Effects of Transboundary Transport on Korean Aerosol Pollution: Application of Geostationary Satellite Observations

Air quality of South Korea is closely related to the local emissions and long-range transport from the upwind region. To solve the air turbidity problems in South Korea, therefore, it is important to find out the main sources and quantitative characterization of transboundary transport of air pollutants. Among various observation types used for the analysis and monitoring of air pollutants, satellite-based observations have the advantage of wider spatial coverage than ground-based and airborne measurements. Particularly, geostationary satellite observations with high temporal resolution can detect the highly variable movements of air pollutants in near real-time. Taking these advantages, this study suggests a method to detect the transboundary transport of aerosol into South Korea and estimate the flux rate of transported aerosol masses using aerosol optical properties from Geostationary Ocean Color Imager (GOCI) observation. First, we defined the transboundary transport cases using aerosol optical depth (AOD) from GOCI and back-trajectories generated from National Ocean and Atmospheric Administration (NOAA) HYbrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model. For transboundary transport cases, satellite images showed high AOD plumes connecting Eastern China and South Korea, through the Yellow Sea, and also captured the movement of aerosol plumes transported into South Korea. The PM2.5 (particulate matter with diameter less than 2.5 microns) concentrations during transboundary transport cases increased by 28%, 24%, 41%, and 57% from 2015 to 2018, respectively, compared to the annual average of PM2.5. Next, for the investigation of quantitative characterization of transboundary transport of aerosols, we estimated the flux rate of transported aerosols into the Korean peninsula by combining the GOCI AOD and the wind fields from European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis data. In general, large flux rates of transported aerosol masses are related to high surface PM concentrations. We analyze the factors that may cause errors in the estimation of the flux rates and then evaluate the error of the estimated flux rates of aerosols.