Another milestone toward making cell phones the future of weather observations


Heavy rain passes through Namibia in 2011. (NASA)

While the future of cell phone-derived weather data remains unclear, scientists have found that it is possible to monitor global rainfall using the telephone antenna network. With the lack of weather data in many technology-poor locations, including Africa, this could prove be a game-changer in the future of global weather observations and forecasting.

Rainfall data is hard to come by in many parts of the world. The ground-based observing network comprises sparse, outdated weather stations, and satellite technology is still not able to completely make up for the lack of measurements. However, a study published in the journal Geophysical Research Letters, scientists detail how a simple measurement of the loss in signal between telephone antennae can predict whether or not it’s raining. Science Daily explains:

Two phenomena are involved. On the one hand, they absorb a fraction of the energy carried by the waves. On the other hand, they spread these waves and turn them away from their original course. So, when it rains between two antennas, the intensity of the signals received falls.

Fortunately, telephone companies monitor this data closely in order to assess the state of their networks. Researchers were able to use the data recorded by a telephone company in the African country of Burkina Faso during the 2012 monsoon to test the hypothesis. Comparing the telephone signal data to ground-based rainfall measurements, scientists concluded that changes in telephone signal strength can predict whether or not its raining with 95 percent reliability.

Related: NASA launches game-changing satellite for tracking global precipitation

Scientists hope that this method can bridge the weather data gap, given that 90 percent of the globe’s inhabited areas is covered by mobile phone antennas.

Beyond the potential to gather rainfall data via cell phone signal, the role of cell phones in future weather data gathering remains promising, but uncertain. The addition of weather sensors on cell phones have opened up the possibility of mobile, pocket-size personal weather stations that could be recording and feeding data to improve the quality of forecasts.

A few phones, like the Samsung Galaxy S4 for example, carry a barometer, hygrometer for humidity, a thermometer, and lightmeter. And there are apps that are already taking advantage of these sensors to gather weather information.

However, the quality of that data has been called into question. As it turns out, phones might not be the best measuring devices for a number of reasons, and John Celenza, lead software developer and meteorologist at Weather Underground, remains cautious but curious when considering the value that these devices could add to their personal weather station network.

“Even with algorithms to correct temperature, it’s really hard to figure out ambient temperature via a phone. There are so many sources of error,” Celenza says. “Correcting for these seems unlikely to any significant level of accuracy. You might be able to get within five degrees or so, but that’s not good enough for weather reporting, we really need accuracy with two degrees.”

Related: How smart phones may improve weather forecasts

Even pressure, which seems to be the easiest measurement to gather from a cell phone, is wrapped in uncertainty. “If everyone stayed at sea level, pressure sensing would work well,” says Celenza. Unfortunately, GPS can only estimate your elevation within an accuracy of about 60 feet, which translates to an error of two millibars. “This is a significant amount for weather,” he says.

Nonetheless, the idea of a cell phone weather station network is enticing. Having millions of weather stations walking around the earth like a mobile mesonet could improve not only the quality of day to day forecasts, but could help meteorologists to predict fine-scale weather phenomena, like severe thunderstorms and high precipitation events.

So while the potential for cell phones to revolutionize weather data and subsequent forecasts remains high, Celenza says some of the details need to be hammered out before they would consider adding the data to their network. “We are looking to do this, but only if accuracy can be proven.”

Angela Fritz is an atmospheric scientist and The Post's deputy weather editor.
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