Characterization of Rain Microphysical Processes from the Combination of Doppler Spectra Observed by Dual Frequency Cloud Radars

Over the last few years, a novel technique combining K_a and W-band radars Doppler spectra profiles has been developed for the retrieval of spectral rain drop size distributions (DSD) and air state parameters. Comparisons with a disdrometer show that rain parameters such as rain rate, mean volume diameter and concentration parameter are retrieved with great accuracy close to the ground. The vertical evolution of the DSD can therefore be used to characterize the rain microphysical processes. Focusing on a light rain event where evaporation is the dominant microphysical process, the profile and shape of DSDs show the signatures of evaporation and are in quantitative agreement with the relative humidity (RH) profile retrieved by a collocated Raman lidar, within a 10% RH difference. These results suggest that, in the future, other rain microphysical processes (collision, collection, break-up) could be studied by combining the radar-based DSD retrieval with ancillary RH observations.