The authors have performed radar backscattering measurements with a scatterometer in a wind-wave tank under different wind and rain conditions. The aim of these experiments was to gain further insight into those mechanisms which are responsible for the combined rain- and wind-induced modifications of the water-surface roughness and, thus, of the radar backscatter. The results from their measurements imply that the ratios of the co-polarization and cross-polarization backscatter may help to estimate rain rates, and therefore enable the authors to interpret radar images of rain cells more quantitatively.