WeatherSignal smartphone app crowdsources the weather

Join the largest amateur weather network in the world. WeatherSignal's app collects data from the many sensors in Android smartphones to produce a global map of weather conditions. 

As Moore’s Law marches on, the supercomputers we carry around with us every day can do more than ever. Modern smartphones have a suite of sensors built into them that measure position and motion, pressure and temperature, and GPS and compass location. In a paper prepared for the Bulletin of the American Meteorological Society, atmospheric scientist and weather blogger Clifford Mass wrote about smartphones’ potential as a sensor network (PDF). Given the penetration rate of smartphones and the adoption of sensor technology, Mass and his co-author estimate that smartphones could increase weather data volume 10,000 times.

British startup company OpenSignal created a crowdsourcing smartphone app that measures cellular and WiFi signal coverage. Along the way OpenSignal’s developers noticed something interesting about the data coming from the smartphone’s battery temperature sensor. It lets the smartphone know when the lithium-ion battery is too hot to charge safely. The heat produced inside the phone, combined with the owner’s body heat, shouldn’t let the sensor measure air temperature. But it can. 

Working with the Royal Meteorological Society of the Netherlands, they published a peer-reviewed paper demonstrating the accuracy of smartphone temperature measurements. The researchers developed a heat transfer model that lets them derive the air temperature from the battery data. The researchers analyzed 2.1 million data points collected from people in eight cities over a four month period. Their calculations came within a few degrees of government weather stations’ official readings.

OpenSignal launched the WeatherSignal app for Android smartphones in 2013. It collects temperature, air pressure, humidity, and magnetic field data. The app adds time and location data before sending them to WeatherSignal’s service. With over 45,000 people regularly submitting data, WeatherSignal has become the largest amateur weather network in the world.

WeatherSignal has some limitations. It depends on people choosing to download and run its app. It also depends on people having Android smartphones with the full suite of sensors. On top of that, nobody knows how the varied urban environment and the different ways people carry their smartphones affects the data. Researchers at Birmingham University’s Climate Lab will compare the WeatherSignal data to their dense network of weather stations to document how well smartphones serve as portable weather sensors.