中文摘要：

利用SODA资料和ECCO资料计算得到的北太平洋副热带海洋环流强度,和国家气候中心整编的中国160站逐月降水资料,结合NCEP/NCAR再分析资料和Hadley中心海表面温度资料,分析了1970-2007年海洋环流强度异常同期的大尺度大气环流异常特征及对中国东部夏季降水的影响。结果表明：海洋环流强度变化与长江中下游地区降水存在密切的反相关。环流强度异常可以通过影响西太平洋副热带高压的南北位置异常进而影响长江中下游降水。海洋环流偏弱时,副高位置偏南,长江中下游地区受气旋性环流异常影响,来自副高西北侧的强西南水汽输送至此,在该地区形成强水汽辐合中心,同时伴随上升运动加强和对流的加强,进一步导致该地区降水偏多;当海洋环流偏强时,西太平洋副高位置偏北,长江中下游地区受反气旋性环流异常影响,伴随辐散下沉及水汽辐散,导致该地区降水偏少;海洋环流强度异常导致的中纬度海区海表面温度异常,可能是导致副高南北位置异常的主要原因。

英文摘要：

The impact of variability in the strength of the subtropical circulation in the North Pacific Ocean on the summer precipitation over the eastern China is investigated.The intensity of subtropical circulation in the North Pacific is diagnosed from SODA and ECCO dataset;the atmospheric circulation and the sea surface temperature（SST） are diagnosed from the NCEP/NCAR reanalysis dataset and the Hadley SST;the precipitation data is based on the monthly rainfall observations over 160 stations in China.This study is focused on the interaction between the atmospheric and oceanic circulations over the periods of 1970-2009.The results show that there exists a strong negative correlation between the variability of the sutropical circulatioin and the summer rainfall in the middle and lower reaches of the Changjiang River. When the subtropical gyre is relatively weaker（stronger） than normal,the subtropical high is located further south（north） than normal;an abnormal cyclonic（anticyclonic） circulation prevails over the Changjiang River basin,companied by the vigorous（weak） southwestern moisture transporting here to form a strong moisture convergence（divergence） center.This gives rise to an ascending vertical motion and at the same time the convection is strengthened（weakened）.As a result,a very favorable large-scale circulation is established,which can sustain the heavy（weak） rainfalls in the middle and lower reaches of the Changjiang River.Furthermore,the variation in the subtropical wind-driven gyre can generate SST anomaly at middle latitudes,which may be the primarily reason for meridional shifting of the subtropical high in the North Pacific Ocean.