An analyses of long-term precipitation variability based on entropy over Xinjiang, northwestern China

Abstract. Precipitation is one of important supply of water resources in arid and semiarid region of northwestern China, plays the vital role to maintain the fragile ecosystem. The entropy method was employed to detect the spatial variability of precipitation over monthly, seasonal and annual timescales in Xinjiang. The spatial distribution of precipitation variability was significantly affected by topography, and was zonal on annual, seasonal and monthly. The non-parametric Mann-kendall test was used to analyze the change point of trend. A precipitation concentration index has been developed categorize the variability of annual precipitation. The summer variability contributed less than that of other seasons to the annual variability. There is a great difference in the contribution of the different monthly variabilities to the annual mean variability in different years. Overall, the variability of precipitation was shown increase north of Xinjiang, especially in mountainous regions where the increase was statistically (P = 0.05) significant. South of the Xinjiang, the variability increased only slightly, consistent with the distribution of precipitation.