2000～2014年西藏高原积雪覆盖时空变化

利用MODIS/Terra积雪产品MOD10A2较系统地分析了2000~2014年西藏高原(以下简称高原)积雪面积和覆盖率的时空变化特点,并与同期主要气象要素之间的关系进行了研究。主要结论如下:(1)高原平均积雪面积是19.0×104km2,占整个高原面积的15.8%,其中冬季最大,为高原总面积的23%,其次是春季(22%)和秋季(16%),夏季最小(5%);(2)过去14a高原年平均积雪面积呈现微弱减少态势,其中秋冬两季积雪面积略显上升趋势,春季略有减少,夏季减少趋势显著,积雪面积变化与气温之间存在负相关关系,与同期降水量之间的关系不大;(3)2000~2014年,羌塘高原北部和西南喜马拉雅山脉积雪覆盖率增加趋势明显,而在那曲东南部、喜马拉雅山脉东段和阿里地区北部积雪覆盖率减少趋势明显;(4)高原积雪覆盖变率具有明显的空间差异,且由春秋两季主导,秋季年际变率要大于春季,高原中东部和周围高大山脉及其附近是高原积雪覆盖年际变率最大的区域,而雅鲁藏布江中下游谷地、藏东南干暖河谷以及藏北高原中西部是年际变率最小的地区;(5)积雪年际变率大值区是高原主要的牧区和雪灾频发区,是高原积雪监测和防灾减灾的重点。 

Spatial-Temporal Variations of Snow Cover on the Tibet Autonomous Region from 2000 to 2014 Using MODIS Data

Snow cover is an important component of the cryosphere and the study of snow cover trends is essential for understanding regional climate change and managing water resources. In this study,the spatio-temporal variations of snow covered area(SCA) and snow cover fraction(SCF) on the Tibet Autonomous Region(TAR) are analyzed based on the MODIS 8-day snow cover products(MOD10A2) from 2000 to 2014 using GIS spatial analysis techniques and relationships with main climate variables(temperature,precipitation) are discussed. Main results are as follows:(1) the averaged annual mean SCA on the TAR from 2001 to 2014 is 19. 0 × 104km2,accounting for 15. 8% of the total area of TAR,and mean maximum SCA occurs in winter with covering 23% of the total area of TAR,followed by spring(22%) and autumn(16%),and mean SCA reaches a minimum in summer with 5% of total TAR area.(2) Over the last 15 years,there is a weak decreasing trend in annual mean SCA,in which a slight increasing trend in SCA exists in autumn and winter while a decreasing trend is found in other seasons with a significant decreasing trend in summer. There is a negative linear correlation between SCA and temperature whereas there is no certain relationship between SCA and precipitation.(3) The spatial differences of change trend of SCF on the TAR from 2000 to 2014 are large. The more obvious increasing trend of SCF exists in north part of TAR and southwestern Himalayas while more obvious decreasing trend of SCF mainly occurs in west and middle part of Nyainqentanglha mountains,eastern Himalayas with the most apparent decreasing trend in southeastern Naqu region. These spatial differences of SCF is dominated by snow cover changes in spring and autumn,and SCF overall is decreasing in spring and increasing in autumn over the last 15 years.(4) Likewise,the spatial differences of interannual variability of SCF on the TAR,dominated by snow cover variations in spring and autumn,also are large,and variability of SCF in autumn is greater than that in spring. General spatial distribution of interannual variability of SCF is similar with mean SCF of the TAR. More obvious variability of SCF is located at alpine interior,surrounding high mountains and their around regions. The smallest variability of SCF occurs in the middle and lower reaches of Yarlung Zangbo River valley,arid-warm valley of southeastern Tibet and middle and west part of North Tibet.(5) The regions with larger variability of SCF is main pastoral and snow disaster affected areas in the TP,which are key zone of snow cover monitoring and disaster prevention and mitigation.