Scatterometry of a drop impact on a salt water surface

Experiments of scatterometry at 135 and 36GHz, W polarization have been conducted in the new Rain-Sea Interaction Facility at NASA Wallops. Radar backscatterings of rain drop impacts on a sail water surface have been measured with an incidence angle of 30° for various dropsizes at terminal fall velocity. Results for 2-8 mm drops are presented. Surface features were imaged by an ultra high speed digital camera synchronized with the radar data acquisition. Backscattered powers from crowns, craters, stalks and ringwaves were measured. These measurements confirm that for the scatterometric configuration under consideration, ringwaves are the dominant scattering contribution and that stalks scattering is much smaller but not negligible.