19 August 2009 Environmental effects in ocean color remote sensing
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Abstract
Ocean color imagery, when viewed from space, is degraded due to scattering by the atmosphere. The effect, also known as the adjacency effect, is especially important near the coast, sea-ice, and clouds, i.e., where the environment reflectance is much different from the target reflectance. The adjacency effect, however, may not be negligible in the open ocean. This is demonstrated by processing SeaWiFS imagery acquired over a typical upwelling system off the coast of Namibia, Africa. Ignoring the atmospheric point-spread function in the atmospheric correction algorithm or, equivalently, using a large-target formalism to describe the top-of-atmosphere reflectance, errors reaching over 10% are made on chlorophyll concentration retrievals. The structure of the spatial field of chlorophyll concentration is changed significantly after correction of the adjacency effect, with the influence of local processes comparatively decreased with increased distance. Correcting systematically (i.e., not only near the coast) Level 1b ocean color imagery for the adjacency effect is recommended. As a result, the accuracy, quality, and daily coverage of aerosol and ocean-color products would be improved substantially over water surfaces contiguous to land surfaces, sea-ice, clouds, and generally regions where spatial contrast is relatively large.
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Robert Frouin, Pierre-Yves Deschamps, François Steinmetz, "Environmental effects in ocean color remote sensing", Proc. SPIE 7459, Ocean Remote Sensing: Methods and Applications, 745906 (19 August 2009); doi: 10.1117/12.829871; https://doi.org/10.1117/12.829871
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