Evaluation of a multiple-Doppler vortex detection and characterization technique using real radar observations

A new multiple-Doppler radar analysis technique is presented for the objective detection and characterization of tornadoes and other intense vortices. The technique consists of fitting radial wind data from two or more radars to a simple analytical model of a vortex and its near-environment. The model combines a uniform flow, linear shear flow, linear divergence flow (all of which comprise a broadscale flow), and modified combined Rankine vortex. The vortex and its environment are allowed to translate. A cost-function accounting for the discrepancy between the model and observed radial winds is evaluated over space and time so that observations can be used at the actual times and locations they were acquired. Doing so avoids the need for time interpolation, moving reference frames or other ad-hoc procedures. The parameters in the low-order model are determined by minimizing this cost function.

The technique has been extensively tested and modified using analytically- and numerically-simulated observations of tornadoes. Experiments with real dual-Doppler observations of tornadoes and other sub-storm scale vortices are underway. The technique shows skill in detecting such vortices and retrieving their size and strength. The latest experiments, including tests with Doppler on Wheels observations of a small tornado and CASA (Collaborative Adaptive Sensing of the Atmosphere) observations of a low-level mesocyclone, will be presented.