(1.Lhasa Branch of Chengdu Plateau Meteorological Research Institute of China，Meteorological Administration，Lhasa 850001，China；
2.Tibet Institute of Plateau Atmospheric and Environmental Science Research，Lahasa 850001，China；
3.Tibet Lhasa Meteorological Bureau，Lhasa 850001，China；
4.Key Laboratory of Digital Earth Science，Institute of Remote Sensing and Digital Earth，Chinese Academy of Sciences，Beijing 100094，China)
Abstract：The snow cover variation in Yarlung Zangbo from July 2002 to April 2015，as the mother river of Tibet，has been analyzed in this article.The hydrological year is from September of the year to August of the next year.The snow cover variation was studied used by cloudless snow cover data at 500 m and surface temperature from MODIS，digital elevation model (DEM) and meteorological data.The relationship was established between surface temperature from MODIS and major meteorological factors.The results show that the average snow cover in the study area is 3.56× 104km2 in the past 12 years，showing an overall decreasing trend.The area with large snow cover is in the upper and lower reaches of the basin，and the stable and seasonal snow dominate the rural area in the middle reaches and valley basins，with perennial less snow distribution.The stability of snow and perennial snow distribution is more than 4 000 meters above the sea level，which the snow lasts for more than 180 days.And the seasonal snow is mainly less than 4 000 meters above sea level with large variation of snow cover in the area.The inversely relationship is between the air temperature and the area of snow cover，but not significant between the precipitation and the area of snow cover.And the correlation in the surface temperature and the area of snow cover is obvious.In Short，the rising temperature is the main driving factor of snow area reduction in the basin.
2018, Vol. 33 
