Weather & Climate,Physics Where will lightning...

Weather & Climate, Physics

Where will lightning strike?Dangerous and dazzling, thunderbolts give scientists a peek into storms

By Stephen Ornes 8:49am, September 16, 2014

Sean McQuilken (left) and his brother Michael (right) were hiking in California when their hair stood on end.Lightning struck minutes later, injuring Sean and killing another hiker.

Michael McQuilken

Michael McQuilken will never forget the day lightning struck his younger brother.

On August 20, 1975, he and Sean hiked to the top of Moro Rock together withtheir sister Mary and her friend Margie. This granite dome resides in California’sSequoia National Park. As dark clouds gathered overhead, a light rain started tofall. Another hiker noticed Mary’s long hair standing on end.

Michael snapped his sister’s picture. Laughing, Mary told him that his hair, too,

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This heat map highlights lightning strikes aroundthe world. Areas with warmer colors (red andyellow) receive more lightning per squarekilometer than regions in blue. Central Africa issubject to the most lightning; polar regions seethe least.Jeff De La Beaujardiere, Scientific VisualizationStudio

was standing on end. So was Sean’s. Michael passed the camera to Mary, whotook a photo of her smiling brothers. Then the temperature fell, bringing hail,Michael recalls. So their team headed down. They didn’t realize they were indanger. Immediate danger.

Within minutes, lightning would injure Sean — and kill another hiker nearby.

Being struck by lightning is very unlikely but very dangerous. Lightning heats theair to nearly 28,000° Celsius (50,000° Fahrenheit). That’s energetic enough tobreak the molecules in the air into individual atoms.

No wonder lightning can be fatal.

Around the world, lightning occurs about100 times every second of every day. Mostof those strikes don’t touch anyone. Butlightning does injure about 240,000people and kill 24,000 each year,according to a 2003 study. In 2012, 28people died from lightning in the UnitedStates. Overall, that means that onaverage, lightning strikes about one inevery 700,000 people there each year.

Although dangerous, lightning also is oneof nature’s most dazzling displays. Forcenturies, scientists have been trying tounderstand what triggers lightning. Moreimportantly, they want to know where —or who — lightning is likely to hit. Researchers have looked for common threads inthe stories of lightning’s victims. They’ve tracked flashes using sensors on theground and in space, including one on the International Space Station. And theyhave created lightning in the laboratory.

However, scientists are still struggling to understand exactly how a spark startsand how to predict where it might connect with the ground. Some researcherseven suspect lightning could be used as a tool to better understand the globalclimate — if they only knew how to wield it.

Warming up

Thousands of years ago, people associated lightning’s sparks with angry gods. Inancient Norse mythology, the hammer-wielding god Thor hurled lightning bolts athis enemies. In the myths of ancient Greece, Zeus threw lightning from atopMount Olympus. The early Hindus believed the god Indra controlled lightning.


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Lightning can move from cloud to cloud or from acloud to the ground.Sean Waugh NOAA/NSSL

But over time, people began associating lightning less with supernatural forcesand more with nature.

Scientists now know that the visible,bright bolt and roaring thunder are just asmall part of a much bigger sequence ofnatural events that unfolds in the clouds.It begins when heat from the sun warmsEarth’s surface. Water vapor evaporatesfrom lakes, seas and plants. That warmmoist air is lighter than cooler dry air, so itrises to form giant cumulonimbus clouds.These clouds often give birth to storms.

“Thunderstorms are like huge vacuumcleaners that suck up water vapor,” saysColin Price. He’s an atmospheric scientistat Tel Aviv University in Israel. “Some gets vented out the top of storms,” he saysof the water vapor. But most of it in the upper atmosphere comes from Earth'ssurface.

Scientists suspect that turbulence within a cloud — strong vertical winds — causesthe cloud’s water droplets, snow, hail and ice particles to smash into each other.These collisions can pry particles called electrons from the water drops and ice asthey rise to the top of the cloud. Electrons are responsible for electricity. When anuncharged object loses an electron, it is left with an overall positive charge. Andwhen it gains an electron, it gains a negative charge.

