Remote Sensing, Vol. 9, Pages 858: Deriving Hourly PM2.5 Concentrations from Himawari-8 AODs over Beijing-Tianjin-Hebei in China (Remote Sensing)

Monitoring fine particulate matter with diameters of less than 2.5 ?m (PM2.5) is a critical endeavor in the Beijing-Tianjin-Hebei (BTH) region, which is one of the most polluted areas in China. Polar orbit satellites are limited by observation frequency, which is insufficient for understanding PM2.5 evolution. As a geostationary satellite, Himawari-8 can obtain hourly optical depths (AODs) and overcome the estimated PM2.5 concentrations with low time resolution. In this study, the evaluation of Himawari-8 AODs by comparing with Aerosol Robotic Network (AERONET) measurements showed Himawari-8 retrievals (Level 3) with a mild underestimate of about -0.06 and approximately 57% of AODs falling within the expected error established by the Moderate-resolution Imaging Spectroradiometer (MODIS) (±(0.05 + 0.15AOD)). Furthermore, the improved linear mixed-effect model was proposed to derive the surface hourly PM2.5 from Himawari-8 AODs from July 2015 to March 2017. The estimated hourly PM2.5 concentrations agreed well with the surface PM2.5 measurements with high R2 (0.86) and low RMSE (24.5 ?g/m3). The average estimated PM2.5 in the BTH region during the study time range was about 55 ?g/m3. The estimated hourly PM2.5 concentrations ranged extensively from 35.2 ± 26.9 ?g/m3 (1600 local time) to 65.5 ± 54.6 ?g/m3 (1100 local time) at different hours.