Spatial and Temporal Variation of Annual Precipitation in a River of the Loess Plateau in China

Empirical orthogonal function (EOF) decomposition and geostatistical (semivariogram) analysis are used to analyze the spatial and temporal patterns of annual precipitation in the Weihe basin based on the data from 1960 to 2011 at 30 national meteorological stations within and surrounding the Weihe basin area of the Loess Plateau in China. Then the Mann-Kendall method is used to discriminate the variation points of precipitation series at each station. The results show that, during the study period, there was an overall reduction in annual precipitation across the basin and there were two spatial patterns: increase in the northwest, decrease in southeast and increase in the west, decrease in east. Variation points in the annual precipitation series at each meteorological station in the basin were detected, and they occur earliest in the southeast and downstream, then progressively later in the northwest and upstream areas. These variations were most frequent during the 1970s and 1980s. The findings have significant implications for the variations research of runoff in the basin and formulate robust strategies to adapt to climate change and mitigate its effects.