Caroline Muller looks at clouds differently than most people. Where others may see puffy marshmallows, wispy cotton candy or thunderous gray objects storming overhead, Muller sees fluids flowing through the sky. She visualizes how air rises and falls, warms and cools, and spirals and swirls to form clouds and create storms.

But the urgency with which Muller, a climate scientist at the Institute of Science and Technology Austria in Klosterneuburg, considers such atmospheric puzzles has surged in recent years. As our planet swelters with global warming, storms are becoming more intense, sometimes dumping two or even three times more rain than expected. Such was the case in Bahía Blanca, Argentina, in March 2025: Almost half the city’s yearly average rainfall fell in less than 12 hours, causing deadly floods.

Atmospheric scientists have long used computer simulations to track how the dynamics of air and moisture might produce varieties of storms. But existing models hadn’t fully explained the emergence of these fiercer storms. A roughly 200-year-old theory describes how warmer air holds more moisture than cooler air: an extra 7 percent for every degree Celsius of warming. But in models and weather observations, climate scientists have seen rainfall events far exceeding this expected increase. And those storms can lead to severe flooding when heavy rain falls on already saturated soils or follows humid heatwaves.

Clouds, and the way that they cluster, could help explain what’s going on.

A growing body of research, set in motion by Muller over a decade ago, is revealing several small-scale processes that climate models had previously overlooked. These processes influence how clouds form, congregate and persist in ways that may amplify heavy downpours and fuel larger, long-lasting storms. Clouds have an “internal life,” Muller says, “that can strengthen them or may help them stay alive longer.”

Other scientists need more convincing, because the computer simulations researchers use to study clouds reduce planet Earth to its simplest and smoothest form, retaining its essential physics but otherwise barely resembling the real world.

Now, though, a deeper understanding beckons. Higher-resolution global climate models can finally simulate clouds and the destructive storms they form on a planetary scale — giving scientists a more realistic picture. By better understanding clouds, researchers hope to improve their predictions of extreme rainfall, especially in the tropics where some of the most ferocious thunderstorms hit and where future rainfall projections are the most uncertain.

First clues to clumping clouds

All clouds form in moist, rising air. A mountain can propel air upwards; so, too, can a cold front. Clouds can also form through a process known as convection: the overturning of air in the atmosphere that starts when sunlight, warm land or balmy water heats air from below. As warm air rises, it cools, condensing the water vapor it carried upwards into raindrops. This condensation process also releases heat, which fuels churning storms.

But clouds remain one of the weakest links in climate models. That’s because the global climate models scientists use to simulate scenarios of future warming are far too coarse to capture the updrafts that give rise to clouds or to describe how they swirl in a storm — let alone to explain the microphysical processes controlling how much rain falls from them to Earth.

To try to resolve this problem, Muller and other like-minded scientists turned to simpler simulations of Earth’s climate that are able to model convection. In these artificial worlds, each the shape of a shallow box typically a few hundred kilometers across and tens of kilometers deep, the researchers tinkered with replica atmospheres to see if they could figure out how clouds behaved under different conditions.

Intriguingly, when researchers ran these models, the clouds spontaneously clumped together, even though the models had none of the features that usually push clouds together — no mountains, no wind, no Earthly spin or seasonal variations in sunlight. “Nobody knew why this was happening,” says Daniel Hernández Deckers, an atmospheric scientist at the National University of Colombia in Bogotá.

In 2012, Muller discovered a first clue: a process known as radiative cooling. The Sun’s heat that bounces off Earth’s surface radiates back into space, and where there are few clouds, more of that radiation escapes — cooling the air. The cool spots set up atmospheric flows that drive air toward cloudier regions — trapping more heat and forming more clouds. A follow-up study in 2018 showed that in these simulations, radiative cooling accelerated the formation of tropical cyclones. “That made us realize that to understand clouds, you have to look at the neighborhood as well — outside clouds,” Muller says.

Once scientists started looking not just outside clouds, but also underneath them and at their edges, they found other small-scale processes that help to explain why clouds flock together. The various processes, described by Muller and colleagues in the Annual Review of Fluid Mechanics, all bring or hold together pockets of warm, moist air so more clouds form in already-cloudy regions. These small-scale processes hadn’t been understood much before because they are often obscured by larger weather patterns.

Hernández Deckers has been studying one of the processes, called entrainment — the turbulent mixing of air at the edges of clouds. Most climate models represent clouds as a steady plume of rising air, but in reality “clouds are like a cauliflower,” he says. “You have a lot of turbulence, and you have these bubbles [of air] inside the clouds.” This mixing at the edges affects how clouds evolve and thunderstorms develop; it can weaken or strengthen storms in various ways, but, like radiative cooling, it encourages more clouds to form as a clump in regions that are already moist.

Such processes are likely to be most important in storms in Earth’s tropical regions, where there’s the most uncertainty about future rainfall. (That’s why Hernández Deckers, Muller and others tend to focus their studies there.) The tropics lack the cold fronts, jet streams and spiraling high- and low-pressure systems that dominate air flows at higher latitudes.

Supercharging heavy rains

There are other microscopic processes happening inside clouds that affect extreme rainfall, especially on shorter timescales. Moisture matters: Condensed droplets falling through moist, cloudy air don’t evaporate as much on their descent, so more water falls to the ground. Temperature matters too: When clouds form in warmer atmospheres, they produce less snow and more rain. Since raindrops fall faster than snowflakes, they evaporate less on their descent — producing, once again, more rain.

These factors also help explain why more rain can get squeezed from a cloud than the 7 percent rise per degree of warming predicted by the 200-year-old theory. “Essentially you get an extra kick … in our simulations, it was almost a doubling,” says Martin Singh, a climate scientist at Monash University in Melbourne, Australia.

Cloud clustering adds to this effect by holding warm, moist air together, so more rain droplets fall. One study by Muller and her collaborators found that clumping clouds intensify short-duration rainfall extremes by 30 to 70 percent, largely because raindrops evaporate less inside sodden clouds.

Other research, including a study led by Jiawei Bao, a postdoctoral researcher in Muller’s group, has likewise found that the microphysical processes going on inside clouds have a strong influence over fast, heavy downpours. These sudden downpours are intensifying much faster with climate change than protracted deluges, and often cause flash flooding.

The future of extreme rainfall

Scientists who study the clumping of clouds want to know how that behavior will change as the planet heats up — and what that will mean for incidences of heavy rainfall and flooding.

Some models suggest that clouds (and the convection that gives rise to them) will clump together more with global warming — and produce more rainfall extremes that often far exceed what theory predicts. But other simulations suggest that clouds will congregate less. “There seems to be still possibly a range of answers,” says Allison Wing, a climate scientist at Florida State University in Tallahassee who has compared various models.

Scientists are beginning to try to reconcile some of these inconsistencies using powerful types of computer simulations called global storm-resolving models. These can capture the fine structures of clouds, thunderstorms and cyclones while also simulating the global climate. They bring a 50-fold leap in realism beyond the global climate models scientists generally use — but demand 30,000 times more computational power.

Using one such model in a paper published in 2024, Bao, Muller and their collaborators found that clouds in the tropics congregated more as temperatures increased — leading to less frequent storms but ones that were larger, lasted longer and, over the course of a day, dumped more rain than expected from theory.

But that work relied on just one model and simulated conditions from around one future timepoint — the year 2070. Scientists need to run longer simulations using more storm-resolving models, Bao says, but very few research teams can afford to run them. They are so computationally intensive that they are typically run at large centralized hubs, and scientists occasionally host “hackathons” to crunch through and share data.

