A model-based approach for rainfall rate retrieval over the sea surface through rain radar

Vertical rainfall profile retrieval based on reflectivity data collected by spaceborne rain radars can be improved through the techniques that exploit an estimation of the sea surface normalized radar cross section (NRCS) as an additional information. However, errors that can currently be made in predicting the sea surface NRCS may significantly affect their performance. Therefore in this paper we first address the problem to evaluate the NCRS of the sea surface perturbed by rain, when observed at nadir. For this purpose, the dominant effect of ring waves generated by rainfall is considered. The joint effect of wind is also considered. The proposed model is based on the full wave model (FWM) theory. Some comparisons are made with an alternative, less flexible model based on the Integral Equation Model (IEM) theory, and partial comparisons are also made with experimental data, which authorize to consider the proposed model well grounded and exploitable for application. Then, we show that the model can be usefully exploited to improve rainfall rate vertical profile retrieval over the sea surface, in the case of nadir looking, single frequency radars.