Retrieving PM2.5 with high spatio-temporal coverage by TOA reflectance of Himawari-8

Particulate matter with an aerodynamic diameter less than 2.5 μm (PM2.5) has drawn considerable concern due to its significant air quality and public health effects. Aerosol optical depth (AOD) from polar-orbiting satellites has been widely used for estimating ground-level PM2.5 concentration. However, the PM2.5 estimation from the polar-orbiting satellites AOD are limited in spatio-temporal coverage due to its low revisit rate and the applicability issue of the AOD retrieval method. This study proposed a method to estimate PM2.5 distributions using the top-of-the-atmosphere reflectance (TOAR) of the Himawari-8 geostationary satellite over China. The results show that PM2.5 estimations from AOD and TOAR present a similar accuracy, with an R2 (RMSE) of 0.86 (17.2 μg/m3). For the marginal regions where valid AOD observations unavailable, the R2 (RMSE) of PM2.5 estimated from TOAR also reaches 0.83 (23.7 μg/m3). The spatio-temporal coverage of PM2.5 estimated by TOAR is about four times based on AOD data, which is important to capture the true distribution of fine particles and explore their diurnal evolution.