Improvement of the GK2B/GEMS surface reflectance retrieval algorithm

Until present, a new surface reflectance retrieval algorithm has been developed for the Geostationary Environment Monitoring Spectrometer (GEMS) onboard the Geostationary Earth Orbit (GEO)-Korea Multi-Purpose Satellite (KOMPSAT)-2B (GK-2B) satellite. The algorithm was designed and tested to use the characteristics of the simulated input data using satellite data. The first version was tested with the continuous spectral characteristics of the OMI sensor which is similar to that of GEMS sensor. In order to reflect the continuous observation times of geostationary orbit, the algorithm has been modified in the second version. This was tested by using a new geostationary sensor, Advanced Himawari Imager (AHI) sensor from the Himawari-8 satellite. This algorithm has been reflect the geometrical changes in a region of interest which can derive geometry dependent reflection function at a given satellite observation time. Finally, the algorithm used the GEMS L1b radiance data simulated by the extensive radiative transfer calculations. Recent validation results showed that the GEMS surface reflectance products have RMSE of 0.0087 and mean bias of 0.0025. These results suggest that the current GEMS surface reflectance algorithm with the GK-2A/GEMS are promising with its enhanced spatial and temporal resolution. Acknowledgement: This work was funded by the Korea Ministry of Environment (MOE) as "Public Technology Program based on Environmental Policy (2017000160003)".