Tag Archives: lightning

This 768-km-long lightning flash over southern US is the longest ever recorded

Two separate lightning flashes, both occurring in 2020 in different parts of the world, have just been certified as the longest lightning strikes in recorded history. One is the longest in terms of distance, having stretched across 768 kilometers, the other is the longest-lasting lighting, having flashed for nearly 17.1 seconds before vanishing into the air.

The branching pattern overlaid over this grid map of the southern U.S. shows the extent of the current record holder for the longest lightning strike. Credit: WORLD METEOROLOGICAL ORGANIZATION.

The longest geographically-speaking lightning strike occurred above North America’s Great Plains on April 29, 2020, stretching across the southern United States, from Texas to Mississippi. Elsewhere, in the Río de la Plata basin in South America, a lightning strike flashed for about 17 seconds on June 18, 2020, during a thunderstorm that engulfed Uruguay and northern Argentina.

After careful measurements and double-checks, the Weather and Climate Extremes for the World Meteorological Organization (WMO) certified the two records and reported the findings this week in the Bulletin of the American Meteorological Society. According to the WMO, both new record ‘mega flashes’ were observed in hotspots for mesoscale convective system thunderstorms (a collection of thunderstorms that act as a system).

“These are extraordinary records from single lightning-flash events,” said Professor Randall Cerveny, rapporteur for the WMO. “Environmental extremes are living measurements of the power of nature, as well as scientific progress in being able to make such assessments,” Cerveny said. “It is likely that even greater extremes still exist, and that we will be able to observe them as lightning detection technology improves.” 

Since the 1950s, researchers have been aware of lightning discharges on the order of 100 km in length, thanks to radar-based findings. Later, around 1989, scientists discovered “sprites” — large-scale electrical discharges that occur high in the atmosphere at about 50−90 km, within so-called “mesoscale convective systems”. One such sprite, which formed in 2007 over Oklahoma, was 321 km in length, making it the longest officially documented lightning flash of its time. Since then increasingly larger lightning flashes have been recorded every year.

Left: new record for longest duration lightning flash. Right: the other record for the longest covered distance by a single lightning strike. Credit: WORLD METEOROLOGICAL ORGANIZATION.

The fact that the new record holder is hundreds of kilometers longer than those observed just a decade ago may sound startling. However, these findings are no indication that lightning is becoming more extreme — it’s just a matter of much better the monitoring instruments now at scientists’ disposal are.

Both record-holding flashes from 2020, just like previous other heavyweights more recently, were spotted by specialized instruments on geostationary satellites, which have a far wider field of view than radar and conventional weather monitoring stations. That’s not to say that climate change may not make extreme lightning more common. That’s something that scientists may establish several years from now once they’ve built a sizable historical record of lightning satellite observations.

That being said, lightning flashes aren’t all for show. They can start devastating fires and claim lives when they directly hit people. In the U.S., about 50 people are killed each year by lightning strikes, although 2021 saw a record-low number of lightning-related fatalities: only 11 deaths, according to the National Lighting Safety Council.

During dangerous thunderstorms, the World Health Organization (WHO) advises following the 30-30 rule – if the time between flash and thunder is less than 30 seconds, go inside and wait 30 minutes after the last observed flash to resume outdoor activities.

COVID lockdowns led to less lightning in the sky

Credit: Pixabay.

During the spring of 2020, when the coronavirus pandemic caught everyone with their pants down, governments scrambled to close their borders and impose strict lockdowns in order to curb the spread of a virus that was rife with uncertainty. Human activity slowed to a crawl and, as a result, the air and water became cleaner. Fewer vehicles on the road meant urban spaces became safer for animals and much quieter. There were even viral reports of dolphins in the canals of Venice, Italy, and pumas in the streets in Santiago, Chile, prompting many to triumphantly claim ‘nature is healing’.

The ‘healing’ part is hyperbolic, but what’s clear is that nature went through significant changes as a result of our lockdowns — and it even showed in the sky. At the recent American Geophysical Union meeting in New Orleans, scientists at MIT reported that a drop in atmospheric aerosols due to shuttering of activity coincided with a drop in lightning.

According to a new study, reduced human activity lowered the number of aerosol emissions — microscopic particles in the atmosphere too small to see with the naked eye that can result from pollution due to fossil fuels — affecting the electrical charge of clouds and their ability to form lightning.

Between March 2020 and May 2020, there were 19% fewer intracloud flashes (the most common type of lightning) compared to the same three-month period in 2018, 2019, and 2021.

Earle Williams, a physical meteorologist at the Massachusetts Institute of Technology, and colleagues used three different methods to measure lighting, all of which pointed to the same trend of diminished lightning activity associated with diminished aerosol concentration.

Atmospheric aerosols absorb water vapor thereby helping form cloud droplets. Without any aerosols, we wouldn’t have clouds. When there are more aerosols in the atmosphere, the water vapor becomes more widely distributed across droplets, making them smaller and less likely to coalesce into rain droplets. As a result, clouds grow larger but precipitation is suppressed.

Furthermore, clouds seeded with fewer aerosols have fewer positively charged ice particles in the clouds to react with negatively charged hail in the lower part of the cloud, which explains why we had less lightning that strikes the surface or discharges into the air.

For instance, lightning flashes are more frequent along shipping routes, where freighters emit particulates into the air, compared to the surrounding ocean. And the most intense thunderstorms in the tropics brew up over land, where aerosols are elevated by both natural sources and human activity.

Areas with the strongest reduction of aerosols also experienced the most dramatic drops in lightning events. These include Southeast Asia, Europe, and most of Africa. North and South America also experienced a reduction in lightning, but not as dramatic as in other places. Researchers believe that some of the drop in aerosol pollution due to human activity in the Americas was offset by the catastrophic wide-scale fires experienced in 2020.

Lightning is an important component of the weather system, which is why scientists are so interested in understanding it better. Also, from an ecological perspective, lighting interacts with air molecules to produce nitrogen oxide, a family of poisonous, highly reactive gases.

Lightning discharges help clean the air of some greenhouse gases

Lightning could have an important ecological function, a duo of new paper reports. According to the findings, such discharges play an important role in clearing gases like methane from the atmosphere.

Image credits Abel Escobar.

As we all know, thunderbolt and lightning, very, very frightening. However, they also seem to be quite fresh. The immense heat and energy released by lightning bolts break apart nitrogen and oxygen molecules in the air, which mix into hydroxyl radicals and hydroperoxyl radical — OH and HO2, respectively. In turn, these highly reactive chemical compounds go on to alter the atmosphere’s chemistry, in particular jump-starting the processes that degrade greenhouse gas compounds such as methane.

Bolt Cleaning

“Through history, people were only interested in lightning bolts because of what they could do on the ground,” says William H. Brune, distinguished professor of meteorology at Penn State and co-author on both of the new papers. “Now there is increasing interest in the weaker electrical discharges in thunderstorms that lead to lightning bolts.”

Data for this research was collected by an instrument plane flown above Colorado and Oklahoma in 2012. The plane followed thunderstorms and lightning discharges in order to understand their effect on the atmosphere.

