Two meteorologists warned that Beijing would encounter a possibly high frequency of lightning during the Olympic season next summer and protection should be made in those particularly vulnerable areas.
The China Meteorological Administration (CMA) announced on Thursday that lightning strikes have killed 306 Chinese from June 25 to Aug. 16. To date, lightning has killed 499 Chinese. That is 199 more than the same period last year, the CMA reported. Figures from the CMA show that 19,982 accidents involving lightning strikes occurred in 2006 nationwide, claiming 717 lives and injuring 640 people.
In an academic paper submitted Thursday to the ongoing 13th International Conference on Atmospheric Electricity, Guo Hu, head of the Beijing Meteorological Observatory (BMO), and his fellow researcher Xiong Yajun concluded, after studying the 11-year lightning disaster data from 1995 to 2005, that Haidian District was the area most seriously affected by lightning disasters.
Haidian was among the high-frequency region of natural lightning while lots of universities, research institutes, tall buildings and electric equipment were based there, they said.
Most of the 31 Beijing Olympic venues are located in Haidian and some are open-aired. Many of the Olympic stadiums and gymnasiums are under construction, which are prone to be stricken by lightning.
The main venue, which is nicknamed as "bird nest" because of its shape, uses huge amount of steel and concrete. Construction workers are supplied with a detailed operation manual for the summer thunderstorm season.
During thunderstorms and lightning s, the manual prohibits workers from walking near edges of metal frames, climbing on tower cranes, using cell phones or walkie-talkies, or using solar-powered bathing facilities.
The manual also stipulates that high-rise cranes and other big machines, as well as electric appliances must have proper grounding and be equipped with additional safety protection devices.
A lightning disaster prevention expert Cai Zhenxin, who led the lightning protection system for the Shanghai International F1 Race Track, suggested a systematic layout of lightning protection in Olympic venues.
Besides the traditional preventive method of installing lightning rods and surge protection devices (SPDs), Cai suggested, a unified grounding web should be built for protecting electric appliances. Important cables and phone lines must be shielded by non-conducting materials.
"It'll be effective to channel all cables and lines into underground metal pipes at least 50 meters away from buildings," Cai said.
Cai also advised that computer centers and other rooms full of key electric equipment should be placed in middle floors of buildings.
Experts said lightning protection will be much more successful if precise forecast and early warning are issued.
Engineers are testing a new lightning positioning and tracking system (LPATS) over the Chinese capital. The system produces three-dimensional data on lightning and calculates lightning possibility of certain areas 30 to 60 minutes in advance. Early warning will be immediately sent to Olympic venues.
Chinese meteorologists are working to meet rigorous requirements of the International Olympic Committee (IOC) for an Olympic host country on issuing precise weather forecasts in every three hours.
The statistics showed that the lightning disaster frequency in Haidian is 4.73 times every year, which was followed by Fengtai, Chaoyang and Tongzhou at 2.5 times a year, Guo and Xiong said in the paper.
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 northeast part of Pinggu County was as high as 16 times per square kilometers 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 Aug. 8, exactly one year before the opening ceremony of the 2008 Beijing Olympics. The BMO reported three times on possible thunderstorms, gales or lightning s to the Olympic organizing committee. At least six additional observation points have been built around the Olympic venues for weather surveillance.
(Xinhua News Agency August 17, 2007)
