Estimating ground-level PM<sub>2.5</sub> in eastern China using aerosol optical depth determined from the GOCI satellite instrument

Abstract

<p><strong>Abstract.</strong> We determine and interpret fine particulate matter (PM_2.5) concentrations in eastern China for January to December 2013 at a horizontal resolution of 6 km from aerosol optical depth (AOD) retrieved from the Korean geostationary ocean color imager (GOCI) satellite instrument. We implement a set of filters to minimize cloud contamination in GOCI AOD. Evaluation of filtered GOCI AOD with AOD from the Aerosol Robotic Network (AERONET) indicates significant agreement with mean fractional bias (MFB) in Beijing of 6.7 % and northern Taiwan of −1.2 %. We use a global chemical transport model (GEOS-Chem) to relate the total column AOD to the near-surface PM_2.5. The simulated PM_2.5 / AOD ratio exhibits high consistency with ground-based measurements in Taiwan (MFB = &amp;minus;0.52 %) and Beijing (MFB = &amp;minus;8.0 %). We evaluate the satellite-derived PM_2.5 versus the ground-level PM_2.5 in 2013 measured by the China Environmental Monitoring Center. Significant agreement is found between GOCI-derived PM_2.5 and in situ observations in both annual averages (<i>r</i>² = 0.66, <i>N</i> = 494) and monthly averages (relative RMSE = 18.3 %), indicating GOCI provides valuable data for air quality studies in Northeast Asia. The GEOS-Chem simulated chemical composition of GOCI-derived PM_2.5 reveals that secondary inorganics (SO₄^2-, NO₃^-, NH₄⁺) and organic matter are the most significant components. Biofuel emissions in northern China for heating increase the concentration of organic matter in winter. The population-weighted GOCI-derived PM_2.5 over eastern China for 2013 is 53.8 μg m⁻³, with 400 million residents in regions that exceed the Interim Target-1 of the World Health Organization.</p>