Effect of near-surface water vapor density on surface radiation in permafrost regions:a case study in Beiluhe area,Qinghai province,China
Under the background of climate warming and humidity increase on the Qinghai-Tibet Plateau,atmospheric water vapor is increasing.The impact of atmospheric water vapor on land surface radiation will inevitably affect the energy distribution and thermal stability of permafrost.Based on the meteorological and hydrothermal data of the Beiluhe station located in the central Qinghai-Tibet Plateau,the effects of relative humidity at the height of 2 m and typical summer rainfall events on land surface albedo and radiation components were analyzed.The results are as below.Atmospheric water vapor can effectively weaken short-wave radiation,absorb long-wave radiation from the ground,increase downward long-wave radiation,and thus reduce surface albedo.The influence of atmospheric water vapor on land surface radiation has obvious seasonal characteristics.In summer,atmospheric water vapor has the most obvious weakening effect on solar short-wave radiation,and releases more downward long-wave radiation.In winter,the weakening effect of atmospheric water vapor on solar short-wave radiation is relatively weak,and less downward long-wave radiation is emitted.During the study period,for every 10%increase in the relative humidity of the atmospheric in the Beiluhe region in summer and winter,the daily average value of solar short-wave radiation will decrease by 54.9 and 9.8 W/m2,respectively.At the same time,the daily average value of downward long-wave radiation will increase by 14.8 and 3.9 W/m2,respectively.In autumn,the change in atmospheric water vapor has the most significant impact on the surface albedo.When the relative humidity in the atmosphere decreases by 10%in autumn,the surface albedo increases by 0.15.In contrast,the impact in spring is the smallest.When the relative humidity in the atmosphere increases by 10%in spring,the surface albedo only decreases by 0.01.Different typical rainfall events in summer lead to an increase in near-surface water vapor density and soil moisture content at shallow depths,which reduces surface albedo,and the reduction is positively correlated with rainfall intensity.The research results provide a reference for the analysis of surface energy balance in permafrost regions on the central Qinghai-Tibetan Plateau under the background of climate warming and wetting.
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