POSTER Session 3

ASSESSING THE GLOBAL APPLICABILITY OF THE 2SEACOLOR MODEL ACROSS COASTAL AND INLAND WATER SYSTEMS

The 2SeaColor model, based on the analytical solution of the two-stream radiative transfer equations, has demonstrated good accuracy in deriving inherent optical properties and biogeochemical variables within specific water systems. Its validation across a broader and more heterogeneous dataset, however, remained unexplored. This study aims to further develop the model parametrization and verify its applicability to optically diverse coastal and inland waters. We validate the model against the GLObal Reflectance community dataset for Imaging and optical sensing of Aquatic environments (GLORIA). The 2SeaColor model can derive chlorophyll-a concentration (Chl-a) from remote-sensing reflectance (Rrs) spectra with reasonable accuracy (R2=0.64, MARD=63%) for more than 3,600 data pairs from aquatic systems worldwide. Distinguishing between different water types reveals more accurate retrievals for chlorophyll and suspended particulate matter (SPM)-dominated waters, and poor performance for clearer waters (SPM<3 g/m3 and Chl-a<2 mg/m3), consistent with the conditions for which the model was originally developed. Retrievals of the backscattering coefficient of suspended particles at 555 nm and diffuse attenuation coefficient at 490 nm show strong power law relationships with SPM concentration (R=0.72) and Secchi depth (R=-0.68) respectively. While it is not a direct validation, it suggests potential in adapting the model to derive those variables. Retrieval of the absorption coefficient of combined detritus and gelbstoff remains a challenge. Finally, analysis of the residual Rrs spectra serves as a flag for model failure and indicates the need for better parametrization of phytoplankton absorption and fluorescence in 2SeaColor.

*Amanda de Liz Arcari, University of Twente, Faculty ITC, the Netherlands, [email protected], https://orcid.org/0000-0002-7443-2290

Daphne van der Wal, University of Twente, Faculty ITC, the Netherlands, [email protected]

Suhyb Salama, University of Twente, Faculty ITC, the Netherlands, [email protected]

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