Researchers also need more real-world observations to get at some of the biggest unknowns about clouds. Although a flurry of recent studies using satellite data linked the clustering of clouds to heavier rainfall in the tropics, there are large data gaps in many tropical regions. This weakens climate projections and leaves many countries ill-prepared. In June of 2025, floods and landslides in Venezuela and Colombia swept away buildings and killed at least a dozen people, but scientists don’t know what factors worsened these storms because the data are so paltry. “Nobody really knows, still, what triggered this,” Hernández Deckers says.

New, granular data are on their way. Wing is analyzing rainfall measurements from a German research vessel that traversed the tropical Atlantic Ocean for six weeks in 2024. The ship’s radar mapped clusters of convection associated with the storms it passed through, so the work should help researchers see how clouds organize over vast tracts of the ocean.

And an even more global view is on the horizon. The European Space Agency plans to launch two satellites in 2029 that will measure, among other things, near-surface winds that ruffle Earth’s oceans and skim mountaintops. Perhaps, scientists hope, the data these satellites beam back will finally provide a better grasp of clumping clouds and the heaviest rains that fall from them.

Research and interviews for this article were partly supported through a journalism residency funded by the Institute of Science & Technology Austria (ISTA). ISTA had no input into the story.

This article originally appeared in Knowable Magazine, a nonprofit publication dedicated to making scientific knowledge accessible to all. Sign up for Knowable Magazine’s newsletter.

This striking satellite photo shows multiple examples of a rare meteorological phenomenon, known as "von Kármán vortices," swirling off at least six different islands in the Atlantic Ocean. Very rarely have so many of these swirling cloud trails been seen at once and over such a large area.

Von Kármán vortices occur when a prevailing wind encounters a landmass, disturbing the airflow and creating "a double row of vortices which alternate their direction of rotation," according to the National Oceanic and Atmospheric Administration (NOAA). These vortices then propagate downstream of the landmass and become visible when clouds get caught up in them.

In this photo, giant cloud swirls collectively cover an area of around 260,000 square miles (670,000 square km), making this one of the most widespread examples of concurrent vortices ever seen, according to NASA's Earth Observatory.

The most intricate swirls in the photo are seen in the vortices off Madeira, a Portuguese archipelago, at the top of the image (see below). Here, the high concentration of clouds reveals the detailed movements of the disturbed air in exceptional detail.

Related: See all the best images of Earth from space

Less-defined swirling trails are also seen trailing off the Spanish Canary Islands. From left to right, these are: La Palma, El Hierro, La Gomera, Tenerife and Gran Canaria. If you look closely (see below), you can see that the vortices from La Gomera and Tenerife interfere with each other, almost canceling them out completely.

Madeira and the Canary Islands are among the best places on Earth to see von Kármán vortices, according to the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT). This is because they have high peaks, high temperatures and are reasonably separated from their respective continents.

These swirls are also commonly spotted coming from Guadalupe, a group of six French-owned islands in the Caribbean, on the opposite side of the Atlantic. On rare occasions, the swirls have also coincided with other phenomena, such as a warped "double rainbow."

While the vortices mostly occur in tropical climates, they can also be seen in the Arctic, such as on Svalbard's Bear Island, where they can sometimes appear alongside swirling algal blooms.

On average, a pair of von Kármán vortices is created somewhere on Earth every eight hours, according to EUMESTAT.

The universe's missing matter may have finally been found.

Astronomers think regular matter — that is, the stuff that isn't dark matter — makes up about 15% of the universe's total mass. However, for years, researchers have run into a problem when trying to quantify it: They haven't been able to find about half of that "normal" matter in the stars, galaxies and other space structures we can see.

But now, a large, international team of researchers has found that the diffuse hydrogen gas surrounding most galaxies is significantly more extensive than scientists previously thought — so extensive, in fact, that it could account for most of the universe's missing matter, the team says.

"The measurements are certainly consistent with finding all of the [missing] gas," study co-author Simone Ferraro, an astronomer at the University of California, Berkeley, said in a statement. The study is currently available on the preprint server arXiv and is undergoing peer review for publication in the journal Physical Review Letters.

The hunt for the missing matter

For their investigation, the researchers used data from the Dark Energy Spectroscopic Instrument (DESI) at Kitt Peak National Observatory in Arizona, as well as from the Atacama Cosmology Telescope in Chile.

Related: 'The universe has thrown us a curveball': Largest-ever map of space reveals we might have gotten dark energy totally wrong

Using DESI observations, the team stacked images of approximately 7 million galaxies to measure the faint halos of ionized hydrogen gas at the galaxies' edges. These halos are typically too faint to be seen by normal methods. So instead, the team measured how much the gas dimmed or brightened radiation from the cosmic microwave background — leftover radiation from the Big Bang that is prevalent throughout the universe.

The team also discovered that the clouds of ionized hydrogen formed ghostly, nearly invisible filaments between galaxies. If it connects most of the galaxies in the universe, this cosmic web would easily span far enough to account for the previously undetected matter.

Black holes on duty

The discovery also may change what we know about black hole behavior. Scientists initially thought the supermassive black holes at the hearts of most galaxies only spewed jets of gas early in their life cycles. But the presence of such extensive diffuse gas clouds indicates that these black holes probably become active more frequently than previously thought.

"One of the hypotheses is that [black holes] turn on and off occasionally in what is called a duty cycle," first study author Boryana Hadzhiyska, an astronomer at the University of California, Berkeley, said in the statement.

The next step will be to incorporate the new measurements into existing cosmological models. "There are a huge number of people interested in using our measurements to do a very thorough analysis that includes this gas," Hadzhiyska said.

This striking satellite image reveals a giant, near-perfect cloud circle that formed in the heart of the Pacific Ocean more than a decade ago. While this type of cloud is not uncommon, it is extremely rare to find one isolated and in the middle of nowhere, experts say.

The strange structure, which is approximately 280 miles (450 kilometers) wide, was spotted "a few thousand kilometers southwest of the Hawaiian Islands" by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite, according to NASA's Earth Observatory.

The fluffy ring is made up of cumulus clouds that have been sculpted into a Rayleigh-Benard convection cell — a meteorological phenomenon powered by the rising and falling of air that's been warmed or cooled to different temperatures, known as convection.

There are two types of cloud cells: closed cells, which occur when cold air sinks around the cells' border, causing clouds to form at their centers; and open cells, which occur when cold air sinks at the cells' center, triggering clouds to form around their borders, according to the National Oceanic and Atmospheric Administration (NOAA). The cloud ring in the satellite photo was formed by a closed cell.

Cloud cells are normally hexagonal and usually appear alongside other cells of the same type, creating noticeable patterns in the sky. Open-cell clouds often form wispy honeycomb-like lattices, but for some reason, this cell appears to be all on its own.

Related: See all the best images of Earth from space

The lone cloud ring was likely triggered by a parcel of warm air over a small island or patch of water that was superheated by the sun, according to the Earth Observatory.

"As the warm air became buoyant and rose, cumulus clouds and eventually patches of light rain probably developed. The rain would have cooled the air beneath the clouds, causing a downdraft that sent rain-cooled air outward from the original location of the clouds," Earth Observatory representatives wrote. "When the rain-cooled air encountered warmer air at the edge of the cell, it likely pushed the warm air up, which caused the ring of cumulus clouds to form."

The cloud cell was located just south of the Intertropical Convergence Zone (ICZ) — a low-pressure belt near the equator where the trade winds trigger frequent thunderstorms and heavy rainfall. This may have also played a role in the cloud's creation, according to the Earth Observatory.

The ocean surface to the east (right) of the cloud ring appears to have a metallic shine. This is the result of a sunglint, where sunlight bounces off the sea and directly back to an observing instrument in space. This can transform large patches of the ocean into swirling silver mirrors.

Cloud cells were only discovered in 1961, thanks to images from NASA's Television Infrared Observation Satellite 1 (TIROS-1) satellite — the first full-scale weather satellite ever launched into space. Before then, the intricate patterns of the cells had gone largely unnoticed by meteorologists, according to the Earth Observatory.

