This article was taken from the June 2011 issue of Wired magazine. Be the first to read Wired's articles in print before they're posted online, and get your hands on loads of additional content by subscribing online.
The weary traveller who spies a puddle in the desert may no longer have merely fallen foul of a mirage.
Scientists in Abu Dhabi claim to have developed the technology to create downpours in one of Earth's most parched climates. Jim Dale, senior risk meteorologist at British Weather Services, explains how these techniques could work.
Kick up some dust "To make rain, you need nuclei (dust) for water droplets to form around," says Dale. Abu Dhabi has ionisers -- 10m-high poles topped by a 2m squared electric grid that generates negatively charged particles -- to send dust into the atmosphere.
Optimise humidity
The hot desert air aids sending the negatively charged particles high into the sky by convection. Meteo Systems, which makes ionisers, claims you'll need humidity levels of around 30 per cent at ground level before switching on the emitters.
Charge particles
The theory is that at the right altitude, the particles attract water molecules in the atmosphere, which will begin to condense around them. The longer these stay at this altitude, the more chance of clouds forming, and then water droplets.
Seed clouds
Alternatively, an aircraft can "seed" the atmosphere with dry ice (CO2) or silver iodide. Dale explains: "The idea is that the nuclei grow into a crystal large enough to produce precipitation." Bigger crystals mean bigger drops of water.
This article was originally published by WIRED UK
