Beijing Olympics' forecast - clear blue skies

BEIJING - Ravaged by a seven-year drought and choked by poisonous dust storms, China will "seed" the clouds looming over its cities with rockets and chemical pellets to bring welcome rain and clear its polluted skies for the Olympics in 2008.

China leads the world in using cloud seeding to induce rainfall. It has become a tradition in Beijing to seed the clouds ahead of major public holidays, to ensure rain disperses pollution, clears dust and ensures crystal clear skies.

China has pitched the Beijing Olympics in 2008 as the "Green Games" and as a showcase for the country's efforts to combat pollution and encourage sustainable energy use. The World Bank says 16 of the world's 20 most polluted cities are in China, and include Beijing. Officials in China say that economic losses caused by environmental pollution may account for about 10 per cent of China's GDP.

The joke commonly heard in Beijing is that the Government will close the factories and coal-fired power plants near the city for the duration of the Olympics. But cloud seeding is a more serious option which the Government will be examining.

Some studies show cloud seeding can increase precipitation by up to 30 per cent. It is often used in China to offset the effects of drought.

Much of the country is short of water, and the water table is dropping at an alarming rate in many places.

Weather specialists induced rain in early May in Beijing to help relieve drought and wash tonnes of dust from the Gobi desert dumped on the capital by a rash of sandstorms.

Artificially-induced rain was used to help put out three major forest fires that raged in north and northeast China for 10 days before they were subdued last Friday.

THE RAINMAKERS

* Chinese Air Force has flown 3000 rainmaking flights over the past five years.

* The flights released 210 billion cubic metres of water.

* Rainmaking rockets and shells are used in 1952 counties, employing 3000 people.

* They use 7000 cannons and 4687 rocket launchers.

HOW IT WORKS

* Cloud seeding began in the 1940s.

* Particles are injected into a cloud, which act as freezing nuclei.

* Cloud droplets stick to the particles and fall to the ground as rain or snow. The right clouds are needed for it to work.

* The earliest attempts at cloud seeding involved dropping pellets of crushed dry ice, or carbon dioxide, into the top of a cloud. Later, scientists used silver iodide because it was more effective.

- INDEPENDENT