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To reveal the characteristics of the spatial-temporal variations of water vapor over Gansu Province,the variation of the atmospheric water vapor content over the area from 1961 to 2000 was studied by means of EOF,REOF,wavelet and Petitt jump-point methods.The results show that there were four sensitive areas(spatial pattern) in water vapor variation in Gansu: the eastern and western parts are the most sensitive;the central part is the second;the temporal variation show obviously phasic feature.Abrupt changes occurred in 1977 and 1977: there were a decreasing trend before 1977,fluctuation in 1977-1987,an obvious increasing trend after 1987.The wavelet analysis indicates that there was remarkable oscillation in water vapor with the periods being 2 to 4 years,strong in variability before the 1970s,relativity weak after the 1980s.