Characteristics of the Starting and Ending Dates of Snow Cover in Northern Xinjiang Region

Based on daily snow depth data from 32 stations in Xinjiang Region from 1961 to 2006,the climate characteristics of starting date and ending date of snow cover and their temporal variation in northern Xinjiang Region are analyzed. The results show that the starting date and ending date of snow cover have obvious regional difference,which is mainly caused by the terrain height change. The oscillations with 12 a and 8 a periods are the main temporal characteristics of starting date of snow cover,while the oscillations with 5 a and 8 a periods are the main temporal characteristics of ending date of snow cover. Snow cover starts earlier with altitude increasing,and snow cover ends later with altitude increasing in lower altitude (≤1 000 m),but in higher altitude (1 001~2 000 m),it is opposite. The variation of starting date is more significant than that of the ending date. By correlation and composite analyses,it is found that the starting date and ending date of snow cover have a positive relation with altitude. With altitude ascending,the starting date becomes earlier,and the ending date later.