Oral Session 5

Semianalytical modeling and inversion of the bidirectional water reflectance

Several methods were developed in ocean color remote sensing over the three decades to model the anisotropy of the upwelling radiant field with respect to observation and solar-illumination geometries, also denoted as bidirectional reflectance distribution function (BRDF). An EUMETSAT-funded study has reviewed BRDF correction models (e.g. Morel et al., 2002: M02; Park and Ruddick, 2005: P05; Lee et al., 2011: L11). By testing them against high quality in situ data at different geometries and against satellite to in situ matchup, the superior performance of the model detailed in L11 was identified. The modularity of L11 facilitated the identification of elements suitable of improvement. This work will present the proposed new model, based on L11, that incorporates updated model equations, and named O23. O23 has been tested against the same high-quality data as the previous models, showing superior performance. As such, O23 has been incorporated to the EUMETSAT processor to operationally produce OLCI fully normalized marine reflectance from Sentinel3-OLCI observations. Additional features in O23 are the definition of a BRDF applicability range, uncertainty estimates of the BRDF correction results, and the capability to reverse the BRDF correction steps in view of independent user evaluation and alternative methods testing. Although implemented for OLCI, the model is wavelength-agnostic and is easily adaptable to any other band configuration that contains at least one blue one green and one red band, such as Landsat/Sentinel 2 data, multispectral sensors such as VIIRS or hyperspectral as PACE.

Vittorio Brando, National Research Council Institute of Marine Sciences (CNR ISMAR), Italy

Ryan Vandermeulen, NOAA National Marine Fisheries, USA

Amir Ibrahim, NASA, USA

Kaytee Pokrzywinski, NOAA National Centers for Coastal Ocean Science, USA

Sachidananda Mishra, Consolidated Safety Services, Inc., USA

Timothy Wynne, NOAA National Centers for Coastal Ocean Science, USA

Andrew Heidinger, NOAA National Environmental Satellite, Data, and Information Service, USA

Pamela Sullivan, NOAA National Environmental Satellite, Data, and Information Service and NASA, USA

Andrew Latto, NOAA National Environmental Satellite, Data, and Information Service, USA

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