Winston
Lorenzo von Matterhorn
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Spying on a Storm's Infrasonic Signals to Improve Tornado Warnings
https://spectrum.ieee.org/tech-talk...rnados-infrasonic-signals-to-improve-warnings
Excerpt:
Today, weather agencies issue tornado warnings by closely observing storms for characteristic air movements. Warnings typically come about 10 minutes in advance. But most warnings are false alarms, says Brian Elbing, a professor of mechanical and aerospace engineering at Oklahoma State University. Seventy-five percent of the time, tornadoes dont occur, he says. The high rate of error causes warning fatigue, which can be deadly.
In the late 1990s, scientists at the National Oceanic and Atmospheric Administration found that tornado-producing storms can emit infrasound signals up to two hours before tornado-genesis. NOAA deployed a demonstration infrasonic network to monitor tornados in 2003. Researchers including Elbing have more recently started their own observations, and are trying to improve the hardware and software to detect tornadoes by infrasound.
Tornados themselves also emit infrasound signals in the 0.5 to 10 Hz range depending on their size, Elbing says. He and his colleagues have set up a simple infrasonic array on the university campus to collect signals from both tornados and storms. The array consists of three commercial infrasound microphones placed in a triangle, spaced about 60 meters apart.
The challenge is to distinguish infrasound signals from wind noise. Its like being in a loud room trying to listen to somebody talk softly, Elbing says. So the team has enclosed each microphone inside a container with four openings. A hose is attached to each opening, and the hoses are stretched out in opposite directions. Each hose manages to catch and funnel some infrasonic waves to its microphone, while reducing the amount of wind that reaches it.
Computers compare the signals recorded at each microphone, and perform filtering and signal processing to further minimize noise. If all three signals look alike, that rules out wind, Elbing says, because the noise from wind would be not coherent. By analyzing those signals, the researchers can then create a simple computer model of the fluid mechanism that produces the infrasound waves.
Their system had its first success last May, when a tornado hit Perkins, Oklahoma, which is about 20 kilometers from the university. Ten minutes before the tornado hit, the array picked up extremely strong signals. Based on the frequency, the researchers predicted a tornado size of 46 meters. That was precisely the official width of the twisters destruction path.
https://spectrum.ieee.org/tech-talk...rnados-infrasonic-signals-to-improve-warnings
Excerpt:
Today, weather agencies issue tornado warnings by closely observing storms for characteristic air movements. Warnings typically come about 10 minutes in advance. But most warnings are false alarms, says Brian Elbing, a professor of mechanical and aerospace engineering at Oklahoma State University. Seventy-five percent of the time, tornadoes dont occur, he says. The high rate of error causes warning fatigue, which can be deadly.
In the late 1990s, scientists at the National Oceanic and Atmospheric Administration found that tornado-producing storms can emit infrasound signals up to two hours before tornado-genesis. NOAA deployed a demonstration infrasonic network to monitor tornados in 2003. Researchers including Elbing have more recently started their own observations, and are trying to improve the hardware and software to detect tornadoes by infrasound.
Tornados themselves also emit infrasound signals in the 0.5 to 10 Hz range depending on their size, Elbing says. He and his colleagues have set up a simple infrasonic array on the university campus to collect signals from both tornados and storms. The array consists of three commercial infrasound microphones placed in a triangle, spaced about 60 meters apart.
The challenge is to distinguish infrasound signals from wind noise. Its like being in a loud room trying to listen to somebody talk softly, Elbing says. So the team has enclosed each microphone inside a container with four openings. A hose is attached to each opening, and the hoses are stretched out in opposite directions. Each hose manages to catch and funnel some infrasonic waves to its microphone, while reducing the amount of wind that reaches it.
Computers compare the signals recorded at each microphone, and perform filtering and signal processing to further minimize noise. If all three signals look alike, that rules out wind, Elbing says, because the noise from wind would be not coherent. By analyzing those signals, the researchers can then create a simple computer model of the fluid mechanism that produces the infrasound waves.
Their system had its first success last May, when a tornado hit Perkins, Oklahoma, which is about 20 kilometers from the university. Ten minutes before the tornado hit, the array picked up extremely strong signals. Based on the frequency, the researchers predicted a tornado size of 46 meters. That was precisely the official width of the twisters destruction path.
