VHF Wind-Profiler Data Quality and Comparison of Methods for Deducing Horizontal and Vertical Air Motions in a Mesoscale Convective Storm

Abstract

Very high frequency (VHF) Doppler radar measurements of the horizontal and vertical winds are used to examine three procedures to extract mean profiles of horizontal and vertical winds. These are 1) time averaging of first-moment estimates of radial velocity from the high time resolution Doppler spectra; 2) time averaging of radial velocities estimated from a least-squares fitting of either one or two Gaussians to the spectra in order to account for the double peaks corresponding to turbulent and precipitation scattering that appear in the spectra during heavy rain; and 3) consensus averaging of the least-square-fitted radial velocities. Horizontal winds produced by these procedures were compared to each other and to those from two 5-cm radars operating nearby. Least-squares fitting yielded the best wind estimates, although a slight relaxation of the consensus criterion was sometimes found to be necessary in order to avoid the failure to find a consensus. The simple first-moment method produced comparable results, except below the melting level, where it performed more poorly. Vertical winds from the fitted VHF spectra were compared with those derived from the 5-cm-radar data using the extended velocity-azimuth display (VAD) technique. Reasonable agreement was found at heights above the freezing level.