Spatio-temporal Characteristics And Influencing Factors Of Aerosol Optical Depth Over East China

Atmospheric aerosol Optical Depth(AOD)are important factors of the climate and the atmospheric environment,and have an important impact on humans.This paper analyzed the spatio-temporal variations of Aerosol Optical Depth(AOD)and driving factors by combining various meteorological raster data and surface data,using the MODIS C6 data from March2001 to February 2018.This study established the response relationship model of the principal component driving factor to the aerosol optical thickness spatial distribution,and using the correlation analysis and geo-detector method to analyzed the AOD spatial distribution feature driving factors.The AOD variation rules are classified based on the pixel scale,the influence of driving factors on AOD time variation is studied from the perspective of frequency domain and regional differentiation law.Based on the geometric similarity of time series,the relationship between the monthly variations of AOD and the monthly change of driving factor are analyzed.This study mainly obtained the following research conclusions:(1)In terms of AOD spatial distribution,the AOD value in eastern China is high in the plain area and low in the mountain plateau.The spatial variation gradient of the AOD value inside the plain is small,and there is a large spatial variation gradient in the boundary between the plain and the mountain.The particle size of anthropogenic aerosols is highly uncertain,and the?ngstr?m constant is at a medium level in areas with high population density in eastern China;The relationship between fourteen driving factors and the spatial distribution of AOD are analyzed by correlation analysis and geographic detector analysis method.The four numerical driving factors and the three types of driving factors that passed the significance test throughout yearly indicated that the spatial distribution of AOD in eastern China is mainly affected by human factors.(2)In view of AOD temporal features,the ISODATA algorithm is used to classify AOD time series.The clustering results are less spatially fragmented and have a good overall spatial autocorrelation,indicating that clustering analysis has a good effect.which can avoid the problem of regular confounding;It analyzed the temporal variations of Aerosol Optical Depth(AOD)over different typical regions,using the Ensemble Empirical Mode Decomposition(EEMD)method.Results showed that the occasional events have an important impact on the inter-annual variation of AOD,and its impact on the AOD temporal series of the magnitude and impact period are unstable.while the effect of AOD seasonal variation on the AOD temporal series is relatively stable.RES showed that the AOD values of the seven typical areas have increased first and then decreased since 2001.The temporal variations of AOD in eastern China were resulted from multiple fluctuation rules superimposed together;Based on the grey correlation degree,the geometric similarity between the monthly change of AOD and the driving factor in different typical areas is analyzed.The driving factors affecting the seasonal change of AOD are mainly relative humidity.,radiation,vegetation index and wind speed.(3)Based on the seasonal variation characteristics of AOD temporal series extracted by band-pass filtering,the research shows that the AOD temporal series change has an important relationship with the position of the direct solar spot.The month closest to the direct sun point in the year is the highest AOD value of the latitude.The AOD change period in the area north of the Tropic of Cancer and the south of the Tropic of Cancer is 12 months.Areas in the interior the Tropic of Cancer have a short period and a long period,and the AOD period in the equatorial region is 6 months.At the global scale,the seasonal variation of AOD has a consistent change with the seasonal variation of LST.