Research on temporal and spatial distribution of precipitation changes in southern Shaanxi

Southern Shaanxi is located in the source of water area of the middle route project of South-to-North water diversion.The precipitation would influence this district,the water transfer project and the intake area.Using the precipitation data within almost 30 years from the meteorological agencies of Southern Shaanxi and the surrounding area,we calculated and decomposed the data using the method of empirical orthogonal function(EOF).We analyzed the feature vector distribution of precipitation.The results showed that:(1) precipitation changes of in southern Shaanxi present the feature of differences between the south and the north,differences between the east and the west,and relative uniformity;(2) The time-coefficient series of precipitation changes of in southern Shaanxi has a significant inter-annual variation,and the fluctuation continues to grow stronger during the year.