塔克拉玛干沙漠和青藏高原地区沙尘气溶胶光学特性及其加热率的时空分布特征

Spatial and temporal characteristics of optical properties and heating rate of dust aerosol over Taklimakan Desert and Tibetan Plateau in China

沙尘不同的垂直分布对大气的加热作用不同,通过卫星观测结合数值模拟,可以更清楚地了解沙尘辐射加热作用,有利于理解沙尘对该地区大气热结构的影响机制.因此,本研究利用CALIPSO气溶胶产品和SBDART模式,分析了2007—2020年塔克拉玛干沙漠和青藏高原沙尘气溶胶及其短波加热率的时空分布特征.结果表明,塔克拉玛干沙漠和青藏高原的年平均沙尘气溶胶光学厚度(DAOD,532 nm)分别为0.300~0.350和0.086~0.108,平均值分别为0.328和0.097.塔克拉玛干沙漠季节平均DAOD的最大、最小值分别出现在春季和冬季,而青藏高原的最大、最小值分别出现在夏季和秋季.塔克拉玛干沙漠和青藏高原的沙尘消光系数(σ_(D))最大值分别出现在春季和夏季.2007—2020年,两地的σ_(D)在春季均呈增加趋势,而在秋季则呈减小趋势.春季和夏季的短波沙尘加热率(SW DHR)均大于其它两个季节,其中春季最大,塔克拉玛干沙漠上空冬季最弱,青藏高原上空秋季最弱.春夏季,青藏高原北坡存在较强沙尘加热层,其顶部高于5 km,其强度及高值区从春季到冬季逐渐减小.从年变化来看,春季短波加热率呈加强趋势,秋季呈减弱趋势.柴达木盆地是青藏高原上空沙尘加热率(DHR)最高的区域,对高原沙尘输送和辐射加热有重要作用.

Different vertical distributions of dust have different heating effects on atmospheric structure.Through satellite observation and numerical simulation,the radiative heating effect of dust can be understood more clearly,which is conducive to understand the influence mechanism of dust on atmospheric thermal structure in this region.Therefore,the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations(CALIPSO)aerosol products and Santa Barbara DISORT Atmospheric Radiative Transfer(SBDART)model were used to analyze the spatial-temporal distribution characteristics of dust aerosols and their shortwave heating rates over the Taklimakan Desert and Tibetan Plateau from 2007 to 2020.The results showed that the annual mean dust aerosol optical depths(DAOD,532 nm)for Taklimakan Desert and Tibetan Plateau were 0.300~0.350 and 0.086~0.108,with total averages of 0.328 and 0.097,respectively.The maximum and minimum of seasonal average DAOD of Taklimakan Desert appeared in spring and winter,while those of Tibetan Plateau appeared in summer and autumn,respectively.The maximum values of the dust extinction coefficient(σ_(D))of Taklimakan Desert and Tibetan Plateau appeared in spring and summer,respectively.From 2007 to 2020,theσDof the two regions showed an increasing trend in spring while a decreasing trend in autumn.The shortwave dust heating rates(SW DHR)in spring and summer were greater than that in the other two seasons,showing the largest in spring.The smallest DHR appeared in winter and in autumn over Taklimakan Desert and Tibetan Plateau,respectively.A strong dust heating layer appeared over the northern slope of TIBETAN PLATEAU in spring and summer,with the top higher than 5 km and showing a decreasing trend from spring to winter for its intensity and the high-value area.To its annual change,the SW DHR showed a strengthening trend in spring while a weakening trend in autumn.The Qaidam Basin was the highest DHR region on the TIBETAN PLATEAU,which played an important role in local dust transport and radiation heating.