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