Geostationary Environment Monitoring Spectrometer (GEMS) AOD retrieval: assessment of version V2.1 update

The Geostationary Environment Monitoring Spectrometer (GEMS) is the first UV-VIS hyperspectral satellite instrument in GEO. GEMS monitors air quality in Asia (5°–45°N, 75°–145°E) hourly with the fine spatial resolution. GEMS provides hyperspectral measurements covering 300-500 nm at 0.2 nm spectral sampling and 0.6 nm full width at half maximum (FWHM) spectral resolution. We present the atmospheric aerosol monitoring results from GEMS over Asia. GEMS Aerosol Optical Depth (AOD) is scheduled for a V2.1 update. GEMS AOD V2.1 has improved compared to V2.0. V2.1 extends the AOD node in the LUT to retrieve high AOD and considers background AOD to decrease the uncertainty of surface reflectivity. Additionally, the aerosol type selection now takes into account the diurnal variation of the aerosol index. The surface reflectivity climatology has been extended from 2 years to 3 years. Furthermore, the initial value of aerosol layer height has been adjusted using the climatology of the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP). The validation indices of V2.1 have improved, and it has been confirmed that biomass burning cases can be better identified. This research presents the current status of GEMS AOD V2.1 and compares V2.0 and V2.1. Additionally, we discuss possibilities for future improvements. Future versions of GEMS AOD will also take into account the accuracy of aerosol type selection and regional LUT.