Initially, the team assumed that the spikes in OH and HO2 signals (atmospheric levels) their devices were picking up must be errors, so they removed them from the dataset to study at a later time. The issue was that the instrument recorded high levels of hydroxyl and hydroperoxyl in stretches of the cloud where there was no visible lightning. A few years ago, Brune actually took the time to analyze it.

Working with a graduate student and research associate, he showed that the spikes could be produced both by sparks and “subvisible discharges” in the lab. After this, they performed a fresh analysis of the thunderstorm and lightning data from 2012.

“With the help of a great undergraduate intern,” said Brune, “we were able to link the huge signals seen by our instrument flying through the thunderstorm clouds to the lightning measurements made from the ground.”

Planes avoid flying through the center of thunderstorms because it’s simply dangerous for them, Brune explains, but they can be used to sample the top portion of the clouds which spread in the direction of the wind — this area of a storm is known as ‘the anvil’. Visible lightning is formed in the part of the anvil near the thunderstorm core.

Most bolts never strike the ground, he adds. This lightning is particularly important for affecting ozone and some greenhouse gas in the upper atmosphere. While we did know that lightning can split water to form hydroxyl and hydroperoxyl, this is the first time it has actually been observed in a live thunderstorm.

The researchers found hydroxyl and hydroperoxyl in areas with subvisible lightning, but very little evidence of ozone and no signs of nitric oxide (which requires visible lightning to form) in these areas. If this type of lightning occurs routinely, its outputs of hydroxyl and hydroperoxyl should be included in atmospheric models (they are not, currently).

Both of these compounds interact with some gases like methane, breaking them down through chemical reactions, and preventing them from realizing their full greenhouse potential.

“Lightning-generated OH (hydroxyl) in all storms happening globally can be responsible for a highly uncertain but substantial 2% to 16% of global atmospheric OH oxidation,” the team explains.

“These results are highly uncertain, partly because we do not know how these measurements apply to the rest of the globe,” said Brune. “We only flew over Colorado and Oklahoma. Most thunderstorms are in the tropics. The whole structure of high plains storms is different than those in the tropics. Clearly, we need more aircraft measurements to reduce this uncertainty.”

The first paper “Extreme oxidant amounts produced by lightning in storm clouds” has been published in the journal Science.

The second paper, “Electrical Discharges Produce Prodigious Amounts of Hydroxyl and Hydroperoxyl Radicals” has been published in the Journal of Geophysical Research: Atmospheres.

Ancient lightning could have sparked life on Earth

Researchers may have found one of the missing puzzle pieces for the emergence of life on Earth. According to a new study, one key mineral for life may have formed thanks to an unexpected phenomenon: lightning.

Early Archean Earth Caption: An artist’s rendition of the early Earth environment. Lightning generated by storms and volcanic plumes frequently strikes volcanic rocks. Image credits: Lucy Entwisle.

Rare minerals and life

The emergence of life on Earth required a very specific cocktail of ingredients. You can’t have any of them missing, otherwise, it just doesn’t work — and one of the most troubling ingredients is phosphorous.

The early Earth harbored phosphorous, but it wasn’t useful as it was locked away inside minerals. You’d need bioavailable, reactive phosphorous to form DNA, RNA, and cell membrane lipids. There is one exception where the phosphorous could have come from: the mineral schreibersite.

Schreibersite is a rare mineral. It’s only found in a few places on Earth, like Greenland or the Levant. But this earthly schreibersite formed thanks to carbon-rich rocks, so this couldn’t have worked in the early Earth because there was no life to produce carbon-rich rocks.

“You cannot have schreibersite forming under normal terrestrial conditions, and the few unusual occurrences of it that we find depend on material created by life in the past,” said corresponding author Benjamin Hess from Yale University, in an email. “So then, how do we get it on early Earth?”

There’s one place schreibersite could have come from: outer space. Meteorites are suspected to be a source of the much-needed phosphorous, which is why many researchers believe meteorites “seeded” life on Earth — it’s not that they brought lifeforms along, but rather that they brought the necessary ingredients.

But Hess and colleagues have a different idea. In their new study, they explain that schreibersite can also be formed when lightning strikes specific minerals. In other words, life may have not been seeded on Earth, it may have been sparked.

“Traditionally, the answer has been meteorites because they formed under less oxygen-rich conditions. But in our new work, we are arguing that you can actually get schreibersite through lightning strikes as well which serve to reduce (remove oxygen from) the material they strike.”

The spark of life

A photo taken during the excavation of the fulgurite in Glen Ellyn, IL, USA.
Image credits: Stephen Moshier.

When some rocks or soils are hit by lightning, they are transformed into fulgurites. And using a suite of spectroscopic techniques, the team found that schreibersite can form in fulgurites.

It’s not the first time schreibersite was discovered in fulgurites. Previous research has linked it with lightning. But this is the first time that lightning strikes have been suggested as a widespread mechanism, Hess says.

“The previous reports of schreibersite in other fulgurites was actually encouraging because it indicates that this isn’t a strange one-off event. It provides more bite to the new model and my estimates of how much schreibersite would have formed,” he adds.

The team estimated the amount of schreibersite that might have been produced by each strike, and the suitable land area on the early Earth. They calculated that lightning strikes could have accounted for between 110 and 11,000 kilograms of phosphorus per year — large enough to fuel the first life forms, and maybe even more than what meteorites brought.

There’s another reason why lightning is a better candidate than meteorites: most of the schreibersite brought by minerals was in large meteorites of 1 km or greater in size. The problem with large meteorites, however, is that they would have wiped out everything around them.

It could still have been a meteorite or several that brought the phosphorous to Earth, but lightning just seems a bit more likely in some ways, Hess comments.

“So, I guess it’s a question of: did life hit the jackpot and have a meteorite that landed in the perfect way to supply a large amount of phosphorus needed all at once? Or was life supplied by the continual supply of phosphorus that built up through time as lightning inevitably and frequently strikes tropical landmasses?”

“The latter makes me more comfortable but certainly, it could have been either. And to be fair, the mechanism we are proposing needs to be tested as well; I do hope there will be new studies soon of natural fulgurites from basaltic islands (like Hawaii) that can demonstrate whether this does efficiently reduce phosphorus in the envisioned environment.”

A bajillion lightning strikes

A slice of schreibersite-containing meteorite. Image in public domain.

Of course, the odds of lightning striking in the exact right place to create the required chemistry are also very small. But there were a lot of lightning strikes to make the odds better. How many? Hess did the math:

“We estimate that 100-1,000 million strikes occurred a year (modern Earth has ~150 million strikes a year). The lower bound being because we don’t know how much land was actually exposed so we have a very conservative lower bound even though the atmosphere would have been more lightning-rich.”

“Over the 1 billion years we are interested in (4.5 to 3.5 billion years ago), that comes out to 0.1 to 1 quintillion lightning strikes. That is 100,000,000,000,000,000 to 1,000,000,000,000,000,000 strikes. I found that pretty crazy (but realistic). I didn’t know how frequent lightning was on Earth until this study!”

It’s difficult to compare the likelihood of lightning-linked schreibersite to that of meteorites. But at some point, if you have enough lightning, it just becomes less “lucky”. The odds of the right meteorite falling in the right place are pretty slim, but there were far more lightning strikes than meteorites, especially as time went on: the planet was bombarded by meteorites in its early history, but after the atmosphere formed, the meteorite bombardment declined drastically.

