Comparison of polarimetric algorithms for hydrometeor classification at S and C bands

The paper contains description of the latest version of the hydrometeor classification algorithm (HCA) recommended for polarimetric prototype of the S-band WSR-88D radar and its adaptation for C band. The S-band version of HCA has been extensively tested in central Oklahoma (USA), whereas the C-band HCA was evaluated in Southern Ontario (Canada) and in Alabama (USA) for a number of storms of different types. Polarimetric observations at C band were made with the Environment Canada radar in King City, Ontario, and the EEC-built Sidpol radar in Alabama. Examined storm events include continental hailstorms, mesoscale convective systems, and tropical rain showers.

It is demonstrated that effects of resonance scattering at C band cause substantial differences in polarimetric characteristics of large hydrometeors between the two radar frequencies. The impact of resonance scattering is especially pronounced in hail-bearing storms. In the presence of large hydrometeors (e.g., big raindrops or melting hailstones), differential reflectivity at C band is higher than the one at S band for a given Z, whereas cross-correlation coefficient is lower at C band than at S band. As a result, the HDR technique for discrimination between rain and hail proven efficient at S band requires significant modification for application at C band.

Recommendations for adapting S-band membership functions in HCA for C band are substantiated by scattering model simulations and analysis of polarimetric measurements from a large and diverse set of weather events.