29 representative stations of northwest china are selected using eof analysis , and the detailed results of characteristics are given for temporal and space variation of interarmual change and decadal change . the main conclusions are followed : ( 1 ) the tendency of precipitation in northwest china is positive to the west of 103 e longitude and opposite to the east of it . there is a periodic oscillation of quasi - three years of precipitation and a mutation in the middle of 80s in spring precipitation of northwest china 用eof分析方法选取西北地区29个代表站,分别对其春季和夏季近50a降水进行年际变化和年代际变化时空特征分析,结果发现( 1 )西北地区近50a降水时空趋势变化以103 e为基准线,以西为正,以东为负,并有准3a的振荡周期, 80年代中期西北地区春季降水出现了气候突变。