“Lightning strikes are a mechanism that doesn’t have a deadline. Meteorite impacts decrease through time but lightning doesn’t necessarily. The early bombardment is a one-off event at the beginning of a solar system. But lightning, so long as an appropriate atmosphere is maintained, is continuous throughout a planet’s history. This proposed lightning strike mechanism would help life to form on other Earth-like planets at any time in the planet’s history, not just at the beginning,” Hess concludes.

The emergence of life on Earth remains one of the most captivating events in our planet’s history. Researchers believe all life on Earth has descended from a single ancestor.

The details of how this would have happened are not clear, and no one has managed to create life from scratch in the lab, but the prevailing hypothesis is that it wasn’t a singular event that produced life from abiotic elements — it would have been a gradual transition of increasing complexity, from molecular self-replication, self-assembly, autocatalysis, and the emergence of cell membranes. With studies like this one, we’re getting closer and closer to understanding it.

Massive 700-km ‘megaflash’ stretching from Argentina to Brazil is longest lightning bolt on record

The largest lightning bolt in recorded history happened on October 31, 2018 in southern Brazil, although the flash stretched from eastern Argentina all the way to the Atlantic, the World Meteorological Organization (WHO), a United Nations agency, said. The discharge, which stretched over 700 km, is equivalent to the distance between Boston and Washington DC.

Satellite image of record extent of lightning flash, Brazil, 31 October 2018. Credit WMO

But this wasn’t the single record that was certified. The WMO’s group of experts on weather and climate extremes also reported another record for the longest lightning flash over northern Argentina. The single flash lasted for a total of 16,73 seconds and, like the one in Brazil, also spanned through several hundred kilometers.

The new records were more than double the previously known record-holders, the WHO said in a statement. The previous record for duration was of 7.74 seconds, measured on August 30, 2012, in southern France. Meanwhile, the previous record for length was 321 kilometers (199 miles) and was registered in Oklahoma on June 20, 2007.

The new measurements reveal “extraordinary records from single lightning flash events,” Randall Cerveny, the chief rapporteur in the WMO expert committee, said in a statement. “It is likely that even greater extremes still exist, and that we will be able to observe them as lightning detection technology improves,” he said.

The previous records were registered using data obtained by so-called ground-based lightning mapping array networks, which WMO experts claim have upper limits in the scale of lightning that can be observed. But recent advances in space-based lighting mapping now allow researchers to measure flash extent and duration much better.

Credit WMO

This has allowed for the detection of “previously unobserved extremes in lightning occurrence, known as ‘megaflashes’,” Michael Peterson, of the Space and Remote Sensing Group of Los Alamos National Laboratory in the US, said in a statement. Megaflashes “are defined as horizontal mesoscale lightning discharges that reach hundreds of kilometers in length,” he said.

For years, lightning was understood as a local event, resulting from an imbalance of electrical charge. But new research by WMO experts recently showed that some lightning events can be “mesoscale” in nature, reaching the scale of the occasionally massive sprawling storm complexes that create them.

Lightning is indeed a major hazard that claims many lives every year. For example, in the United States, lightning strikes kill on average 48 people per year, also injuring hundreds. Although most lightning occurs in the summer, people can be struck at any time of year. The most people killed by a single strike of lightning were 21 people in Zimbabwe in 1975.

Low-latitude areas experience far more lightning than higher-latitude areas, a study showed in 2017. Tropical regions can get hit by lightning strikes year-round whereas northern latitudes experience lightning only half that time. One square kilometer of Lake Maracaibo receives 233 flashes of lightning each year, more than any other place on Earth

The findings highlighted important public lightning safety concerns for electrified clouds where flashes can travel extremely large distances. The WHO advises to follow the 30-30 rule – if the time between flash and thunder is less than 30 seconds, go inside and wait 30 minutes after the last observed flash to resume outdoor activities.

Scientists have found a record-breaking 500-km-long mega lightning bolt

Credit: Pixabay.

Some thunderstorms are so intense that the vivid lightning and crashes of thunder may keep you up at night. Here’s a thought that will surely keep you awake during such restless storms: some lightning bolts are so large they can extend across multiple states. According to scientists who analyzed satellite imagery, one such lighting bolt measured more than 500 kilometers (310 miles).

Mega flashes

Since the 1950s, researchers have been aware of lightning discharges on the order of 100 km in length, thanks to radar-based findings. Later, around 1989, scientists discovered “sprites” — large-scale electrical discharges that occur high in the atmosphere at about 50−90 km, within so-called “mesoscale convective systems” (MCSs). One such sprite, which formed in 2007 over Oklahoma, was 321 km in length and has been certified by the World Meteorological Organization as the longest officially documented lightning flash.

But, this kind of record will be broken time and time again in the near future, judging from a recent study published in the Bulletin of the American Meteorological Society.

The study, authored by Walter Lyons at FMA Research in Fort Collins, Colorado, and colleagues, employed ground-based lightning detectors and an instrument aboard the GOES-16 spacecraft, which was launched in 2016. On October 22nd, 2017, the Geostationary Lightning Mapper (GLM) sensor on the spacecraft detected “a lightning discharge that originated in northern Texas, propagated north-northeast across, Oklahoma, fortuitously traversed the Oklahoma LMA (OKLMA), and finally terminated in southeastern Kansas.” According to Lyons and colleagues, the discharge was more than 500 km long, illuminating an area of 67,845 square kilometers.

Such exceptional sprites are the result of propagating lightning channels that tap into huge reservoirs of positive charge present within a MCS’ stratiform region. According to the researchers, typically a lightning discharge originates near the top of the convective cell (~8-10 km in altitude), then travels rearward and downward, following the trajectory of descending positively charged ice crystals.

Although the 2017 megaflash originating in Texas dwarfs the current official record holder for the longest lightning flash, researchers expect to encounter even larger ones. Already, other scientists claim they’ve spotted flashes as long as 673-km in the GOES data. In the future, these observations will help researchers gain a better understanding of how electrical events in the atmosphere occur.

“A megaflash, once initiated, appears able to propagate almost indefinitely as long as adequate contiguous charge reservoirs exist in the secondary precipitation maxima of MCS stratiform regions. Is it possible that a future megaflash can attain a length of 1,000 km? We would not bet against that. Let the search begin,” the researchers wrote.

Lightning ‘superbolts’ incoming from November to February, study reports

According to a newly-published global survey of lightning “superbolts”, the Southeastern U.S should expect to see massive lightning discharges starting November.

Image via Pixabay.

A new study from the University of Washington study maps the location and timing of “superbolts”: bolts of lightning that release more than 1 million Joules’ worth of electricity — roughly a thousand times more than the average lightning bolt. According to the results, while the lightning season in the Southeastern U.S is almost finished, the peak season for these massive strikes won’t begin until November.

Lightning, boltyer.

“It’s very unexpected and unusual where and when the very big strokes occur,” said lead author Robert Holzworth, a UW professor of Earth and space sciences who has been tracking lightning for almost two decades

Holzworth manages the World Wide Lightning Location Network, a UW-managed research body that operates about 100 lightning detection stations around the world. By using readings from three (or more) stations at a time, the network allows researchers to determine a bolt’s size and location. The World Wide Lightning Location Network has been in operation since the early 2000s.

