Diel changes of the optical backscattering coefficient of oceanic particulate matter determined from diel changes in apparent optical properties: a case study in the Mediterranean Sea (BOUSSOLE site)

Malika Kheireddine, David Antoine, Vincenzo Vellucci, Bernard Gentili

Research output: Contribution to journalArticlepeer-review

Abstract

Using in situ measurements of radiometric quantities and of the optical backscattering coefficient of particulate matter (bbp) at an oceanic site, we show that diel cycles of bbp are large enough to generate measurable diel variability of the ocean reflectance. This means that biogeochemical quantities such as net phytoplankton primary production, which are derivable from the diel bbp signal, can be potentially derived also from the diel variability of ocean color radiometry (OCR). This is a promising avenue for basin-scale quantification of such quantities because OCR is now performed from geostationary platforms that enable quantification of diel changes in the ocean reflectance over large ocean expanses. To assess the feasibility of this inversion, we applied three numerical inversion algorithms to derive bbp from measured reflectance data. The uncertainty in deriving bbp transfers to the retrieval of its diel cycle, making the performance of the inversion better in the green part of the spectrum (555 nm), with correlation coefficients >0.75 and a variability of 40% between the observed and derived bbp diel changes. While the results are encouraging, they also emphasize the inherent limitation of current inversion algorithms in deriving diel changes of bbp, which essentially stems from the empirical parameterizations that such algorithms include.
Original languageEnglish (US)
Pages (from-to)5735-5748
Number of pages14
JournalApplied Optics
Volume61
Issue number19
DOIs
StatePublished - Jun 27 2022

Bibliographical note

KAUST Repository Item: Exported on 2022-09-14
Acknowledgements: Agence Nationale de la Recherche; European Space Agency; Centre National d’Etudes Spatiales; Centre National de la Recherche Scientifique; Institut national des sciences de l’Univers; Sorbonne Université, Institut de la Mer de Villefranche (IMEV); Conseil Régional Provence-Alpes-Côte d’Azur. The authors are grateful to the BOUSSOLE technical staff for their work in performing buoy deployments and maintenance, monthly cruises, and laboratory analyses. Our thanks go in particular to Emilie Diamond and Melek Golbol for the monthly cruises, and to Joséphine Ras, Céline Dimier, and Mustapha Ouhssain for the phytoplankton pigment analyses (SAPIGH analytical platform of the Laboratoire d’Océanographie de Villefranche, CNRS, France). This study is a contribution to the ANR Bio-optics and Carbon Experiment (BIOCAREX) and BOUSSOLE projects. Finally, we are grateful to the external reviewers for providing constructive comments to the paper.

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics

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