Large raindrops against melting hail: calculation of specific differential attenuation, phase and reflectivity

The specific differential attenuation caused by large raindrops and a special form of melting hail is computed and studied. Raindrops of smoothed conical shapes and hailstones modelled by an ice sphere surrounded by a water torus are considered. For the former, scattering computation is carried out by the T-matrix method, while the higher-order method of moments in the surface integral equation formulation is used for the latter. Results show a much higher specific differential attenuation factor for hail particles, with the smallest hail showing values similar to the largest raindrops. This can explain the higher than expected differential attenuation observed by C-band radars in intense storms as reported in some previous studies. Results also show that the melting hail particles exhibit higher specific differential phase factor than large raindrops, but have similar differential reflectivity.