Upwind–Downwind Asymmetry of the Sea Backscattering Normalized Radar Cross Section Versus the Skewness Function

From the first-order small slope approximation, this paper presents a closed-form expression of the sea backscattering normalized radar cross section (NRCS) versus the skewness function to predict the upwind-downwind asymmetry. This effect is produced by the fact that the surface height distribution slightly deviates from a Gaussian one. Introducing the azimuthal property of the sea height autocorrelation and skewness (spatial) functions, the integration over the azimuthal direction can be done analytically, whereas the integration over the radial distance can be done using the property that the skewness correlation distance is much smaller than that of the gravity waves. Then, the backscattering NRCS is expressed from the sea skewness spectrum at a wavenumber different of the Bragg wavenumber. In addition, a simple inversion algorithm is proposed to perform the parameters of the skewness function from experimental data in C and Kubands.