中文摘要：

采用ERA Interim再分析资料和160站逐月站点降水资料,运用经验正交函数（EOF）分析、合成分析等方法揭示了西北东部3个分区的水汽输送的区域气候特征、与降水EOF气候模态相对应的整层水汽输送特征以及降水偏多（少）年的水汽输送异常特征。结果表明：西北地区东部夏季经向水汽输送的大值区处于900 h Pa～800 h Pa高度上;纬向水汽输送大值位于700 h Pa～500 h Pa高度上。对西北东部降水做EOF分析,第一模态为全区一致型,与降水相对应的西风影响区主要盛行西风水汽输送,季风边缘区的南部盛行西南风水汽输送;第二模态为东南-西北型,东风、东北风水汽输送流入西北东部地区;第三模态为东北-西南型,西风和西北风水汽输送将水汽带到西风影响区内。

英文摘要：

On the basis of ERA Interim reanalysis data and monthly precipitation observation station data of 160 stations over the eastern northwest China（32.5°N-42.5°N,100°N-112.5°N）during 1979-2015,the regional climatic characteristics of water vapor transportation over eastern northwest China,characteristics of vertically integrated water vapor transportation corresponding with the EOF modes of precipitation,characteristics of geopotential height and water vapor transportation anomaly during strong（weak） precipitation years were revealed through empirical orthogonal function（EOF）analysis,composite analysis methods. The results show that the strongest summer latitudinal vapor transportation is at 700-500 h Pa,and the strongest summer longitudinal vapor transportation is at 900-800 h Pa over the eastern northwest China. The first EOF mode of eastern northwest China precipitation is consistent over the whole area. Corresponding to the first precipitation mode,there is a cyclonic anomaly to the east of Lake Baikal and an anticyclonic anomaly over south-east China and the water vapor transported by west wind almost prevails the whole area. Water vapor transported by wet south-west wind from prevails to the south of Monsoon Fringe. The second EOF mode of precipitation shows southeast-northwest pattern. Corresponding to the second EOF mode,an anticyclonic anomaly centers around Siberia and the westerly wind area is located to the north of the anticyclonic anomaly. Water vapor is mainly transported by easterly wind.The strongest precipitation area is around the east boundary because the water vapor transported through east boundary is reduced at the transportation process. There is a cyclonic anomaly around the Yellow Sea. Qinghai-Tibet Plateau and the monsoon fringe area are to the north-west of the cyclonic anomaly. Water vapor is mainly transported by north-east wind from the ocean to the east of China. The third mode shows northeast-southwest pattern. Corresponding to this mode,there is a cyclonic anomaly in