Storms in Africa? Get your brolly

IT SOUNDS more like folklore than science, but meteorologists have discovered that lightning in Africa could be a warning of cloudy skies in Britain.

Thunderstorms over central and east Africa were found to create an electrical charge in the sky above Scotland, 8,000 miles away.

The researchers say this “fair weather electric field” could influence the weather by triggering clouds and even rain.

The finding has been hailed as an example of the “butterfly effect”, in which a seemingly minor event has a big impact elsewhere.

“This shows just how intricate the climate system is,” said Prof Giles Harrison, head of the department of meteorology at the University of Reading and leader of the research team.

“A current flows from the tropical thunderstorms into the ionosphere [upper atmosphere] and back down again to regions where there are clear skies. It can be thought of as a kind of giant electric circuit looping around the Earth.”

Prof Harrison and his colleagues, writing in the Institute of Physics journal Environmental

Research Letters, explain a phenomenon that has baffled scientists since 1753, when LouisGuillaume Le Monnier, a French scientist, discovered that the atmosphere could become electrified even on clear days. An electric charge is usually associated with cloudy days.

Prof Harrison analysed 60 years of Met Office data on the electrical field above Lerwick in Shetland, and found that peaks in the electric field at times when skies were blue correlated with times of thunderstorms in Africa. Smaller peaks also coincided with storms in Australia and America, indicating a global circuit of electrical activity.

He also showed that electrical activity could help to turn water droplets in clouds into larger drops, increasing the chances of rainclouds and rain.