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Last Updated: Wednesday, 14 July, 2004, 13:11 GMT 14:11 UK
China rain-making creates a storm
Relations between neighbouring Chinese cities have become stormy over the use of controversial technology which encourages rainfall.

Drought-stricken central Henan province has been using a method called cloud seeding, in which chemicals are shot at clouds, the China Daily reported.

The method did bring rain to Henan - but not equally to all areas.

Meteorological officials in one city accused neighbouring colleagues of over-using the method, the paper said.

Graphic showing how clouds are seeded
1. Aircraft or artillery spray chemicals (often silver iodide or dry ice) into clouds to encourage tiny vapour droplets to coalesce
2. Droplets of supercooled water (liquid below freezing) coalesce into snow and melt as they fall
3. Heat released as the droplets freeze boosts updrafts, which pull more moist air into the cloud
The five cities of Pingdingshan, Zhumadian, Luohe, Xuchang and Zhoukou have all been suffering from drought, but were finally blessed with rain as a result of cloud seeding on Saturday, the China Daily reported.

However, while Pingdingshan received more than 100mm of rainfall, less than 30mm fell on Zhoukou.

One Zhoukou official accused Pingdingshan of intercepting clouds that would probably have drifted to other places.

"They (Pingdingshan) were still launching rockets to make rain when they already had rain falling," he is reported as saying.

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.

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