【摘要】 １９９５年初秋，西北地区出现持续１３天的连阴雨天气过程，降雨主要集中在１０５°Ｅ以西和陕南。５００ｈＰａ环流特征为乌拉尔山高压脊稳定，脊前西伯利亚维持宽广的大低压，西太平洋副热带高压南撤到３０°Ｎ后稳定，有几次东西振荡。正涡度中心的移动同降雨中心相吻合。正涡度主要在４２°Ｎ和３５°Ｎ附近东移，造成南北两个降雨中心。两个正涡度之间为负涡度区，对应相对少雨带。５００ｈＰａθｓｅ湿舌从青藏高原向北伸展，７００ｈΡａ湿舌从高原东侧伸向西北。中低层湿舌北上维持，降雨持续；湿舌减弱南退，降雨结束。更多还原

【Abstract】 In early autumn of1995,continuous rain during thirteen days appeared in the Northwest China,precipitation was mainly collected on the west of105°Eand in the south of Shanxi 500hPa circulation feature was high pressure ridge stability of the Ural Mountain Before pressure ridge broad large low pressure maintained in the Siberia West pacific sub tropical high steadied when it had moved on the south of30°N It had several east-west os cillations When moving,positive vorticity centre accorded with precipitation centre Positive vorticity principally runed in the east direction around42°Nand35°N,that formed two pre cipitation centres about south and north Negative vorticity region that corresponded to rela tive little precipitation zone was located between two positive vorticity regions 500hPa θ se moist tongue extended from Qingzhang Plateau to north direction 700hPa θ se moist tongue extended from the east of Plateau to northwest direction Precipitation continued when moist tongue of middle-low layer moved to north direction and remained Precipitation finished when moist tongue moved to south direction and reduced更多还原