Sea surface slope statistics derived from Sun glint radiance measurements and their apparent dependence on sensor elevation

Abstract

Sea surface slope variances are obtained by inverting narrowband (444, 501, 677, and 864 nm) Sun glint radiance measurements using a detailed analytical specular sea surface bidirectional reflectance distribution function (BRDF) that includes mutual wave shadowing and hiding. The resulting data set spans a wide range of environmental conditions including wind speeds from 0.5 to 13.5 m s−1 and many different viewing and source geometries. Analysis against wind speed and atmospheric stability produces trends similar to those found in previous studies, as well as finer tendencies that were formerly difficult to detect. Furthermore, the detailed nature of the BRDF model used in the analysis permits an investigation of the correlation of the statistics with viewing geometry, revealing a strong relationship between sensor elevation and measured slope variance, especially at grazing angles.