Research Of Snow Process And Snow Drift On The Typical Steppe In Xilin Gol

Xilin Gol Grassland is the most Typical steppe,which is important production base of animal husbandry,also is important ecological barrier in the north of China.The study area is located in one of the three largest snow cover areas in China,with abundant snow resources.the snow disaster occurred frequently because of severe winter and strong wind conditions,which seriously hindered the development of regional economy.snow densification process and movement of snow drift and snow redistribution were analyzed through field observation on snow drift,which under the base of analysis of environmental and meteorological factors and snow factor dynamic analysis and time scale in typical steppe area of snow.the main results were as follows:1.The snowfall and snow cover days had no mutation occurred in 45a,the snow depth occurred two times mutation at 2000 and 2003;The main period of snowfall,snow cover days and snow depth both was 11a;The analysis of correlation showed that snowfall,humidity,evaporation and wind speed have great effect on the number of blowing snow days.It had a gradually decreasing trend in the next ten years by using BP neural network forecast.2.At stable snow cover period,the snow densification process were divided into very fast(the early 24 hours after snow fall),fast(24 to 48 hours)and slow stages(after 48 hours)according to the variation of snow depth and snow density.there was no significant change of depth and density of snow cover in the period of unstable snow cover.the densification process was significantly faster than that of stable snow cover.the density of snow gradually increased with the deposition time.3.Stipa grandis grassland under multi wind gradient,the snow drifting intensity decreased sharply following the increase of height in the range of 100cm from snow surface.The range of snow drift activity is increased following wind speed(2 meter)increase.The function of snow drift structure changed from the logarithmic function to the power function.more than 80%of snow is concentrated in the 20cm above surface;The average snow drifting intensity was significant as a power function with wind speed(at a height of 2m).formula was Q= a·Vb,and b=5.The average snow drifting intensity changed from slowly increasing to dramatically increasing with the increasing of wind speed.4.operation of snow drift were effected by exposed height of vegetation,snow deposition time,snow depth,terrain conditions,or the snow itself.The intensity of snow removal and the rate of single width of snow decreased significantly with the increase of vegetation height and exposed vegetation coverage.the longer the snow deposition,the weaker the snow drift.the height and intensity of snow drift on windward side was stronger than that of in leeward slope and the most prominent position in the middle of the slope due to the influence of topography on wind speed profile.5.snow cover depth,in Stipa grandis grassland,increased linearly with vegetation height,Correlation for Grazing>mowing>fencing.The depth of snow cover increased as logarithmic way with the vegetation coverage(r2>0.9).the snow depth increased slowly when the vegetation coverage increased to a certain extent.the depth of snow cover in the grassland was more abundant in the year of abundant snowfall,and it was more obvious in the grassland with low utilization.