OLYMPICS/ Spotlight
Beijing warned of lightning during Olympic season
(Xinhua)
Updated: 2007-08-17 17:17
An electric current, lightning is a bright flash of electricity produced by a thunderstorm. All thunderstorms produce lightning and are dangerous. Within a thundercloud way up in the sky, many small bits of frozen raindrops bump into each other as they move around in the air, which creates electric charges.
The China Meteorological Administration released that lightning disasters resulted in 12 deaths, 30 injuries and 246 damage reports from 1997 to 2005 in Beijing.
The meteorologists employed four indexes for evaluating vulnerability of lightning disaster areas in Beijing. The indexes include flash density which is from data gathered by satellite-board lightning imaging sensor (LIS) and optical transient detector (OTD), historical disaster frequency, economic vulnerability module and population-related vital vulnerability module.
Analyzing the vulnerability degrees, the meteorologists summarized that districts of Dongcheng, Xicheng and Fengtai are the most vulnerable while Haidian, Chaoyang and Tongzhou districts are among the second tier of vulnerability.
Compared with other parts in north China, Beijing is more likely to be hit by thunderstorms and lightning due to geography and meteorological conditions, the experts said.
Historical data showed that the flash density in the northeastern part of Pinggu County was as high as 16 times per square kilometer per year.
The sky over Beijing has been monitored by the country's best facilities. There are four lightning monitors covering most areas of Hebei Province, which is adjacent to Beijing. A Doppler radar takes the mission of scanning 300 square kilometers surrounding Beijing. In addition, a satellite surveys most part of north China, Guo said.
Guo said the prediction and warning system is able to produce the next 24-hour thunderstorm potential objective forecast and the next 2-hour thunderstorm warning.
The real-time radar and other parts of the monitoring system would collect lightning and sounding data, which are automatically categorized by the BMO neural networks. Meteorologists then use the dynamic fit for tracking algorithm to analyze the mobile vector of thunderstorms and, subsequently, forecast areas which would be possibly affected by the thunderstorms.
The BMO tested its contingency plan for thunderstorm forecast service around August 8, exactly one year before the opening ceremony of the 2008 Beijing Olympics. The BMO reported three times on possible thunderstorms, gales or lightnings to the Olympic organizing committee. At least six additional observation points have been built around the Olympic venues for weather surveillance.
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