On March 29, a partial solar eclipse swept across parts of the Northern Hemisphere. The edge of the moon's shadow passed across Greenland, most of Europe, northern Asia, northwestern Africa and northeastern North America, including parts of 13 U.S. states.

A partial solar eclipse occurs when the moon passes between Earth and the sun but only partially covers the sun's disk. Unlike in a total solar eclipse, the moon didn't completely block out the sun this time, so observers needed equipment such as eclipse glasses or pinhole cameras to view the sun safely.

Because the eclipse happened at sunrise in North America, seeing the spectacle at its best depended on having a clear view of the eastern horizon and cloudless weather. In European time zones, the eclipse unfolded at midday, making it an easier viewing experience. Sungazers in Greenland and Europe captured these stunning images of the moon taking a "bite" out of the sun.

Nuuk, Greenland

The moon slowly traverses the sun behind a statue of Lutheran missionary Hans Egede in Nuuk, Greenland. Nuuk saw nearly 90% of the sun blacked out during the March 29 eclipse.

Rouans, France

Observers in Rouans, France, were treated to glimpses of the partial eclipse behind clouds around midday.

Brighton, England

The moon carves a bite out of the sun in Brighton, England.

Liverpool, England

Ghostly clouds obscure the sun in this eerie image of the partial eclipse behind the Liver Bird statue in Liverpool, England.

Nuuk, Greenland

A slim crescent of the sun peeks out from behind the moon above a home in Nuuk, Greenland.

Turnov, Czech Republic

Some areas, like the Czech town of Turnov, had their view of the eclipse completely obscured by clouds. Luckily, observers at the Turnov Observatory could watch livestreams of the eclipse on their phones.

Berlin, Germany

Viewers in Berlin, Germany caught the beginnings of the eclipse behind an overcast sky.

The next partial solar eclipse will be visible from parts of Australia and Antarctica on Sept. 21, 2025. Those who wish to experience totality should mark their calendars for Aug. 12, 2026, when a total solar eclipse will be visible in Greenland, Iceland, Spain and Russia, while other parts of Europe, as well as Africa and North America, will experience a partial eclipse that day.

This stunning satellite photo shows one of the world's most famous and potentially dangerous volcanoes, Mount Vesuvius, playing a game of peek-a-boo with an orbiting spacecraft through a strangely shaped hole in the clouds.

Vesuvius is a 4,203-foot-tall (1,281 meters) stratovolcano located next to the city of Naples along the western Italian coastline. It is most famous for a massive eruption in A.D. 79, which destroyed the Roman cities of Pompeii and Herculaneum, and killed around 2,000 people, around half of which were perfectly preserved by the pyroclastic flows, along with their homes and possessions.

Today, around 800,000 people live on the volcano's slopes and up to 3 million people reside within the potential danger zone of future eruptions, making Vesuvius "one of the world's most dangerous volcanoes," according to NASA's Earth Observatory.

In the image, Vesuvius' caldera — a large bowl-like depression caused by the collapse of the mountain's summit during a previous eruption — appears to peer up through a gap in the clouds like a giant eye.

A large curved ridge can also be seen near the top of the cloud gap. This is the remnant of Mount Somma — an ancient volcano that once stood in the same spot as Vesuvius, before the newer volcano's cone grew from its center.

Related: See all the best images of Earth from space

It is unclear exactly what caused the gap in the otherwise thick clouds covering Vesuvius and Naples.

However, the circular shape of the hole is similar to circular holes punched in the clouds by airplanes, known as "fallstreak holes." It is, therefore, plausible that a plane taking off or landing from Naples International Airport could have created the hole.

"Ticking time bomb"

Vesuvius is part of the Campanian volcanic arc — a string of volcanoes in Italy, including the currently active Mount Etna, that sits on a boundary between the African and Eurasian tectonic plates.

The volcano's last major eruption concluded in 1944. Since then, the region surrounding Vesuvius has experienced several earthquake swarms, most recently in 1999, according to the Global Volcanism Program at the Smithsonian Museum of Natural History.

Scientists also believe that the next big eruption may not be too far around the corner.

In a 2011 paper published in Nature, researchers described Vesuvius as "Europe's ticking time bomb" and warned that scientists and the civil authorities can't agree on how to prepare for a future eruption.

This striking satellite shot shows a pair of simultaneous phenomena painting parallel swirls in the sea and sky surrounding Bear Island. The isolated land mass, also known as Bjørnøya, is located in Norway's Svalbard archipelago and is surrounded by highly radioactive waters that may endanger local wildlife — which, ironically, does not include many bears.

In the upper left corner of the image, a gap in the clouds is trailed by a series of interlinked cloud swirls that appear to have been platted together like a pretzel. These swirls, known as von Kármán vortices, are formed when clouds get caught up in an airflow that has been disrupted by a tall landmass, most often above an ocean, according to NASA's Earth Observatory.

In this case, the vortices are created by clouds passing over Miseryfjellet, the largest mountain on Bear Island. Miseryfjellet, which translates to "misery mountain," has three peaks: Urd, Verdande and Skuld, named after a trio of deities from Norse mythology, known as the Norns. The tallest peak, Skuld, stands around 1,759 feet (536 meters) above sea level.

In the center of the image, a gigantic bloom of photosynthetic algae, or phytoplankton, can be seen swirling near the surface of the Barents Sea. The light green hues of the algal artwork are the result of chlorophyll — the pigment in algae and plants that allows them to convert sunlight into energy, via photosynthesis. The spiraling shapes of the bloom, which spans up to 250 miles (400 kilometers) across, are the result of ocean currents.

Related: See all the best images of Earth from space

The simultaneous appearance of von Kármán vortices and the algal bloom is a complete coincidence and the two phenomena are in no way connected, according to Earth Observatory.

Bear Island

Dutch explorers first discovered Bear Island in the late 16th century and named it after a polar bear (Ursus maritimus) that was seen swimming nearby. However, polar bears are rarely seen on the island, which is one of the most southern points in Svalbard and is rarely accessible to the white bears via Arctic sea ice.

For example, in 2019, researchers stationed at the Bjørnøya weather station spotted a polar bear for the first time in more than 8 years, according to PolarBearScience.com.

Instead, the island's most abundant residents include foxes, seals and seabirds. In total, around 1 million seabirds gather along the island's cliffs every year during the breeding season, according to Earth Observatory.

However, in recent years, fears have been raised about how these birds and the rest of the island's ecosystem could be impacted by an unusual spike in radioactivity leaking from a Cold War-era nuclear submarine, K-278 Komsomolets, which sunk to the seafloor in 1989 roughly 115 miles (185 km) southwest of Bear Island.

In 2019, the BBC reported that the levels of radiation in the water surrounding the submarine were 800,000 times higher than normal, thanks to continued leakage from the vessel's reactor. However, it is still unclear whether this could be impacting the wider marine environment.

New photos have revealed a pair of gigantic white thunderstorms raging in one of Jupiter's large reddish brown belts. The swirling storms, which are likely spewing giant green lightning bolts through the gas giant's cloudy atmosphere, could end up diluting the belt's rusty color, drastically changing the planet's appearance, experts say.

Astrophotographer Michael Karrer captured the stunning new images on Nov. 30 using an 8-inch Celestron telescope from near his home in Austria. The photos show two large white patches sitting side by side in the gas giant's Southern Equatorial Belt (SEB) — an enormous dark band of clouds that spins around Jupiter as it rotates.

"These [white patches] are giant thunderstorms," John Rogers, an astronomer at the British Astronomical Association who specializes in Jupiter, told Spaceweather.com. "The last time we saw storms like this [on Jupiter] was 8 years ago in 2016-17."

