Polarimetric characteristics of melting hail at S and C bands

Numerous radar observations indicate that polarimetic signatures of dry and melting hail are profoundly different because melting hail is commonly mixed with rain and melting hailstones acquire water shell which changes their effective dielectric constant, shape and orientation.

In this study, the thermodynamic model of Rasmussen and Heymsfield (1987) is utilized for describing the process of melting of individual hailstone, and arbitrary size distribution of ice particles is prescribed at the freezing level. Vertical profiles of radar reflectivity factor Z, differential reflectivity Z_DR, specific differential phase K_DP, cross-correlation coefficient ρ_hv, specific attenuation A_h, and specific differential attenuation A_DP are modeled at S and C bands for different size distributions of ice particles aloft, different maximal sizes of hail and various profiles of temperature and humidity in the atmosphere.

The model explains most observed polarimetric signatures and their difference between S and C bands which will be illustrated in the presentation. These include Z_DR enhancement and anomalous differential attenuation at C band among others.

Important practical implications for hydrometeor classification, attenuation correction, hail detection, and discrimination between small and large hail at S and C bands will be discussed.