高寒草原水热交换的季节性特征显著， 土壤冻融过程对地‐气水热交换有着重要的影响。本文利用黄河源区汤岔玛小流域2014年5月至2015年5月陆面过程观测数据， 将土壤冻融过程划分为完全融化（TT）和完全冻结（FF）两种状态与融冻（T‐F）和冻融（F‐T）两个过程， 并分析了期间高寒草原下垫面净辐射、 感热通量、 潜热通量和地表热通量不同状态和过程中的变化， 以此探究土壤冻融过程中地气间的水热交换特征。研究表明： （1）净辐射通量在完全融化阶段的平均值要普遍大于其他三个阶段， 最大值达到了203.7 W·m^-2， 冻融阶段冻土融化， 土壤含水量逐渐增加， 净辐射比完全冻结阶段明显增大， 完全融化阶段净辐射日变化值最大， 达到了717.6 W·m^-2， 完全冻结阶段最小， 冻融阶段次之。（2）感热通量与潜热通量在完全融化和完全冻结阶段的配置不同。完全融化时， 由于降水和土壤含水量等原因， 净辐射主要转换为潜热通量， 潜热通量日变化最大值为193.7 W·m^-2， 而感热通量只有80.0 W·m^-2左右。融冻阶段、 冻融阶段与完全冻结时感热与潜热的日平均相差不大， 潜热在三个阶段平均值为21.9 W·m^-2， 感热为20.3 W·m^-2； 而感热日变化在三个阶段均大于潜热， 土壤发生冻融循环， 地气温差较小， 含水量产生变化， 净辐射在这期间主要转换为感热。（3）土壤热通量在完全融化（冻结）状态下为正（负）， 表明地表从大气吸收（释放）热量， 其日变化幅度大（小）。以上结果说明， 土壤冻融状态与过程对近地面陆‐气间水热交换过程表现出不同的特征。

The seasonal characteristics of water and heat exchange in the alpine grasslands are significant， and the freezing‐thawing process has an important impact on the land‐atmospheric water and heat exchange.Based on the observation data of the land surface process in the Tangchama small watershed in the source area of the Yellow River from May 2014 to May 2015， this research divides the soil freezing‐thawing process into thawed stage （TT）， frozen stage （FF）， thawing to freezing （T-F） and freezing to thawing （F-T）， and the changes in the different states and period of the net radiation， sensible heat flux， latent heat flux and surface heat flux of the underlying surface of the alpine grassland are analyzed to explore the characteristics of water and heat exchange between the land‐atmosphere in the soil freezing‐thawing process.The results are as follows： （1） The average value of the net radiation flux in the thawed stage is generally greater than that of the other three stages， and the maximum value reaches 203.7 W·m^-2.The frozen soil melts in the freezing‐thawing stage， and the soil moisture content gradually increases.The radiation ratio increased significantly during the frozen stage， the net radiation diurnal variation was the largest in the thawed stage， reaching 717.6 W·m^-2， and the frozen stage was the smallest， followed by the freezing‐thawing stage.（2） The proportion of sensible heat flux and latent heat flux is different in the thawed and frozen stages.When completely thawed， due to precipitation and soil moisture content， the net radiation is mainly converted into latent heat flux.The maximum diurnal variation of latent heat flux is 193.7 W·m^-2， while the sensible heat flux is only about 80.0 W·m^-2.The diurnal average of sensible heat and latent heat in the thawing‐freezing phase， the freezing‐thawing period and the frozen period is not much different.The mean latent heat in the three period is 21.9 W·m^-2， and the sensible heat is 20.3 W·m^-2； The diurnal variation is greater than the latent heat in the three period， the soil suffers a freezing‐thawing cycle， the soil temperature difference is small， and the water content changes， and the net radiation is mainly converted into sensible heat during this period； the diurnal variation of sensible heat was greater than that of latent heat in the three stages.The freezing-thawing cycle occurred in the soil， the difference between ground and air temperature was small， and the moisture content changed.During this period， the net radiation was mainly converted to sensible heat.（3） The soil heat flux is positive （negative） in thawed （frozen） state， indicating that the surface soil absorbs （releases） heat from the atmosphere， and its daily variation range is large （small）.The above results show that the state and process of soil freezing and thawing have different characteristics for the water and heat exchange process between the land and atmosphere.