Using Lidar To Analyze The Typical Dust Transport Process In East Asia

Dust aerosol has important climate and environmental effects,which could affect the air quality of the downstream areas,interact with local air-borne dust and local pollutants during the dust transport process,and further has a profound impact on the environment.Asian dust is an important part of the dust aerosols,and has always been a hot research topic for international scholars.Most of the current researches focus on the analysis of the optical properties of dust aerosols in the process of dust weather by a single spaceborne or ground-based lidar,or discuss the the meteorological causes of the dust weather.The internal mixing mechanism between the dust aerosols and the an-thropogenic aerosols is not fully understood yet.However,the contribution of the dust aerosols on local AOD values and air quality can be estimated by comparing two differ-ent anthropogenic emission scenarios.Base on the above reasons,this paper used both the CALIOP lidar carried by CALIPSO and the ground-based lidar data to determine the optical characteristics of aerosols,the vertical distribution of aerosol types,and the contribution of dust aerosols during the dust transmission.At the beginning of 2020,COVID-19 has had a profound impact on the global economy and climate change,etc.During this period,anthropogenic activities have been greatly restricted,resulting in the reduction of the anthropogenic aerosols.There-fore,the two dust transport processes before and after the epidemic were screened as two different anthropogenic emission scenarios,which are in March 2018 and March2020 respectively.These two dust transport processes have similar meteorological back-ground conditions and similar dust transport paths.Ignoring other differences,the two-year difference in the optical properties of various aerosols and the changes in the air quality are analyzed by the multi-source data,exploring the impact of anthropogenic activities on various aerosols under dust weather conditions,and the main conclusions obtained are as follows:(1)The dust aerosols exist at a high altitude of 5-10km in the Pacific region,and the depolarization ratio and the color ratio of the dust are 0.14 and 1.29,respectively.After the comprehensive analysis of the data from the space-borne and ground-based lidar,it is found that the dust is transmitted to Jeju in South Korea and Fukuoka in Japan,and the dust aerosols contribute to the station dust observations on average of 39.25%and 35.43%,respectively.During the dust process,the concentration of particle matters increases significantly.The maximum concentration of PM10 surpasses 1500?g/m³,which is about 30 times of the national first-level standard.On May 11th and 14th,the mean values of PM2.5and PM10 are very high in Gansu Province,which reach 7 times and 12 times of the national first-level standard,respectively,while the ratio of PM10and PM2.5reaches above 6 at many places in Gansu and Xinjiang Provinces.(2)The color ratio in 2018(without anthropogenic control)and 2020(with an-thropogenic control)had declined by 10.56%and 4.85%,respectively.It demonstrated that the reduction of anthropogenic activities had slowed the attenuation of dust parti-cles.Due to the reduction of the anthropogenic emissions,the AOD value was signifi-cantly smaller.At the same time,the AOD value had also decreased during the eastward transmission of the dust in both two years.The data shows that the change of AOD in2020 was only half of that in 2018.(3)The concentration of PM_2.5 in 2020 was reduced by 57.47%compared with that in 2018.The reduced human activities had also cut the gaseous precursors of O3(VOC and NO2)and reduced the O3 concentration on the ground by 47.54%.During the dust transport process in 2020,the marine aerosols and elevated smoke had a profound impact(about 80%)on the AOD values in the Pacific in 2020.The main contribution of AOD in the Pacific region came from local emissions,and the contribution of long-distance transport was less than 20%.