Dual-Doppler wind analysis using the vertical vorticity equation: Tests with real and simulated supercell data

The vertical component is typically the most difficult velocity component to retrieve in dual-Doppler wind analysis. One of the main problems is that the lowest radar scan may be a kilometer or more above the surface of the earth, thus limiting the low-level divergence information available to the mass conservation constraint. Our work focuses on a new method of dual-Doppler wind analysis with an emphasis on improving the retrieval of the vertical velocity field in the presence of substantial low-level data voids. The analysis proceeds in a three-dimensional variational (3DVAR) framework with the anelastic form of the vertical vorticity equation imposed along with traditional mass conservation and smoothness constraints. The method is general enough to include data from multiple radars but tests have thus far been restricted to two radars. Previous tests of the technique with analytical wind data were reported in Shapiro et al. (2009).

Experiments with emulated radial wind observations of a supercell simulated by the Advanced Regional Prediction System (ARPS), as well as with real dual-Doppler observations of the 8 May 2003 Oklahoma City tornadic supercell, will be presented. Special attention will be given to the impact of accounting for the translation and intrinsic evolution of the horizontal wind field.