China held a rain reduction drill in Hohhot Wednesday to ensure that the opening and closing ceremonies of the Beijing Olympic Games next year will not be interrupted by rain.

Three planes carrying 30 technicians flew for about 3 hours within a 80 km-radius area about 8,000 meters high above Hohhot, capital city of north China's Inner Mongolia Autonomous Region, spreading silver iodide and 2,800 kg of diatomite into the clouds.

Although the clouds were not as thick as expected and other weather conditions were unfavorable, the drill still collected sufficient data, said Liu Xiaolin, official with the Inner Mongolia weather control office.

The two types of catalyzer help to absorb vapor in the cloud and prevent it from forming precipitation.

Apart from the commonly-used silver iodide, the environment-friendly diatomite, a kind of white or gray-colored mineral, was for the first time used in rain reduction in China, and its effect is yet to be further studied, said Liu.

Rain reduction only works in a small area, and it would fail in thick or large-scale clouds containing large amounts of water, according to Liu.

The drill, overseen by weather authorities of Beijing and Inner Mongolia, was just part of the rain reduction program to be launched if needed next August, a month when Beijing is prone to rain.

In addition to rain blocking above the venue area, cloud seeding will be made between 15 km to 120 km away to induce rainfall before it moves to the site of the event.

Rockets would be fired to disperse clouds in case of thunderstorms and other weather conditions which are too risky for piloted flights.

"We have done a good job in rainmaking, while more research and practices are needed in rain reduction," said Liu.

Beijing has set up 26 bases around the city to carry out rain reduction projects for the grand sports event next year.

The city has been trying to improve meteorological services to serve the event, including accurate weather forecast and air quality reports.

Liu denied suspects that the drill would worsen the drought plaguing the western and middle Inner Mongolia recently, saying the practice just temporarily suspend precipitation.

(Xinhua News Agency August 10, 2007)