For the new study, the team analyzed 2 billion lightning strikes recorded between 2010 and 2018. Out of these, some 8,000 events were confirmed superbolts. That’s around one in 250,000 strokes, or four-millionths of a percent, making these superbolts quite rare.

The findings paper show that superbolts are most common in the Mediterranean Sea, the northeast Atlantic and over the Andes, with lesser hotspots east of Japan, in the tropical oceans and off the tip of South Africa.

While regular lightning strikes occur most often over land (roughly 90% of all strikes), superbolts tend to strike over water. The Southeastern U.S. sees the most lightning strikes per year in the USA, and the islands of Southeast Asia also see many strikes. The team also adds that average stroke energy over water is greater than the average stroke energy over land.

“Superbolts happen mostly over the water going right up to the coast,” Holzworth said. “In fact, in the northeast Atlantic Ocean you can see Spain and England’s coasts nicely outlined in the maps of superbolt distribution.”

“Until the last couple of years, we didn’t have enough data to do this kind of study,”

The timing of superbolts also doesn’t follow the rules for typical lightning. The latter mostly occurs in the Americas, sub-Saharan Africa and Southeast Asia during summer thunderstorms. In contrast, superbolts are more common in the Northern Hemisphere and strike both hemispheres between the months of November and February. The team doesn’t yet know why the two classes of lightning have different distributions.

The number of recorded superbolts also varies year by year. The late 2013 was an all-time high, Holzworth says, with late 2014 being the next highest. Other years have far fewer recorded events.

“We think it could be related to sunspots or cosmic rays, but we’re leaving that as stimulation for future research,” Holzworth said. “For now, we are showing that this previously unknown pattern exists.”

The paper “Global Distribution of Superbolts” has been published in the Journal of Geophysical Research: Atmospheres.

Credit: Pixabay.

Astronomers say exploding stars might have forced our ancestors to walk upright

Credit: Pixabay.

Credit: Pixabay.

One of the most distinguishable human features is our upright mode of locomotion, which is unique among mammals. Scientists have proposed many ideas that might explain the circumstances that enabled our species to evolve as bipeds. Perhaps the most ‘out there’ theory proposed thus far comes from astronomers at the University of Kansas who claim that human bipedalism might have been triggered by giant cosmic explosions. But before you laugh, read on because, wild as it may sound, this theory has some interesting evidence backing it up.

Some time ago, scientists reported that ancient seabeds contain a layer of iron-60 isotopes. These rare isotopes cannot be made on Earth, which means their origin must be extraterrestrial, most likely the result of a supernova —  a transient astronomical event that occurs during the last stellar evolutionary stages of massive star’s life. Because iron-60 has a known half-life, it is relatively easy to accurately date when the supernovae’s cosmic rays reached our planet.

Scientists traced the isotopic signatures to two major events: one 6.5 to 8.7 million years ago (300 light-years away from Earth) and the second 1.7 to 3.2 million years ago (163 light-years). That’s around the time of Homo habilis, the upright human ancestor nicknamed “handyman” because of their ability to master stone tool technology.

Based on this information, Adrian Melott and colleagues at the University of Kansas hypothesized what kind of changes these cosmic rays might have caused on Earth. One of the first things that should have happened was a dramatic increase in the rate of ionization of the lower atmosphere.

Ionization is the process by which an atom or molecule acquires a negative or positive charge by gaining or losing electrons. In this case, the cosmic rays knocked off electrons from molecules in the atmosphere. According to Melott, the supernova events would have increased ionization in the atmosphere by 50-fold. With so many free electrons in the atmosphere, cloud-to-ground lightning would have been much easier to occur, increasing the odds of forest fires.

“The bottom mile or so of atmosphere gets affected in ways it normally never does,” Melott said. “When high-energy cosmic rays hit atoms and molecules in the atmosphere, they knock electrons out of them — so these electrons are running around loose instead of bound to atoms. Ordinarily, in the lightning process, there’s a buildup of voltage between clouds or the clouds and the ground — but current can’t flow because not enough electrons are around to carry it. So, it has to build up high voltage before electrons start moving. Once they’re moving, electrons knock more electrons out of more atoms, and it builds to a lightning bolt. But with this ionization, that process can get started a lot more easily, so there would be a lot more lightning bolts.”

In time, savannas replaced torched forests in northeast Africa. Now, walking was far more advantageous for our ancestors than climbing trees. The upsurge in global wildfires is supported by the discovery of carbon deposits found in soils that correspond with the timing of the cosmic-ray bombardment.

“It is thought there was already some tendency for hominins to walk on two legs, even before this event,” said Melott, professorof physics & astronomy at the University of Kansas. “But they were mainly adapted for climbing around in trees. After this conversion to savanna, they would much more often have to walk from one tree to another across the grassland, and so they become better at walking upright. They could see over the tops of grass and watch for predators. It’s thought this conversion to savanna contributed to bipedalism as it became more and more dominant in human ancestors.”

That’s quite a great deal of speculation but the evidence suggests that such a scenario might have been possible — however improbable as it may sound. What about something like happening in the future? Slim chance, say the researchers who point to the fact that the nearest supernova candidate is now 652 light-years away from Earth. Instead, Melott says we should be cautious about a more immediate threat — solar flares.

“Betelgeuse is too far away to have effects anywhere near this strong,” Melott said. “So, don’t worry about this. Worry about solar proton events. That’s the danger for us with our technology — a solar flare that knocks out electrical power. Just imagine months without electricity.”

The findings appeared in the Journal of Geology.

Jupiter Lightning.

The curious case of Jupiter’s lightning, solved by the Juno craft

Lightning bolts on Jupiter are both similar and completely different from those on Earth, research suggests.

Jupiter Lightning.

Artist’s concept of lightning in Jupiter’s northern hemisphere. The image is based on a JunoCam image.
Image credit:sNASA/JPL-Caltech/SwRI/JunoCam.

A new paper published by NASA’s Juno mission comes to flesh out our understanding of Jovian lightning. Their existence was first confirmed when the Voyager 1 craft flew past Jupiter in March 1979 — but that encounter also left us with more unanswered questions. Radio emissions produced by these lightning bolts didn’t match the signatures of those on Earth, for example.

God of Lightning

“No matter what planet you’re on, lightning bolts act like radio transmitters—sending out radio waves when they flash across a sky,” said lead author Shannon Brown of NASA’s Jet Propulsion Laboratory in Pasadena, California.

“But until Juno, all the lightning signals recorded by spacecraft were limited to either visual detections or from the kilohertz range of the radio spectrum, despite a search for signals in the megahertz range. Many theories were offered up to explain it, but no one theory could ever get traction as the answer.”

Fancy science-speak for ‘we didn’t have a clue what was up’. The Juno mission, however, gave researchers a chance to dig deeper into Jupiter’s lightning. The craft has been orbiting the gas giant since July 4, 2016. Among other onboard equipment, it boasted a Microwave Radiometer Instrument (MWR) to record emissions across a wide spectrum of frequencies

During its first eight flybys of Jupiter, Juno detected 377 lightning discharges, the team reports. Emissions were recorded in both the megahertz and gigahertz range, “which is what you can find with terrestrial lightning emissions,” according to Brown.