The storms likely extend around 60 miles (100 kilometers) below Jupiter's swirling surface and, although their exact widths have not been calculated yet, both storms "are wide enough to swallow Earth with room to spare," according to Spaceweather.com.

Related: 7 solar system worlds where the weather is crazy

The storms are not large enough to stay intact for long periods, like Jupiter's famous Great Red Spot, and will instead get pulled apart, Rogers explained. As this happens, the thunderstorm’s ghostly hues will mix in with the rest of the SEB’s rusty clouds, "causing the familiar brown belt to fade as its color is diluted by the white storm front," Spaceweather.com reported. If you look closely at the image, you can already see this starting to happen as several thin streams of white trail behind the thunderstorms.

This color-changing has happened before. In fact, the SEB had previously become so diluted by storms that it "disappeared" between 1973 and 1991, and briefly in 2010, according to Astronomy Magazine. However, it's too soon to say whether these new storms will erase the current rust-colored belt.

Thunderstorms on Jupiter are powered by convection, or churning, within clouds similarly to their terrestrial counterparts, and also produce lightning. However, unlike Earth's lightning, which often has a blue hue caused by water vapor, Jovian lightning bolts tend to be green, thanks to atmospheric ammonia, according to NASA.

Jupiter has just passed its closest point to Earth, known as "opposition," making it bright enough to clearly see with the naked eye and a great target for backyard astronomers and photographers like Karrer. The planet reached its closest point to us on Friday (Dec. 6) when Earth is directly between the solar system's largest world and the sun, but will remain clearly visible for the next few weeks.

If you have a decent backyard telescope or a pair of stargazing binoculars then you can get a good look at Jupiter for yourself by searching for it in the Taurus constellation.

Clouds form when water vapor — an invisible gas in the atmosphere — sticks to tiny floating particles, such as dust, and turns into liquid water droplets or ice crystals. In a newly published study, we show that microplastic particles can have the same effects, producing ice crystals at temperatures 5 to 10 degrees Celsius (9 to 18 degrees Fahrenheit) warmer than droplets without microplastics.

This suggests that microplastics in the air may affect weather and climate by producing clouds in conditions where they would not form otherwise.

We are atmospheric chemists who study how different types of particles form ice when they come into contact with liquid water. This process, which occurs constantly in the atmosphere, is called nucleation.

Related: Humans inhale a staggering amount of microplastic every week. Here's where it ends up.

Clouds in the atmosphere can be made up of liquid water droplets, ice particles or a mixture of the two. In clouds in the mid- to upper atmosphere where temperatures are between 32 and minus 36 F (0 to minus 38 C), ice crystals normally form around mineral dust particles from dry soils or biological particles, such as pollen or bacteria.

Microplastics are less than 5 millimeters wide — about the size of a pencil eraser. Some are microscopic. Scientists have found them in Antarctic deep seas, the summit of Mount Everest and fresh Antarctic snow. Because these fragments are so small, they can be easily transported in the air.

Why it matters

Ice in clouds has important effects on weather and climate because most precipitation typically starts as ice particles.

Many cloud tops in nontropical zones around the world extend high enough into the atmosphere that cold air causes some of their moisture to freeze. Then, once ice forms, it draws water vapor from the liquid droplets around it, and the crystals grow heavy enough to fall. If ice doesn't develop, clouds tend to evaporate rather than causing rain or snowfall.

While children learn in grade school that water freezes at 32 F (0 C), that's not always true. Without something to nucleate onto, such as dust particles, water can be supercooled to temperatures as low as minus 36 F (minus 38 C) before it freezes.

For freezing to occur at warmer temperatures, some kind of material that won't dissolve in water needs to be present in the droplet. This particle provides a surface where the first ice crystal can form. If microplastics are present, they could cause ice crystals to form, potentially increasing rain or snowfall.

Clouds also affect weather and climate in several ways. They reflect incoming sunlight away from Earth's surface, which has a cooling effect, and absorb some radiation that is emitted from Earth's surface, which has a warming effect.

The amount of sunlight reflected depends on how much liquid water vs. ice a cloud contains. If microplastics increase the presence of ice particles in clouds compared with liquid water droplets, this shifting ratio could change clouds' effect on Earth's energy balance.

How we did our work

To see whether microplastic fragments could serve as nuclei for water droplets, we used four of the most prevalent types of plastics in the atmosphere: low density polyethylene, polypropylene, polyvinyl chloride and polyethylene terephthalate. Each was tested both in a pristine state and after exposure to ultraviolet light, ozone and acids. All of these are present in the atmosphere and could affect the composition of the microplastics.

We suspended the microplastics in small water droplets and slowly cooled the droplets to observe when they froze. We also analyzed the plastic fragments' surfaces to determine their molecular structure, since ice nucleation could depend on the microplastics' surface chemistry.

For most of the plastics we studied, 50% of the droplets were frozen by the time they cooled to minus 8 F (minus 22 C). These results parallel those from another recent study by Canadian scientists, who also found that some types of microplastics nucleate ice at warmer temperatures than droplets without microplastics.

Exposure to ultraviolet radiation, ozone and acids tended to decrease ice nucleation activity on the particles. This suggests that ice nucleation is sensitive to small chemical changes on the surface of microplastic particles. However, these plastics still nucleated ice, so they could still affect the amount of ice in clouds.

What still isn't known

To understand how microplastics affect weather and climate, we need to know their concentrations at the altitudes where clouds form. We also need to understand the concentration of microplastics compared with other particles that could nucleate ice, such as mineral dust and biological particles, to see whether microplastics are present at comparable levels. These measurements would allow us to model the impact of microplastics on cloud formation.

Plastic fragments come in many sizes and compositions. In future research, we plan to work with plastics that contain additives, such as plasticizers and colorants, as well as with smaller plastic particles.

The Research Brief is a short take about interesting academic work.

This edited article is republished from The Conversation under a Creative Commons license. Read the original article.

Wildfire blowups, fire whirls, towering thunderstorms: When fires get large and hot enough, they can actually create their own weather.

In these extreme fire situations, firefighters' ordinary methods to directly control the fire don't work, and wildfires burn out of control. Firefighters have seen many of these risks in the enormous Park Fire burning near Chico, California, and other wildfires in summer 2024.

But how can a fire create weather?

I'm an atmospheric scientist who uses data collected by satellites in weather prediction models to better anticipate extreme fire weather phenomena. Satellite data shows fire-produced thunderstorms are much more common than anyone realized just a few years ago. Here's what's happening.

The wildfire and weather connections

Imagine a wildland landscape with dry grasses, brush and trees. A spark lands, perhaps from lightning or a tree branch hitting a power line. If the weather is hot, dry and windy, that spark could quickly ignite a wildfire.

When vegetation burns, large amounts of heat are released. This heats the air near the ground, and that air rises like a hot air balloon because hot air is less dense than cool air. Cooler air then rushes in to fill the void left by rising air.

This is how wildfires create their own wind patterns.

What happens next depends on the stability of the atmosphere. If the temperature cools rapidly with elevation above the ground, then the rising air will always be warmer than its surroundings and it will keep rising. If it rises high enough, the moisture will condense, forming a cloud known as a pyrocumulus or flammagenitus.

RELATED: Earth's weather is getting weirder. Here's why.

If the air keeps rising, at some point the condensed moisture will freeze.

Once a cloud has both liquid and frozen water particles, collisions among these particles can lead to electrical charge separation. If the charge buildup is large enough, an electrical discharge — better known as lightning — will occur to neutralize the charges.

Whether a fire-induced cloud will become a thunderstorm depends on three key ingredients: a source of lift, instability and moisture.

Dry lightning

Wildfire environments typically have limited moisture. When conditions in the lower atmosphere are dry, this can lead to what's known as dry lightning.

No one living in a wildfire-prone environment wants to see dry lightning. It occurs when a thunderstorm produces lightning, but the precipitation evaporates before reaching the ground. That means there is no rain to help put out any lightning-sparked fires.

