A Simulation Study On The Source And Transmission Of The Dust Aerosol To The UTLS Over The Yunnan Province

Using the latest version of CALIPSO satellite(V4.10)Level 2 aerosol profile data from 2007 to 2016.the vertical distribution characteristics of lower tropospheric stratosphere(UTLS)aerosols over Yunnan Province are studied.Combined with the South Asian summer monsoon and the South Asian high anticyclone circulation,the correlation analysis of dust aerosols transport mechanism to UTLS region is carried out.Then,numerical simulation is used to study the transmission characteristics of dust aerosols over Yunnan Province.The source and transport process of dust aerosols were analyzed.The main conclusions are as follows:(1)The vertical distribution of sand-dust aerosols in Yunnan is mainly in the form of multi-layer aerosol layer.The aerosol layer in UTLS region is obvious.From May onwards,the aerosol layer in UTLS region rises continuously to July,and the height of UTLS aerosol layer decreases from August to September.With the intensification of the South Asian summer monsoon,the dust aerosols in UTLS area over Yunnan and south of Qinghai-Tibet Plateau increased.This is due to the intensification of the South Asian summer monsoon,which corresponds to the intensification of the rising motion in the southern part of the Qinghai-Tibet Plateau.The dust aerosols in UTLS area south of the Plateau increased with the increase of deep convective activities.When the South Asian high increased,The backscattering coefficient of the dust aerosols in UTLS area over Yunnan were decreases at 13-17 km,and the backscattering coefficient increases above 17 km.The enhancement of the South Asian high results in the enhancement of the updraft and the upward transport of dust aerosols in Yunnan.The water vapor increases with the increase of ascending activity,and the moisture absorption of particles increases,which enhances the backscattering ability of dust aerosols.(2)In the two typical dust weather over Yunnan mainly come from the Taklimakan and Gobi deserts in Western China and the Tar Desert in South Asia.The dust particles from the height of 15 km mainly come from the surface.They rise vertically over the Qinghai-Tibet Plateau and its southeastern side,and are transported over Yunnan with the anticyclone circulation of the South Asian High.(3)The high concentration channel of dust particles in the convective area is mainly caused by convective activities.In the upper troposphere(UT),the distribution of dust aerosols is consistent with that of deep convection.The dust aerosols are uplifted from the source to the north and south slopes of the Qinghai-Tibet Plateau and transported eastward to the plateau area.The uplift of the plateau area is strong,and the dust aerosols continue to rise to the southeast side of the Qinghai-Tibet Plateau.With the increase of altitude,dust aerosols mainly distribute in the lower troposphere(LS)of South Asia,which indicates that dust aerosols are brought directly from boundary layer air to convective outflow height with deep convective activity.Then,with the slow vertical upward movement of large scale,the distribution of dust aerosols is controlled by the South Asia High Anticyclone and is transmitted over Yunnan with the form of anticyclone circulation.