TOTAL REFLECTANCE OF WIND-ROUGHENED SEA SURFACES - DIRECTIONAL PROPERTIES

Development of global algorithms for remote sensing of oceans in the o ptical channels requires quantitative estimates on directional propert ies of sea-surface reflectance to isolate the surface reflected light from the ocean color and the atmospheric haze. Experimental data on di rectional sea-surface reflectance for different sea states are scarce to nonexistent because no such measurements are made at sea whereas th eoretical computations on surface reflectance are rendered difficult b ecause of uncertainties regarding the contribution because of foam. In this paper, we present a unified model to compute directional sea-sur face reflectance which is based on the first principles of Fresnel's r eflection laws for a semitransparent medium as applied to a nonflat co ntinuously moving boundary such as a wind-roughened sea surface. We ha ve incorporated the contribution resulting from foam by separately com puting the reflection from a Lambertian surface for that fraction of s ea surface which is covered by foam. Sample results obtained from the model are in agreement with the theoretical estimates established by o ther authors. The model computes the sea-surface reflectance for any g iven sea state and for any look angle of a satellite sensor. Source co de listing of a FORTRAN computer program for the model proposed in the paper also is presented to allow users to compute the surface reflect ance for user-defined inputs.