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Proceedings Paper

Atmospheric correction of satellite ocean-color imagery in the presence of semi-transparent clouds
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Paper Abstract

An algorithm is proposed to perform atmospheric correction of ocean-color imagery in the presence of semi-transparent clouds. The atmospheric “path” reflectance, due to scattering by molecules, aerosols, and droplets, absorption by aerosols, and reflection by the surface, including coupling terms, is modeled by a polynomial with three terms, i.e., three unknown coefficients. The marine reflectance is modeled as a function of chlorophyll concentration and a backscattering coefficient that accounts for scattering by non-algal particles (or deviation from the backscattering coefficient specified for typical phytoplankton), i.e., two additional unknown variables. The cloud transmittance, assumed constant spectrally, is estimated separately from top-of-atmosphere reflectance in the near infrared. The five unknowns are retrieved by an iterative, spectral matching scheme. The methodology, including the decomposition of the top-of-atmosphere signal and the modeling of the path reflectance, is evaluated theoretically and applied to actual MODIS imagery acquired over relatively thin clouds. Chlorophyll concentration is retrieved adequately under the clouds, and continuity is good between the cloudy and adjacent clear regions. Values are similar to those obtained with the SeaDAS algorithm in clear sky conditions, but cloud coverage is increased considerably. The algorithm is applicable operationally, but needs to be further evaluated in varied cloudy situations.

Paper Details

Date Published: 21 November 2014
PDF: 15 pages
Proc. SPIE 9261, Ocean Remote Sensing and Monitoring from Space, 926108 (21 November 2014); doi: 10.1117/12.2074008
Show Author Affiliations
Robert Frouin, Scripps Institution of Oceanography, Univ. of California San Diego (United States)
Lucile Duforêt, Lab. d'Océanologie et de Géosciences, Univ. du Littoral Côte d’Opale (France)
François Steinmetz, Hygeos (France)

Published in SPIE Proceedings Vol. 9261:
Ocean Remote Sensing and Monitoring from Space
Robert J. Frouin; Delu Pan; Hiroshi Murakami, Editor(s)

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