Infrasound and low frequency sound emitted from tornados

Abstract

The NCPA, in collaboration Hyperion Technology Group, has performed a series of measurements of infrasound and low-frequency sound generated by tornadic thunderstorms near Oklahoma City, OK, during a large-scale outbreak on May 24, 2011. Ground truth for tornado tracks as well as meteorological data were available for these storms. Infrasound and low-frequency sound were identified separately for a long duration EF-5, an EF-4, and an EF-2 tornado. As reported by Frazier et al. [JASA 135, 1742 (2014)], infrasound in two distinct regions were noted: An infrasound band between approximately 1-10 Hz and a low-frequency audible band located between roughly 40-200 Hz (center frequency around 80-100 Hz). As part of the NOAA VORTEX-SE initiative, the NCPA will be collecting additional infrasound data in the Northern portion of Alabama, centered on Huntsville and the Sand Mountain region. Current plans are to install to 10 infrasound arrays, with seven elements per array. As part of the same VORTEX-SE initiative, seven additional arrays will be deployed by the University of Alabama Huntsville. We will report here on the status of infrasound generated by tornadic thunderstorms, as well as discuss the status of modeling efforts to understand the origins of these emissions.