中文摘要：

利用1980-2010年NCEP/NCAR再分析资料和美国NOAA向外长波辐射（outgoing longwave radiation,OLR）资料,根据关键区500 hPa位势高度的变化定义了西太平洋副高东西位置指标,利用该指标围绕东亚夏季风系统开展分析,详细对比了夏季6月、7月副高东西向活动异常时,季风区相应的环流及对流活动差异.结果表明：副高东西位置的年际变化反映了亚洲夏季风的强弱变化,副高偏西（东）年,南海夏季风偏弱（强）,副热带夏季风偏强（弱）;副高的东西进退与东亚夏季风系统成员之间相互影响、相互制约;副高偏西年,南亚高压偏东、偏强,季风槽不发展、强度偏弱,西风带长波槽发展加深,南半球马斯克林高压和澳大利亚高压减弱,越赤道气流减弱,而副高偏东年情况则反之.

英文摘要：

Using the NCEP/NCAR reanalysis data and the OLR （outgoing longwave radiation） data from NOAA during 1980-2010,an index is defined to describe the longitudinal position of the western Pacific subtropical high based on 500 hPa potential height variation in the key areas.With the index,an investigation is carded out closely with the East Asian summer monsoon system,and the circulation and convective activity differences are revealed in the monsoon area as the subtropical high position is abnormal in June and July.Results show that the abnormal eastern-western position of the subtropical high reflects the Asian summer monsoon intensity,that is,when the subtropical high position is west（east）,the South China Sea＇s summer monsoon is weak（strong）,and the subtropics summer monsoon is strong （weak）.There exists some interaction between the advance and retreat of the subtropical high and members of the East Asia monsoon system.In the western subtropical high years,the South Asia high is strong with eastern position,the monsoon trough is weaker,the long-wave trough develops deeper,the Mascarene high and the Australia high is weaker,and the cross-equatorial flow is also weaker.The situation is contrary in the eastern subtropical high years.