Snow cover in the upper Yangtze River basin and its influence on the streamflow of Yangtze River

Quantitatively assessing snow cover is a very difficult task due to strong spatial variability in snow accumulation,especially for regions with complex terrain and sparse surface observation stations.Since the 1970 s,satellite retrieved snow/ice data have become available and filled the gaps where surface stations do not exist.However,many satellite remote sensing systems based on visible light and infrared are also limited by daylight availability and cloud cover,which has very high frequencies of occurrence in high latitude and highland regions.In this study,the National Snow and Ice Data Center(NSIDC) snow cover data retrieved from passive microwave remote sensing systems are used to quantify the snowpack within the upper Yangtze River Basin(YRB).The passive microwave remote sensing systems have the advantage of all-time and all-weather operations.Using this dataset,the contributions of snow accumulation to the Yangtze River streamflow at three gauging stations in the upper YRB(Gangtuo,Shigu,and Wanxian) were examined for the period 1978-2002.We found that the snow water equivalent(SWE) in the upper YRB had significant influences on streamflow in the spring season,and its indirect effects showed up in the following summer and fall seasons.In general,the influence of snow accumulation decreased from the headwater toward downstream.Results from this study will shed lights on the influence of snow melt over the Tibetan Plateau on the Yangtze River streamflow under the current and future climatic conditions.