Abstract
Previous work suggests that acoustic waves at frequencies below human hearing (infrasound) are produced during tornadogenesis and continue through the life of a tornado, which have potential to locate and profile tornadic events and provide a range improvement relative to current radar capabilities, which are the current primary measurement tool. Confirming and identifying the fluid mechanism responsible for infrasonic production has been impeded by limited availability and quality (propagation-related uncertainty) of tornadic infrasound data. This paper describes an effort to increase the number of measurements and reduce the uncertainty in subsequent analysis by equipping storm chasers and first responders in regular proximity to tornadoes with mobile infrasound measurement capabilities. The study focus is the design, calibration, deployment, and analysis of data collected by a Ground-based Local INfrasound Data Acquisition (GLINDA) system that collects and relays data from an infrasound microphone, GPS receiver, and an IMU. GLINDA has been deployed with storm chasers beginning in May 2020 and has provided continuing real-time automated monitoring of spectrum and peak detection. In analysis of sampled severe weather phenomena, the signal measured from an EFU tornado (Lakin, KS) show an elevated broadband signal between 10 and 15 Hz. A significant hail event produced no significant increase infrasound signal despite rotation in the storm. The consistency of these observations with existing fixed array measurements and real-time tools to reduce measurement uncertainty demonstrates the value of acquiring tornado infrasound observations from mobile on-location systems and introduces a capability for real-time processing and display of mobile infrasonic measurements.
Highlights
This paper describes an effort to increase the number of measurements and reduce the uncertainty in subsequent analysis by equipping storm chasers and first responders in regular proximity to tornadoes with mobile infrasound measurement capabilities
The study focus is the design, calibration, deployment, and analysis of data collected by a Ground-based Local INfrasound Data Acquisition (GLINDA) system that collects and relays data from an infrasound microphone, GPS receiver, and an IMU
We introduce a portable infrasound measurement tool that may be carried by storm chasers and first responders, combined with a realtime interface portal
Summary
Tornadoes remain a significant hazard to life and property. In the United States, 800-1400 annually reported tornadoes claim an average of 55 lives (Ashley, 2007; Paul and Stimers, 2012) with 76 confirmed fatalities in the United States in 2020 20 (NOAA/SPC, 2021). Contemporary tornado infrasound results continue to be reported primarily in conference papers (Noble and Tenney, 2003; Bedard et al, 2004b, a; Prassner and Noble, 2004), project reports (Rinehart, 2018), 40 and oral presentations (Rinehart, 2012; Goudeau et al, 2018) Exceptions to this trend include four journal articles focused on infrasound observations from tornadoes (Bedard, 2005; Frazier et al, 2014; Dunn et al, 2016; Elbing et al, 2019). The fixed nature of this array limited the proximity to tornadoes and radar sites, and though 2019 included a historically high number of tornadoes (NOAA, 2020c), no 2019 observations had both reliable infrasound and radar data To address this gap, a mobile 4-microphone infrasound array was developed (Petrin et al, 2020), heliotrope solar hot air balloons (Bowman et al, 2020) were equipped with infrasound sensors (Vance et al, 2020), and a Ground-based Local INfrasound Data Acquisition (GLINDA) system was developed in 2019-20 to be carried by storm chasers and first responders.
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