Rain generated ring-waves: Measurements and modelling for remote sensing

We present an analysis of ring-wave and scatterometer data from a water surface that was agitated by simulated rain. Water droplets of 2.8 mm diameter impacted the water surface at almost terminal velocity, and the rain rates cover a wide range of conditions (5 to 200 mm hr(-1)). Both the ring-wave energy and backscattered power from the GHz scatterometer increase as R increases, but the growth rates slacken at higher rain intensities. Ring-wave frequency spectra and wavenumber spectra are well represented by log-Gaussian spectral models. The results can be used to guide development of microwave scattering models.