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Proceedings Paper

Effects of the wind direction on the light-field reflected from a wind roughened sea surface
Author(s): Frank Fell; Rene Preusker
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Paper Abstract

A method is presented which allows for an approximate treatment of the radiative transfer above an asymmetrically reflecting wind roughened sea surface. The radiative transfer model used for this purpose is based on the matrix operator method. The efficiency of this method is mainly due to the separation of zenith and azimuth dependence, expanding the latter into a Fourier series. In the case of light fields symmetric with respect to the principal plane, the Fourier expansion of all relevant parameters consists of cosine terms only and the radiative transfer is calculated independently for each Fourier coefficient. However, when taking the effects of the wind direction into account, the light field produced at the rough sea surface is asymmetric. As a result, cosine and sine coefficients of all spectral frequencies are coupled in the layer representing the sea surface. The problem is considerably simplified, when the asymmetric reflection at the sea surface is only applied to the direct solar radiation, and symmetric reflection is assumed for the diffuse radiation incident on the sea surface. Using this simplified treatment, the Fourier coefficients again decouple, and the asymmetrically reflecting rough sea surface can easily be incorporated into the matrix operator method. The effect of the wind direction on the light field at the sea surface and at the top of the atmosphere is shown for a few examples. The calculations show that the radiances at the top of the atmosphere is shown for few examples. The calculations show that the radiances at the top of the atmosphere are altered up to 10 percent to 30 percent in the sunglint affected angular domains, depending on wind speed and direction. In contrast to that, the fluxes remain fairly independent on the wind direction.

Paper Details

Date Published: 6 February 1997
PDF: 6 pages
Proc. SPIE 2963, Ocean Optics XIII, (6 February 1997); doi: 10.1117/12.266386
Show Author Affiliations
Frank Fell, Freie Universitat Berlin (Germany)
Rene Preusker, Freie Universitat Berlin (Germany)

Published in SPIE Proceedings Vol. 2963:
Ocean Optics XIII
Steven G. Ackleson; Robert J. Frouin, Editor(s)

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