Study: GPS systems can give accurate measurements of hurricane winds

July 15, 2013 at 4:11 PM
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HAMPTON, Va., July 15 (UPI) -- The distortion of GPS signals in storms could have a positive effect, U.S. researchers say, by providing a way to measure and map the wind speeds of hurricanes.

The information could be gathered by determining the amount of disturbance GPS satellite signals experienced when bouncing around in a storm, they said.

Writing in Radio Science, a journal of the American Geophysical Union, researchers said improved wind speed measurements could help meteorologists better predict the severity of storms and help track where they might be headed.

When a signal from a GPS satellite strikes the surface of a body of water, such as the ocean, about 60 percent of the signal reflects back toward the sky, lead researcher Stephen Katzberg at the NASA Langley Research Center in Hampton, Va., said.

Unlike a mirror, however, the surface of the ocean is rarely calm and flat as wind generates heaving waves.

"Imagine you blow on a hot bowl of soup," he said. "The harder you blow, the bigger the 'waves' are in the bowl."

The rough surface created by waves distorts the reflection of GPS satellite signals by scattering them in various directions.

"The radio wave bounces off the waves," Katzberg said. "As the surface gets rougher, the reflections get more disturbed and that's what we measure."

Comparing signals coming directly from satellites above with the reflections from the sea below, a computer can calculate an approximate wind speed with better than about 11 miles per hour accuracy, the researchers said.

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