Analysis and Comparison of Several Methods for Processing VHF Doppler Radar Wind Profiler Data Obtained during a Mesoscale Convective Storm

On June 10-11, 1985, a squall line passed the VHF Doppler radar wind profiler at McPherson, Kansas, during the O-K PRE-STORM experiment. The mature squall line had an intense convective leading edge and a broad trailing stratiform precipitation region. A planned mesoscale network of radar wind profilers will often operate in conditions similar to those associated with the system. The availability of 5-cm Doppler radar data in addition to wind profiler data for the period has made it possible to assess various procedures used to extract mean representative hourly or half-hourly horizontal winds over the 3-4 hr period around the passage of the squall line. Since some of the Doppler power spectra for the period in the lower height ranges exhibited double peaks corresponding to turbulent scattering and precipitation scattering during the periods of heavy rain, a nonlinear least-squares fitting of the spectra was applied in order to estimate the mean radial velocity separately for the two types of scatterers. Simple first moment calculations were also used. Consensus averaging and straight temporal averaging were applied to the results and the wind profiles were compared to the 5-cm radar data. The results indicate that the nonlinear least-squares fit and temporal averaging give the best results. First moment estimates and averaging produce comparable, although slightly poorer, results. The consensus technique, however, did not produce acceptable wind estimates in the conditions associated with the mesoscale convective system. The vertical wind velocities derived from the fitted profiler data were compared with vertical winds obtained from the 5-cm radar data by the extended VAD technique and showed good agreement between the two sets of measurements. The mesoscale dynamics of the storm have been investigated by examination of the power spectra of vertical velocity fluctuations and calculation of the vertical flux of horizontal momentum and its divergence. A discussion of numerical models used to simulate the behavior of mesoscale convective phenomena is included, with emphasis on the potential for wind profilers to provide input for initialization and correction.