1977-2017年雅江流域中下游大气/地面冻融指数时空变化特征  

Spatial and temporal characteristics of air/ground freezing and thawing index in the middle and lower reaches of the Yarlung Zangbo River during 1977-2017

作　　者：刘磊 罗栋梁 LIU Lei;LUO Dongliang(State Key Laboratory of Frozen Soil Engineering,Northwest Institute of Eco-Environment and Resources,Chinese Academy of Sciences,Lanzhou 730000,China;University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国科学院西北生态环境资源研究院冻土工程国家重点实验室,甘肃兰州730000 [2]中国科学院大学,北京100049

出　　处：《冰川冻土》2020年第3期812-822,共11页Journal of Glaciology and Geocryology

基　　金：国家自然科学基金项目(91747201,41671060);冻土工程国家重点实验室自主研究项目(SKLFSE-ZT-38)资助。

摘　　要：冻结指数是某个地区冻结期长短和严寒程度的综合表征,融化指数是某个地区融化期长短及正积温高低的综合度量,冻融指数也是计算活动层厚度和季节冻结深度的关键参数,并可用于多年冻土分布预报。利用雅鲁藏布江(雅江)流域中下游11个气象站点的逐日气温、地面温度数据计算了1977-2017年大气及地面冻融指数,并分析其时空变化趋势。结果表明:雅江流域中下游近40年来冻结指数呈显著下降趋势,大气冻结指数、地面冻结指数、大气融化指数、地面融化指数多年变化范围分别为208.4~508.0、136.9~371.0、2171.8~2499.8、3350.2~4315.2℃·d;其气候倾斜率分别为-36.6、-48.7、90.7、115.8℃·d·(10a)^-1。雅江流域大气和地面冻结指数以海拔4488.8m的嘉黎最大,海拔2991.9m的林芝最小;大气和地面融化指数则以海拔3560m的泽当最大,海拔4488.8m的嘉黎最小。流域内大气负温日数变化规律与地面负温日数变化趋势基本一致,其气候倾向率分别是-6.28d·(10a)^-1和-5.57d·(10a)^-1。研究结果可为雅江流域冻土预报,冻融作用所形成的冰缘地貌研究及其引发的地质灾害如冻融滑塌、冻融泥流等灾害的监测与预防提供借鉴。Freezing index is a comprehensive representation of the length and cold severity of winter,and the thawing index is the length and>0℃accumulated temperature of the thawing season in a certain region.The freezing/thawing index are key parameters to calculate the thickness of active layer and the seasonal soil freezing depth,and it can be used in prediction of the permafrost distribution.In this study,the air and ground freezing/thawing indices and their spatial and temporal variation trends from1977 to2017 in the middle and lower reaches of the Yarlung Zangbo River Basin(YZRB)were calculated and analyzed on the basis of the daily air and ground surface temperatures obtained from11 national meteorological stations.Results showed dramatic changes of freezing/thawing indices in the middle and lower reaches of the YZRB over the past four decades.The air freezing index,ground surface freezing index,air thawing index,and ground surface thawing index ranged from 208.4℃·d to 508.0℃·d,and from 136.9℃·d to371.0℃·d,and from 2171.8℃·d to 2499.8℃·d,and from 3350.2℃·d to 4315.2℃·d respectively,with a climate tendency rate of-36.6,-48.7,90.7 and 115.8℃·d·(10 a)^-1,respectively.Both the air and ground surface freezing indices of this study area were highest at Jiali Station with an altitude of 4488.8 m,and lowest at Linzhi Station with an altitude of 2991.9 m.The air and ground surface thawing indices were highest at Zedang Station with an altitude of 3560 m,and lowest at Jiali Station with an altitude of 4488.8 m.The days with negative air temperature within a year decreased at a rate of-6.28 d·(10 a)^-1,and the changes of the days with negative ground surface temperature within a year showed similar trend[-5.57 d·(10 a)^-1].The periglacial landforms,which is formed under the presence of the freezingthawing cycles could provide a reference for the monitoring and prevention of geological disasters,such as thawing slumps and solifluctions,are worthy of great attentions in future studies.

关 键 词：青藏高原 雅鲁藏布江流域 大气冻/融指数 地面冻/融指数 

分 类 号：P423[天文地球—大气科学及气象学]