Session 8A.3 Preliminary numerical simulations of infrasound generation processes by severe weather using a fully compressible numerical model

Wednesday, 6 October 2004: 8:30 AM
Melville E. Nicholls, Colorado State University, Fort Collins, CO; and R. A. Pielke Sr. and A. J. Bedard Jr.

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A numerical model was used to investigate the generation mechanisms responsible for infrasound emanating from tornadic storms. The model is fully compressible, nonlinear, three-dimensional and includes parameterizations of cloud microphysical processes. It was found that a strong vortex perturbed marginally from a cyclostrophic balance produces a train of infrasonic waves with a frequency similar to that observed from tornadic storms. Model output was analyzed to determine if radial vibrations of the vortex core generated the infrasound. Additionally, a simulation of a non-supercell tornadic storm was conducted. A land spout type of tornado developed with wind speeds of approximately 35 m/s. Infrasound was generated with a frequency and amplitude in reasonable agreement with those observed from this type of tornadic storm. Results suggest that small scale heating fluctuations may also have contributed to the generation of infrasound in this simulation.
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