2006年川渝地区夏季干旱的成因分析

摘要

Based on the NCEP/NCAR reanalysis monthly mean data,the 160 stations rainfall data in China,the OLR(outgoing longwave radiation)data and the calculated heat source data,the anomalies of atmospheric circulation in summer 2006 have been analyzed,and the relation between heat source a-nomalies and summer precipitation in the Sichuan-Chongqing region has been investigated.It is shown that the vertically integrated moisture transport from south to north in summer 2006 was weaker than normal.The western Pacific subtropical high(WPSH) was stronger and shifted northwestward and the subsidence flow prevailed over the Sichuan-Chongqing region.There was no blocking high over the U-ral Mountains and Northeast Asia,and the cold air activities were weaker than normal.The South Asia high Was also stronger than normal,and controlled persistently the area over eastem Sichuan and Chongqing.One reason that the WPSH Was stronger and shifted northwestward,is that the heat sources over the Tibetan Plateau were weaker while the western Pacific warm pool Was stronger.The summer rainfall over Sichuan-Chongqing has a close relation with the WPSH;in the summer drought years of Sichuan-Chongqing,the WPSH shifts northwards.The reason for that is the same for the summer case of 2006.%利用NCEP/NCAR再分析月平均资料、全国160站降水资料、向外长波辐射OLR(outgoing longwave radiation)资料和所计算的热源资料,分析了2006年夏季东亚大气环流的异常特征,并研究了热力异常与川渝地区夏季降水的关系.结果表明,2006年夏季由南向北的水汽输送较常年偏弱;西太洋副热带高压较常年异常偏强,脊线位置明显偏北,川渝地区受高压系统影响盛行下沉气流.中高纬环流场则表现为乌拉尔山地区和东北亚区域无明显阻塞高压形势,冷空气活动比常年弱:南亚高压比常年偏北偏强,持续控制川渝地区;2006年夏季青藏高原热源偏弱,热带西太平洋暖池区热源偏强,是引起西太平洋副热带高压偏北偏强的重要原因之一.川渝地区夏季降水与西太平洋副热带高压的异常变化有密切关系,川渝地区夏季干旱年,西太平洋副热带高压偏北,并且引起西太平洋副热带高压偏北的原因与2006年类似.