Beijing has successfully managed to stop light rainfall in experiments aimed at guaranteeing a dry opening ceremony at August's Olympic Games, officials said.

With no roof on the showpiece Bird's Nest stadium, the Beijing Meteorological Bureau has been charged with developing methods of preventing wet weather spoiling what promises to be a spectacular start to the Games on the evening of August 8.

"Our experiments with rain mitigation have been aimed at light rain," Zhang Qian, head of weather manipulation at the bureau, told a news conference.

"With heavy rain it is more difficult. The results with light rain have been satisfactory."

Qian said different strategies were used to stop rain on different types of clouds, but both had proved not to harm the environment.

"For cold clouds below zero degrees (Celcius), we use a coolant made from liquid nitrogen to increase the number of droplets while decreasing their mean size," she added.

"As a result, the smaller droplets are less likely to fall and precipitation can be reduced.

"For clouds above zero degrees we use the seeding agent silver iodide to accelerate the droplets' collision and coalescence, producing a downdraft which suppresses the formation of clouds."

China has long used weather manipulation to increase rainfall in the parched north of the country, firing seeding agents into the clouds using anti-aircraft guns.

This method might also be used to prevent wet weather at the stadium by inducing the rain to fall before it reaches the target area, said Wang Yubin, deputy chief engineer at the bureau.

"Rain mitigation is a very complex process, though," he added.

The weather bureau is also working hard on preparing for one of the pre-Games highlights, the ascent of the Olympic torch to the top of Mount Everest.

"We will have very detailed forecasts," Wang added. "We will be able to tell the organisers: the winds are too strong, you cannot do it on this day, or, you can do it on this day."

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