Water droplets, ice and hail come in a range of sizes. Large ones sink to thebottom of the cloud. Small ice crystals rise to the top. Those tiny ice crystals atthe top tend to become positively charged. At the same time, the large hail andwater droplets at the cloud’s bottom tend to become negatively charged. As such,Price likens a storm cloud to a battery standing on end.

Those charges in the clouds can cause changes on the ground. When the lowerpart of the cloud becomes negatively charged, objects in the air and on theground below become positively charged.

On that day back in 1975, positive charges climbed through the hikers’ hair,standing it on end. (To safely see something similar to this firsthand, rub yourhead with a balloon to transfer electrons from your hair to the balloon. Then liftthe balloon.) The hikers’ hair-raising experience might have looked funny — but italso was a warning sign that conditions were right for a lightning strike.

Ka-boom!


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Lightning follows a jagged path to get from acloud to the ground.NOAA

As they were coming down from Moro Rock, the hikers saw lightning's fury upclose. Too close.

“My entire vision was nothing but brightwhite light,” McQuilken says of the strike.“Margie, who was about 10 feet behindme, says she saw tentacles or ribbons oflighting.” The bolt knocked McQuilken tothe ground. Time, he recalls, appeared toslow down. “The entire experienceoccurred in a matter of milliseconds, butthat feeling of floating and moving my feetin the air seemed to last five or tenseconds.”

The lightning missed Michael, Mary andMargie, but not eight-year-old Sean.McQuilken found his brother on his knees with smoke “pouring from his back.”Sean’s clothes and skin were badly burned. But he was alive and would survive.McQuilken carried his brother down from the granite dome to get him help.Another hiker nearby was not so lucky. Lightning killed him.

Air between the ground and a cloud usually separates their charges. The air actslike an insulator, which means electricity — such as lightning's giant spark — can'ttravel through it. But when enough charge accumulates in the cloud, it finds a wayto get to the ground, and lightning strikes. This electrical discharge zips from oneplace to another to even out the imbalance in charge between the ground and thetop of the cloud. The discharge may move from cloud to cloud, or it may zap theground.

That’s no mystery.

But what causes lightning to start its spark is “one of the great unansweredquestions in lightning physics,” explains Phillip Bitzer. He’s an atmosphericscientist who studies lightning at the University of Alabama in Huntsville.

Looking for the spark

Scientists think lightning sparks in one of two ways. According to one idea, thecharged hail, rain and ice inside a storm cloud magnifies the electric field withinthe cloud. (An electric field is the region where the charges can do work.) Thatadded boost gives the charges enough oomph to spark lightning. The other idea isthat lightning is sparked when cosmic rays, powerful bursts of energy from space,deliver particles with enough energy to launch a strike.


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Phillip Bitzer, who studies lightning at theUniversity of Alabama in Huntsville, helpeddevelop this sensor. It sits on top of a universitybuilding and can measure the electric field of alightning strike.Mike Mercier/UAH

To better understand how lightning starts,Bitzer helped design a new sensor. It lookslike a large, upside-down salad bowl. Andit's one of several scattered in and aroundHuntsville (including atop a universitybuilding).

Together, these sensors make up the Huntsville Alabama Marx Meter Array, orHAMMA. When a storm passes by and abolt of lightning flashes, HAMMA candetermine where the strike happened. Italso measures the electric field producedby the strike. Its sensors can peer inside acloud during that critical split-secondbefore lightning develops. Bitzer describedHAMMA’s first successful tests in Journal ofGeophysical Research: Atmospheres on April 25, 2013.

HAMMA also measures lightning’s return stroke. This is the second — and moreenergetic — part of a strike.

Lightning begins with a leader. This stream of negative charge leaves the cloudand searches for a path through the air to the ground. (In rare cases, leaders starton the ground and move upward.) Though every strike is different, a leader maytravel about 89,000 meters (290,000 feet) per second. It often looks branched. Ittends to produce dim light that can only be caught by high-speed cameras.

