Column Effective Imaginary part of refractive index derived from UV-MFRSR and SKYNET in Seoul, and implications for retrieving UV Aerosol Optical Properties from GEMS measurements

Information about spectral dependence of column aerosol absorption in extended UV-Vis spectral window is required for satellite aerosol and trace gas retrievals. Such measurements of column average refractive index and single scattering albedo (SSA) from ultraviolet (UV) to visible (VIS) wavelengths are routinely performed at Yonsei University, Seoul since 2016 by combining co-located measurements from NASA's AERONET Cimel sun-sky photometer, NASA's PANDORA sun spectrometer, US Department of Agriculture UV-B Monitoring and Research Program's Multifilter Rotating Shadowband Radiometer (MFRSR), and SKYNET Prede Sun-sky photometer. We investigated the spectral dependence aerosol absorption in UV-VIS spectral range for three predominant aerosol types (Absorbing fine, Dust, Weakly absorbing). We use this information as an a-priori spectral dependence assumed in the satellite aerosol retrieval algorithm for Geostationary Environment Monitoring Satellite (GEMS). The correlation coefficient of GEMS aerosol retrievals (applied to the Ozone Monitoring Instrument (OMI) measurements) with ground-based measurements improved significantly as result of applying the UV-MFRSR data. These results corroborate the advantage using derived spectral aerosol absorption from UV to VIS with respect to physically different aerosol types in the GEMS UV-Vis aerosol algorithm over East Asia. Moreover, this study shows the spectral dependence of aerosol absorption in East Asia is different from other regions.