Rain affects wind retrievals from scatterometric measurements of the sea surface. To depict the additional roughness caused by rain on a wind driven surface, we use a ring-wave spectral model. This enables us to analyse the rain effect on K-u band scatterometric observations from two laboratory experiments. Calculations based on the small perturbation method provide good simulation of scattering measurements for the rain-only case, whereas for combined wind and rain cases, the boundary perturbation method is appropriate.
Craeye, C., Sobieski, P., & Bliven, LF. (1997). Scattering by artificial wind and rain roughened water surfaces at oblique incidences. International Journal of Remote Sensing, 18(10), 2241-2246. https://doi.org/10.1080/014311697217864 (Original work published 1997)