青藏高原积雪变化及其影响

青藏高原积雪具有特殊的自然属性,是"亚洲水塔"的重要组成部分,其空间分布特征与变化不仅是天气和气候变化的产物,也会对全球和区域变化产生显著的影响。文章通过多种遥感数据分析了青藏高原积雪时空分布及变化特征,并探讨其水文与气候效应。结果表明:(1)青藏高原积雪主要分布在山区,其中唐古拉山和念青唐古拉山积雪最丰富,多年平均积雪日数在120天以上,年平均雪深超过10 cm;高原腹地平坦地区及柴达木盆地积雪属于瞬时积雪,多年平均积雪日数小于15天,年平均雪深小于1 cm。(2)1980—2018年,青藏高原积雪呈下降趋势,尤其在2000年以后,积雪覆盖日数和雪深明显下降。(3)高原内积雪较多的山脉地区可以产生较大的积雪辐射强迫,最大可超过15 W m~(-2),其反照率反馈机制对气候系统的影响至关重要。(4)青藏高原是多条大江大河的发源地,积雪融水是春季土壤水分和河川径流的重要补给。(5)受天气过程产生的雪灾频次有所增强,建立早期预警和防护措施是减少牧区雪灾损失的重要手段。

Snow Cover Variation and Its Impacts over the Qinghai-Tibet Plateau

Snow cover over the Qinghai-Tibet Plateau (QTP) is a key element of Asian Water Tower. It is also an important indicator of weather and climate change. Its spatio-temporal changes can influence the regional climate and ecosystem. In this study, the spatiotemporal distribution and trends of snow cover were analyzed based on remote sensing data, and its hydrological and climate effects were also explored. The results show the followings:(1) Snow cover was dominantly distributed in mountainous areas, and the largest snow depth and Snow Cover Days (SCD) were found in the Dangla and Nianqing Dangla Mountains, with the average SCD of over 120 days, and annual average snow depth of over 10 cm; whilst there was few snow cover in the plain area and Qaidam Basin, e.g. ephemeral snow cover, with average SCD of less than 15 day and annual snow depth of less than 1 cm. (2) Snow cover days and depth were decreased in the period of 1980-2018, especially after the year of 2000. (3) There was large radiative forcing in the mountainous areas with deep snow and large SCD, and the maximum value beyond 15 W m^-2; thus, the snow cover over QTP plays important feedbacks to the climate system. (4) The QTP is the source of runoff in headwater regions of many rivers, and snow melt water contributed to the soil moisture and river runoff in spring. (5) The frequency of snow disaster was increased by extreme weather events, and early warning system and protective measures should be enhanced to minimize the loss caused by snow disaster.