“We think the reason we are the only ones who can see it is because Juno is flying closer to the lighting than ever before, and we are searching at a radio frequency that passes easily through Jupiter’s ionosphere,” she adds.

These recordings show that lightning on Jupiter is very similar to that on Earth — but there are also differences.

Most striking of all is how these discharges are distributed across the planet’s surface. On Jupiter, these bolts of lightning flash frequently across the giant’s poles, but never over the equator. This doesn’t hold true on Earth. The reason behind this, the team believes, is how heat is distributed across the two planets.

The overwhelming majority of heat on Earth comes from the Sun. Our equator receives a much larger slice of this energy than the rest of the planet (that’s why it’s the hottest bit), meaning air masses above the equator have a lot of energy at their disposal to move around through convection. This movement is what fuels the thunderstorms which, in turn, produce lightning.

On Jupiter, however, sunlight is much, much dimmer. The giant is, after all, five times farther away from the Sun than Earth. This means the planet receives 25 times less heat than our planet. Most of the energy in Jupiter’s atmosphere is derived from its solid core. However, the team explains, that tiny quantity of heat it does receive from the Sun does heat up its equator more than the poles. The team believes that this difference in temperature is enough to stabilize Jupiter’s upper atmosphere around the equator, preventing gases further below to rise through convection.

The atmosphere around Jupiter’s poles, which receive less energy, isn’t stable — warm gases rising from below drive convection processes, creating lightning.

“These findings could help to improve our understanding of the composition, circulation and energy flows on Jupiter,” said Brown. But another question looms, she said. “Even though we see lightning near both poles, why is it mostly recorded at Jupiter’s north pole?”

The paper “Prevalent lightning sferics at 600 megahertz near Jupiter’s poles” has been published in the journal Nature.

lightning

Lightning reacts with the atmosphere to produce nuclear reactions and antimatter

Lightning is powerful enough to set off nuclear reactions in the atmosphere, a new study found. Japanese researchers report that the powerful electrical discharge produces gamma rays — the most powerful waves or radiation in the electromagnetic spectrum — which react with the air. The reaction produces radioisotopes and even positrons, the antimatter counterpart of electrons.

lightning

Credit: Pixabay.

Scientists knew for some time that lightning and thunderclouds emit gamma rays but this is the first time someone demonstrated that they’re also responsible for nuclear reactions in the atmosphere. The findings were reported by a team from Kyoto University led by Teruaki Enoto.

In 2015, Enoto and colleagues set up gamma-ray detectors across Japan’s western coast which is often hit by lightning and thunderstorms. At one point their research was jeopardized by funding problems. They went to the internet for help where they convinced generous donors to crowdfund the research.

[panel style=”panel-info” title=”What is lightning” footer=””]Lightning is a giant discharge of electricity accompanied by a brilliant flash of light and a loud crack of thunder. The spark can reach over five miles (eight kilometers) in length, raise the temperature of the air by as much as 50,000 degrees Fahrenheit (27,700 degrees Celsius), and contain a hundred million electrical volts. Lightning may actually be the ultimate life bringer, though it may sometimes cause fatalities. The immense heat and energy discharged during a strike can convert elements into compounds that are found in organisms, so during the planet’s primal period lightning may have helped spur life – like a defibrillator.[/panel]

In early 2017, the scientists installed four detectors in Kashiwazaki city, which picked up a lightning bolt which struck the ground only a few hundred meters away. Upon analyzing the data, the researchers found they had recorded three gamma-ray bursts. The first only lasted for one-thousandth of a second, the second was a gamma-ray afterglow which faded off after a few milliseconds while the third was a prolonged emission that lasted about one minute.

 Credit: Kyoto University/Teruaki Enoto.

Credit: Kyoto University/Teruaki Enoto.

The second afterglow was produced by lightning’s reaction with nitrogen from the atmosphere. Lightning is powerful enough to remove a neutron out of nitrogen. When the neutron is reabsorbed, an afterglow is produced. The prolonged emissions are the result of the unstable nitrogen atoms which release positrons. The antimatter collides with electrons which annihilate each other, producing gamma rays in the process.

[panel style=”panel-success” title=”How lightning forms” footer=””]Every day, some four million lightning strikes hit the surface of the planet. Despite this, how lightning – and subsequently thunder – is formed is not completely understood at a physical level. We know one thing for sure: it comes from clouds (dust, water and ice). Ice inside the cloud rubs against each other becoming electrically polarized or charged (the exact mechanism is a bit fuzzy, which is why the whole thing is debatable). The lighter ice will move upwards while the heavier ice will stay below separating the negative and positive charges.[/panel]

“We have this idea that antimatter is something that only exists in science fiction. Who knew that it could be passing right above our heads on a stormy day?” says Enoto.

“And we know all this thanks to our supporters who joined us through ‘academist’. We are truly grateful to all.”

There are now ten gamma-ray detectors on Japanese coast currently collecting data. Enoto hopes to gain even deeper insight into the fascinating atomic world that lightning triggers.

Scientific reference: Teruaki Enoto et al, Photonuclear reactions triggered by lightning discharge, Nature (2017). DOI: 10.1038/nature24630. 

Credit: Free Great Picture.

The world’s most lightning-prone areas. The top spot gets zapped more than 200 times/square kilometer

Credit: Free Great Picture.

Credit: Free Great Picture.

Each year, on average, 48 people from the United States get killed after being struck by lightning. Is that a lot? To answer this question you have to put the fatality count in relation to the frequency of lightning strikes. According to the National Severe Storms Laboratory, each day the planet is hit by eight million lightning strikes but not all places get pounded equally the same. Now, a new analysis of satellite imagery offers the best estimates so far of lightning prone area from all around the world.

Using data gathered between 1997 and 2015 by a satellite called the Tropical Rainfall Measuring Mission, scientists made a list of the top 500 places most hit by lightning. The tally was organized based on the number of flashes observed per square kilometer per year. Only locations that were under the satellite’s instruments could be measured, a path that included every spot between 38°N (Athens, Greece) and 38°S (Melbourne, Australia).

According to the analysis, you should stand clear of Lake Maracaibo, Venezuela, where thunderstorms loom 297 nights each year. One square kilometer of Lake Maracaibo receives 233 flashes of lightning each year, more than any other place on Earth.

The top lightning hot spots from around the world. The Democratic Republic of the Congo (DRC) took five places out of the top ten. Credit: Weather Channel.

What makes Lake Maracaibo such a big lightning hot spot is its geography which favors the formation of thunderstorms. The lake is surrounded by lofty peaks, whose cold air clashes with the warm tropical waters of Maracaibo, a situation which we can also find in lakes Victoria and Tanganyika in Africa, two other massive lightning hot spots.