The leader's path can conduct electricity through the cloud. The return stroke,which comes from the ground, follows the path laid out by the leader likeelectricity on a wire. It moves in the opposite direction. And it’s more intense: Thereturn produces the blinding flash that can be seen day or night. That’s the partyou’re most likely to notice. Compared to the leader, the return stroke is a speeddemon. It can travel 90 million meters (295 million feet) per second — or more. Bytracking this return stroke, HAMMA can help scientists better track the totalenergy unleashed during a strike. Such energy data, from HAMMA and othernetworks, could help scientists determine how lightning strikes start.

Besides his work on HAMMA, Bitzerhelps make devices that detectlightning from space. When theGOES-R weather satellite heads intoorbit in 2015, it will carry theGeostationary Lightning Mapper.That device, partly developed at the University of Alabama in Huntsville, will track

Watch lightning travel from a cloud to the groundin slow-motion.

PHILLIP BITZER


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It’s not common, but sometimes lightning strikeswhen a tornado is on the ground.National Weather Service/F. Smith

lightning flashes from above. It’s not the first device to watch lightning fromspace, but it will improve on previous efforts.

“At the present time, we don’t have good global coverage of lightning,” says Price,at Tel Aviv University. “However, in the next few years, satellites with opticalsensors will look at Earth continuously.” That will let scientists connect lightningstrikes to other weather phenomena, such as hurricanes and tornadoes. Thesedata also may show whether climate change has been altering lightning patterns.

The pulse of the storm

Price says lightning strikes are like the pulse of a storm. By tracking how oftenlightning sparks, scientists can learn something about a storm’s behavior.

Price worked on a study of hurricanes published in 2009. It found a connectionbetween lightning strikes and the intensity of those storms. Price and hiscolleagues studied data from 58 hurricanes and compared them to records oflightning strikes. The intensity of lightning peaked about 30 hours before thehurricane winds reached their maximum.

That connection could help scientists predict when the worst part of a hurricane iscoming — and warn people to prepare or evacuate before it’s too late.

Price also has investigated lightningbehavior during big, non-hurricane storms.Lightning seems to “ramp up” before atornado touches down, he’s found — eventhough there’s little lightning when thetornado is on the ground. In addition,lightning activity changes by day andnight, and from season to season, Priceand his colleagues showed. For instance,lightning activity increases during times ofwarmer temperatures — during the dayand in seasons when the Earth gets moreheat from the sun. One example: ElNiño events when the Earth is slightlywarmer.

It even appears that lightning can change its behavior, Price finds.

He has been studying connections between lightning and climate change. In a2013 paper, he showed how rising temperatures due to global warming can boostlightning activity. He published his findings in the journal Surveys in Geophysics.


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Moments after this picture was taken of MaryMcQuilken, her brother Sean was struck bylightning. Overall, fewer women are struck bylightning than men. But if you can hear thunder,you may be at risk of being struck, scientists say.Another clue: Beware of hair standing on end.Michael McQuilken

How not to get struck

Of the people killed by lightning in the United States between 2006 and 2012,most were enjoying outdoor activities. That’s the finding of a 2013 study by theNational Weather Service (NWS).

“Being outside is dangerous any time there’s a thunderstorm in the area,” saysJohn Jensenius. The NWS meteorologist in Silver Spring, Md., tracks lightningdeaths and studies lightning safety. He also worked on the 2013 study.

People fishing in small boats — mostly on lakes and streams — or standing nearthe shore accounted for most of those deaths. In second place: peopleparticipating in outdoor sports. Here, soccer led the pack in terms of lightningfatalities. And though golfers have a reputation for being particularly susceptibleto lightning, golf, Jensensius says, is “down the list quite a ways.” (Lightning killedseven times as many anglers as golfers.)

On average, lightning also kills about fourtimes as many men as women. Jenseniushas some ideas about why.

“It’s probably a combination of things,” hesays. “Men may be outside doing morevulnerable activities than women. Or menmay be more reluctant to go inside if theyhear thunder.”

Lightning even can send jolts throughelectrical or water lines into a house,injuring the people inside. That’s why,Jensensius says, it’s a bad idea to bathe,wash dishes or use appliances during astorm.

