Under the context of global warming,understanding of spatio-temporal variation of snow depth on the Tibetan Plateau (TP) is particularly important because climate observations in high-altitude regions have shown more sensitivity to climate change.The snow depth on the TP,as one of key components of cryosphere,is related to water availability downstream of major river basins in Asia and its anomalies may potentially affect subsequently regional weather/climate and monsoon systems over eastern and southern Asia through mechanical forcing and changing surface heat and moisture fluxes.Therefore,in this study,the spatio-temporal variation of snow depth on the TP is analyzed using observation data from 94 meteorological stations for the period from 1981 to 2010.The main results are as follows.(1) The highest snow depth record mainly takes place in the southern Himalayas Mountains and the lowest snow depth is found in dry-warm valleys in southern TP and Qaidam Basin in the northern TP.(2) There is a significant decreasing trend in annual mean maximum snow depth on the TP with a rate of 0.55 cm every 10 years in the last 30 years and abrupt climate change of snow depth from high to low occurs around 1997.(3) On seasonal scales,mean maximum snow depth in spring also has a very significant decreasing trend at a rate of 0.47 cm every 10 years,and abrupt climate change of snow depth in spring from high to low occurs around 1998.In autumn and winter,the decreasing trend in mean maximum snow depth is not noticeable.At a specific station,the changing trend of snow depth varies from region to region.In autumn,snow depth decreases at 56％ stations but increases at 31％ stations on the TP.In winter,the decrease in snow depth occurs at 61％ stations and stations with higher decreasing rate are primarily distributed in the southwestern TP while the increasing trend of snow depth is found at 31％ stations,which are mainly located in eastern part of the TP.In summer,snow cover on the TP is very scarce,primarily distributed in alpine region of high altitude and latitudes.Over the last 30 years,the decreasing trend of snow depth in summer is also significant.%利用1981-2010年地面雪深观测资料较系统地分析了近30年青藏高原(以下简称高原)积雪深度的时空变化特点.主要结论如下:(1)高原雪深大值区主要在喜马拉雅山脉南麓,小值区则在高原南部干暖河谷和北部柴达木盆地,30年间高原平均最大雪深出现了显著减少趋势,减幅达0.55 cm·(10 a)-1,1997年前后高原雪深出现了由大到小的气候突变.(2)春季是高原平均积雪深度最大的季节,30年里平均最大雪深下降趋势非常显著,下降幅度为0.47 cm·(10 a)-1,且在1998年出现了由大到小的气候突变.(3)秋、冬季,高原平均最大雪深减少趋势不明显,但在不同区域雪深增减趋势不尽相同.秋季56％的台站呈减少趋势,而31％的台站有不同程度的增加;冬季61％的台站出现了减少趋势,而且减幅较大的台站基本分布在高原西南,而31％的台站则出现了增加趋势,多数分布在高原东部.(4)夏季高原积雪分布极为有限,仅在海拔和纬度较高的高寒地区有积雪,近30年雪深减少趋势同样显著.
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