Analysis on Spatial and Temporal Distribution of Precipitation Variation in Shaanxi Province

Based on monthly precipitation data of 97 cities and counties from 1961-2005 in Shanxi Province,the rainfall spatial distribution of Shaanxi Province is studied with EOF(Empirical orthogonal function) method.The article takes the precipitation set degree to describe precipitation differentiation during the whole year this area.And it explores the time variation of rainfall by seeking the precipitation field time trend coefficient.The results show that the rainfall in the southern part of Shaanxi Province is more than it in the northern part.It has four kinds of rain type,the precipitation was seasonal changes in most areas,the precipitation overall slow decline,and the seasonal changes is that spring,autumn decline and summer,winter rose.