近15a青藏高原积雪覆盖时空变化分析

Spatiotemporal Variations of Snow Cover on the Tibetan Plateau over the Last 15 Years

利用MOD10A2积雪产品分析了2000~2014年青藏高原(以下简称高原)积雪面积和覆盖率的时空分布和变化特点。主要结论如下:1近15a高原年平均积雪面积减少趋势不明显,但季节差异很大,秋季积雪面积略显上升趋势,其他3个季节略有减少趋势,其中夏季减少趋势相对较明显;积雪面积变化与同期气温之间存在负相关关系,且与最高气温的关系更为密切;2过去15a高原积雪覆盖率变化趋势的空间差异明显。青海南部至藏北羌塘高原北部及西南喜马拉雅山脉北麓增加趋势较明显,其中青海南部覆盖范围最广,而念青唐古拉山中西段、喜马拉雅山东段、高原东南地势较低区域和西北部存在较明显的减少趋势,其中那曲东南减少最为明显;3高原积雪覆盖率的年际变率空间差异同样很大,总体上与高原平均积雪覆盖分布相似,即高寒内陆和周边的高大山脉及其周边地区是积雪年际差异明显区域,且主要是由春秋两季的年际变率导致的,高原积雪年际变率较大区域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地区。

The spatial-temporal variations of snow covered area （SCA） and snow cover fraction （SCF） over the Tibetan Plateau （TP） 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（tempera- ture,precipitation） are discussed in this study. Main results are as follows： ①the averaged annual mean SCA over the TP from 2001 to 2014 is 41.7× 10^4 km^2 ,accounting for 17% of the total area of TP,and max- imum SCA occurs in winter and spring with covering 21% of the total area of TP, followed by autumn （18%） ,and SCA reaches a minimum in summer with 5% of total TP area.The overall decreasing trend of SCA on the TP in recent 15 years is not obvious in addition to its inherent seasonal changes. However,sea- sonal variations and differences of SCA over the TP are large.In recent 15 years there is a slight increasing trend of SCA in autumn while a decreasing trend is founded in other seasons with more obvious in summer. The apparent negative correlation exists between SCA and temperature with more obvious relationships between SCA and maximum temperature, whereas there is no certain relationships with precipitations. ②There are apparently spatial differences in change trend of SCF over the TP from 2000 to 2014.The more obvious increasing trend of SCF exists in southern Qinghai, northern Tibet and southwestern Himalayas with the largest cover extent in southern Qinghai,while more obvious decreasing trend of SCF mainly oc- curs in west and middle part of Nyainqentanglha mountains,eastern Himalayas, northwestern TP and low- er-elevation regions in southeastern TP with the most apparent decreasing trend in southeastern Naqu re- gion.③Likewise,the spatial differences of interannual variability of SCF over the TP are large, and in gen- eral its spatial distribution is similar with mean SCF of the TP. More obvious variability of SCF, mainly caused by snow variations in spring and autumn, is located at alpine interior, surrounding high mountains and their around regions. Annual variability of SCF in spring is larger in lower latitude regions such as southeastern TP while in autumn is larger in higher latitude region such as Kunlun Mountain range.The re- gions with larger variability of SCF is main pastoral and snow disaster affected areas in the TP,which are key zone of snow cover monitoring ,disaster prevention and mitigation.