The diffuse attenuation coefficient model in the Yellow Sea for the Korean Geostationary Ocean Color Imager (GOCI)

Abstract

The first geostationary ocean color sensor, Geostationary Ocean Color Imager (GOCI), on board the Korean Communication Ocean and Meteorological Satellite (COMS), was successfully launched on June 26 of 2010. GOCI includes 8 spectral bands in visible and near-infrared wavelengths with a coverage area of 2,500×2,500 km2 centered at 36°N and 130°E over the Korean seas. GOCI will provide an important capability to monitor ocean phenomenon with one hour temporal and 500 m spatial resolutions for a better understanding of biogeochemical processes in the Korean seas. However, there are uncertainties in estimating bio-optical properties since water properties in large areas of Koreans are optically characterized as Case-2 waters due to strong tidal mixing and large amount of river discharges. The newly-developed semi-analytical algorithm of diffusion attenuation coefficient at the wavelength of 490 nm, Kd(490), for the turbid coastal waters was assessed using in situ radiometric and Kd(490) measurement obtained from clear and turbid waters over the global ocean. Results of the Kd(490) data using the new model is well correlated with the in situ Kd(490) measurements. Synoptic maps of Kd(490) data from the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard the Aqua satellite using the new model were derived in the Yellow Sea and East China Sea. The MODIS-derived Kd(490) data show significant increased values along the turbid coastal waters including the Bohai Sea and the Yangtze River Estuary. In general, the highest Kd(490) appeared in winter and the lowest Kd(490) are presented in summer over the all area. Interannual variability of Kd(490) in timing and magnitude is apparent, but there is no consistent trend of interannual variability across all areas.