Climatic Characteristics of Daily Precipitation from May to September in Recent 45 Years in Qilian Mountains

The different level rainy days and its homologous precipitation quantity are obtained by using the daily precipitation data from May to September (1960-2004) of 17 stations in the Qilian Mountain area,thus,we know the daily precipitation intensity of light rainfall and moderate rainfall(and more) at each station.Based on regional mean value of the different level rainy days and rainfall intensity in Qilian Mountain area,the tendency of the different level rainy days and rainfall intensity was analyzed using linear trend coefficient and 5 levels main value function.The results show that both precipitation and different level rainy days from May to September in Qilian Mountain area presented more in the west side and less in the east side in the same latitude area,and more in the east and less in the west part of Qilian Mountain.In recent 45 years,the light rainfall days was descending,but the moderate rainfall days was ascending.The precipitation intensity of light rainfall and moderate rainfall (and more) presented ascending trend too from May to September in Qilian Mountain area.The morlet wave analysis show that the light rainfall days had a period of five years,but the period of the moderate rainfall (and more) days was more complex.