基于MODIS数据的我国天山典型区积雪特征研究

准确监测天山地区积雪面积和积雪日数对合理利用水资源及分析区域气候变化有重要意义。MODIS每日积雪产品可以为大面积快速积雪制图与监测提供依据,但因云量较高成为其应用的瓶颈。利用结合MODIS产品的时间与空间信息有效地减少了云对MODIS积雪产品的影响,并利用改进的MODIS积雪数据和DEM分析2002~2009年天山地区积雪面积和积雪日数的变化特征。结果表明:积雪频率总体上随着海拔升高而增大;不同坡向积雪面积差异明显,西北坡积雪覆盖率最高,北坡、西坡和东北坡次之,南坡和东南坡的积雪覆盖率最低;2006~2008年研究区积雪面积出现低值,年内最大积雪面积呈逐年减少的趋势;随着海拔下降,积雪日数逐渐变小,天山南部地区积雪日数仅为40 d以下;积雪日数大的区域年际积雪日数变化相对稳定,积雪日数少于40 d的区域积雪日数的变异系数最大,年际积雪日数变化不稳定。

A Study on Snow Cover Variability Using MODIS in the Typical Area of Tianshan Mountains, China

Monitoring the extent and duration of snow cover in Tianshan mountains is significant for fully utilizing water resources and understanding the regional impact of climate change.Daily MODIS snow cover data can provide a basis for large scale snow cover mapping.However,the high cloud obscuration limits its applications.This study uses a four-step approach to remove cloud from the daily data.Using improved MODIS snow cover data and DEM analyse the spatial and temporal variability of snow cover extent and duration from 2002 to 2009 in the Tianshan Mountains of China.Snow cover extent is closely related to terrain factors.The snow cover frequency as a whole becomes higher with increasing altitude.The ratio of snow cover is higher at the northwest,north and west aspect than that at the south and southeast aspect.The snow cover extent of the whole area is small from 2006 to 2008.Maximum snow cover extent increases yearly on average.The regions snow cover duration exceeds 200 days,which are mainly in the high-altitude perennial snow cover areas,and their Coefficient of Variation (COV) is low.The snow cover duration in the southern Tianshan mountains and other low-altitude areas is very short,and change substantially due to seasonal climate situations.