Remote Sensing Research of Snow Cover Distribution and Variation in Qilian Mountains in the Winter Half Year of 1996—2002

Using the dekad snow cover data in the winter half year of 1996-2002 provided by National Satellite Meteorological Center,combined with the temperature and snow data observed by meteorological ground stations and the DEM data of Qilian Mountains,the distribution and variation characteristics of snow cover in Qilian Mountains are studied.The results showed that the snow cover in Qilian Mountains had a band distribution with the mountains orientation in the winter half year,in ridge area with more snow,but in the valley and southen basin less.The characteristic of distribution frequency is that the highest is in west segment,then in east segment and the lowest in middle segment.The basic trend of average distribution height of different frequency snow cover is that the higher the snow cover frequency is,the higher the distributing height is.As far for the snow cover of different frequencies,the lower frequency takes the larger proportion. For mean snow cover frequency,the east and middle segments both is reducing trend reduced before the winter half year of 1998/1999 while increased after it,and the increment of mean snow cover frequency in east and middle segments are quite close,while the west segment increased in the winter half year of 1996/1997,and its mean snow cover frequency is higher than the east and middle segments significantly.The snow cover of three segments all increase as the height increases,only in middle segment of 1999 —2001 didn′t increase with height increasing apparently,it might has relation with the complex effects of weather system and topography in middle segment.