Observation And Modeling Studies On Dust Aerosols And Their Regional Transport Over East Asia

Long-range transport of dust aerosols in atmosphere will not only affect the air quality,but also the global climate and environment.Currently,the researches of East Asian dust aerosols are mainly on a single city,a single aerosol type or short time-scale regional transport of dust aerosols,however how East Asian dust aerosols transport over East Asia and contribute to the local atmosphere is not clear and how large scale topography affects spatial and temporal distribution and long-range transport of East Asian dust aerosols is need to be found.This research evaluated the differences of East Asian dust aerosol AOD using CALIPSO and MODIS satellites,analyzed regional transport structure of dust aerosols during a sandstorm event over East Asia,explored the vertical structure,horizontal distribution,and regional transport characteristics of dust aerosols over East Asia based on CALIPSO data,and carried out a sensitive experiment on effect of trans-Eurasian dust aerosols on themselves and their size distribution,aiming to comprehensively understand the dust areosol and its regional transport characteristics.The main conclusions are listed as follows:(1)A comparative analysis of the seasonal variation of East Asian dust aerosols using CALIPSO and MODIS satellites.The study proved the CALIPSO satellite data could reflect the seasonal distribution characteristics of dust aerosols over East Asia.The results show that the distribution characteristics of AOD in the region obtained by CALIPSO and MODIS are basically the same,but there are differences in magnitude.CALIPSO can obtain relatively accurate distribution characteristics of AOD,but with lower value of AOD than MODIS.(2)Observation and modeling studies on dust Aerosols and their regional transport during a sandstorm event over East Asia.A typical sandstorm event on August8-11,2010 was chosen to analyze the transport process of dust aerosol from Taklimakan Desert to the western Pacific Ocean based on total scattering coefficient,aerosol types of CALIPSO,four-days of HYSPLIT model,and the MODIS AOD.At the same time,establish the transmission model of east Asian sand aerosol with MODIS(AQUA and TERRA)and CALIPSO satellites data and HYSPLIT forward trajectory model can directly study how dust aerosols transport from dust source areas to downwind regions and a connection between dust source areas and downwind regions.(3)Three-dimensional variation characteristics of atmospheric dust aerosols over East Asia.The present study analyzed the seasonal vertical and horizontal variation of dust aerosols and regional transport over East Asia using CALIPSO retrievals.Results confirmed that large amounts of dust particles were emitted from the dust regions(Taklimakan Desert and Gobi Desert).The emitted dusts formed a dust belt within a latitudinal range of 25°N to45°N and extended to eastern China,Japan,Korea and the Pacific Ocean.FDOs showed to isolated centers over the Taklimakan Desert and Gobi Desert,implying limitations of the diffusion and long-range transport of the dust aerosols over the Taklimakan Desert.Vertically,FDOs peaked at about 2 km over the dust source regions.In contrast,FDOs decreased with altitude over the downwind regions.The vertical profile of the extinction coefficient revealed the predominance of pure dust particles in the dust source regions and a mixture of dust particles and pollutants in the downwind regions.(4)Effect of trans-Eurasian dust aerosols on themselves and their size distribution.This research analyzed the vertical structure,horizontal distribution,and regional transport of dust aerosols over East Asia and its 5 typical regions based on the evaluation of global dust aerosols simulated by global climate model CAM5.1 during 2 years(2002-2003).The results showed that dust aerosols emitted from East Asia will mainly affected the local atmospheric aerosols.The seasonal patterns of the foreign dust contribution to tropospheric dust loading and surface dust concentrations were generally similar,but the contribution rate to dust loading was 10-40%higher than surface dust concentrations,meaning dust aerosols from other dust souce regions in North Hemisphere will more affect climate change than local air quality.Trans-Eurasian dust aerosols can largely change the vertical and size distribution of dust aerosol over East Asia,cause peak values of dust coarse aerosols(PM_>2.5)over downwind regions like East China and Korea-Japan region raise to 3-5km in the atmosphere,and affect the size distribution of dust aerosols over thoese downwind regions especially for fine particles(PM<_2.5).Dust contribution transported from Eurasia and East Asia to tropospheric dust loading over East China and Korea-Japan region were similar,but have different effects on vertical and size distribution of dust aerosol over East Asia.Compared to regional-transport of dust aerosols over East Asian deserts,trans-Eurasian dust aerosols have significant influence on climatic change over East Asia.