Regional Differentiation Characteristics of Precipitation Changing with Altitude in Xinjiang Region in Recent 50 Years

According to the rate of precipitation changing with altitude and the principle that a subzone must be contiguous,the 120 meteorological stations was divided into two types with six precipitation subzones in Xinjiang Region.There are three subzones below 2 500 m a.s.l.,of which precipitation varies linearly with the altitude.There are three subzones above 2 500 m a.s.l.,of which precipitation varies approximately as quadratic equation of altitude.When the variation of precipitation with altitude is linear,the maximum precipitation takes place in the mountaintop.Otherwise,the maximum precipitation takes place in the mountainside.What's more,the maximum precipitation altitude changes with season and drought degree.The maximum precipitation altitude in summer is higher than that in winter;and the drier the climate,the higher the altitude.The maximum precipitation altitude and precipitation amount has significant difference among the six precipitation subzones.The maximum precipitation altitude in Subzone 1 is 3 190 m a.s.l.,with the mean annual precipitation of 226.9 mm;the maximum precipitation altitude in Subzone 4 is 3 332 m a.s.l.,with the mean annual precipitation of 86.9 mm;the maximum precipitation altitude in Subzone 6 is 3 840 m a.s.l.,with the mean annual precipitation of 36.4 mm.