POSTER Session 4

CHARACTERIZATION OF SOURCES OF UNCERTAINTY IN AN OCEAN RADIATIVE TRANSFER MODEL FOR THE BLACK SEA

A numerical radiative transfer model is coupled with a 3D physical-biogeochemical model of the Black Sea. The radiative transfer model describes the propagation of surface irradiance on a water column in downward (direct and diffuse) and upward streams, with a spectral resolution of 25nm in the visible range. It takes into account the optical properties of four water constituents: water molecules, phytoplankton cells, detrital matter and CDOM (Colored Dissolved Organic Matter). The model is used as an observation operator, one-way coupled to the biogeochemical model and forced by the simulated fields of optically active components. The simulated irradiance and PAR (Photosynthetically Active Radiation) profiles are then compared with BGC-ARGO data. Surface fields of irradiance are also used to derive sea surface reflectance fields, which are compared with satellite ocean color products. Stochastic perturbations are then introduced into the model to account for the large uncertainties that exist in its parameterization (mostly in the inherent optical properties of water constituents and the surface forcing). Absorption and scattering properties of phytoplankton, detrital matter and CDOM are thus perturbed to evaluate the uncertainties in the model related to their parameterization. The resulting ensemble experiments are useful to evaluate the ability of the model to reproduce distributions of sea surface reflectance in agreement with remote-sensed reflectance. We also use the model to provide new insights into the comparison between satellite ocean color products to both chlorophyll fields simulated by the biogeochemical model and those derived from the simulated reflectance using ocean color algorithms.

*Loïc Macé, University of Liège, Belgium, [email protected]

Luc Vandenbulcke, University of Liège, Belgium, [email protected], https://orcid.org/0000-0001-9870-6199

Jean-Michel Brankart, Institut des Géosciences de l’Environnement, Centre National de la Recherche Scientifique (CNRS), France, [email protected], https://orcid.org/0000-0002-0330-6019

Pierre Brasseur, Institut des Géosciences de l’Environnement, Centre National de la Recherche Scientifique (CNRS), France, [email protected], https://orcid.org/0000-0002-6665-503X

Marilaure Grégoire, University of Liège, Belgium, [email protected], https://orcid.org/0009-0008-3112-4256

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