Simulated WSR-88D velocity and reflectivity signatures of numerically modeled tornadoes

Super-resolution reflectivity and Doppler velocity data are displayed at 0.5° instead of 1.0° azimuthal sampling intervals and reflectivity data are displayed at 0.25-km instead of 1.0-km range intervals. Since a mean Doppler velocity value is the reflectivity-weighted mean of the radial motion of all the radar scatterers within a radar beam, a nonuniform distribution of scatterers produces a different mean Doppler velocity value than does a uniform distribution of scatterers.

Nonuniform reflectivities within the effective resolution volume of the radar beam can bias the indicated size and strength of the tornado's core region within the radius of the peak tangential velocities. As shown in the simulation results, the Doppler-indicated radius of the peak wind underestimates the true radius and true peak tangential velocity when the effective beamwidth is less than the tornado's core diameter and there is a weak-reflectivity eye at the center of the tornado.

As the beam becomes significantly wider than the tornado's core diameter with increasing range, the peaks of the Doppler velocity profiles continue to decrease in magnitude but overestimate the tornado's true radius. With increasing range from the radar, the prominence of the weak-reflectivity eye at the center of the tornado is progressively lessened until it finally disappears. As to be expected, the Doppler velocity signatures and reflectivity eye signatures were more prominent and stronger with super-resolution sampling than those with legacy-resolution sampling.