Combining wind and rain in spaceborne scatterometer observations: modelling the splash effects in the sea surface backscattering coefficient

Scatterometer wind retrievals are widely used by the oceanographic and meteorological communities for several applications. However, rain strongly affects such wind retrievals, especially at Ku band and higher frequencies. Although several semi-empirical techniques have been already developed to correct scatterometer wind retrievals, the implementation of a physical forward model representing the realistic behavior of ocean surface in presence of atmospheric events may lead to a more accurate approach in estimating winds. A physical forward model can also open the opportunity to ingest an inversion algorithm to jointly estimate wind and rain as well as to evaluate the uncertainty of the rain rate estimates which, in turn, affect the uncertainty in the wind speed and direction retrievals. In this work we present the first step of our approach in developing such physically-based model. The purpose is to include the rain rate parameter in the sea surface backscattering coefficient by physically implementing the effects due to the impact of the raindrops on the ocean surface. Numerical results confirm that the proposed model is physically consistent as it is able to reproduce the expected behavior of the surface backscattering coefficient at Ku band