Optimization of a composite surface model for the radar backscattering cross section of the ocean surface as measured by wind scatterometers

A calibrated composite surface model for the calculation of absolute normalized radar backscattering cross sections (NRCS) of the ocean surface is presented. The model is based on a Taylor expansion of the NRCS, as given by Bragg scattering theory, up to second order in the surface slope. Measured NRCS values for a variety of radar frequencies, polarizations, incidence angles, azimuthal radar look directions, and wind speeds can be well reproduced after some reasonable tuning of the input ocean wave spectrum. The model can thus be considered as an advanced wind scatterometer model based on physical principles. Due to this fact it is also well suited for general applications like the calculation of NRCS variations associated with distortions of the wave spectrum in the presence of surface current gradients.