Fire whirls

As air rises in the atmosphere, it may encounter different wind speeds and directions, a condition known as wind shear. This can cause the air to spin. The rising air can tilt the spin to vertical, resembling a tornado.

These fire whirls can have powerful winds that can spread flaming ash, sparking new areas of fire. They usually are not true tornadoes, however, because they aren't associated with rotating thunderstorms.

Decaying storms

Eventually, the thunderstorm triggered by the wildfire will begin to die, and what went up will come back down. The downdraft from the decaying thunderstorm can produce erratic winds on the ground, further spreading the fire in directions that can be hard to predict.

When fires create their own weather, their behavior can become more unpredictable and erratic, which only amplifies their threat to residents and firefighters battling the blaze. Anticipating changes to fire behavior is important to everyone's safety.

Satellites show fire-created weather isn't so rare

Meteorologists recognized the ability of fires to create thunderstorms in the late 1990s. But it wasn't until the launch of the GOES-R Series satellites in 2017 that scientists had the high-resolution images necessary to see that fire-induced weather is actually commonplace.

Today, these satellites can alert firefighters to a new blaze even before phone calls to 911. That's important, because there is an increasing trend in the number, size and frequency of wildfires across the United States.

Climate change and rising fire risks

Heat waves and drought risk have been increasing in North America, with rising global temperatures more frequently leaving dry landscapes and forests primed to burn. And climate model experiments indicate that human-caused climate change will continue to raise that risk.

As more people move into fire-risk areas in this warming climate, the risk of fires starting is also rising. With fires come cascading hazards that persist long after the fire is out, such as burn-scarred landscapes that are much more susceptible to landslides and debris flows that can affect water quality and ecosystems.

Communities can reduce their vulnerability to fire damage by building defensible spaces and firebreaks and making homes and property less vulnerable. Firefighters can also reduce the surrounding fuel loads with prescribed fire.

It's important to remember that fire is a natural part of the Earth system. As fire scientist Stephen J. Pyne writes, we as humans will have to reorient our relationship with fire so we can learn to live with fire.

This edited article is republished from The Conversation under a Creative Commons license. Read the original article.

This 2023 astronaut photo captures the striking beauty of a pair of perfectly aligned, arrow-shaped wave clouds rippling above the Crozet Islands — an archipelago of uninhabited French islands in the Southern Ocean, located roughly halfway between South Africa and Antarctica. 

Wave clouds are repeating bands of cloud and non-cloud that look like wispy streaks floating in the sky when viewed from above or below. These bands are created when stable air moves over raised land. The topography pushes the air upward before gravity pulls it back down, causing the air to oscillate up and down, according to NASA's Earth Observatory.

When the air rises, it cools down, and water vapor condenses into clouds. But when gravity pulls the air downward, it is compressed by increased atmospheric pressure, which heats it up via a process called adiabatic heating and forces any clouds in the air to evaporate, according to the National Oceanic and Atmospheric Administration.  

Wave clouds are also known as gravity waves. This should not be confused with "gravitational waves," which are ripples in space-time created by extreme cosmic entities such as black holes and colliding galaxies.

Related: 12 amazing images of Earth from space 

The wave cloud on the left of the image is formed by air passing over Mount Marion-Dufresne, a 3,576-foot-tall (1,090 meters) peak on East Island; the pattern on the right is caused by Mascarin Peak, a mountain on Possession Island that stands 3,064 feet (933 m) tall. The two islands are separated by around 10 miles (16 kilometers) of water.

Wave clouds are rare but can be found more often over large bodies of water because the air there is more stable, which makes it more prone to oscillating if it is disturbed, according to NASA. 

Similar wave clouds were spotted over the Crozet Islands in 2012 and 2014 but did not look as perfectly aligned as the pair in this photo.

The Crozet Islands are uninhabited apart from a small research station on Possession Island, from where scientists study the islands' more than 5 million penguins and other marine wildlife, according to NASA's Earth Observatory.

In the past, these islands have also temporarily been home to several groups of marooned sailors who survived being shipwrecked by the jagged rocks along the islands' steep cliffs, according to Encyclopedia Britannica. In 1876, half of the 88 passengers and crew onboard the shipwrecked vessel Strathmore survived on Possession Island for seven months before being rescued, according to The New Zealand Herald.

Astronomers think they've detected an extremely rare, luminous phenomenon known as a "glory" in the hellish atmosphere of a distant exoplanet. If the finding is confirmed, it would be the first time one of these rainbow-colored light shows has been spotted outside the solar system.

The exoplanet, WASP-76 b, is located around 637 light-years from Earth. It was first discovered in 2013 by the Wide Angle Search for Planets (WASP) project, which looks for planets as they pass between, or transit, their parent star and Earth.

The exoplanet — which may have cannibalized a smaller, Mercury-size neighbor in the past — is around 90% the mass of Jupiter but about twice as wide. It is unusually close to its home star, orbiting around 20 times closer than Mercury orbits the sun. As a result, it takes WASP-76 b just 1.8 days to complete one trip around its star.

In 2020, researchers discovered that the planet is tidally locked, meaning one side is always facing its home star, just as the moon faces Earth. As a result, the exoplanet's sunlit side is around 4,350 degrees Fahrenheit (2,400 degrees Celsius), while its dark side is slightly cooler. Researchers think that, due to this subtle temperature difference, metals like iron could be vaporized on the light side and then condense into rain on the dark side.

In a new study, published April 5 in the journal Astronomy & Astrophysics, researchers examined new data on WASP-76 b collected by multiple spacecraft, including the European Space Agency's (ESA) Characterising Exoplanet Satellite and NASA's Transiting Exoplanet Survey Satellite. This analysis revealed a "bright spot" of light coming from the exoplanet's eastern limb, along the boundary where the planet's permanent day and night meet.

The researchers think this bright spot could be a "glory." This rare visual phenomenon, when seen on Earth, is normally made up of concentric rainbow rings forming a giant circle.

Related: 10 extreme exoplanets that are out of this world

On Earth, glories are formed when sunlight squeezes through small holes between water molecules in clouds or fog, bending the light and separating it into its individual wavelengths. This is similar to how rainbows work, except with glories, the light is bent by diffraction, which is when light is bent around an obstruction, instead of refraction, or when light is bent as it passes through different mediums.

"It requires very peculiar conditions," study lead author Olivier Demangeon, an astronomer at Portugal's Institute of Astrophysics and Space Sciences, said in a statement. "First, you need atmospheric particles that are close-to-perfectly spherical, completely uniform and stable enough to be observed over a long time." The observer also has to be at just the right orientation to be able to see the diffracted light, he added.

However, it is possible that, if given similar conditions, the effect might happen on other planets. We have already seen this phenomenon elsewhere in the solar system, on Venus, according to ESA.

Researchers are unsure exactly how a glory would form on WASP-76 b. But given that the bright spot has been visible across multiple years, the medium that diffracts the light is likely a lot more stable than the water vapor in our planet's atmosphere.

However, the glory theory is based on an "incredibly faint signal," so it's not certain, Matthew Standing, an exoplanet scientist at ESA who was not involved in the study, said in the statement.

"Further proof is needed to say conclusively that this intriguing 'extra light' is a rare glory," Theresa Lüftinger, an ESA astrophysicist who was not involved in the study, said in the statement. We will likely need more powerful instruments, like those on the James Webb Space Telescope, to get this proof, she added.

If it is a glory, researchers could use the data to hunt for more extrasolar examples of these light shows in the atmospheres of other exoplanets to learn more about this puzzling phenomenon.

For the total solar eclipse on April 8, many people will strive to be within the path of totality, where the sun's face will be completely blocked by the moon's shadow. But even if you're within this path, it doesn't guarantee you'll have clear skies on eclipse day.

