Observations of Stratiform Rain by cm- and mm- Wavelength Radars

During the Cirrus Regional Study of Tropical and Cirrus Layers (CRYSTAL) Florida Area Cirrus Experiment field campaign in southern Florida, stratiform rain were observed by 3.2 mm and 3.2 cm wavelength airborne Doppler radars. This paper presents interpretation of the melting processes in the stratiform rain using the dual wavelength reflectivity and velocity observations. Features that were observed in the melting region include: 1) the reflectivity profile at 3.2 cm wavelength is typical for the stratiform rain and has a maximum in the melting band. The reflectivity profiles at 3 mm wavelength often shows a minimum at top of melting band as a result of attenuation and Mie-scattering before reaching a maximum downward in the melting band; 2) in snow, the velocities are more or less the same at both wavelengths. As melting starts, the velocities start increasing with distance downwards and stabilize in the rain region with greater velocities at the cm wavelength. The stabilization occurs earlier for the mm-wavelength. Complete melting is probably achieved where the cm wavelength velocity has stabilized to the rain value. In the paper, these observations will be interpreted in terms of particle melting process and scattering cross-sections of melting particles at the two wavelengths.