降雨对青藏高原多年冻土区地表辐射的影响——以北麓河地区为例

青藏高原地表辐射变化影响多年冻土地表能量收支平衡、热工计算温度场边界条件以及冻土热稳定性。降雨变化是影响地表辐射的重要因素，以青藏高原北麓河地区的地表辐射资料和浅层地表水热监测数据为基础，分析了降雨对多年冻土区地表辐射特征的影响。研究表明：受降雨影响，辐射分量具有明显的日变化和年际变化特征，短波辐射被严重削弱，地面长波辐射削弱程度较低，而太阳长波辐射增强。小雨作用后，太阳短波、地面短波、地面长波辐射日积分量分别减少24.6%、37.9%、4.2%，太阳长波增加了4.3%；中雨作用后，太阳短波、地面短波、地面长波辐射日积分量分别减少32.2%、43.4%、1.7%，太阳长波增加了11.6%；大雨作用后，太阳短波、地面短波、地面长波辐射日积分量分别减少56.3%、65.5%、4.4%，太阳长波增加了10.7%；降雨作用后地表反照率减小，且呈不对称“U”形变化，地表净辐射增加，长期时间尺度上降雨对净辐射影响不明显；降雨对辐射特征的影响程度与降雨强度呈正相关且地表辐射对降雨变化的响应有滞后效应。在暖湿化背景下，冻土热工计算中应考虑降雨对多年冻土区地表能量平衡和水热边界的影响。

The effects of rainfall on the surface radiation of permafrost regions in Qinghai-Tibet Plateau:a case study in Beiluhe area

Changes of surface radiation on the Qinghai-Tibet Plateau affect the energy balance of the permafrost region， the boundary conditions of the temperature field in thermal calculation and the thermal stability of permafrost. Rainfall is the key factor affecting the surface radiation. Based on the surface radiation and shallow surface water-heat data of the Qinghai-Tibet Plateau Beiluhe area， the effects of rainfall on surface radiation were analyzed. The results show that under the influence of precipitation the radiation component has obvious diurnal and interannual variation characteristics. The short-wave radiation is seriously weakened， the long-wave radiation on the ground is slightly weakened， while the long-wave radiation of the sun is enhanced. After the action of light rain， the daily volume of solar short wave， ground short wave and ground long wave decreased by 24.6%， 37.9% and 4.2% respectively， and the solar long wave increased by 4.3%.After the action of rainfall， the daily volume of solar short wave， ground short wave and ground long wave decreased by 32.2%， 43.4% and 1.7% respectively， and the solar long wave increased by 11.6%.After the effect of heavy rain， the daily volume of solar short wave， ground short wave and ground long wave decreased by 56.3%， 65.5% and 4.4% respectively. The solar long wave increased by 10.7%. Rainfall decreases the surface albedo and increases the net surface radiation. The surface albedo presents an asymmetric U-shape and the effect of long-term rainfall on net radiation is not obvious. The effect of rainfall on radiation characteristics is positively correlated with rainfall intensity and the response of surface radiation to rainfall has a hysteresis effect. In the climate warming and wetting scenario， the effect of rainfall on the surface energy balance and water thermal boundary of permafrost regions should be considered in the thermal calculation of permafrost and the thermal simulation of frozen soil.