So what happens if it's cloudy where you are on April 8? Will you notice anything as the moon's shadow sweeps over you?

That depends on how thick and how extensive the clouds are. Regardless, you will certainly notice some very unusual effects when the moon's shadow passes by. I have had the misfortune of being completely clouded out of two of the 13 total solar eclipses I have journeyed to, and in a third case, I managed to sneak in a view of the corona even though virtually the entire sky was clouded over.

So, based on those three experiences, here is what you can expect to see if the weather does not work in your favor and you ultimately must utter those two words every eclipse chaser does not want to hear: "Clouded out!"

Passage of the moon's shadow

Should there be considerable cloud cover on "E-Day," the clouds may actually have an advantage: They will provide a projection screen of sorts to view the rapid approach and departure of the moon's dark umbral shadow. Isabel Martin Lewis described the effect in her 1924 book "A Handbook of Solar Eclipses."

"At the time of eclipse when the shadow of the moon sweeps over us we are brought into direct contact with a tangible presence from space beyond and we feel the immensity of forces over which we have no control," Lewis wrote. "The effect is awe-inspiring in the extreme. In fact, the passing of the moon's shadow, if one is fortunate to observe it, will be one of the most impressive features of the eclipse."

Mid-to-high-level clouds

If your sky is covered with mid-to-high-level clouds — cirrostratus, altostratus and/or cirrocumulus — you will likely be able to see the forward edge of the elliptical shadow move rapidly toward you and then over you just prior to and at the onset of totality. And with its passage may come a remarkable change in the overall quality of light on the surrounding landscape and a dramatic change in the clouds' color.

On July 10, 1972, at my very first total solar eclipse, my family and I were located just outside Cap-Chat, Quebec, a sleepy Canadian community of 2,000 whose population swelled to nearly 30,000 on eclipse day. The eclipse began under bright sunshine, mixed with some wispy high clouds. But as more and more of the sun became covered, the high cloudiness quickly increased and began to lower so that, at the onset of totality, virtually the whole sky was covered by a swath of battleship-gray clouds.

But upon the arrival of the moon's shadow, we saw its distinctly sharp edge move in. For those of a certain age who might remember the long-running television soap opera "The Edge of Night," whose opening showed an animation with a line of darkness sweeping over a city, that's exactly what I was reminded of as we were enveloped by the moon's umbral shadow. Once you actually experience it for yourself, it becomes easy to understand why this sight was so terrifying to ancient people.

Related: 'Zeus made night from mid-day': Terror and wonder in ancient accounts of solar eclipses

Along with the sudden darkness came a change in the clouds' color. Behind the forward-moving edge of the moon's shadow were strange and exotic colors. The dull gray suddenly became yellow-orange and tints you'd see while looking through a beer or iodine bottle. Indeed, along the very edge of the disappearing sun at the start and end of totality, an arc of ruby red or fuchsia associated with the solar chromosphere appeared. It looked bright red because the hydrogen in the sun was emitting a reddish light at high temperatures, and some of this light may become evident in the clouds at the beginning and end of totality.

Some final comments regarding my 1972 eclipse experience. Despite the heavy cloud cover, we managed to catch sight of the totally eclipsed sun through a fortuitous opening in the overcast sky, some 30 seconds after totality began. As totality was ending, we saw the back edge of the shadow distinctly, projected on the clouds, racing away to the northeast. I remember my grandfather calling out to my grandmother, "Inez! Look, look! It's going that way." Meanwhile, my sister Lisa, taking this all in, said simply, "That was weird!"

"Incredible sight!"

Interestingly, in March 1970, during special coverage of the total solar eclipse on CBS TV , correspondent Bill Plante (1938-2022) was stationed in Halifax, Nova Scotia, under cloudy skies. Yet he was quite attentive to the changes taking place as the lunar shadow swept in.

"In the last 30 seconds we have witnessed the most incredible sight — in spite of the fact that we cannot see the sun — for it has become as dark as night!" he said. "The light has fallen so quickly, from an acceptable twilight or reading level or cloud-cover level, to virtual night. And just off to the north and to the east, beneath this layer of dark, dark sky, there is a lovely pink and orange horizon; an orange and gold color. We say again, it was just an incredible and fascinating phenomenon, to have the skies go so suddenly dark, in less than 30 seconds, and now we have this totality of an eclipse!"

It sounds like Plante was impressed, despite the clouds.

Just a few clouds

Sometimes, you're lucky enough to get a mainly clear sky. But even then, unfortunately, one of the few clouds in the sky might happen to be in front of the sun during the total phase of the eclipse.

That happened to me on Oct. 12, 1977, in Colombia, South America. During the 38-second interval of totality, a single rag of cloud drifted in front of the sun. Should something like that happen to you, the best you can do is look around the darkened sky for some of the brighter stars and planets and try to watch for the passage of the moon's shadow.

As I noted in my personal journal later on, "When totality arrived, virtually the entire sky was clear and the seeing and transparency were close to excellent. We were able to easily see seven stars and were awed at third contact by the passage of the moon's umbral shadow cone retreating rapidly to the east. And in the east, part of a rainbow changed to all red just as totality began.

"There was only one thing wrong: The sun was behind a cloud! It began encroaching upon the sun a few minutes before totality and left just a minute or two after the sun began to reappear. As if to rub salt into the wound, not another cloud interfered, even as the partially eclipsed sun set behind the Andes! For me, Colombia was Cap Chat in reverse. What goes around, comes around!"

For more on this misadventure, read my colleague Glenn Schneider's comments.

Thick, low clouds

Finally, there is the possibility that on eclipse day, your view will be covered by clouds at low altitudes, generally below 6,500 feet (1,980 meters). They tend to be thick, low, flat clouds that cover large areas and often bring precipitation.

In December 2021, my wife Renate and I were on board an icebreaker, sailing off the coast of Antarctica, when we encountered the moon's shadow for a total eclipse lasting just over a minute and a half. Unfortunately, our skies were heavily overcast with low clouds and spotty, light precipitation.

In such a situation, the effects of a total solar eclipse can best be described as being in a lighted room where someone turns a dimmer switch down and then turns it back up, causing the light to return.

As I noted in my story for Space.com, "Totality lasted 97 seconds. No distinct shadow or cone of darkness was noted. Rather, just an amorphous darkening of the sky — like someone turning down a rheostat or dimmer switch. No colors were seen and the end of totality seemed more pronounced as the light seemed to come back quicker than it when it faded away. During totality, it actually began to drizzle very lightly and a few minutes after third contact it actually started to snow lightly. The air temperature hovered at around 0°C (32°F), but factoring in the winds made it feel noticeably colder."

Final thoughts

I suppose Antarctica was the most disappointing of all my eclipse experiences; aside from getting dark and light again, there really wasn't much more to see. I hope everyone who positions themselves in the path of the moon's dark shadow will get a clear view of the April 8 eclipse. But as you can see, unless the clouds are low and thick with some rain or snow falling, the moon's shadow racing by and the eerie colors accompanying it should still make for quite a show!

Originally posted on Space.com.

The splendor of a solar eclipse is unique to our world — nowhere else in the solar system does a planet's moon so perfectly block the light of the sun. The fast and fleeting darkness of those events affects many things on Earth, including animal behavior and waves in the ionosphere. Researchers have now found that cumulus cloud cover fell by more than a factor of 4, on average, as the moon's shadow passed over Earth during a recent annular eclipse. This little-studied aspect of solar eclipses has important lessons for geoengineering efforts aimed at blocking sunlight, the team proposed.

Experiments in the sky

Solar eclipses occur anywhere from 2 to 5 times per year, and these events confer neat opportunities for scientific investigations, said Victor J. H. Trees, a geoscientist at Delft University of Technology in the Netherlands. "Solar eclipses are unique experiments." They allow researchers to study what happens when sunlight is rapidly obscured, he said. "They're very different than the normal day-night cycle."

