2002-2009年中国干旱区积雪时空分布特征

以中国干旱区为研究对象，利用MODIS和AMSR-E融合后的2002-2009年8个水文年份（8月1日至7月31日）的无云积雪产品，计算并验证了用遥感方法提取研究区积雪日数、初雪日期和终雪日期的精度，结合积雪日数制图和积雪面积统计，分析了研究区8 a来积雪时空分布特征。结果显示：① 与气象台站观测资料获取的积雪参数的对比验证表明，遥感方法提取积雪参数的精度较高，误差日数大多在20 d以内，主要表现为遥感方法积雪日数的低估，初雪日期的延后和终雪日期的提前。② 除山地冰川和永久积雪外，天山和阿尔泰山山系间的北疆地区是研究区内季节性积雪最为丰富的地区，积雪日数一般在60 d以上，不过积雪的分布不均匀，大体上从边缘山区向内部盆地中心积雪日数递减，初雪日期延后，终雪日期提前。③ 干旱区在2005年、2007年和2002年积雪面积较大，而2008年和2006年积雪面积较小。各年稳定积雪存在的地区和范围相对稳定，面积变化不大，其年际变化主要体现在积雪日数的增减上；不稳定积雪的面积一般高于稳定积雪，且年际变化较大，积雪日数大多在20 d以内。

Spatiotemporal Distribution of Snow Cover in Arid Regions in China

Based on MODIS and AMSR-E combined cloud-free snow cover product,in this paper the snow cover duration days(SCD),snow cover onset date(SCOD) and snow cover ending date(SCED) in arid regions of China were calculated and evaluated for 8 hydrological years from 2002 to 2009.Spatiotemporal distribution of snow cover in the study area was analyzed through mapping of SCD and statistical results of snow cover area(SCA).The results are as follows:(1) The compared results reveal that the accuracy of snow cover parameters extracted from remote sensing images is high and close to the data observed at the weather stations,the duration errors are mostly within 20 days;(2) Except for the regions covered with glaciers and firn in the alpine zone,north Xinjiang between the Tianshan Mountains and Altay Mountains is the region with the thickest seasonal snow cover,SCD was mostly longer than 60 days,but the distribution of seasonal snow cover is uneven.Holistically,the SCD becomes shorter,the SCOD becomes later and SCED becomes earlier from the marginal zone of the mountains to the central area of the basins;(3) The total areas of snow cover in arid regions were comparatively large in 2005,2007 and 2002 but small in 2008 and 2006,respectively;The area and distribution of stable snow cover were comparatively stable,with the inter-annual changes being mainly the fluctuation of the number of SCD;the area of unstable snow cover were generally larger than stable snow cover,with obvious inter-annual fluctuations and the number of SCD mostly lower than 20.