Even long before we had these satellite imagery analyzed, people knew the Venezuelan lake — sometimes called the most electric place on Earth — is one of the most lightning prone areas around the world from anecdotal evidence alone. The lightning is so consistent year round here that for centuries ships have used Lake Maracaibo as a natural lighthouse for navigation purposes. The flashes of light around Maracaibo even helped thwart two invasions. The first attempt was in 1595 when it illuminated ships led by Sir Francis Drake of England, revealing his surprise attack to Spanish soldiers in Maracaibo. The other was during the Venezuelan War of Independence in 1823, when it betrayed a Spanish fleet trying to sneak ashore.

https://www.youtube.com/watch?v=tHzujX8mkhw

Despite Maracaibo taking the top spot, the new study suggests that Central Africa is where you can find the most lightning prone areas. Here, broad areas are afflicted by thunderstorms and 283 of the world’s top 500 spots reside.

Other important findings worth mentioning include:

  • Low-latitude areas experience far more lightning than higher-latitude areas.Tropical regions can get hit by lightning strikes year-round whereas northern latitudes experience lightning only half that time.
  • Although a lake seeks the most lightning flashes, lightning occurs more frequently over land than over oceans and lakes, more in the summer than in the winter, and most often between noon and 6 P.M.
  • Africa is the continent with the most lightning hotspots, followed by Asia, South America, North America, and Australia.
  • Most of the principal continental maxima are located near major mountain ranges, revealing the importance of local topography in thunderstorm development.

Scientists observe 200-mile long lightning bolt – 10 times longer than we thought possible

Scientists have just observed the longest lightning bolt on record by a long shot. The lightning was spotted in Oklahoma, stretching almost from one edge to the other of the state.

Andreas Øverland/Flickr

The United Nation’s World Meteorological Organisation (WMO) officially made the announcement, stating that it easily beats the previous US record at 321 km (200 miles). In fact, it’s so long and it lasted for so long that it might force us rethink our understanding of lightning. Meteorologists believed lightning peaked up after 1 second, but this one lasted several seconds.

“The committee has unanimously recommended amendment of the AMS Glossary of Meteorology definition of lightning discharge as a ‘series of electrical processes taking place within 1 second’,” the team writes, “by removing the phrase ‘within 1second’ and replacing with ‘continuously’.”

It’s not the first time such a lightning has been spotted. According to the WMO, France holds the record for the longest-lasting lightning strike, with a flash in 2012 lighting up the sky for a whopping 7.74 seconds.

But as impressive as this really is, scientists believe that even more extreme events are happening in nature – we just haven’t monitored them yet. Every system used for detecting lightning has limitations. Most notably, ground-based lightning networks must be able to detect a flash with at least three antennas to locate it with an acceptable margin of error. This often leads to the rejection of cloud-to-cloud lightning, as one antenna might detect the position of the flash on the starting cloud and the other antenna the receiving one. Still, space-based systems to do exist and they are free from this limitation, but it can be quite resource-intensive to monitor lightning from space.

This also shows that the ‘danger zone’ around a thunderstorm could be much larger than we previously thought. John Jensenius from the National Weather Service told Angela Fritz from The Washington Post that the new record “demonstrates the far-reaching effects of lightning, and just how far around a thunderstorm the atmosphere can be electrified”. He urges people to be conscious of this.

“People need to be aware that any time a thunderstorm is in the area, there is a threat of a potentially deadly lightning strike,” he added.

New measuring method shows that lightning can be as powerful as 20 cars hitting the earth at 60mph

Researchers in Florida have developed a new method of calculating a cloud-to-earth lighting strike’s energy by using geological methods. University of South Florida School of Geosciences Associate Professor Matthew Pasek and his colleague Marc Hurst of Independent Geological Sciences study fulgurites to measure how much energy was discharged into the soil — even strikes thousands of years old.

Image credits Andrew Malone / flickr.

Image credits Andrew Malone / flickr.

Lightning strikes are one of nature’s more conspicuous show of force. They light up the sky, cause huge booms and scare dogs the world over under tables. Such power undoubtedly requires a huge expenditure of energy, but according to Pasek, measuring exactly how much is really difficult. Atmospheric physicists can estimate it, based on electrical current and temperature measurements of the bolts as they occur, but the figures are approximations at best.

In order to find an exact figure, Pasek and Hurst have turned to geology to measure the discharge “after-the-fact,” rather than measuring energy during a strike. By using this method, they can even measure the energy in a bolt of lightning that struck Florida sand thousands of years ago.

Pasek explains that because bolts of lightning carry extremely high voltage, they can heat the air around the bolt to more 30,000 degrees Kelvin (over 53,000 degrees Fahrenheit) — this causes a rapid expansion which you hear as thunder. When lightning hits the ground, electrical current flows through it and heats the material to above its vaporizing level. Rapid cooling produces the fulgurite.

“When lightning strikes the sand, it may generate a cylindrical tube of glass called a fulgurite, said Pasek.

“The structure of the fulgurite, created by the energy and heat in a lightning strike, can tell us a lot about the nature of the strike, particularly about the amount of energy in a single bolt of lightning.”

The duo collected more than 250 fulgurites of various ages from sand mines in Polk County, Florida, a site that’s believed to have been hit by lightning for thousands of years. The area’s rich history is important because it allows the team to measure lightning strike history over a wide region near Tampa and Orlando, known today as the I-4 Corridor. They analyzed the properties of the fulgurites, paying particular attention to the length and circumference of the glass cylinders because the amount energy released is revealed by these dimensions.

Fulgurites collected from the field area in Polk County, Florida. Surficial differences likely result from different initial physical conditions (such as water content in the sand.)
Image credits Dr. Matthew Pasek/University of South Florida.

“Everyone knows there is a lot of energy in a lightning bolt, but how much?” Pasek said.

“Ours is the first attempt at determining lightning energy distribution from fulgurites and is also the first data set to measure lightning’s energy delivery and its potential damage to a solid earth surface.”

According to Pasek, the energy released by lightning is measured in megajoules, also expressed as MJ/m.

“For example a single megajoule is equivalent to about 200 food calories, or the energy from leaving a microwave on for 20 minutes to cook food,” he explains.

“It can also be compared to a 60 watt lightbulb’s energy use if left on for about four hours. It’s also the same as the kinetic energy a car has traveling about 60 mph.”

The team found that lightning strike energy peaks at values greater than 20MJ/m — equivalent to 20 cars all crashing into a surface the diameter of your pinky at the same time. The researchers also found a way to separate the “normal” lightning strikes from the “abnormal.”

Definitely abnormal.
Image credits permutate / Deviantart.

“While we presented a new method for measuring by using fossilized lightning rocks, we also found – for the first time – that lightning strikes follow something called a ‘lognormal trend,” explained Pasek.

“A lognormal trend shows that the most powerful lightning strike happen more often than would be expected if you made a bell curve of strikes. This means that the big lightning strikes are really big.”

According to Pasek, who is also an expert in astrobiology, geochemistry and cosmochemistry, lightning strikes the Earth about 45 times per second, with 75 to 90 percent of the strikes over land masses.

“About a quarter of these strikes occur from a cloud to the ground, so the fulgurite-forming potential is great, with up to 10 fulgurites formed per second globally,” said Pasek.

Well then, maybe my dog has legitimate cause for concern.

The full paper, “A Fossilized Energy Distribution of Lightning,” has been published in the journal Scientific Reports.

