Zach Wienhoff-April 13

An investigation of the relationship between Doppler vortex signatures and polarimetric debris signatures in strong, damaging tornadoes

Over the past seven years, a number of high spatial and temporal resolution datasets have been collected by a rapid-scan, X-band, polarimetric Doppler radar (RaXPol) within close-range of strong tornadoes. In most of these cases, strong divergence in the sampled velocity field as result of centrifuging debris is observed, followed by oscillations between convergence and divergence after debris is shed from the vortex. In several cases, deviations in the tornado’s track and increases in intensity were observed to follow these periods of heavy destruction, posing questions of causation versus coincidence.  While RaXPol observations have offered interesting questions regarding potential effects of debris on tornado vortices, observational limitations present more questions than answers in these cases.

This presentation will outline a framework for utilizing CM1 LES simulations of tornado vortices (e.g., Dahl et al. 2017) in tandem with a polarimetric Doppler radar simulator which allows to begin examining debris influences on tornado vortex signatures in an idealized scenario. SimRadar, the polarimetric Doppler radar simulator (Cheong et al. 2017), produces realistic trajectories of both hydrometeors and several types of tornado debris, allowing us to emulate the effects of heavy debris loading on the radar signal. Early results of the simulated vortex signatures will be briefly examined and compared to RaXPol observations, and plans for future modifications to this experiment will be discussed.