A novel approach using absorption-based SPM algorithm for the Northeast Asia Seas from clear ocean to extremely turbid waters

Abstract:

The Suspended Particulate Matter (SPM) is one of the most valuable indicators in the ocean that is as important as phytoplankton. Especially, SPM is an important parameter for water quality monitoring, erosion and deposition system, and light fields of the biogeochemical cycles in coastal and estuarine ecosystem. The Northeast Asian Seas are the region with high utilization of satellite-derived SPM data to monitor for water quality, coastal erosion and deposition, contaminant movement, surface currents, and so on. The marine environment in this area has a diverse distribution of SPM, consisting of clear ocean (e.g. southern part of the East China Sea and Southwest waters of Japan) and extremely turbid coastal waters (e.g. estuarine area of the Yangtze River). As the World’s first ocean color sensor, Geostationary Ocean Color Imager (GOCI) has continuously observed the Northeast Asian waters in a geostationary orbit. The GOCI was successfully launched in June 2010 and is currently observing these areas. Several SPM algorithms have been developed, but those algorithms showed the under-estimation problems for the highly turbid waters. In this study, we developed new SPM algorithm to overcome the limitation of existing algorithms for GOCI. Mostly used SPM algorithms have been developed by the empirical method using R_rs, integrated optical data on the sea surface. But there is a limit to retrieve the SPM concentration owing to the complex interactions between SPM, chlorophyll, DOM (dissolved organic matter). To use the inherent optical property for SPM, we separated the absorption coefficient of SPM using re-tuned semi-analytical model. Totally 1,300 sets of R_rs, SPM concentration, absorption coefficient for SPM, chlorophyll and DOM, and particle back-scattering data were analyzed. Newly developed SPM algorithm was verified and compared with the other SPM algorithms develop for the Northeast Asian Sea using in-situ dataset collected on the sea area around the Korean Peninsula.