| Central Asia is one of the important dust aerosol sources in the world,and its ecological environment and air quality issues have been widely concerned by the community.Aerosols can change the radiation and energy balance of the earth-atmosphere system by absorbing and scattering solar radiation,which has a significant impact on the global climate.It is of far-reaching significance to develop the spatiotemporal heterogeneity of aerosols and its relationship with land cover types in Central Asia for understanding the air pollution situation in Central Asia accurately,and it can provide a scientific reference for comprehensive understanding of aerosol optical properties in Central Asia and improvement of atmospheric environment.This study,based on the long-term sequence MODIS aerosols and land cover products,combined with ground-based observation data and meteorological reanalysis data,comprehensively used STL time series analysis,HYSPLIT model and gray correlation methods to systematically analyze the characteristics of aerosol optical depth and land cover types in Central Asia,and explored the comprehensive influence of LUCC on aerosol.The main results of this study are as follows:(1)MCD19A2 aerosol products have good application advantages in Central Asia.They have good consistency with ground-based observations,R=0.737,R~2=0.543,RMSE=0.067,and are significantly better than MODIS DB aerosol data in terms of data abundance and accuracy.(2)AOD of Central Asia has significant seasonal variation and spatial distribution characteristics.The overall AOD trend has increased during the 19 years.The seasonal performance is spring>summer>winter>autumn,in which the AOD values of Aral Sea and Taklimakan Desert in China are high in spatial distribution.The direction of particulate matter diffusion in Central Asia is mainly northeast and east,and it can float to the North Pacific as far as possible,with a diffusion height of up to 5000 m.(3)The land use types in Central Asia are mostly bare land and grassland,and construction land is often accompanied by farmland.The area of bare land and grassland are decreasing,and the forest land,farmland,water body and construction land area are increasing.The dynamics of integrated land use in Central Asia showed a slight increase.Among them,the dynamics of forest land,farmland,and water body change drastically,and bare land,grassland and construction land are relatively flat.(4)From 2001 to 2018,the corresponding average AOD of each land-use category from small to large is as follows:grassland,woodland,construction land,farmland,bare land and water body.The average AOD above the water body is 0.212,followed by bare land 0.193,grassland has the smallest AOD is 0.127,and the greater the AOD is,the greater the range of change and the instability are.(5)Grassland has the highest percentage of air quality superior grades,up to71.356%,followed by forest land.Bare land has the highest percentage of good air quality grades,up to 73.744%,followed by construction land.The slight pollution of air quality does not account for a high proportion of the six types of land-use,and it appears slightly more in the range of water bodies and forest land.Severe air quality pollution accounts for a large proportion of all types of land,especially farmland area.(6)Each land-use category has a significant effect on the change of AOD,and the correlation coefficients are all above 0.680.The correlation coefficients of various land-use categories on AOD are not much different,the highest is forest land,followed by construction land.On the whole,grassland and bare land have the most significant contribution to AOD.In the case of removing the area base of each land-use category alone,forest land and construction land have an indispensable influence on the change of AOD. |
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