Sue Broom looks at the science behind a weather modification technique known as cloud seeding.
Cloud seeding is a long-practised technology which uses rockets, planes, cannons or ground generators to fire particles, usually silver iodide, into clouds to encourage water vapour to gather round them and eventually fall as rain.
It's a technique that's used in many places all over the world - from Australia, Iran and South Africa to China and some of the drier States in the United States.
It is usually used to make rain, but it can also be used to prevent rain; by making clouds rain out before they reach the region where rain needs to be prevented.
Listen to the programme
First broadcast 5th August 2008
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