Analyzing Spatial and Temporal Distributions of Precipitation in the Southern Part of Shaanxi Province

Southern Shaanxi refers to the southwestern part of Shaanxi, and from the west to the east of Shaanxi Province, there are three cities: Hanzhong, Ankang and Shangluo. The annual precipitation data of 8 meteorological stations in the southern part of Shaanxi Province from 1977 to 2017 were selected, and the area was analyzed by EOF (empirical orthogonal function method). The results show that the EOF method can well reveal the temporal and spatial distributions of precipitation field. For the southern part of Shaanxi Province, the first two eigenvectors reveal two typical distribution fields, which are global and eastwest patterns. Its cumulative contribution rate is 79.90%. In general, the eigenvectors of the two fields are expressed as the western region is larger than the eastern region. And high-value centers appear in Hanzhong City. The analysis of the time coefficient corresponding to the eigenvectors shows that the precipitation fields in the southern part of Shaanxi Province mainly show four types. Which includes the wetter in the whole region, the drier in the whole filed, the wetter in west and drier in east, and the wetter in east and drier in west. Compared to the statistical results of 41 year, these results were consistent with the typical precipitation fields.