The spatio-temporal variations of precipitation based on entropy in Tianshan Mountain

Precipitation plays a major role in maintaining the water supply in Mountainous area, which directly impacts the development of ecology environment and economic society in the mid and down streams of arid regions. Due to the technical and geographical limitations, one difficult problem in precipitation study is to accurately observe the meteorological factors. The entropy is used in this study to investigate the spatio-temporal variations of precipitation in annual, seasonal and monthly time series from 31 stations located in the Tianshan Mountain during 1960-2008. The results showed that there was an obvious spatial-temporal variability of precipitation in the Tianshan Mountain. The variability of precipitation of annual entropy was less than that of the seasonal, which is in turn less than the monthly. The decreasing trend of annual entropy was significant. In seasons, the variability of entropy was very significant in winter, but not in summer. The variability of entropy exhibited difference between precipitation and elevation for seasons. There was an increasing trend in the precipitation in northern slope with the elevation increase, while decreasing in southern slope of Tianshan Mountain in spring, summer and fall. The precipitation increased from April to September, and decrease from October to March of next year. The variability of monthly entropy and precipitation were antithetical. The spatial variability of entropy was more radical in southern and eastern slope than northern and western slope. The variability of entropy was minimal in Ili River valley. Obviously, the spatio-temporal variations of precipitation can be depicted by entropy, and supply a scientific basis to the rational development of water resources in Mountain area.