Now, researchers believe these phones can play an integral part in the collection of weather data – data that one day may improve forecasts.
Researchers and smartphone application developers have discovered a way to correlate the temperature of a smartphone’s battery with the air temperature at the users’ location, according to a published article in Geophysical Research Letters.
Smartphones come with built-in thermometers to track the battery temperature of the phone and help prevent the phone from overheating. Now, the battery temperatures are being dumped into a crowd-sourcing application.
The London-based OpenSignal application, whose temperature collection is available for phones running the Android operating system, records hundreds of thousands of data readings from users who are running the app. The data collected by the research team, after calibration, have come within an average of 3 degrees Fahrenheit of the actual air temperature in eight major cities where the data have been analyzed.
While each of the eight cities has its own credible weather station (London, LA, Paris, Mexico City, Rome, San Paulo, Buenos Aires, and Moscow), the researchers hope data collected by the app can provide extremely localized temperature information, down to the city block level.
“The ultimate end is to be able to do things we’ve never been able to do before in meteorology and give those really short-term and localized predictions,” said James Robinson, who developed the OpenSignal application.
Robinson said over 700,000 people actively use the application, and 90 percent of users voluntarily opt-in to the data collection.
When beginning the research, Robinson and his team speculated 4G phones ran hotter than 3G phones and older network phones. When no difference between the temperatures on different data networks was discovered, the researchers took a second look at the data.
“Just sort of for fun we started looking to see if there was a correlation with anything else,” said Robinson. His group discovered that the data curves for cell temperatures and air temperatures in London had a similar shape.
“It was amazing how easily the correlation sort of popped out,” he said. “We didn’t do any handpicking of data—it sort of just emerged.”
Temperature is not the only weather variable many smartphones can sense. A number of devices also contain pressure sensors
University of Washington atmospheric science professor Cliff Mass of the University of Washington believes smartphone pressure readings have even more potential for use in weather forecasts than temperature. He said that the exposure issues for cell phone battery temperatures make the data difficult to work with.
Mass, who presented on how a dense network of pressure readings could be “revolutionary” for localized weather forecasts at a conference last week, expects half-a-billion cell phones to have pressure reading devices by 2016.
“[S]urface pressure is a uniquely valuable surface observation since it reflects the atmosphere above,” Mass writes on his blog. “Recent research has revealed that with sufficient surface pressure senors and a sophisticated model-based data assimilation system, one can accurately reconstruct the three-dimensional structure of the atmosphere.”
Mass is encouraging anyone with a smartphone containing a pressure sensor to download the Culumonimbus app which aggregates pressure readings.
Beyond temperature and pressure readings sensed by phones internally, independent efforts are surfacing to measure other weather variables using external hardware. Danish startup Vaavud has developed a wind meter which plugs into many smartphone devices.
* Adam Rainear is a Capital Weather Gang summer intern