Remote sensing of diffuse attenuation coefficient using MODIS imagery of turbid coastal waters: A case study in Bohai Sea

The objectives of this study are to evaluate the applicability of three existing retrieval algorithms of diffuse attenuation coefficients of downwelling irradiance at 490 nm, Kd(490), for turbid Case II waters, and to improve these existing models using a simple semi-analytical (SSA) model. In this study, based on comparison of the Kd(490) predicted by these models with field measurements taken in the Bohai Sea and Yellow Sea, it is shown that the SSA model provides a stronger performance than these three selected existing models. The atmospheric influences on the MODIS data are removed using an improved shortwave infrared band-based (ISWIR-based) model, which is capable of retrieving spectral remote sensing reflectance within 19% uncertainty. The Kd(490) data was quantified from the MODIS images after atmospheric correction using the SSA model and Wangʹs model. The study results indicate that the SSA model produces 31.51% uncertainty in deriving Kd(490) from MODIS data, which is 12.1% higher than Wangʹs model. This study demonstrates the potential of the SSA model in estimating Kd(490) even in highly turbid coastal waters.