Spatial-Temporal Variation Characteristics of Aerosols in Xuzhou Using Multi-Sources Observations
The aerosol inversion products of AERONET(Aerosol Robotic Network),MODIS(Moderate-resolution Imaging Spectroradiometer),CALIPSO(Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation)and MERRA-2(Modern-Era Retrospective analysis for Research and Applications,Version 2)and CHAP PM2.5 products were synthetically used to analyze the horizontal and vertical distribution of aerosol optical properties,aerosol components and the spatiotemporal changes of PM2.5 mass concentration in Xuzhou from 2014 to 2020.Analysis of AERONET data showed that the AOD(Aerosol Optical Depth,550 nm)in Xuzhou was high in summer and low in winter,while the opposite for AE(Ängström Exponent),with the seasonal averages of AOD and AE ranging from 0.53-0.71 and 1.11-1.33,respectively.The average AOD from 2014 to 2018 was 0.70-0.47,showing a significant decreasing trend.The particles showed a clear bimodal size distribution with significant seasonal differences,which showed the dominant of coarse particle in spring and fine one in summer,while both of them were equivalent in autumn and winter.The effective radius of particles presented the largest in spring and the smallest in summer.The smallest SSA(Single Scattering Albedo,440-1 020 nm)and the largest AAOD(Absorption AOD,440 nm)was in winter,while the opposite in summer.The aerosol direct radiative forcing(ARF)was positively correlated with AOD,which was more sensitive at the bottom of the atmosphere(BOA).It appeared a strong negative correlation of the efficiency of ARF(ARFE)with SSA at BOA.From CALIPSO aerosol profiles,it showed a faster decreasing of aerosol extinction coefficient with height in winter and spring,while a much slower one in summer contributed by a higher boundary layer.The near-surface aerosol extinction coefficient decreased during the period,with a faster decline in winter and spring.From MODIS,it showed higher AOD in urban area than that in the surroundings.The mean AOD of Xuzhou showed a significant decreasing trend,with the faster of-0.12 per year in the urban area.From the CHAP product,the highest region of PM2.5 in Xuzhou was in the northwestern area.It showed a decreasing trend in all seasons,with the fastest annual decline of-6 μg/m3 in winter.According to MERRA-2 reanalysis dataset,the dust contributed the largest proportion in the column mass concentration of aerosols,followed by sulfate.The column mass concentration decreased during the study period,with an annual decline of-0.29 mg/m2,and the dust decreased the fastest.