利用经验正交函数 (EOF) 分析方法和1951-2004年NCEP/NCAR月平均再分析资料及160个中国地面测站月降水资料，对夏季东亚地区水汽输送的年代际变化特征及其对中国东部降水的影响进行分析。研究结果表明：20世纪70年代中后期至90年代初期，中国东部夏季降水以“南北旱中间涝”分布型为主，90年代初期之后则以“南涝北旱”分布型为主，呈现出显著的年代际变化特征，即20世纪90年代后雨带南移的特征开始明显；夏季整层水汽输送通量主模态的空间结构及其时间系数可以较好地反映出近50年来东亚大陆东部经向水汽输送从1974年起由强变弱的“转折点”特征及其年代际减弱变化趋势；印度大陆和孟加拉湾北部、长江中下游地区、南海以及热带西太平洋地区纬向水汽输送从1973年起由弱变强的“转折点”特征及年代增强变化趋势。揭示了东亚夏季水汽输送年代际分量主模态的时空演变造成中国东部夏季降水从“南北旱中间涝”分布型转向“南涝北旱”分布型，即中国东部夏季雨带呈现出南移年代际变化特征的关键因素之一。

This paper analyzes the interdecadal variation of water vapor transport over East Asia and its impacts on rainfall over eastern China in summer by using EOF analysis method, NCEP/NCAR monthly reanalysis data and monthly rainfall data covering 160 stations over China from 1951 to 2004 in summer. The results show that the main distribution mode of summer rainfall over eastern China is south and north flooding/middle drought from the mid- and late of the 1970s to the beginning of the 1990s and presents a south flooding/north drought pattern since the beginning of the 1990s. The interdecadal variation of summer rainfall over eastern China is very significant and rain belt shifts southward obviously since the 1990s. The leading mode of EOF and its time series coefficients reveal that the meridional water vapor transport over east of East Asia Mainland is characterized by a turning point from strong to weak and a decadal weakening trend since 1974. The zonal water vapor transport over India Mainland and northern part of Bay of Bengal, middle and lower reaches of Yangtze River Valley, South China Sea and tropical Pacific region is characterized by a turning point from weak to strong and a decadal enforcing trend since 1973. The temporal-spatial evolution in summer water vapor transport over East Asia is one of key factors that trigger a shift from south and north flooding/middle drought to south flooding/north drought, which leads to the induction of the rain belt shifting southward.