Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Lightning really does strike more than twice

16.01.2003


NASA-funded scientists have recently learned that cloud-to-ground lightning frequently strikes the ground in two or more places and that the chances of being struck are about 45 percent higher than what people commonly assume.




Recently, William C. Valine and E. Philip Krider in the Institute of Atmospheric Physics at the University of Arizona, co-authors of the study, took to the field using video and other technology to study lightning, which is one of the biggest weather-related killers in the United States, superseded only by extreme heat and flooding.

They recorded 386 cloud-to-ground (CG) lightning flashes on videotape during the summer of 1997 in Tucson, Arizona. They found that within their sample of 386 flashes, 136 flashes (35 percent) struck the ground in two or more places that were separated by tens of meters (yards) or more. There were a total of 558 different strike points; therefore, on average, each cloud-to-ground flash struck the ground in 1.45 places.


"Most people assume that lightning strikes in only one place. In this research, we’ve documented that lightning definitely strikes more than one place about a third of the time," Krider said. "If you want to quantify the chances of being struck by lightning, they are about 45 percent higher than the number of flashes because, on average, there are about 1.45 strike points per CG flash."

Within that group of 136 flashes, termed "multiple channel flashes," 88 had two or more separate and distinct channels (or paths) between the cloud base and the ground. Thirty-seven of the flashes forked below the cloud base and struck ground in two or more places. Eleven flashes exhibited both types of behavior. In other words, during the observations in Arizona, for every fork below the cloud there were approximately twice as many flashes that had separate and distinct paths, a ratio that is consistent with previous measurements in Florida.

Valine and Krider also confirmed that after an initial stroke, 67 percent of the new strike points were produced by the second stroke in the flash, rather than the third or fourth stroke. In other words, if any subsequent stroke is going to strike a place different from the first stroke, it is usually the second stroke that does so. The third and fourth strokes usually follow the same path as the second stroke.

Lightning occurs when there is a discharge of electricity between large volumes of excess positive and negative charge that accumulate in thunder clouds. Lightning most commonly occurs in thunderstorms, but it also can occur in snowstorms, sandstorms, in the ejected material over volcanoes. Most lightning takes place within or between clouds; on average, only about one-third of all discharges actually strike the ground. The peak temperature in a lightning channel is around 60,000 degrees Fahrenheit, or about 5 times hotter than the surface of the Sun.

According to the National Weather Service, lightning causes an average of 93 deaths and 300 injuries in the United States each year. The National Severe Storms Laboratory recommends that a safe distance from a previous flash is at least 10 to 13 km (6 to 8 miles) as opposed to the 3 to 5 km (2-3 miles) that experts had previously advised.

The article appears in the latest print issue of the American Geophysical Union’s Journal of Geophysical Research - Atmospheres, and publication of the results was funded entirely by NASA.

For additional information and images, see: http://www.gsfc.nasa.gov/topstory/2003/0107lightning.html

For more information about lightning and lightning safety, see: http://www.erh.noaa.gov/er/cae/svrwx/ltg.htm

The National Severe Storms Laboratory on Lightning: http://www.nssl.noaa.gov/researchitems/lightning.shtml

Global Hydrology and Climate Center (GHCC) Lightning Team:
http://thunder.msfc.nasa.gov/

Rob Gutro | EurekAlert!
Further information:
http://www.gsfc.nasa.gov/topstory/2003/0107lightning.html
http://www.erh.noaa.gov/er/cae/svrwx/ltg.htm
http://www.nssl.noaa.gov/researchitems/lightning.shtml

More articles from Earth Sciences:

nachricht By saving cost and energy, the lighting revolution may increase light pollution
23.11.2017 | Helmholtz-Zentrum Potsdam - Deutsches GeoForschungsZentrum GFZ

nachricht Frictional Heat Powers Hydrothermal Activity on Enceladus
23.11.2017 | Universität Heidelberg

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Frictional Heat Powers Hydrothermal Activity on Enceladus

Computer simulation shows how the icy moon heats water in a porous rock core

Heat from the friction of rocks caused by tidal forces could be the “engine” for the hydrothermal activity on Saturn's moon Enceladus. This presupposes that...

Im Focus: Nanoparticles help with malaria diagnosis – new rapid test in development

The WHO reports an estimated 429,000 malaria deaths each year. The disease mostly affects tropical and subtropical regions and in particular the African continent. The Fraunhofer Institute for Silicate Research ISC teamed up with the Fraunhofer Institute for Molecular Biology and Applied Ecology IME and the Institute of Tropical Medicine at the University of Tübingen for a new test method to detect malaria parasites in blood. The idea of the research project “NanoFRET” is to develop a highly sensitive and reliable rapid diagnostic test so that patient treatment can begin as early as possible.

Malaria is caused by parasites transmitted by mosquito bite. The most dangerous form of malaria is malaria tropica. Left untreated, it is fatal in most cases....

Im Focus: A “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

Im Focus: Novel Nano-CT device creates high-resolution 3D-X-rays of tiny velvet worm legs

Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.

During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

Water cooling for the Earth's crust

23.11.2017 | Earth Sciences

Nano-watch has steady hands

23.11.2017 | Physics and Astronomy

Batteries with better performance and improved safety

23.11.2017 | Power and Electrical Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>