On-orbit ocean color instrument inter-comparison of GOCI-II with VIIRS and PACE

The Geostationary Ocean Color Imager (GOCI) series provides unique high-frequency observations—ranging from diurnal to interannual timescales—across both turbid coastal and oligotrophic waters in Northeast Asia. GOCI-II, launched in February 2020, has been operational for nearly five years. In contrast, polar-orbiting sensors such as Visible Infrared Imaging Radiometer Suite (VIIRS) offer global ocean coverage with different spatial and temporal characteristics. To enhance the accuracy and temporal consistency of GOCI-II data, we applied a comprehensive calibration framework, including on-orbit sensor calibration, atmospheric correction, and vicarious calibration, which were all integrated into the 2024 Reprocessing data. These advancements significantly improve the inter-sensor consistency of monthly chlorophyll-a (Chl-a) data between GOCI-II and VIIRS, demonstrating notable progress from the original GOCI-II dataset to the 2024 Reprocessing data. The tendency of GOCI-II to overestimate Chl-a has been significantly reduced in the 2024 update. Further improvements are planned by incorporating in situ observations into a regionally optimized OC4 chlorophyll-a algorithm.