Semianalytical Derivation of Phytoplankton, CDOM, and Detritus Absorption Coefficients From the Landsat 8/OLI Reflectance in Coastal Waters

Abstract

The Operational Land Imager (OLI) onboard Landsat 8 has potential for mapping the water bio-optical properties with high spatial resolution. Landsat 8/OLI generates the remote sensing reflectance (Rrs) at four visible bands (λ1-4 = 443, 482, 561, and 655 nm) and is lack of a 412-nm band commonly included for ocean color sensors. This spectral configuration has limited the use of Landsat 8/OLI reflectance product for analytical derivation of light absorption coefficients of phytoplankton, colored dissolved organic matter (CDOM), and detritus. In this study, we proposed a hybrid approach to fill this gap. First, we developed an algorithm to estimate the reflectance in a virtual band centered at λ0 = 412 nm from the OLI reflectance spectra Rrs(λ1-4). Both the estimated Rrs(λ0) and measured Rrs(λ1-4) were then used together to retrieve the water component absorption coefficients with existing algorithms including the quasi-analytical algorithm. We assessed the model performance using in situ measurements from the global waters. It was found that the proposed approach could estimate Rrs(412) with a median absolute percentage difference of ~9%. The subsequent retrievals of the component absorption coefficients were satisfactorily accurate, with median absolute percentage difference roughly equal to 35%, 40%, and 60% for phytoplankton, CDOM, and detritus, respectively. The results suggest the feasibility to generate analytically the component absorption coefficients from the Landsat 8/OLI reflectance.