Towards an improved wind and rain backscatter model for ASCAT

The ASCAT scatterometer measures the backscatter from the ocean surface with which it infers the near-surface wind vector. When rain is present in the observation area the windinduced backscatter is modified by the rain. This paper uses co-located observations from TRMM PR to model the effects of rain on the ASCAT observed backscatter. Two model types are considered, a phenomenological rain model and a lumped effect rain model which are comparable for most rain rates. For low rain events the ASCAT observed backscatter due to rain is not substantial, however for moderate to high rains the rain-induced backscatter from the ocean surface can be significant, and for extreme rain rates the atmospheric scattering and attenuation are dominant.