Improving Vertical Velocity Retrievals from Doppler Radar Observations of Supercells

Vertical velocity (w) is generally the most difficult wind component to synthesize accurately from Doppler wind observations of intense convection, particularly when data are unavailable at low levels. The retrieval of w may be improved by including a vertical vorticity constraint in dual-Doppler analysis. This constraint requires an estimate of the local vertical vorticity tendency, which may be obtained through simple local time discretization of the horizontal wind field at adjacent observation times (the "brute force" method) or by applying advection correction.

To evaluate the performance of these methods when substantial data voids are present, we perform dual-Doppler analyses on synthetic radar observations of a high-resolution supercell simulation. Volume scan times from 10 to 150 s and radar ranges from ~10 to ~50 km are tested, and results with and without observations within the lowest 1 km AGL are compared. We find that including the vertical vorticity constraint consistently improves the w retrieval when a spatially-variable advection correction is applied, whereas the "brute force" method only has value for volume scan times on the order of 10 s.