Wind Speed Effects on Sea Surface Emission and Reflection for the Along Track Scanning Radiometer

Abstract

Abstract The emission and reflection properties of a rough sea surface are investigated, with particular emphasis on the wavelengths and viewing geometry relevant to the Along Track Scanning Radiometer. The authors start from Fresnel's equations for a flat water surface and calculate the effect of changing sea state on direct emissivity and reflectivity. The authors then investigate the role of surface-emitted surface-reflected (SESR) radiation, which enhances emissivity at high wind speeds. The effect of foam and whitecaps at high wind speeds is referred to briefly in the appendix but essentially remains an unknown quantity. Radiative transfer calculations that employ emissivity models also have to consider the reflection of downwelling radiance from the atmosphere. Although energy conservation requires that reflectivity is 1 minus emissivity, the variability of the sky brightness with zenith demands that one consider also the angular distribution of the reflected radiance. Additionally, the extended sta...