Semi-analytical approach to retrieve the chromophoric dissolved organic matter absorption coefficient in non-turbid waters: preliminary application to Medium Resolution Imaging Spectrometer (MERIS) data

Abstract

Based on the NASA Bio-Optical Marine Algorithm Dataset and in situ datasets collected from the East China Sea and Lake Qiandaohu, a novel approach was developed to analytically retrieve the absorption coefficient of chromophoric dissolved organic matter (aCDOM) in non-turbid waters. This approach comprised two parts: (1) a green–red band quasi-analytical algorithm, used to accurately derive the total absorption coefficient (a); and (2) the use of the retrievals from (1) are to semi-analytically retrieve aCDOM. This approach for partitioning aCDOM from a was based on the blue band line height at 443nm, LH(443), which uses the summed absorption coefficients of phytoplankton and CDOM (aphc) at three characteristic wavelengths (412, 443 and 490nm). This proposed algorithm was then tested and validated using the three datasets. The algorithm was found to perform reasonably well in retrieving aCDOM, with respective mean R2 and mean absolute percentage error (MAPE) values of 0.84 and 42.8%, compared with 0.64 and 72.9% for the empirical model and 0.40 and 66.2% for the extended quasi-analytical algorithm. Furthermore, the algorithm was able to retrieve aCDOM from Medium Resolution Imaging Spectrometer (MERIS) satellite data. One implication for the MERIS satellite data, which exhibit reasonable seasonal variability over the East China Sea, is that it can be used to explore biogeochemical effects on aquatic environments.