Space-time statistics for the number of specular points in sea surface GNSS reflectometry

Abstract

The average density of specular points plays an important role in the investigation of the sea surface features with remote sensing systems. Evidently, the number of specular reflectors has a direct physical link with the surface roughness that is, in turn, modified by the wind velocity, by the presence of internal waves, oil films and geometric modifications of the sea surface. The main attempt of this paper is to provide an accurate model for the statistics of the number of wind-induced specular points on the sea surface whose spatial correlation properties are provided by the Elfouhaily sea-spectrum model and the temporal correlation is obtaind by introducing a birth-death-immigration process for the number of specular points. Although the model can be also considered for other applications, it is here applied to GNSS-reflectometry where the small scale roughness can be neglected and time decorrelation is given by the motion of the sea waves and by the navigation of the satellite platforms.