1981-2010年青藏高原积雪日数时空变化特征分析

全球气候变暖大背景下, 作为冰冻圈最为活跃和敏感因子, 青藏高原积雪变化备受国内外关注. 本文利用青藏高原(以下简称高原)1981-2010年地面观测积雪日数资料, 较系统地分析了近30年来高原积雪日数的时空变化特点. 主要结论如下: (1) 近30年内高原平均年积雪日数出现了非常显著的减少趋势, 减少幅度达4.81 d·(10a)^-1, 其中冬季减幅最为明显, 为2.36 d·(10a)^-1, 其次是春季(2.05 d·(10a)^-1), 而夏季最少(0.21 d·(10a)^-1); (2) 30年间, 积雪日数较少的年份多数出现在本世纪初10年内, 且2010年属于异常偏少年, 高原积雪日数在1997年左右发生了由多到少的气候突变; (3) 在空间上, 北部柴达木盆地及其附件区域部分气象台站观测的年积雪日数出现了不显著的增加趋势之外, 高原91.5%的气象站年积雪日数呈减少趋势, 且高寒内陆中东部和西南喜马拉雅山脉南麓等高原历年积雪日数高值区域减少最为明显; (4) 由于受到气象台站所在地理位置、地形地貌、地表类型、海拔高度、局地气候以及大气环流等综合影响, 高原平均年积雪日数的空间差异很大, 最多达146 d, 最少的则不足1 d, 平均仅为38 d, 其中高寒内陆中东部是积雪日数最长的区域, 而东南部海拔和纬度较低的干热河谷地区积雪日数最少.

The variations of snow cover days over the Tibetan Plateau during 1981-2010

As the most important component of the cryosphere with the largest seasonal and spatial variations, snow cover is a vital fresh water resources in the Tibetan Plateau (TP)and downstream regions,and also a significant indicator of climate change in the TP and its surrounding areas.Therefore,under global climate warming the variation of snow cover over the TP is concerned by international scientific community.In this study,the spatial and temporal variations of snow cover days are analyzed based on the observation data from 94 meteorological stations on the Tibetan Plateau for the period from 1981 to 2010.The main results are as follows:(1)there was a very significant decreasing in annual mean snow cover days over the TP with a rate of 4.81 days decade-1 in the last 30 years,in which the decreasing rate was most obvious in winter,2.36 days decade-1 ,fol-lowed by spring,2.05 days decade-1 ,and the least decreasing rate was found in summer (0.21 days dec-ade-1 );(2)the abrupt climate change of snow cover days occurred around 1997 and the most of less annual snow cover days were found in the later 10 years,especially in 2010,an anomalous snowless year;(3)over the last 30 years,9 1 .5%of the stations had experienced a decrease in snow cover days,especially in alpine regions of the TP interior and its eastern areas and south slopes of the southwestern Himalayans,where there were the longest snow cover days on the TP in the historic snow observation records,and increasing trend was only found in several stations in Qaidam Basin and its surrounding areas;(4 )there was a great spatial variation in snow cover days on the TP due to the differences in geographic location,topography,surface feature,regional climate and elevation of the meteorological stations and the impact of atmospheric circulation etc.The areas of snow cover days more than 100 days were mainly located at the interior of the TP and its eastern regions;the shorter snow cover days,less than 5 days,was mainly distributed in the dry and warm valleyes of the southeastern TP.