Microphysical characteristics of heavy, Mediterranean rainfall retrieved from polarimetric radar measurements during the Hymex field campaign

Polarimetric radar observations of storms during the Hydrological Cycle in the Mediterranean Experiment (HyMeX) are used to document microphysical characteristics of heavy rainfall in the Cevennes-Vivarais region of the South of France. Radar data are analyzed using a simplified, one-dimensional modeling of the vertical profile of radar variables derived according to the particle size distribution, phase and density of hydrometeors coupled with an electromagnetic scattering model. The method takes into account the polarimetric variables subject to radar sampling with range, low signal-to-noise ratio, attenuation, etc. It identifies altitudes separating ice, melting ice and liquid phase using the radar bright band observations. The density of ice hydrometeors is inferred from the bright band features, and their melting is simulated assuming mass flux conservation.

The method is applied to an intense rain event recorded during the experiment to provide consistent physical insights into the microphysics of the system. The microphysical retrieval framework will be extended to integrate data from multiple radar wavelengths, aircraft data, disdrometers, etc. The retrieved vertical profiles of microphysics can be used to simulate passive-based microwave observations from satellite sensors.