Accurate rainfall distribution is difficult to acquire based on limited meteorological stations,especially in remote areas like high mountains and deserts.The Hexi Corridor and its adjacent regions(including the Qilian Mountains and the Alxa Plateau)are typical districts where there are only 30 available rain gauges.Tropical Rainfall Measuring Mission(TRMM)data provide a possible solution.After precision analysis of monthly 0.25 degree resolution TRMM 3B43 data from 1998 to 2012,we find that the correlations between TRMM 3B43 estimates and rain gauge precipitation are significant overall and in each station around the Hexi Corridor; however,the biases of annual precipitation differ in different stations and are seriously overestimated in most of the sites.Thus,Inverse Distance Weighting(IDW)interpolation method was used to rectify TRMM data based on the difference between TRMM 3B43 estimates and rain gauge observations.The results show that rectified TRMM data present more details than rain gauges in remote areas where there are few stations,although they show high coherence of distribution.Precipitation decreases from southeast to northwest on an annual and seasonal scale.There are three rainfall centers(>500mm)including Menyuan,Qilian and Toson Lake,and two low rainfall centers(<50mm)including Dunhuang and Ejin Banner.Meanwhile,precipitation in most of the study area presents an increasing trend; especially in northern Qilian Mountains(>5mm/a),Badain Jaran Desert(>2mm/a),Toson Lake(>20mm/a)and Qingtu Lake(>20mm/a)which shows a significant increasing trend,while precipitation in Hala Lake(<-2 mm/a)and Tengger Desert(<-3mm/a)demonstrates a decreasing trend.
