David Bodine - October 1

Convective Meteorology (Mesoscale Dynamics)

High-Resolution Radar Observations and Simulations of Tornadoes

David Bodine

Friday, October 1

3:00pm

Location:

NWC 5600

High-resolution mobile radar observations and numerical simulations are indispensable tools for understanding tornadoes and tornadic storms. High-resolution mobile radar data capture the three-dimensional evolution of microphysical and dynamic processes that lead to tornado formation and impact the subsequent tornado and parent storm lifecycle. Fine-scale numerical simulations enable controlled studies of physical processes impacting tornado dynamics, resolving finer scales (few meters) and all three-dimensional wind components that cannot be captured with existing radars. In this talk, tornado research incorporating both high-resolution radar observations and numerical models is presented to 1) examine rapidly evolving processes in different tornado lifecycle stages, 2) investigate factors controlling the three-dimensional distributions of tornado debris and associated polarimetric signatures, and 3) assess how residential structures impact the tornado’s wind structure and evolution.

In the first part of the study, analyses of high-resolution observations from the Atmospheric Imaging Radar (AIR) are presented, focusing on tornadogenesis, tornado dissipation, and the vertical structure of intense horizontal vortices. These analyses leverage the AIR’s unique simultaneous and vertically continuous scans to document changes in rotation through a deep column. Next, observations and numerical simulations of tornado debris signatures (TDSs) will be presented, focusing on the relationships among tornado debris characteristics, tornado wind speeds, and the polarimetric TDS, as well as methods to correct Doppler velocities biased by tornado debris. Finally, a suite of high-resolution tornado simulations is presented to document how tornado wind speeds change in response to residential structures in different neighborhood layouts. An immersed boundary method (IBM) is implemented in the Large-Eddy Simulation model to simulate residences, including a parameterization to permit tornado damage (e.g., partial or full removal of simulated structures). Analyses of these simulations reveal that neighborhood layouts strongly influence near-surface tornado wind characteristics. Moreover, a sheltering effect is also noted where wind loading is reduced on downstream structures if upstream structures remain largely intact. However, once significant structural damage occurs to upstream structures, low-level winds increase considerably, leading to greater damage severity and a wider damage path.