A Numerical Modeling Investigation of Infrasound Generated by Tornadic Storms

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Observations have shown that tornadoes and severe storms produce acoustic waves at a frequency below the range of human hearing (called infrasound). Tornado infrasound has a frequency range of about 0.5-10 Hz, which is higher than other infrasound emanating from severe storms and above the range covered by conventional infrasound studies. If tornadoes can be detected by this distinct frequency signature, it may be possible to develop new advance-warning systems that could be of substantial societal benefit. In this project, the investigators will use a numerical model to simulate the generation of infrasound from tornadic storms. Preliminary simulations have provided the basis for a set of hypotheses regarding how the infrasound is generated, including radial vibration of the vortex core which appears to be the most promising. Existing observations covering this frequency range provide benchmarks for the simulations and will also be examined as case studies in this project. The expected outcome is a better understanding of the mechanisms by which tornadoes generate infrasound. This understanding will also establish a better basis for considering if a detection system based on infrasound could serve as an advance-warning system for tornadoes. Because infrasound propagates over long distances, detection by this method might provide a valuable contribution to public safety.