Cell Phone Networks Double as Rain Gauges

Adrianne Appel
for National Geographic News
May 4, 2006
Cell phone networks worldwide are on the brink of becoming sophisticated weather gauges, researchers say.

For years wireless networks have dealt with impeded signals during rain, snow, fog, or hail. The networks monitor their signals closely and strengthen them as necessary, to maintain a good signal for customers.

(Related wallpaper: man awaiting storm.)

As it turns out, this monitoring and subsequent adjusting provides weather information that may be even more precise than methods currently used by meteorologists, says Hagit Messer.

Messer is vice president for research and development at Tel Aviv University in Israel.

"The weather affects the signal strength dramatically," she said.

If better real-time weather data can be collected, weather prediction will improve, she says.

(Related: "Crocodile, Scientist 'Communicate' by Mobile Phone.")

Big Static Means Big Weather

Messer and her team tested the accuracy of cell phone weather data last year and were impressed enough with the results that they have filed a preliminary patent application for the process.

The degree of signal interference, called attenuation, depends on the size and distribution of the rain droplets, according to the Israeli team, whose paper will be published in tomorrow's issue of the journal Science.

In an experiment during a rainstorm in January 2005, the team collected data every 15 minutes from cell phone networks about signal-strength adjustments.

The team then compared the data collected from the networks to data collected by atmospheric radar and rain guages—technology typically used by meteorologists. All the data were correlated to what the researchers knew to be the actual intensity of the rainfall.

The cell phone network data proved more accurate than those from radar and just slightly less accurate than those from rain gauges, Messer said.

One reason for the cell phone systems' accuracy is that the wireless networks are no more than 20 meters (22 yards) off the ground. Radar, by contrast, collects weather data from high up in the atmosphere.

"The possibilities are endless. We want to look at other weather, not just rain," Messer said.

Air pollution also causes cell-signal disturbance, so it too can be measured, she says.

"We can look at the technology already there and, as scientists, exploit it," she said.

U.S. "More Aggressive"

Meanwhile, in the United States four university teams and the National Science Foundation have joined with private industry in a large, multiyear project to investigate the use of wireless networks for weather monitoring.

"We are turning this nuisance [cell phone static] into a measurement," said electrical engineering professor V. Chandrasekar of Colorado State University in Fort Collins.

The U.S. teams' efforts are "slightly more aggressive,'' than the Tel Aviv group's, Chandrasekar said.

The U.S. researchers started 3 years ago and will continue for another 11. They plan to place radar antennas along the cell networks to enhance the networks' weather-monitoring capability, he said.

A patent is pending for some of the new technology being developed, which precludes him from giving details of the technology, Chandrasekar says.

The need for better weather monitoring is clear, especially in the United States, where hurricanes and tornadoes hit regularly, Chandrasekar says.

"We still lack information about the lowest level of the atmosphere, where people live," he said.

Factors on the ground, like population density and urban activities, influence the weather in ways that higher-level atmospheric monitoring can't measure, he says.

Scientists have developed sophisticated computers to analyze data. But when it comes to gathering the weather data in the first place, the information is comparatively rough, Chandrasekar adds.

"It is time for the measurements to catch up [to the precision of the analyses]," he said.

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