 

Amazing lighting strikes filmed at 7,000 frames per second

Researchers at the Florida Institute of Technology had an awesome day on the field with their 7,000 frames per second high-speed cameras. They set their gear near the university’s Melbourne campus and waited for the thunderstorm show to work its magic.

To the naked eye, a lightning bolt comes and goes in a flash. But technology comes to the rescue, and this brilliant video shows just how intensely intricate a lightning strike can be as it discharges massive amounts of energy. The playback speed of the video is 700 fps.

[panel style=”panel-info” title=”What is lightning” footer=””]Lightning is a giant discharge of electricity accompanied by a brilliant flash of light and a loud crack of thunder. The spark can reach over five miles (eight kilometers) in length, raise the temperature of the air by as much as 50,000 degrees Fahrenheit (27,700 degrees Celsius), and contain a hundred million electrical volts. Lightning may actually be the ultimate life bringer, though it may sometimes cause fatalities.  The immense heat and energy discharged during a strike can convert elements into compounds that are found in organisms, so during the planet’s primal period lightning may have helped spur life – like a defibrillator.[/panel]

[panel style=”panel-success” title=”How lightning forms” footer=””]Every day, some four million lightning strikes hit the surface of the planet. Despite this, how lightning – and subsequently thunder – is formed is not completely understood at a physical level. We know one thing for sure: it comes from clouds (dust, water and ice). Ice inside the cloud rubs against each other becoming electrically polarized or charged (the exact mechanism is a bit fuzzy, which is why the whole thing is debatable). The lighter ice will move upwards while the heavier ice will stay below separating the negative and positive charges.

Just like the cloud, because there’s a lot of charge hovering around, the air below the clouds also become ionized. In turn, the ionized air charges air particle further below in a cascading effect until it eventually reaches the ground. This happens very quickly, and the sections of ionized air look very much like electrical sparks or the static electricity released when you rub your sweater against a balloon. The  ground is very conductive compared to air, and will give up a large amount of electric charge into this completed circuit (between the ground and the cloud) — this is called the return stroke and is basically what you see as lightning. This ionizes the air completely between the ground and the cloud, and this is the part you can see for miles around.[/panel]

 

You're still looking at lightning. Thunder image below. Credit: Flickr Matjs

This is what thunder looks like (kind of)

What does lightning sound like? Thunder. Well, what does thunder look like then? It’s no trick question. Like all acoustic waves, thunder can also be visualized and Maher Dayeh from the Southwest Research Institute in San Antonio was the first to turn a thunderclap into an image. His findings were shown at a meeting of the American Geophysical Union.

You're still looking at lightning. Thunder image below. Credit: Flickr Matjs

You’re still looking at lightning. Thunder image below. Credit: Flickr Matjs

Every day, some four million lightning strikes hit the surface of the planet. Despite this, how lightning, and subsequently thunder, is formed is not completely understood at a physical level. We know one thing for sure: it comes from clouds (dust, water and ice). Ice inside the cloud rubs against each other becoming electrically polarized or charged (the exact mechanism is a bit fuzzy, which is why the whole thing is debatable). The lighter ice will move upwards, while the heavier ice will stay below separating the negative and positive charges. Just like the cloud, because there’s a lot of charge hovering around, the air below the clouds also become ionized. In turn, the ionized air charges air particle further below in a cascading effect until it eventually reaches the ground. This happens very quickly, and the sections of ionized air look very much like electrical sparks or the static electricity released when you rub your sweater against a balloon. The  ground is very conductive compared to air, and will give up a large amount of electric charge into this completed circuit (between the ground and the cloud) that causes a lot of charge to flow from the ground upwards to the cloud (this is called the return stroke and is basically what you see as lightning). This ionizes the air completely between the ground and the cloud, and this is the part you can see for miles around.

Left: long exposure photo of lightning event with downstream in green, and return stroke in purple. Right: audio signature for each return stroke. Image: Nature

Left: long exposure photo of lightning event with downstream in green, and return stroke in purple. Right: audio signature for each return stroke. Image: Nature

 

As for thunder, because the ionization of air described above happens so quickly over a large area, it causes air to move (acoustic pressure) just like a sonic boom or explosion. Now, this sound has been recorded and visualized using processing algorithms by researchers at Southwest Research Institute in Antonio, Texas. Dayeh and team first went to a military installation in Florida, then installed a launch system which would shoot a rocket with a long copper wire trailing behind. The rocket was fired into a thundercloud. Then, it was only a matter of waiting for the rocket to trigger the lightning strike and profit. The lightning traveled down the wire and eventually hit the launch platform which was surrounded 15 microphones spaced 1 meter apart. This helped build an acoustic map, which looks like a contemporary painting. In fact, Dayeh and crew were so stoked by the results they thought they had done something wrong.

“The initial constructed images looked like a colourful piece of modern art that you could hang over your fireplace. But you couldn’t see the detailed sound signature of lightning in the acoustic data,” Dr Dayeh said.

Top: lightning. Bottom: acoustic map of the thunder. Image: Nature

Top: lightning. Bottom: acoustic map of the thunder. Image: Nature

The map also provided a few insights into thunder formation, like the fact that thunderclap depends on the peak electric current flowing through the lightning bolt. [source: Nature]

global-lightning-activity

Map compiled by NASA shows how lightning strikes the Earth

By the time you’ve finished reading this sentence, thousands of lightning bolts have already discharged enormous amounts of energy onto Earth’s surface. Now, a map compiled by NASA using two decades worth of measurements shows which places are hit most often. For instance, land is hit more frequently than the ocean, as is the equatorial region compared to other regions of the globe.

global-lightning-activity

Image: NASA

Lightning is a giant discharge of electricity accompanied by a brilliant flash of light and a loud crack of thunder. The spark can reach over five miles (eight kilometers) in length, raise the temperature of the air by as much as 50,000 degrees Fahrenheit (27,700 degrees Celsius), and contain a hundred million electrical volts. Like all of nature’s powerful mechanisms, lightning may actually be the ultimate life bringer, thought it may sometimes cause fatalities.  The immense heat and other energy given off during a stroke has been found to convert elements into compounds that are found in organisms, so during the planet’s primal period lightning may have helped spur life – like a defibrillator.

The following map was made by researchers at NASA taking note of data taken by the Lightning Imaging Sensor (LIS) on NASA’s Tropical Rainfall Measuring Mission satellite between 1998 and 2013 and the Optical Transient Detector (OTD) on the OrbView-1/Microlab satellite between 1995 and 2000. A researcher explains how the instrument works:

“It’s taking very rapid updates,” said Daniel Cecil, a member of the Global Hydrology and Climate Center’s lightning team. “So it will measure a background scene, and then with very rapid updates check to see if there’s a sudden change in brightness from that background scene.” If there is, the instrument records that as a flash of lightning.

In the map, areas with the fewest lightning strikes are gray and purple, while those with the highest number are in pink. We can immediately distinguish that land gets much more pounded by lightning than the ocean. That’s because land absorbs heat much faster from sunlight, causing stronger convection and higher atmospheric instability, which ultimately causes lightning storms.

Westward on the map, lightning flashes run down Mexico and Central America, before reaching their peak in Colombia and Venezuela; eastward, they peak in Singapore and Malaysia. But the fiercest lightning storms can be found, by far, in Congo. Also, lightning is far more likely to occur near the equator.  Roughly 90 percent of the lightning strikes on Earth occur between the 38th parallel south and 38th parallel north latitudes, said Cecil.

