China to modify weather for Olympics

August is part of Northeast Asia’s rainy season (upper picture) and chances of precipitation over Beijing on any day that month will approach 50 percent.

To prevent rain over the roofless 91,000-seat Olympic stadium that Beijing natives have nicknamed the Bird’s Nest (lower picture), the city’s branch of the national Weather Modification Office–itself a department of the larger China Meteorological Administration–has prepared a three-stage program for the 2008 Olympics this August.





The city’s weather engineers will shoot and spray silver iodide and dry ice into incoming clouds that are still far enough away that their rain can be flushed out before they reach the stadium.

Finally, any rain-heavy clouds that near the Bird’s Nest will be seeded with chemicals to shrink droplets so that rain won’t fall until those clouds have passed over. Zhang Qian, head of Beijing’s Weather Modification Office, explains, “We use a coolant made from liquid nitrogen to increase the number of droplets while decreasing their average size. As a result, the smaller droplets are less likely to fall, and precipitation can be reduced.”

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