A theory on the relative RCS contribution from ocean waves of individual wavelength

The present paper describes a simple theory of interpreting the backscatter radar cross section (RCS) distribution from ocean waves of individual wavelength using the Kirchhoff scattering model. The technique is to compute first the `cumulative´ RCS function from a given waveheight spectrum as a function of wavenumbers; differentiating this function yields the RCS distribution from waves of different wavenumbers. The general trend of the result is that the maximum RCS contribution comes from the ocean waves closer to the Bragg waves as the incidence angle increases. At the incidence angles from 20° to 45° under low wind speeds (~2 m/s), the C-band RCS distribution function is centered close to the Bragg wavenumber; while the RCS contribution from waves longer than the Bragg wavelength increases as the wind speed increases. At L-band, the general feature is the same as that of C-band, but the dependence of the RCS distribution on the wind speeds is not so significant. The consequence of the result is discussed for interpreting the ocean current by radars