Trees and his colleagues recently analyzed cloud cover data obtained during an annular eclipse in 2005, visible in parts of Europe and Africa. They mined visible and infrared imagery collected by two geostationary satellites operated by the European Organisation for the Exploitation of Meteorological Satellites. Going to space was key, Trees said. "If you really want to quantify how clouds behave and how they react to a solar eclipse, it helps to study a large area. That's why we want to look from space."

The researchers focused on a square region spanning 5° in both latitude and longitude centered above South Sudan. With their bird's-eye perspective, they tracked cloud evolution for several hours leading up to the eclipse, during the eclipse, and for several hours afterward.

Related: Places with the best weather to watch the April 8 solar eclipse (and what happens if it's cloudy where you are)

Goodbye, sun; Goodbye, clouds

Low-level cumulus clouds — which tend to top out at altitudes around 2 kilometers (1.2 miles) — were strongly affected by the degree of solar obscuration. Cloud cover started to decrease when about 15% of the sun's face was covered, about 30 minutes after the start of the eclipse. The clouds started to return only about 50 minutes after maximum obscuration. And whereas typical cloud cover hovered around 40% in noneclipse conditions, less than 10% of the sky was covered with clouds during maximum obscuration, the team noted.

"On a large scale, the cumulus clouds started to disappear," Trees said.

To dig into the physics behind their observations, Trees and his colleagues collected land surface temperature measurements from the same two geostationary satellites. The temperature of the ground matters when it comes to cumulus clouds, Trees said, because they are low enough to be significantly affected by whatever is happening on Earth's surface.

Not surprisingly, land surface temperatures dropped as the moon increasingly blocked the sun's light. "We knew that even small changes in solar radiation have an effect on the land surface temperature," said Virendra Ghate, an atmospheric scientist at Argonne National Laboratory in Lemont, Ill., not involved in the research.

The researchers estimated a maximum change in land surface temperature of nearly 6°C for the 2005 eclipse. They also found that surface temperature decreased in lockstep with the obscuration fraction, without any significant time lag. That's consistent with observations made during other solar eclipses.

Follow the heat

The pronounced decrease in land surface temperature during a solar eclipse is what's driving changes in cumulus cloud cover, the researchers concluded. That's logical, Ghate said, because cumulus clouds form when relatively warm and moist air rises from Earth's surface, cools, and eventually condenses into cloud droplets. When land surface temperatures decrease, there's a smaller temperature gradient near Earth's surface and therefore a smaller force driving cloud-forming air upward, he said. "You don't have the source of buoyancy."

The delays that Trees and his colleagues observed — between the start of the eclipse and when clouds started dissipating and also between the time of maximum obscuration and when clouds started returning — also reveal something about the so-called boundary layer, the lowest level of Earth's atmosphere. Each of those lags has a physical meaning, Trees said. "It tells us how quickly the air is rising."

Beyond shedding light on the physics of cloud dissipation during solar eclipses, these new findings also have implications for future geoengineering efforts, Trees and his collaborators suggested. Discussions are underway to mitigate the effects of climate change by, for instance, seeding the atmosphere with aerosols or launching solar reflectors into space to prevent some of the sun's light from reaching Earth. Such geoengineering holds promise for cooling our planet, researchers agree, but its repercussions are largely unexplored and could be widespread and irreversible.

These new results suggest that cloud cover could decrease with geoengineering efforts involving solar obscuration. And because clouds reflect sunlight, the efficacy of any effort might correspondingly decrease, Trees said. That's an effect that needs to be taken into account when considering different options, the researchers concluded.

 This article was originally published on Eos.org. Read the original article.

Eclipse chasing is as much about cloud avoidance as it is about astronomy. On April 8, those within the 115-mile-wide (185 kilometers) path of totality that stretches from northwest Mexico to southeast Canada will be hoping for clear skies.

The prize is an unobstructed view of an eclipsed sun during totality — the only time it's safe to remove solar eclipse glasses and the only time the sun's spectacular corona can be seen with the naked eye.

The southwestern parts of the path of totality, including in Mexico and Texas, are typically warm this time of the year and have a significantly higher chance of clear skies than the northeastern parts of the path, where the weather is usually colder in April.

However, no place in the path of totality has a guarantee of clear weather that day. "Even along the parts of the path with the best climate, there's still a 1-in-3 chance of having some kind of cloud cover," Jay Anderson, a Canadian meteorologist who publishes studies of the climate along eclipse tracks on Eclipsophile, told Live Science.

Without meaningful weather forecasts until a few days before April 8, all we have to go on is historical cloud-coverage data. According to TheSkyLive, everywhere in the path from Mazatlán, on Mexico's Pacific Coast, to Little Rock, Arkansas, has a 50% chance of a "mostly clear or better" sky. The website highlights the U.S.-Mexico border as statistically the most likely to be clear, with Piedras Negras, Mexico, and Eagle Pass and Uvalde, Texas, reaching 59%.

Related: April 8 total solar eclipse: The best places to stargaze near the path of totality

But none of those numbers guarantee clear skies on April 8. "Start seriously looking at weather forecasts five days out, and make plans three days [before]," Anderson advised. "Look at the forecast the night before, and if it looks better someplace else, then divert, if you can, though there are times when you have to make a decision four hours out."

Most eclipse chasers won't have the luxury to move, whether because of planned events and logistics or bad traffic. But wherever you are in the path of totality, there's always hope for clear skies because of a phenomenon called eclipse cooling.

"Clouds are driven by the sun's heating of the ground, so when the ground cools during the eclipse's partial phases, clouds can dissipate," Anderson said. "It can even go from a 70% cloud cover to 1% in the space of five to 10 minutes."

If that doesn't happen and clouds block your view of the sun's corona, don't despair. The moon's shadow will still cover you, and it will get much darker because of the clouds. Whatever the weather, a total solar eclipse never fails to impress.

A cluster of eerily circular holes recently appeared in the clouds above Florida, a stunning new NASA image shows. The rare occurrence, which has previously (and incorrectly) been linked to UFOs, has a surprisingly simple explanation — but it took scientists more than 60 years to figure it out.  

NASA's Terra satellite photographed the bizarre voids, known as fallstreak holes or hole-punch clouds, above the Gulf of Mexico off Florida's west coast on Jan. 30. NASA's Earth Observatory revealed the striking image on Feb. 26.  

Unusual, circular holes like these ones first began to appear in the 1940s, sparking wild theories that they were the result of UFOs, according to the Earth Observatory. However, they are actually created by airplanes flying through the clouds. 

There are two types of clouds in the new photos: cavum clouds, which are large, circular holes; and canal clouds, which have a more oblong shape. Both types most commonly occur in altocumulus clouds — supercooled bands of water vapor that float in the sky between 7,000 and 18,000 feet (2,100 and 5,500 meters) above the surface, much higher than most rain clouds. 

Altocumulus clouds can be as cold as around 5 degrees Fahrenheit (minus 15 degrees Celsius) without their water droplets freezing. This is because there are fewer small particles, such as dust and pollen, at that altitude, which are needed for ice crystals to form in the air. 

However, when air moves around the wings or past the propellers of airplanes, it can further cool the surrounding water vapor by as much as 36 F (20 C). At these extremely low temperatures, the droplets freeze even without particles to form around and begin to fall below the holes, creating wispy strands of cloud, known as virga. 

These wispy clouds often hang below the holes they fell from and can be seen at the heart of the misty voids when viewed from above.

Related: What happens if you skydive through a cloud?

The holes in the new image were all created by planes taking off from Miami International Airport, according to the Earth Observatory.

Cavum and canal clouds can also form naturally when specific regions of the atmosphere cool down, but this is rare.   

