雅鲁藏布大峡谷地区近地面-大气间水热交换特征分析

利用欧洲中期天气预报中心第五代再分析数据产品,归类分析了藏东南雅鲁藏布大峡谷地区水汽输送类别。选取大峡谷地区排龙站、墨脱站两个站点2019年涡动相关系统观测数据,分析不同水汽条件下雅鲁藏布大峡谷地区不同位置近地面水热交换通量的日变化特征。结果表明:高原季风期对应大峡谷地区水汽强输送期和温湿期,高原非季风期则相反。墨脱站、排龙站在高原季风期/非季风期典型晴天/阴天近地面潜热通量日变化对大气水汽条件较为敏感且响应一致,近地面潜热通量在强水汽条件下的日变化均强于弱水汽条件下,墨脱站特征最为显著,在高原季风期典型晴天强水汽条件下潜热通量日均值为84.05 W·m^-2是弱水汽条件下的1.13倍,日变幅达345.37 W·m^-2。两个站点在高原季风期/非季风期近地面感热通量对大气水汽条件响应不同。高原季风期典型晴天下,两个站点在弱水汽条件下的近地面感热通量日变化均强于强水汽条件下,海拔较高的排龙站在弱水汽条件下感热通量日均值(32.71 W·m^-2)和日较差(191.10 W·m^-2)是强水汽条件下的1.66倍和1.26倍。云覆盖和水汽对太阳短波辐射的削弱作用大于其自身的温室效应,墨脱站和排龙站在高原季风期/非季风期典型阴天弱水汽条件下的近地面感热通量日变化均强于强水汽条件下,排龙站在高原季风期/非季风期典型阴弱水气条件下近地面感热通量日均值为35.12 W·m^-2和14.32 W·m^-2分别是强水汽条件下的2.59倍和1.27倍。大峡谷地区存在水汽输送通道,大气水汽的辐射强迫对陆-气间水热交换过程存在显著影响,但近地面能量分配受地表水热属性的制约。

Characteristics Analysis of the Land-atmospheric Water&Heat Exchanges over the Yarlung Zangbo Grand Canyon Region

By using the ECMWF Re-Analyses version5 data,the water vapor transport type over the Yarlung Zangbo Grand Canyon area of southeastern Qinghai-Xizang Plateau(QXP)are categorized,the daily variation characteristics of land-atmospheric water heat exchange fluxes are analyzed at different locations under different water vapor conditions by choosing two observation stations in the Yarlung Zangbo Grand Canyon area,namely,the Pailong Station and the Motuo Station.The results show that:The plateau monsoon period is the period of strong water vapor transport and the warm-wet period in the Yarlung Zangbo Grand Canyon area,while the opposite is true for the Plateau non-Monsoon period.Daily variations of near-surface latent heat fluxes on typical sunny/cloudy days during the Plateau Monsoon/non-Monsoon period are more sensitive and consistent in response to atmospheric water vapor conditions at the Motuo and the Pailong stations.The daily variation of near-surface latent heat flux under strong water vapor conditions is stronger than that under weak water vapor conditions,and the most significant difference in daily variation of near-surface latent heat flux under different water vapor conditions is found at the low altitude and humid Motuo station,where the daily average of near-surface sensible heat flux under strong water vapor conditions(84.05 W·m^-2)is about 1.13 times of that under weak water vapor conditions on a typical sunny day during the non-monsoon period on the plateau,and the daily variation can reach 345.37 W·m^-2.Different characteristics of near-surface sensible heat fluxes at the two sites in response to different water vapor conditions during the highland monsoon and non-monsoon periods.The daily variation of nearsurface sensible heat fluxes at the Pailong and the Motuo stations on typical clear days during the highland monsoon period is stronger under weak water vapor conditions than under strong water vapor conditions.The daily average and variation of near-surface sensible heat flux is most sensitive to the difference of water vapor conditions during the highland monsoon/non-monsoon period at the higher altitude Pailong station,and the daily average and diurnal range of sensible heat flux under weak water vapor conditions(32.71 and 191.1 W·m^-2)is about 1.66 and 1.26 times higher than that under strong water vapor conditions under a typical sunny day during the highland monsoon period.The weakening effect of cloud cover and water vapor on solar short-wave radiation is greater than its own greenhouse effect.The daily variations of near-surface sensible heat fluxes at the Motuo and the Pailong stations under weak water vapor conditions on typical cloudy days during the highland monsoon/non-monsoon period are stronger than those under strong water vapor conditions,and the daily average values of near-surface sensible heat fluxes at the Pailong station under weak water vapor conditions on typical cloudy days during the Plateau Monsoon/non-Monsoon period are 35.12 and 14.32 W·m^-2 which are 2.59 and 1.27 times higher than those under strong water vapor conditions,respectively.The existence of water vapor transport channels in the Yarlung Zangbo Grand Canyon area,the radiation forcing of atmospheric water vapor has significant effects on the land-atmospheric water&heat exchanges process,the energy parting at the surface is controlled by the land surface property.