基于MODIS数据的玛纳斯河山区雪盖年际波动特征研究

Inter-annual fluctuation of snow cover in mountainous area of Manas River basin based on MODIS

基于2000-2010年的MODIS/Terra积雪8 d合成数据(MOD10A2)与DEM数据,通过计算和分析不同高程带、不同坡向和不同坡度的积雪覆盖率,研究了新疆玛纳斯河山区雪盖的年际波动特征。结果表明:(1)鼎盛期积雪覆盖率在研究时段内形成两高两低的总体走势,2000/2001和2007/2008雪年为高值年,2002/2003和2009/2010雪年为低值年。研究期月平均积雪覆盖率最低值通常出现在每年的6～8月之间,各年度的最低值在10%左右上下波动,且波动幅度较小;(2)研究区不同季节不同高程带积雪覆盖率的年际波动的方向有所不同,1月份和10月份积雪覆盖率均呈下降趋势,并且随着海拔上升,下降趋势趋于缓和,4月份呈上升趋势,而7月份在1 600 m以下地区和1 600 m以上地区分别呈下降趋势和上升趋势;(3)随着海拔上升,研究区不同季节积雪覆盖率的年际波动的幅度均逐渐缩小;(4)坡度和坡向在不同季节不同高程带中对雪盖年际变化的影响各不相同,没有发现明显的影响规律。

Snowcover is one of the most active and critical factors in the nature which influences the redistribution of solar radiation energy and water resource.The studies on problems concerning snowcover in cold regions,such as snowcover distribution,snowmelt runoff,snowmelt water management and snowcover-caused disaster,are of great importance in regional development.The imageries obtained from the Moderate Resolution Imaging Spectroradiometer(MODIS),carried on Terra satellite launched in 1999,have been widely used and proved to be effective in various fields at large scale.A variety of snowcover products for various purposes are generated based on MODIS imageries using specific algorithms.In this paper,the inter-annual variation of snowcover in mountainous area of Manas River basin is studied based on snowcover fraction acquired from remotely sensed snowcover product(MOD10A2) from 2000 to 2010.The variation of snowcover in different elevation zones,slope grades and aspects categories is analyzed by combining snow cover fraction and digital elevation model data.In general,the yearly maximum snowcover fraction between 2000 and 2010 has 2 peaks in 2000/2001 and 2007/2008 snow years and 2 troughs in 2002/2003 and 2009/2010 snow years respectively.In different seasons and elevation zones,the direction and range of inter-annual variation of snowcover fraction are quite different.The snowcover fraction appears to be decreasing in January and October and increasing in April respectively from 2000 to 2010.In July,it shows that the snowcover fraction decrease in areas lower than 1 600 m and increase in areas higher than 1 600 m respectively from 2000 to 2010.With the rising of elevation,the inter-annual fluctuation range of snowcover fraction reduces in all seasons.In addition,the slopes of fitting lines,and the coefficients of variation as well,of inter-annual variation of snowcover fraction in each elevation zone,slope grades and aspects category are calculated for the purpose of describing the trend of variation from 2000 to 2010.The slopes of fitting lines tend to approach to zero with rising elevation in all seasons,which indicates that the variation tendency moderates with rising elevation.The coefficients of variation decrease with rising altitude in all seasons,which shows that the variation range tends to descend when elevation ascends.Furthermore,the impacts of slope and aspect on inter-annual fluctuation of snowcover fraction in each season and elevation zone differ from one another.No clear and regular impact of slopes and aspects on snowcover variation are found.