Thunder is the key to safety, he pointsout. Most lightning strikes occur within athunderstorm, but a small percentage canreach miles from the storm center. Sogoing inside only when it starts to rainwon’t keep a person safe. Indeed,Jensenius warns, if you can hear thunder,you are probably within reach of alightning strike. Certainly, he advises:“When thunder roars, go indoors.”


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Michael McQuilken has taken that advice to heart. He’s still an avid hiker andmountaineer (as well as a professional drummer). If a storm is brewing and “I seeclouds beginning to form around a summit, I call it a day,” he says. “Some peoplethink I’m being overcautious. But I don’t want to experience a lightning strike everagain.”

Power Words

angler A term for someone who fishes for food, usually for personalconsumption, not on an industrial scale.

atmosphere The envelope of gases surrounding Earth or another planet.

atom The basic unit of a chemical element. Atoms are made up of a densenucleus that contains positively charged protons and neutrally charged neutrons.The nucleus is orbited by a cloud of negatively charged electrons.

battery A device that can convert chemical energy into electrical energy.

climate change Long-term, significant change in the climate of Earth. It canhappen naturally or in response to human activities, including the burning of fossilfuels and clearing of forests.

cosmic rays Very high-energy particles, mostly protons, that bombard Earthfrom all directions. These particles originate outside our solar system. They areequivalent to the nucleus of an atom. They travel through space at high rates ofspeed (often close to the speed of light).

cumulonimbus A cloud forming a towering mass with a flat base at fairly lowaltitude and often a flat top. These clouds can give rise to thunderstorms.

electric charge The physical property responsible for electric force; it can benegative or positive.

electric field A region around a charged particle or object within which a forcewould be exerted on other charged particles or objects.

electron A negatively charged particle; the carrier of electricity within solids.

global warming The gradual increase in the overall temperature of Earth’satmosphere due to the greenhouse effect. This effect is caused by increasedlevels of carbon dioxide, chlorofluorocarbons and other gases in the air, many ofthem released by human activity.

greenhouse gas A gas that contributes to the greenhouse effect by absorbingheat. Carbon dioxide is one example of a greenhouse gas.


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insulator A substance or device that does not readily conduct electricity.

meteorologist Someone who studies weather and climate events.

molecule An electrically neutral group of atoms that represents the smallestpossible amount of a chemical compound. Molecules can be made of single typesof atoms or of different types. For example, the oxygen in the air is made of twooxygen atoms (O2), but water is made of two hydrogen atoms and one oxygenatom (H2O).

particle A minute amount of something.

supernatural Something that is attributed to unnatural forces, such as gods orghosts.

tornado A violently rotating column of air extending from the ground to athunderstorm above.

Word Find (click here to enlarge for printing)


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Source URL: https://student.societyforscience.org/article/where-will-lightning-strike

Where is lighting striking now, and how often? Check the World Wide LightningNetwork.

The National Weather Service offers more lightning safety tips here.

S. Perkins. “Does lightning sculpt mountains?” Science News for Students. Feb. 4,2014.

A. Grant. “Earthquake-triggered lightning.” Science News for Students. March 12,2014.

Original Journal Source: C. Price. Lightning applications in Weather and ClimateResearch. Surveys in Geophysics. Vol. 34, Issue 6, Nov. 2013, p. 755. doi:10.1007/s10712-012-9218-7

Original Journal Source: C. Price et al. Maximum hurricane intensity precededby increase in lightning frequency. Nature Geoscience. Vol. 2, online April 6, 2009,p. 329. doi: 10.1038/ngeo477

Original Journal Source: P. Bitzer et al. Characterization and applications ofVLF/LF source locations from lightning using the Huntsville Alabama Marx MeterArray. Journal of Geophysics Research: Atmospheres. Volume 118, April 27, 2013,p. 3120. doi: 10.1002/jgrd.50271

Original Source: J. Jensenius. A Detailed Analysis of Lightning Deaths in theUnited States from 2006 through 2013. NOAA, National Weather Service.

Classroom questions: Where will lightning strike?

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