Assessment of OLCI-A and OLCI-B radiometric data products across European seas

The Ocean and Land Color Instruments (OLCI) operated onboard the Copernicus Sentinel-3 satellites are providing globally distributed Ocean Color Radiometry (OCR) data products of relevance for environmental and climate applications. This work summarizes results on the assessment of fundamental OCR d...

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Bibliographic Details
Published in:Remote Sensing of Environment
Main Authors: Zibordi G., Kwiatkowska E., Melin F., Talone M., Cazzaniga I., Dessailly D., Gossn J. I.
Other Authors: Zibordi, G, Kwiatkowska, E, Melin, F, Talone, M, Cazzaniga, I, Dessailly, D, Gossn, J
Format: Article in Journal/Newspaper
Language:English
Published: Elsevier BV 2022
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Online Access:https://hdl.handle.net/10281/495979
https://doi.org/10.1016/j.rse.2022.112911
Description
Summary:The Ocean and Land Color Instruments (OLCI) operated onboard the Copernicus Sentinel-3 satellites are providing globally distributed Ocean Color Radiometry (OCR) data products of relevance for environmental and climate applications. This work summarizes results on the assessment of fundamental OCR data from the Operational Baseline 3 Collection OL_L2M.003.01 of OLCI-A and OLCI-B onboard Sentinel-3A and Sentinel-3B, respectively. Evaluated products are the satellite derived normalized water-leaving radiance LWN(λ), aerosol optical depth at 865 nm τa(865) and Ångström exponent α determined in the near-infrared spectral region. The analyses were performed relying on in situ reference data from the Ocean Color component of the Aerosol Robotic Network (AERONET-OC) from sites representative of diverse water types. The comparison of OLCI-A and OLCI-B with AERONET-OC LWN(λ) for oligotrophic/mesotrophic waters shows cross-mission consistent spectral median percent differences (i.e., biases) varying within ±6% at the blue-green center-wavelengths. The analysis of data from regions characterized by optically complex waters, however, displays systematic negative biases for both OLCI-A and OLCI-B further increasing for waters dominated by chromophoric dissolved organic matter, thus suggesting a dependence of the atmospheric correction on water type. The direct inter-comparison of OLCI-B and OLCI-A LWN(λ) from the Tandem Phase characterized by Sentinel-3B and Sentinel-3A flying 30 s apart on the same orbit, shows spectral median percent differences lower than ±1% in the 412–560 nm interval, of approximately +5% at 620 and 665 nm, and −7% at 400 nm. However, outside the Tandem Phase, the inter-comparison of OLCI-B and OLCI-A data products indicates large and systematic differences explained by a notable dependence on the viewing angle. The evaluation of τa(865) and α across different geographic regions exhibits overestimated values between +48 and + 79% for the former and underestimated values between −28% and − 41% for the ...