Current Status of AERONET Observations in South Korea and Analysis of Long-Term Changes in Aerosol Optical Depth and Aerosol Distribution

This study analyzed the distribution of Aerosol Robotic Network (AERONET) Version 3 Level 2.0 data, spanning over two decades, across South Korea and its six administrative regions (Seoul metropolitan area, Chungcheong, Jeolla, Gangwon, Gyeongsang, and Jeju). The research assessed long-term trends in aerosol optical depth (AOD) and mass concentration of particulate matter (i.e., PM10 and PM2.5), using data from the AERONET direct sun product and AirKorea, respectively. Additionally, eight aerosol types were identified using the scattering angstrom ngstr & ouml;m exponent and absorption angstrom ngstr & ouml;m exponent from the AERONET inversion product. The study further explored their domestic and regional distributions. Findings indicated that AERONET data were predominantly concentrated in the western regions of South Korea, including the Seoul metropolitan area, Chungcheong, and Jeolla, with a higher frequency of data in spring, thus demonstrating spatial and temporal heterogeneity. The annual average AOD exhibited a declining trend of -0.006 yr-1. Similarly, PM10 and PM2.5 mass concentrations decreased by -1.324 mu g m-3 yr-1 and -1.335 mu g m-3 yr-1, respectively. These trends in AOD and PM10 (PM2.5) demonstrated positive correlations, with correlation coefficients of 0.674 (0.753) and statistically significant low p-values of 0.00058 (0.03), respectively. The analysis also revealed that aerosols in South Korea predominantly consisted of black carbon (BC) or BCmixed types (84.09%), with a notable presence of smaller, less absorbent aerosol types (13.11%).