|Extreme Weather: Lightning
Atmospheric Electrostatic Discharges on Planet Earth
Lightning is a flash of light in the sky caused by an electrical discharge between clouds or between a cloud and the Earth's surface.
The flash heats the air and usually causes thunder. Lightning may appear as a jagged streak, as a bright sheet, or in rare cases, as a glowing red ball.
There are some 16 million lightning storms in the world every year and lightning kills more people than hurricanes, tornadoes and snowstorms.
Dr Nick Middleton of Oxford University investigates some of Britain's
most extreme weather conditions, to find out how they are caused, and
why they are so dangerous.
This programme looks at perhaps the
most mysterious and spectacular weather phenomenon: lightning.
Middleton investigates how the raw electric power of lightning is
created, and the dire consequences that occur if we are unlucky enough
to find ourselves in the path of a lightning bolt.
Why are some
buildings set alight by lightning when others remain untouched? How is
it that planes can fly into thunder and lightning storms, and still
Lightning is an atmospheric electrostatic discharge (spark) accompanied by thunder, which typically occurs during thunderstorms, and sometimes during volcanic eruptions or dust storms.
From this discharge of atmospheric electricity, a leader of a bolt of lightning can travel at speeds of 220,000 km/h (140,000 mph), and can reach temperatures approaching 30,000 °C (54,000 °F), hot enough to fuse silica sand into glass channels known as fulgurites which are normally hollow and can extend some distance into the ground.
There are some 16 million lightning storms in the world every year. Lightning causes ionisation in the air through which it travels, leading to the formation of nitric oxide and ultimately, nitric acid, of benefit to plant life below.
Lightning can also occur within the ash clouds from volcanic eruptions, or can be caused by violent forest fires which generate sufficient dust to create a static charge.
- Roy Sullivan held a Guinness World Record after surviving 7 different lightning strikes across 35 years.
- In July 2007, lightning killed up to 30 people when it struck a remote mountain village Ushari Dara in northwestern Pakistan.
- On 31 October 2005, sixty-eight dairy cows, all in full milk, died on a farm at Fernbrook on the Waterfall Way near Dorrigo, New South Wales after being struck by lightning. Three others were paralysed for several hours but they later made a full recovery. The cows were sheltering under a tree when it was struck by lightning and the electricity spread onto the surrounding soil killing the animals.
NOVA (PBS) - Lightning! (1995)
How lightning initially forms is still a matter of debate:
Scientists have studied root causes ranging from atmospheric perturbations (wind, humidity, friction, and atmospheric pressure) to the impact of solar wind and accumulation of charged solar particles.
Ice inside a cloud is thought to be a key element in lightning development, and may cause a forcible separation of positive and negative charges within the cloud, thus assisting in the formation of lightning.
The irrational fear of lightning (and thunder) is astraphobia. The study or science of lightning is called fulminology, and someone who studies lightning is referred to as a fulminologist.
Notable Lightning Strikes
Some lightning strikes have caused either numerous fatalities or great damage.
The following is a partial list:
- In 1660, lightning struck the gunpowder magazine at Osaka Castle, Japan; the resultant explosion set the castle on fire. In 1665, lightning struck the main tower of the castle and it burned down to the foundation.
- A particularly deadly lightning incident occurred in Brescia, Italy in 1769. Lightning struck the Church of St. Nazaire, igniting the 100 tons of gunpowder in its vaults; the resulting explosion killed 3000 people and destroyed a sixth of the city.
- 1902: A lightning strike damaged the upper section of the Eiffel Tower, requiring the reconstruction of its top
- December 8, 1963: Pan Am Flight 214 crashed as result of a lightning strike, killing all 81 people on board.
- July 12, 1970, the central mast of the Orlunda radio transmitter collapsed after a lightning strike destroyed its basement insulator.
- December 24, 1971: LANSA Flight 508 crashed as a result of lightning in Peru, with 91 people killed.
- November 2, 1994, lightning struck fuel tanks in Dronka, Egypt and caused 469 fatalities.