Study On Spatio-temporal Variations Of Snow From 2000 To 2009 In Northeast China

The snow is one of the most complex and active natural factors. It is also an important part of the climate system. The unique radiation characterictics and thermodynamic properties of snow have profound impacts on radiation balance, thermodynamic equilibrium and water balance, thus it can lead to an important effect on atmospheric circulation and hydrological cycle. The snow cover change is a complex process, with the difference of temporal and spatial variation that has different forms and trends. To study the distribution characterictics and variation regularity of snow cover encompass the monitoring of snow which has an important significance to enhance ecological enviromental protection, construction, and promote the industrial and agricultural production and development .Northeast China is one of the three stable snow cover regions with limited research undertaken on the large scale snow cover of the region. The area of study is the Northeast China. The two aspects of snow cover and snow depth combine with meteorological data to discuss the trend of snow cover distribution, temporal and spatial variation, supply a scientific basis for the industrial and agricultural production ,water resource management and the life of people in the northeast region.This paper summarizes the research status at home and abroad about snow cover and snow depth and illustrates the MODIS and AMSR-E sensor parameters and the data characteristics. Using the MODIS data processing software MRT tool to merge, resample and reproject the MOD10A1 daily snow cover product from 2000 to 2009 in the northeast area, then obtained 1908 remote sensing images. The vector layer of the research area clip and reclassify the 1908 remote sensing images, in order to extract the five parameters which are daily snow cover ratio, snow duration days, snow cover onset dates, snow cover melting dates and snow index. The AMSR-E data processing software HEG tool reproject and resample the AMSR-E 5-Day L3 Global Snow Water Equivalent data from 2002 to 2009 in the northeast area and obtain 294 snow water equivalent remote sensing images using the vector layer of research area to clip and resample the data. Then retrieved the snow depth of northeast area by the algorithm of snow water equivalent to snow depth .Using the MODIS data processed, caculate the daily snow cover ratio and snow index, extract the snow duration days, snow cover onset dates and snow cover melting dates. Through the snow water equivalent data processed, using the algorithm of snow water equivalent to snow depth, got the distribution of snow depth of northeast area. Based on the change of the daily snow cover ratio, snow duration days, snow cover onset dates ,snow cover melting dates and snow index and snow depth, disscused the variation trend of snow cover and snow depth. Combined to the temperature and precipitation data to discussed the relationship between them. The result indicates that the snow cover distribution of the northeast area are mainly located in Liaoning-the east part of Jilin ,the north part of Jilin-the middle and south part of Heilongjiang and the northwest part of Inner Mongolia. The area has a much longer snow duration days. The map of snow cover onset dates shows that the time of snowfall is different in different areas. The north part of Inner Mongolia,Xing'an mountains region and the northeast part of Heilongjiang hava a earlier time of snowfall,which begin to snow in November while the most region after December. For most area, the higer the latitude, the eralier the time of snowfall. The map of snow cover melting dates shows that the time of snow melting is different in different regions and different years. Some regions began to melt in early February, and large areas began to melt during the late February and the early March. The snow melted much later in the north part of Inner Mongolia, the middle and north part of Heilongjiang. Most regions began to melt after March. As the same to the snow cover onset dates, the higher the latitude,the later the snow melt. The snow depth retrieved shows the average winter snow depth had a decreasing trend during the seven years from 2002 to 2009. The correlation between snow cover and temperature, precipitation indicates that the snow cover area had positive correlation with temperature, but there is no pronouned correlation with precipitaion.