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Thunderstorms can disrupt GPS device, researcher cautions

A Taiwanese researcher says global positioning systems (GPS) are susceptible to interference from thunderstorms and so should not be relied upon in extreme weather conditions.

Lin Chien-hung (林建宏), an assistant professor at the Plasma and Space Sciences Center of National Cheng Kung University, said the strong atmospheric convections in a thunderstorm can create atmospheric oscillations -- tides -- that rise between 90km and 120km above ground, just under the ionosphere.

ATMOSPHERIC TIDES

Ions from the tides accumulate at that level and could interfere with electromagnetic waves, he said.

When transmission of electromagnetic waves is impeded, Lin said, signals from GPS satellites to GPS devices on the ground will be distorted, causing a phenomenon dubbed "GPS confusion,"in which the device gives inaccurate directions.

"Some of my friends told me stories of using a GPS device in thunderstorms," Lin said.

GETTING LOST

"They hoped the device could lead them out of the mountains despite the heavy rains. But even though they followed the directions given by GPS devices, they found themselves in the middle of nowhere," Lin said.

He said such stories have inspired him to do more research on the interaction of atmospheric convections and GPS devices.

Using the data collected by FORMOSAT-3, a climate satellite launched and operated by the government-funded National Space Organization and its US partners, Lin analyzed atmospheric variations during thunderstorms and observed how atmospheric tides created disruptions in electromagnetic waves.

ANOMALIES

Based on the data gathered by an IMAGE satellite in 2002, the US National Aeronautics and Space Administration has listed four areas as "equatorial regions with anomalies in ionospheric activities."

These regions are: the Amazon valley, the Congo River valley, Indonesia's rain forests and the middle of the Pacific Ocean, where most tropical storms form, he said.

"Taiwan is in the mid-Pacific region, where a thunderstorm near the ground will disturb the upper atmosphere and could impact the functions of a GPS device," Lin said.
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