| Dust aerosol is a major component of aerosols in the atmosphere which has a significant influence on the energy balance of the earth system through direct and indirect effects and affects the concentration and distribution of greenhouse gases by changing atmospheric chemical processes.The Taklimakan Desert(TD)located in southern Xinjiang of China is the main dust source in East Asia,and it has a serious impact on local air quality in spring.Moreover,the dust could also be lifted above the planetary boundary layer for long-distance transportation,thus affecting the air quality of cities along the dust transportation path.Therefore,it is particularly important to study the three-dimensional distribution characteristics and main transport paths of dust aerosol in TD and surrounding areas.The dust transport and spatial-temporal distribution characteristics were analyzed in this study by integrating satellite and reanalysis data in TD and surrounding areas in2020.The main objectives and results in this study are as follows:(1)The spatial-temporal distribution characteristics of AOD(Aerosol Optical Depth)in TD and surrounding areas were analyzed based on MERRA-2(The Second Modern-era Retrospective Analysis for Research and Applications)and MISR(Multi-angle Imaging Spectroradiometer)satellite data products.In addition,the accuracy of dust aerosol of MERRA-2 was verified by comparing with the results from multiplying the monitoring data by the source apportionment results of particulate matter monitoring data based on the Positive Matrix Factorization(PMF)method.Moreover,the spatial-temporal distribution characteristics of dust aerosol were analyzed.In terms of spatial distribution,the high values of dust AOD(DAOD)were mainly located in the northwest of TD(the southwest of Aksu,the northeast of Kashi and the northwest of Hetian).The lower values of DAOD were concentrated in the periphery of southern Xinjiang and the higher values were focused in the middle of TD,in addition,the distribution of DAOD in TD was decreased from northwest to southeast.In terms of temporal distribution,the DAOD was highest in spring(0.25),followed by summer(0.22),autumn(0.2)and winter(0.06),which was consistent with the seasonal variation of wind speed.Furthermore,the spatial distribution of the particulate matter size was shown by?ngstr?m exponent and ratio of DAOD to AOD.(2)The vertical characteristics of dust aerosol in TD and surrounding areas were analyzed by employing the CALIPSO(Cloud-aerosol Lidar and Infrared Pathfinder Satellite Observations)aerosol profile products.The results showed that the extinction coefficient(EC)decreased with the increase of altitude over TD and surrounding areas,and EC was highest in spring and lowest in summer.In spring,the EC could reach0.52km-1 at lower altitude(<2km)and decreased to 0.02 km-1 at 5km.In addition,the vertical distribution of particulate depolarization ratio in spring indicated that there were two obvious dust layers over TD and surrounding areas.The low dust layer was mainly distributed in 0-2km,and the dust could be uplifted higher(4-6km)over Hetian,and the high dust layer was mainly distributed in 8-12km,indicating that the dust over TD was capable of long-distance transport.(3)The local and long-distance dust transport characteristics over TD were discussed depending on the HYSPLIT(Hybrid single-particle Lagrangian Integrated Trajectory)model.The results showed that the transport paths at the altitude of 0.5km,1km and 2km were mainly from the desert center to the northwest and through the south of Aksu,then transported to Bazhou,which mainly influenced the local area due to the higher altitude on the edge of southern Xinjiang.Moreover,the transport paths at the altitude of 3km,4km,6km were mainly from the desert center to the east of Bazhou,then passing through Qinghai,Gansu,Shaanxi,Ningxia,Inner Mongolia,and other places,which implied it could impact the air quality of regions on the long-distance transport path. |
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