USA: Mystery sounds from storms could help predict tornadoes
By Nicola Davis
Mysterious rumbles that herald tornadoes could one day be used to predict when and where they will strike, according to researchers.
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“The three possibilities are core oscillations [in the tornado], pressure relaxation, and latent heat effects,” said Dr Brian Elbing, of Oklahoma State University, who is part of the team behind the research. “They are all possibilities because what we have seen is that the signal occurs before the tornado touches the ground, continues after it touches the ground, and then disappears some time after the tornado leaves the ground.”
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The subject has seen renewed interest in recent years, with Elbing saying it could prove particularly useful for hilly areas such as Dixie Alley, which stretches from Texas to North Carolina. “Infrasound doesn’t need line of sight like radar, so there is hope that this could significantly improve warnings in Dixie Alley where most deaths [from tornadoes] occur,” he said.
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The team say the setup allows them to filter out sounds from normal wind and work out which direction the twister is travelling, while the signal itself offers an idea of the tornado’s size: a frequency of 1Hz indicates a very large tornado, while a 10Hz indicates a small one.
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