黄河源头区地面热状态及冻融特征  

Characteristics of the thermal regime and freeze-thaw cycles on the ground surface in permafrost regions in the Headwater Area of the Yellow River

作　　者：高怡婷 罗栋梁 陈方方 雷汶杰 金会军 GAO Yiting;LUO Dongliang;CHEN Fangfang;LEI Wenjie;JIN Huijun(State Key Laboratory of Frozen Soil Engineering,Northwest Institute of Eco-Environment and Resources,CAS,Lanzhou 730000,China;University of Chinese Academy of Sciences,Beijing 100049,China;School of Civil Engineering,Northeast Forestry University,Harbin 150040,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,兰州730000 [2]中国科学院大学,北京100049 [3]东北林业大学土木工程学院,哈尔滨150040

出　　处：《地理学报》2023年第3期604-619,共16页Acta Geographica Sinica

基　　金：中国科学院西部之光青年学者项目(E2290601);国家自然科学基金项目(U2243214,41671060);西北生态环境资源研究院自主部署项目(E155060501)。

摘　　要：冻土是地层与大气通过地面长期热交换的产物,地面的热状态及其冻融过程既表征了大气和各种下垫面对其复杂的热影响,也决定了浅表层冻土热状态及其变化。本文利用黄河源头区51个监测点的地面温度计算了地面冻结和融化指数,分析了冻融过程,并探究了其分异规律。结果表明:①研究区年均地面温度变化介于-3.06~1.31℃,呈现极强的空间分异特征,区域上的分异主要受海拔、纬度、NDVI制约(P<0.001),垂直递减率约为0.7℃·(100 m)^(-1)。NDVI越大即植被条件越好,夏季地面温度越低,冬季地面温度越高。②地面冻结指数为851.9~1906.6℃·d,平均1253.3℃·d,地面冻结指数与经纬度相关性较弱,地面完全冻结天数为54~219 d,平均137.1 d;地面融化指数为388.4~1727.2℃·d,平均1039.3℃·d,地面融化指数与海拔、NDVI、纬度、经度显著负相关,完全融化天数为61~156 d,平均128.8 d。③地面起始融化时间受地形和局地因素影响较大,发生于3月中旬到5月中旬,起始冻结时间的空间异质性小于起始融化时间,主要发生于9月下旬至10月底。④融化N因子(Nt)多集中于1.2~1.5,平均为1.29±0.21;冻结N因子(Nf)主要集中在0.5~0.65,平均为0.60±0.18;基于地面融化指数计算的活动层厚度为0.99~2.72 m,平均为1.68±0.45 m。本文可为高海拔多年冻土的精准制图及其与高寒生态环境相互作用研究提供基础。Permafrost is a product of long-term thermal exchanges between the ground surface and atmosphere;thus,the ground surface thermal regime and freeze-thaw cycles highlight the complex thermal influences resulting from multi-interactions between the atmosphere and underlying surface characteristics and reflect the variation in the thermal regime of the near-surface shallow frozen soils.Based on the ground surface temperature observations from 51 sites in the Headwater Area of the Yellow River(HAYR),the ground surface freezing and thawing indexes were calculated,the freezing and thawing processes were analyzed,and their spatial differentiations were explored.The results showed that the mean annual ground surface temperature(MAGST)in the HAYR ranges from-3.06 to 1.31℃,exhibiting extremely strong spatial differentiation,the differentiation of ground surface temperature is mainly affected by elevation,latitude,and NDVI(P<0.001)on a regional scale,the MAGST decreases at a vertical lapse rate of about 0.7℃·(100 m)^(-1).The larger value of NDVI represents a better condition of vegetation,leading to lower ground surface temperature in summer and higher ground surface temperature in winter.The ground surface freezing index ranges from 851.9 to 1906.6℃·d and is averaged at 1253.3℃·d,the frost day on the ground surface varies from 54 to 219 d with an average of 137.1 d,and the ground freezing index is slightly correlated to elevation and latitude.The ground surface thawing index ranges from 388.4 to 1727.2℃·d,with an average of 1039.3℃·d,and the thawed day on the ground surface ranges from 61 to 156 d,with an average of 128.8 d.The ground surface thawing index is negatively correlated with elevation,latitude,and longitude.Furthermore,the influence of elevation and NDVI on the thawing index is the largest.The onset date of ground surface thawing is greatly affected by topography and local factors,occurring mainly from mid-March to mid-May,the spatial heterogeneity of the onset date of ground surface freezing is

关 键 词：黄河源头区 多年冻土 地面温度 地面冻结/融化指数 N因子 活动层厚度 

分 类 号：P642.14[天文地球—工程地质学]