April 11, 2008

Beijing to Use Rockets to Prevent Rain at Olympics

To prevent rain clouds from ruining the Olympics opening ceremony, China is preparing an arsenal of rockets and aircraft to disperse clouds so that dignitaries in the roofless "bird's nest" stadium don't get wet.

The Chinese government is well known for its use of cloud seeding, a form of weather modification, which is the attempt to change the amount or type of precipitation that falls from clouds, by dispersing substances into the air that serve as cloud condensation or ice nuclei.

Officials say there is a 47 percent chance of rain during the August 8 opening ceremony and a 6 percent chance of a heavy downpour. They hope to drain the humidity from the clouds before they reach Beijing.

At least 21 stations with a staff of over 100 people surround the city. If the call comes, they will have 10 minutes' notice to fire rockets or cannons containing silver iodide at approaching clouds in an attempt to drain them before they reach the stadium.

Three aircraft will also be on stand-by to drop catalysts to unleash rain from the clouds.

"We've worked with neighboring provinces on a contingency plan for rainstorm and other weather risks during the ceremonies," said Wang Yubin, the deputy chief of China's meteorological service assigned to the Olympics.

The government has spent $500,000 over the last five years to build up Beijing's cloud seeding capacities and authorities will conduct trial runs in June and July.

It typically uses pellets of silver iodide, which is highly insoluble in water and can concentrate moisture to cause rain. Silver iodide (AgI) is a chemical compound used in photography and as an antiseptic in medicine. Silver iodide is highly insoluble in water and has a crystalline structure similar to that of ice, causing it to induce freezing in cloud seeding for the purpose of rainmaking.

"I hope God will not send any storms to Beijing," said Zhang Qiang, head of Beijing's Weather Modification Office.

She believes her staff can fend off drizzle, but could be powerless in the face of a heavy downpour.

The People's Republic of China has the largest cloud seeding system in the world; they believe that it increases the amount of rain over several arid regions where rain is desired. There is even political strife caused by neighboring regions which accuse each other of "stealing rain" using cloud seeding.


On the Net:

Beijing Olympics

Cloud Seeding - Wikipedia