Maps, satellite imagery and more such data is essential to expanding our view of how the climate really works, and consequently help build better models that reflect reality. Soon, NASA plans on mounting lightning imaging sensor to the International Space Station from where it will be continuously able to track certain spots on the planet for storms.

“Right now, we’re piecing together snapshots,” Cecil said. “As a satellite goes over, we get to look at a storm for about a minute and a half. And in this next generation a few years from now, we’re going to have continuous measurements. So as a storm pops up, we’re going to see its entire life cycle from the first flash to the last.”

lightning

Twice as many lightnings expected by 2100 as a result of global warming

Researchers from the  Lawrence Berkeley National Laboratory and the University of California, Berkeley, have devised a model that projects how climate change affects atmospheric lightning discharges. According to their findings, global warming – particularly through more water vapor gathering in the upper atmosphere – will cause lightning strikes to increase in frequency by 50% during this century.

More warming and lightning

lightning

Photo: Chris Kotsiopoulos / National

Lightning is one of the most powerful forces found in nature (if one single lightning strike was harnessed, the energy would power an entire home for a whole week), but at its core we can say that lightning is nothing but a discharge of static electricity. What we know from static electricity is that these discharges are caused by separation of charges into positive and negative ions.  Over time more of one charge builds until its natural attraction to the opposite charge causes it to migrate in an electrical discharge. In the case of lightning, the charge is built up in water. Clouds are made up of condensed water vapor, and one of water’s fantastic molecular properties is its ability to polarize charges.

Because one of the effects of global warming is an increase of water vapor in the atmosphere, it’s expected that thunders storms will intensify and become more frequent in the coming years. So far, we’ve yet to see a reliable model, but the latest predictions reported by US scientists seem to be getting there.

“With warming, thunderstorms become more explosive,” said David Romps, an assistant professor of earth and planetary science, in a statement. “This has to do with water vapor, which is the fuel for explosive deep convection in the atmosphere. Warming causes there to be more water vapor in the atmosphere, and if you have more fuel lying around, when you get ignition, it can go big time.”

The team looked at key atmospheric parameters and correlated these with lightning rates. Namely, they combined precipitation rates (total amount of water hitting the ground from rain, snow, hail or other forms ) and “convective available potential energy” (CAPE) into their model to retrieve a value for mass and energy flow through the ascending air—energy per kilogram per square meter per second.

“CAPE is a measure of how potentially explosive the atmosphere is, that is, how buoyant a parcel of air would be if you got it convecting, if you got it to punch through overlying air into the free troposphere,” Romps said. “We hypothesized that the product of precipitation and CAPE would predict lightning.”

Using actual data from 2011 gathered by weather satellites and radiosondes – ballon-borne instruments that measure CAPE –  calculated CAPE-times-precipitation for multiple locations in the continental United States. The product was then plotted against lightning rates for the same area. Results show that  CAPE-times-precipitation accounts for 77 percent of the observed variation in the tempo of cloud-to-ground lightning. Precipitation alone only accounts for 29 percent, which explains why other models that relied solely on precipitation as the feed-in parameter failed miserably at predicting lightning rates.

[AMAZING] Lightning in slow-mo – VIDEO in 7,207 frames per second

The team then used their model with data from 11 different climate model that predict precipitation and CAPE throughout the century. On average, the models predicted an 11 percent increase in CAPE in the U.S. per degree Celsius rise in global average temperature by the end of the 21st century. If atmospheric temperature is to rise by four degrees Celsius by 2100, as many models predict it to happen, then  a roughly 50 percent increase (+/- 25%) in lightning rate is expected.

Though not that many people die from lightning strikes on a yearly basis, the damage produced by wild fires induced by lightning is considerable. Lightning ignites about 10,000 wild fires each year in the US alone or 4.1 million acres.

Findings appeared in the journal Science.

 

Parasitic vines may serve as lightning rods

The tropical rainforests of Central and South America aren’t threatened only by deforestation – they are also overrun by lianas, parasitic woody vines that clamber up trees and smother the forest canopy as they reach for sunlight. But the vines may actually help the trees in a way – scientists suspect they may in fact act as lightning rods.

Understanding how this works could prove to be instrumental in predicting how the rainforests will change in the coming years, especially given the predicted effects of climate change on both lightning and lianas. This is so important that in July, a group led by Steve Yanoviak, an ecologist at the University of Louisville in Kentucky, will head to Barro Colorado Island in Panama to begin a two-year study of lianas’ potentially protective role in the environment.

“Nobody has ever thought of lianas as anything but a structural parasite,” says Yanoviak. “But they might have this unforeseen secondary effect of protecting trees against strikes.”

Although in many areas of the world, lightning often sparks extremely dangerous forest fires, in the moist tropical forests of Panama, there is little risk of a forest fire. Instead, what lightning does is kill individual trees – something which seems to be not such a big deal. However, Yanoviak believes this could actually be quite important, especially in the context of climate change.

As the climate continues to warm more and more, droughts tend to become more and more pronounced, and the risk of lightning-triggered fires in tropical forests could increase; nobody has studied this yet.

Studies have shown that tropical forests are dealing with a massive liana invasion – by 2007, 75% of Barro Colorado Island’s trees were covered with lianas, up from 32% in 1968. Lianas are very opportunistic, taking advantage of any disturbance, taking over quickly when a fallen tree leaves a gap in the canopy and climbing higher and higher to reach the light.

Yanoviak’s initial studies have revealed that vines have lower resistance to electricity than tree branches, which means that they could serve as lightning rods, protecting the trees. Mark Cochrane, an ecologist at South Dakota State University in Brookings is excited by this idea:

“It’s an interesting hypothesis,” says Cochrane, who is not involved in the study. “But the only way the vines would shield the tree is if their conductivity was so much higher that almost all of the current flowed through the lianas.”

This seems to be indeed the key question, which even Yanoviak acknowledges. But, in his two year study period, he’ll have plenty of time to figure that out.

“At that scale they may not matter, but we don’t know that yet,” he says. “It could be that lightning is such a trivial agent of mortality that it doesn’t matter, but at least we’ll know.”

Nature doi:10.1038/nature.2014.15325

lightning

Lightning in slow-mo – VIDEO in 7,207 frames per second

lightningIn this amazing slow-motion video, the folks from ZT Research used a high resolution camera to capture a full lightning bolt from inception to it striking the ground. NASA‘s APOD serves a scientific explanation of the phenomenon:

“The above lightning bolt starts with many simultaneously creating ionized channels branching out from an negatively charged pool of electrons and ions that has somehow been created by drafts and collisions in a rain cloud. About 0.015 seconds after appearing — which takes about 3 seconds in the above time-lapse video — one of the meandering charge leaders makes contact with a suddenly appearing positive spike moving up from the ground and an ionized channel of air is created that instantly acts like a wire. Immediately afterwards, this hot channel pulses with a tremendous amount of charges shooting back and forth between the cloud and the ground, creating a dangerous explosion that is later heard as thunder. Much remains unknown about lightning, however, including details of the mechanism that separates charges.”

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