新疆积雪覆盖时空变异分析

利用2000-2010年MODIS积雪覆盖产品数据MOD10A2,提取了新疆近10年来积雪覆盖变化信息,并结合地面站点数据,对遥感积雪覆盖估算的精度进行了验证;分析了新疆积雪覆盖的年际、年内变化及南北疆积雪覆盖变化的差异;结合数字高程模型,分析不同高程带下积雪覆盖的时空变化规律,揭示高程因素对新疆积雪时空变化的影响。结果表明:MOD10A2提取的积雪信息能够反映新疆的积雪变化情况,总体精度达92.3%;近10年来,全疆年积雪覆盖率最大值范围为34.0%~51.7%,最小值范围为1.7%~2.6%;积雪覆盖比率的变化在南北疆差异明显,南疆区域积雪覆盖整体不高,年内积雪覆盖比率变化幅度低于50%;而北疆区域由于受复杂地形和气候带的影响,积雪覆盖比率大,年内的变化幅度强,除2008年均达到80%以上;在季节变化上,春季和秋季的积雪覆盖均值波动较为明显,夏季和冬季的积雪覆盖均值则波动较小,这一规律在北疆地区表现更为显著;积雪覆盖的时空分布与变化受高程的影响,在海拔4 000 m以下区域,夏季积雪覆盖比率低,冬季积雪覆盖比率高,而6 000 m以上海拔区域则表现出完全相反的特点,即夏季积雪覆盖比率高,冬季积雪覆盖比率低。

Analyzing spatial-temporal variability of snow cover in Xinjiang

Snow cover is one of the most active factors that influence the environment, and shows high sensitivity to climate changes.Based on the moderate resolution imaging spectroradiometer (MODIS) snow cover products and observed data from 84 meteorological stations within Xinjiang Uygur Autonomous Region of China, we extracted the snow cover information during the last 10 years in Xinjiang and evaluated the accuracy of MOD10A2 products.The inter-annual and seasonal changes of Snow Cover Fraction (SCF), as well as their difference between Northern Xinjiang and Southern Xinjiang, were also examined.In addition, the spatial-temporal variability of SCF in different elevation zones was obtained for assessing the influence of the elevation shift on SCF.The results indicated that: ① the total accuracy of SCF extracted from MOD10A2 data is 92.3%, and can be considered as a credible data source to detect the snow cover change in Xinjiang; ② during 2000 to 2010, the maximum SCF of Xinjiang is in the range between 34.0% and 51.7% and the minimum is in the range between 1.7% and 2.6%.The difference of SCF between Northern Xinjiang and Southern Xinjiang is obvious: the SCF of Southern Xinjiang is relatively low and the fluctuation of SCF is less than 50%; the SCF of Northern Xinjiang is relatively high because of the effects of complex terrain and climate, and the fluctuation of SCF is more than 80% except in 2008.Seasonally, the averaged SCF show significant fluctuations in spring and autumn, however, the SCF does not show obviously change trend in summers and winters.Moreover, the north part of Xinjiang province shows more significant inter-annual and seasonal change than Southern Xinjiang; ③ the SFC typically reach minimum values in summers and maximum values in winters in the areas where the elevations below 4 000 m, but display a converse pattern in the areas above 6 000 m with a minimum in winters and a maximum in summers.