Editing SeaWiFS (section)

==Atmospheric correction==
[[File:Coccolithophore bloom.jpg|thumbnail|A true color SeaWiFS image of a coccolithophore phytoplankton bloom off of Alaska]]
Light reflected from the sub-surface ocean is called water-leaving radiance and is used to estimate chlorophyll concentrations. However, only about 5–10% of light at the top of the atmosphere is from water-leaving radiance.<ref>Gene Carl Feldman, {{cite web |url=http://oceancolor.gsfc.nasa.gov/SeaWiFS/BACKGROUND/SEAWIFS_970_BROCHURE.html |title=SeaWiFS Project 970 BROCHURE |access-date=2013-10-29 |url-status=dead |archive-url=https://web.archive.org/web/20140328024937/http://oceancolor.gsfc.nasa.gov/SeaWiFS/BACKGROUND/SEAWIFS_970_BROCHURE.html |archive-date=2014-03-28 }},"SeaWiFS Project – Detailed Description", OceanColor WEB, 7/30/2003</ref><ref name=Gordon>{{cite journal|last=Gordon|first=Howard R.|author2=Brown, Otis B. |author3=Evans, Robert H. |author4=Brown, James W. |author5=Smith, Raymond C. |author6=Baker, Karen S. |author7= Clark, Dennis K. |title=A semianalytic radiance model of ocean color|journal=Journal of Geophysical Research|date=1 January 1988|volume=93|issue=D9|pages=10909|doi=10.1029/JD093iD09p10909|bibcode = 1988JGR....9310909G }}</ref> The remainder of light is reflected from the atmosphere and from aerosols within the atmosphere. In order to estimate chlorophyll concentrations this non-water-leaving radiance must be accounted for. Some light reflected from the ocean, such as from whitecaps and sun glint, must also be removed from chlorophyll calculations since they are representative ocean waves or the angle of the sun instead of the subsurface ocean. The process of removing these components is called atmospheric correction.<ref name=Franz>{{cite web|last=Franz|first=Brian|title=Algorithm for Retrieval of Remote Sensing Reflectance from Satellite Ocean Color Sensors|url=http://oceancolor.gsfc.nasa.gov/WIKI/AtmoCor.html|work=Ocean Color Web|access-date=29 October 2013|url-status=dead|archive-url=https://web.archive.org/web/20130613065715/http://oceancolor.gsfc.nasa.gov/WIKI/AtmoCor.html|archive-date=13 June 2013}}</ref>

A description of the light, or radiance, observed by the satellite's sensor can be more formally expressed by the following radiative transfer equation:

<math> L_T(\lambda) = L_r(\lambda)+L_a(\lambda)+L_{ra}(\lambda)+TL_g(\lambda)+t(L_f(\lambda)+L_W(\lambda))  </math>

Where L<sub>T</sub>(λ) is total radiance at the top of the atmosphere, L<sub>r</sub>(λ) is Rayleigh scattering by air molecules, L<sub>a</sub>(λ) is scattering by aerosols in the absence of air, L<sub>ra</sub>(λ) is interactions between air molecules and aerosols, TL<sub>g</sub>(λ) is reflections from glint,  t(L<sub>f</sub>(λ) is reflections from foam, and L<sub>W</sub>(λ)) is reflections from the subsurface of the water, or the water-leaving radiance.<ref name=HookerMcClain /> Others may divide radiance into some slightly different components,<ref name=Franz /> though in each case the reflectance parameters must be resolved in order to estimate water-leaving radiance and thus chlorophyll concentrations.