A Direct Method for Deriving Drop-Size Distribution and Vertical Air Velocities from VHF Doppler Radar Spectra

In precipitation environments, sensitive VHF Doppler radars have a capability to detect echoes from both refractive index irregularities and precipitation particles. The purpose of this paper is to propose a direct method to estimate the drop-size distribution N(D), the mean vertical air velocity and turbulence using Doppler spectra obtained by VHF Doppler radars. Because the new method directly estimates turbulence as well as the mean vertical air velocity, the N(D) parameters, deduced from a least-squares fit approach, are free from errors inherent in conventional measurements using microwave Doppler radars. Temporal and spatial variations of N(D) and mean vertical air velocity during a cold front passage are then studied to demonstrate the capability of the present method.