Analysis On Spatiotemporal Variations Of Snow Cover In Xinjiang, China

Snow as an important part of the climate system,due to the particularity of its underlying surface,it has a profound impact on the climate and environmental changes.There are two main types of snow data,observation data and satellite remote sensing data,and these two kinds of methods are used to study the characteristics of snow distribution in Xinjiang,which is important for the climate change in region.Based on the observation data of snow depth and snow pressure data during 1961 and2013 in Xinjiang,the snow cover area and snow water equivalent were analyzed based on the MODIS and AMSR-E data of satellite remote sensing data.Using Degree-day model to calculate the Degree-day factor.Based on the Kriging interpolation,the temporal and spatial distribution of the starting and ending date,the days of snow cover,the average and the maximum snow depth,the snow cover area,the snow density,the snow water equivalent and the Degree-day factor were analyzed.he snow cover in Xinjiang were investigated i spatial distribution characteristics of tn this study.And the spatial distribution of MMK trend test was analyzed.The results were as follows:(1)Snow lasted for 71 to 120 days.For the temporal variations,annual mean starting and ending dates both had decrease trends while snow duration had an increase trend.The average and maximum snow depths fluctuated with a sub-region order of north Xinjiang >entire Xinijang > Tianshan mountains area > south Xinjiang.Four typical types of seasonal daily snow depth curve,i.e.,flat,multi-peak,sharp single-peak and right-skewed,were generalized.For the spatial distributions,the snow cover properties differed from north to south Xinjiang,the starting date ranged from October,5th to February,5th,while the ending date ranged from January,16 th to April.The duration lasted for 14-199 days,the average and maximum snow depths ranged from 1.5 to 24.9 cm,and from 4.0 to 95.0 cm,respectively.The spatiotemperal variations of snow depth supplied a data basis for further analysis of snowmelt.(2)The spatial distribution shows that the snow cover starting date advanced from north to south,the snow ending date advanced from north to south and west to east,the duration of snow cover had decreased trend from north to south and from west to east.(3)The average snow-cover area in Xinjiang was 436,2 thousand km2,the time-curves of snow-cover area presented types of one peak or double peak,and the maximum value ofsnow-cover occurred in December,January and February of the year.The snow-cover area in Xinjiang had an increase trend in October,while in other months had decrease trends,although all trends were not significant.Snow-cover area was positively correlated to snow depth from October to April of the next year with an correlation coefficient of 0.358.Snow-cover area was negatively correlated to minimum temperature.(4)The snow density ranged from 0.12 to 0.27 g/cm3,and the snow density generally showed a steady increase trend from October to the following year in late March.The trend of rapid increase in the early stage increased rapidly.The range of degree-factor is 0-5.73mm??-1?d-1.In the high elevation area of the Tianshan Mountains area and the Kunlun Mountains area,its degree factor is relatively large.