Estimation of ground-level dry PM2.5concentrations at 3 km resolution over Beijing using Geostationary Ocean Colour Imager

In this study, aerosol optical depth (AOD) and fine-mode fraction (FMF) with a 3 km resolution are retrieved from Geostationary Ocean Colour Imager (GOCI) data using a multi-temporal method. The retrieved results are input into a physical model for estimating the fine particulate matter (PM2.5) based on instantaneous satellite-based measurements. The other two input parameters of the model are planetary boundary layer height (PBLH) and atmospheric relative humidity (RH), which are simulated by the Weather Research and Forecasting (WRF) model and have the same spatial resolution as AOD and FMF. For better time-matching, the time of the simulated PBLH and RH is almost the same as that of the retrieved AOD and FMF, and is selected when uniform mixing of aerosols occurs within boundary layer in the afternoon. Finally, the ground-level dry PM(2.5)concentrations at a 3 km resolution are estimated over Beijing. The GOCI-estimated PM(2.5)results are validated by in situ measurements in the study area. The means of GOCI-estimated and in situ results are very close (131.2 mu g m(-3)versus 123.0 mu g m(-3)) and the correlation coefficient is about 0.84 with a linear slope of 0.81 and intercept of 31.1 mu g m(-3), which shows good performance of GOCI in air-quality monitoring.