中国华南3月降水和大气环流的年代际转型及其与PDO的联系

Interdecadal Shift of March Precipitation and Atmospheric Circulation in South China and Their Relationships with PDO

利用1951—2012年华南30个测站逐月降水资料、NCEP/NCAR月平均再分析资料和NOAA全球月平均海表温度等资料,研究分析了中国华南地区3月降水的年代际转型及相关海气异常型。在此基础上,建立基于海表温度的预测模型对华南3月降水进行回报与预测。结果表明:1970年代中后期和1990年代末PDO发生2次位相转换与华南3月降水的年代际变化联系紧密。当PDO位于暖(冷)位相时,北太平洋中部海表温度偏低(高),阿留申低压减弱(加强),使得东北—日本海气压偏高(低),青藏高原气压偏低(高),华南地区处在较强垂直上升(下沉)运动区,且低层有一显著的气旋性(反气旋性)环流异常,有(不)利于低层水汽辐合,从而导致华南3月降水增加(减少)。此外,PDO位于暖(冷)位相时,赤道西太平洋海表温度偏冷(暖),导致菲律宾上空反气旋加强(减弱),南海向我国华南地区的水汽输送增加(减少),致使华南3月降水增加(减少)。

Based on the monthly precipitation data at 30 weather stations in South China during 1951-2012,monthly reanalysis data from NCEP / NCAR and monthly global sea surface temperature（SST） data from NOAA,the interdecadal shift of March precipitation in South China and accompanying change of East Asia circulation were investigated. And on this basis the prediction model of precipitation in March based on SST was established. The results show that the interdecadal change of March precipitation in South China were closely related with two interdecadal shift of the pacific decadal oscillation（PDO） in the mid to late 1970s and the late 1990s. When PDO was in positive（negative） phase,SST in central North Pacific was colder（warmer）,Aleutian low pressure weakened（strengthened）,which led to higher（lower） sea-level pressure（SLP） over Northeast China to Japan sea and lower（higher） SLP over the Tibet Plateau. In the meantime,South China located in the ascending（sinking） motion region,and the cyclone（anticyclone） circulation anomalies existed in lower layer over South China,which was conducive to convergence（divergence） of water vapour to cause the flood（drought） in South China. In addition,when PDO was in positive（negative） phase,SST in equatorial western Pacific Ocean was colder（warmer）,which resulted in the intensification（weakening） of anticyclone over Philippines and increase（decrease） of water vapor transport from South China Sea to South China,and further March precipitation over South China increased（decreased）.