EM models for evaluating rain perturbation on the NRCS of the sea surface observed near nadir

The authors address the problem of evaluating the normalised radar cross-section (NRCS) of the sea surface perturbed by the joint effect of rain and wind, when observed close to nadir. They present a model, based on the full wave theory, for evaluating such an NRCS when varying polarisation, frequency and incidence angle (not far from nadir) for different values of wind velocity and of the root mean square height of the corrugation induced by rainfall. Some comparisons are made with the integral equation model results in the case of rain-induced corrugation alone. The two models are found to be in good agreement. In addition, partial comparisons made with experimental data suggest that the proposed model is well grounded and exploitable for application. It is indeed expected that the model can be exploited to improve precipitation measurements over the sea through spaceborne rain radar and to improve wind measurements using scatterometers in the presence of rain.