'Dropped' calls may measure rainfall

We know that cellphone calls break up and crackle when it rains. But did you ever think that tracking this disruption in cellphone signals could help you calculate the amount of rainfall?

Now researchers in Burkina Faso, a landlocked country in West Africa, have done just that.

Scientists demonstrated that cell phone towers can be used as modern-day rain gauges to accurately collect rainfall data.

"The information collected through cell phone networks can be used to build a local rainfall record that could help the city predict if a large storm could trigger a flood," said Marielle Gosset, a hydro-meteorologist at Geosciences Environment Toulouse in France.

Just like a glass of water absorbs, scatters, and refracts light passing through it, raindrops between cell phone towers both absorb the energy of a microwave link and scatter it in different directions, altering the signal that gets through.

Using data on microwave signal strength shared with them by telecom company Telecel Faso, the researchers calculated how much and for how long it rained.

To test the accuracy of the data, they compared their rainfall results with rain gauges and weather radar, and found their data to be 95 percent accurate.

The technique can benefit places where rain gauge networks are sparse, while the number of cell phone towers is increasing as more people acquire cell phones.

The study is set to be published in a forthcoming issue of the journal Geophysical Research Letters.