the interannual variation of persistent heavy precipitation in the rainy seasons in South China.The results showed that persistent heavy precipitation processes in South China might occur from March to December,of which 94.4%occurred in rainy seasons(April—September).The significant anomaly of local vertical upward movement in South China was a common feature of the two rainy seasons each year,associated with the interannual variation of regional persistent heavy precipitation.However,there were some differences between the two rainy seasons in terms of circulation anomalies,water vapor transport sources and abnormal distribution of SST.When the persistent heavy precipitation in the annually first rainy season was strong,SST anomalies was negative in the equatorial western Pacific region(145~170°E,10°S~13°N).Because of the strong subtropical high of the western Pacific due to the atmospheric Rossby wave response,the water vapor transport from tropical western Pacific to the southern China region was strengthened.This was favorable to regional persistent heavy precipitation.When the persistent heavy precipitation in the annually second rainy season was strong,the SST anomaly was positive in the equatorial Middle and East Pacific(175~140°W,5°S~15°N)and negative in the warm pool from the Eastern Indian Ocean to the Western Pacific.Through the subtropical high in the Northwest Pacific,the intensity of the tropical monsoon in the South China Sea,the water vapor transport,and the vertical circulation,the SST anomalies resulted in the heavy rainfall in South China in the annually second rainy season.