Comparison and Impact Factor Analysis of Ground PM2.5 Retrieved by Aqua and Himawari-8 Satellite Products in Guangdong, China

Fine particulate matter (particles sizes <2.5 mu m; PM2.5) concentrations can be obtained at high spatial resolutions using satellite remote sensing. Previous studies on PM2.5 concentrations in Guangdong have used the aerosol optical depth (AOD) determined by MODIS sensors on the Terra and Aqua satellites, which both have a transit time of once per day. In this study, based on AOD data obtained from the Aqua and Himawari-8 (H8) satellites and ground-based measurements, ground PM2.5 concentrations were compared using radiation theory and a semi-empirical model. The temporal resolution of PM2.5 concentrations retrieved by the H8 satellite improved from once per day to once per hour when compared with the temporal resolution of those retrieved by the Aqua satellite. The data from both satellites were consistent with ground-based measurements (R >= 0.65 and reaching 0.96 for the annual mean), indicating that the retrieved data could characterize the spatial and temporal variations in ground PM2.5 concentrations in Guangdong Province. The two satellites had similar performances for the annual mean, dry season mean, and hourly data; however, H8 performed better than Aqua for the wet season and monthly averages. The performances of both satellites decreased when relative humidity increased and visibility decreased. H8 performed better at high relative humidity, low visibility, and during the PM2.5 pollution process, thus reflecting the advantage of geostationary satellite in capturing PM2.5 pollution distributions. In addition, the data retrieved by both satellites exhibited higher PM2.5 concentrations near the junctions of some cities and regions, indicating a new pollution distribution pattern after the industrial shift that cannot be observed by ground-based measurements. Aerosol scale height is the most important parameter for retrieving PM2.5 concentrations. Thus, improving the computational accuracy of aerosol scale height may improve the effectiveness of satellite-based PM2.5 concentration retrievals.