Peakedness Effects in Near-Nadir Radar Observations of the Sea Surface

The simulation and interpretation of microwave sea radar return in the near-nadir region are still issues in view of the limitations of the geometrical optics approximation and the multiscale and non-Gaussian nature of the surface. We show that an unambiguous and fully consistent physical approach can be reached in the framework of the physical optics. The model is developed on the basis of various satellite and airborne C-, Ku-, and Ka-band measurements using different reference surface roughness spectra. As found, the introduction of a peakedness correction based upon the excess kurtosis of slopes is necessary to obtain consistent analysis across the microwave frequency range. The model yields accurate simulations for the omnidirectional near-nadir normalized radar cross section in different frequency bands, provided the spectrum satisfies some a priori constraints on the distribution of the total and filtered slopes.