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)