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A New Way to Forecast Extreme Events.

Interferometers combine two or more sources of light to form an interference pattern that can reveal information about a studied phenomenon or object. The tool is used in many fields, including astronomy, fiber optics, remote sensing, quantum mechanics, and nuclear and particle physics. Now, researchers at Hendrix College in Arkansas have revealed the technology's potential in early warning systems for natural hazards such as hurricanes and tornadoes.

Regular interferometers separate light waves onto paths of different lengths and then recombine them, creating an interference pattern of alternating bright and dark fringes that moves whenever the path lengths change. A specific version of the device known as a ring laser interferometer sends beams of light in opposing circular directions, creating a beat frequency rather than fringe shifts when they are combined. This frequency is proportional to the ring's rotation, and when mounted at ground level it measures the rotational beat frequency of Earth. Any perturbation that disturbs Earth's beat frequency--such as the low rumbles of tornadoes, hurricanes, and volcanoes known as infrasound, which have frequencies below the limit of human hearing--can be measured. In the new research, the scientists developed a version of this kind of interferometer that according to the study's lead author, Robert Dunn, was able to "clearly show the frequency spectrum of the infrasound."

Using a 2014 EF4 tornado in Arkansas as a test case, the ring laser technology was able to detect infrasound from the developing tornado 30 minutes before the funnel reached ground level; further analysis of other recent tornadoes produced similar results. According to Dunn, when this technology is used with Doppler radar, it "could prove very useful as an early warning system." The ring laser interferometer could similarly be used to detect infrasound from hurricanes and volcanoes, and Dunn noted that the research team plans to "continue exploring how ring lasers can help reduce the impact of natural hazards."

A paper on the study was recently published in the Journal of Applied Physics. [Source: American Institute of Physics]

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Publication:Bulletin of the American Meteorological Society
Geographic Code:1USA
Date:Jan 1, 2017
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