Analyzing spatial-temporal variability of snow cover in Xinjiang

Snow cover is one of the most active factors that influence the environment, and shows high sensitivity to climate changes.Based on the moderate resolution imaging spectroradiometer (MODIS) snow cover products and observed data from 84 meteorological stations within Xinjiang Uygur Autonomous Region of China, we extracted the snow cover information during the last 10 years in Xinjiang and evaluated the accuracy of MOD10A2 products.The inter-annual and seasonal changes of Snow Cover Fraction (SCF), as well as their difference between Northern Xinjiang and Southern Xinjiang, were also examined.In addition, the spatial-temporal variability of SCF in different elevation zones was obtained for assessing the influence of the elevation shift on SCF.The results indicated that: ① the total accuracy of SCF extracted from MOD10A2 data is 92.3%, and can be considered as a credible data source to detect the snow cover change in Xinjiang; ② during 2000 to 2010, the maximum SCF of Xinjiang is in the range between 34.0% and 51.7% and the minimum is in the range between 1.7% and 2.6%.The difference of SCF between Northern Xinjiang and Southern Xinjiang is obvious: the SCF of Southern Xinjiang is relatively low and the fluctuation of SCF is less than 50%; the SCF of Northern Xinjiang is relatively high because of the effects of complex terrain and climate, and the fluctuation of SCF is more than 80% except in 2008.Seasonally, the averaged SCF show significant fluctuations in spring and autumn, however, the SCF does not show obviously change trend in summers and winters.Moreover, the north part of Xinjiang province shows more significant inter-annual and seasonal change than Southern Xinjiang; ③ the SFC typically reach minimum values in summers and maximum values in winters in the areas where the elevations below 4 000 m, but display a converse pattern in the areas above 6 000 m with a minimum in winters and a maximum in summers.