Scientists only discovered what was causing the more frequent artificially created holes within the last 15 years. In a 2011 study, researchers used satellite images and flight data to prove that planes were responsible.

The study also showed that the angle at which planes rise and descend through the clouds affects which type of hole will appear: A steep angle will create the more circular cavum clouds, while a more shallow angle will create stretched canal clouds.  

Cavum and canal clouds normally last around one hour before they close up, but their lifespan can be impacted by other factors such as temperature, cloud density and wind speeds, the study found.

The holes pose no threat to people on the ground but they can slightly increase the amount of precipitation that occurs in the areas surrounding airports, the study showed.

"Spectacular" rainbow-colored clouds have been shimmering in the skies over and around the Arctic for more than three days thanks to an unusual cold snap in the upper atmosphere. And even more of these technicolor treats could appear during the next few months, experts say.

The colorful clouds, known as polar stratospheric clouds (PSCs), were spotted floating high in the sky above parts of Norway, Sweden, Finland and Alaska, and even as far south as Scotland. They began to emerge on Dec. 18 and continued to appear clearly until Dec. 20, according to Spaceweather.com. Some smaller, less distinct clouds were also spotted on Dec. 21, but in general they seem to be disappearing. 

Photographer Ramunė Šapailaitė captured staggering photos of the rare phenomenon above Gran in southern Norway. Her photos revealed the rainbow hues of PSCs and their iridescent shimmer that has inspired the nickname nacreous clouds, due to their similarity with nacre — an iridescent material, also known as mother-of-pearl, that is found in the shells of some mollusks.

"The colors are spectacular," Šapailaitė told Spaceweather.com. "The clouds were visible in the sky all day, but the colors really exploded just before sunset."

The PSCs were caused by a prolonged period of unusually cold temperatures in the sky, according to Spaceweather.com.

Related: 10 bizarre phenomena that lit up the sky (and their scientific explanations)

PSCs are made from tiny ice crystals that refract, or scatter, sunlight. This separates the light into individual wavelengths, or colors, and creates the rainbow-like effect we see from the ground.

There are two types of PSCs: Type I, made from a mix of ice crystals and nitric acid, which produce less spectacular colors and are linked to the formation of ozone holes; and Type II, which are composed of pure ice crystals and produce more vivid colors. The clouds that recently formed over the Arctic were Type II.

The shimmering structures only form in the lower stratosphere, between 9.3 and 15.5 miles (15 to 25 kilometers) above Earth's surface. Normally, clouds do not form this high up in the atmosphere because it is too dry. But at extremely low temperatures — below minus 121 degrees Fahrenheit (minus 85 degrees Celsius) — widely spaced water molecules begin to coalesce into tiny ice crystals that further aggregate into clouds.

Stratospheric temperatures in the Arctic rarely drop below the threshold needed for PSCs to form, so they are normally only spotted a handful of times every year during winter months. The extreme cold snap that led to the recent appearance of PSCs may have been triggered in part by the current El Niño event, which can impact temperatures around the poles. However, human-caused climate change could also be to blame, according to Spaceweather.com.

Experts say there is a high chance that we will see more PSCs in the Arctic over the next few months, according to Spaceweather.com.

A massive, gassy planet 1,300 light-years away is so hot, its clouds are made of quartz crystals. Studying it could help scientists understand more about how clouds form in extreme alien environments.

The finding, published Oct. 16 in The Astrophysical Journal Letters, comes from an international team of researchers using the James Webb Space Telescope (JWST).

WASP-17b is a Jupiter-like exoplanet that scientists first spotted in 2009. It orbits extremely close to its star, which heats its atmosphere up to a blistering 2,700 degrees Fahrenheit (1,500 degrees Celsius). The planet itself is a bit of a lightweight; though WASP-17b's radius is about twice that of Jupiter, it has only about half Jupiter's mass. This makes WASP-17b one of the "puffiest" exoplanets discovered to date.

But astronomers recently discovered that WASP-17b's apparently fluffy clouds are hiding a secret: They're composed of tiny, solid-quartz crystals.

"We knew from Hubble observations that there must be aerosols — tiny particles making up clouds or haze — in WASP-17b's atmosphere, but we didn't expect them to be made of quartz," David Grant, an astronomer at the University of Bristol in the U.K. and first author of the study, said in a statement. "We were thrilled!"

These unexpected crystals are the first silica particles ever detected in an exoplanet's atmosphere. The researchers believe that, unlike the minuscule chips of rock that sometimes circulate in Earth's clouds, these crystals weren't swept up from WASP-17b's surface. Instead, they formed directly in its atmosphere as the result of intense heat and pressure. Based on how the crystals scatter starlight, the team estimates that each gem is about 10 nanometers across — less than one-millionth the size of an average grain of sand.

Right now, it remains unclear how pervasive these quartz clouds are across WASP-17b. The planet is tidally locked, meaning one side constantly faces its star while the other faces away. It's possible that the crystals circulate through the atmosphere on the night side, only to vaporize in the daylight.

WASP-17b's crystalline clouds are just one example of an unusual exoplanet feature discovered using JWST; in September, the telescope made news after detecting potential signs of biological life in the atmosphere of the exoplanet K2-18 b.  Soon, the telescope will turn its instruments on other weird and wonderful worlds — and scientists are waiting with bated breath to see what it spots next.

Look up at the sky and clouds may look like "feather canyons" and "ice cream castles in the air," as they did to Joni Mitchell. 

But why do they look as if they're suspended in mid-air, and are they actually floating? And if so, what keeps them aloft? 

"It's sort of an illusion," Alex Lamers, a meteorologist at the National Weather Service, told Live Science. "It's not like there's a pillow or something that's magically floating in air."

A cloud is a collection of water droplets and ice crystals. These droplets form around a cloud condensation nucleus, which could be a speck of dust or salt, Lamers explained. When a water-laden cloud grows too heavy, precipitation falls as rain, snow or hail. But even before rainfall, these droplets make their way toward Earth, albeit at a leisurely pace.

"They're falling very, very, very slowly," Lamers said. Anything falling to Earth reaches what's known as terminal velocity, or its fastest possible speed as it falls freely. Terminal velocity occurs when drag force from the air perfectly counters gravity. The water droplets are so light that their terminal velocity is super slow — between 60 and 120 feet per hour (18 to 36 meters per hour) for a droplet with a 5- to 10-micron radius. Because clouds are usually thousands of feet high in the atmosphere, this small downward shift isn’t noticeable to the eye.

Related: What happens if you skydive through a cloud?

Lamers likened a water droplet's fall to dust motes swirling in a shaft of sunlight: The motes also fall, but because they are minuscule, they fall slowly. The average size of a cloud water droplet is smaller than the radius of a human hair, according to Mark Miller, a professor of atmospheric science at Rutgers University.

But something counteracts that slow descent, which is where the illusion comes in. Updrafts of rising air keep the coalesced droplets suspended, even as they gradually fall. 

"They appear to float because essentially, they're falling at a rate slower than or equal to the updraft velocity in the cloud," Miller told Live Science. The particles fall and rise at the same time.

Water droplets become "tracers of air motion," Miller said. That is, the rising air nudges millions of droplets into the shape of its path, forming the visible cloud. But it's not just this simultaneous falling and rising at play; while clouds appear at a relatively fixed height, they fluctuate as rising air mingles with droplets as they condense and evaporate. "They're actually forming and evaporating at a rate that makes them seem a bit stationary," Miller said.

A cloud is the visible result of vertical motion and air mixing with water — while the droplets fall slowly to the ground. "You don't really see the cloud droplet motion at all," Miller said. "All you really see is the tracer of the larger-scale motion in the atmosphere." 

Cloud formation requires warm, moist air. Warm air is more buoyant than cold air, so it rises into the atmosphere and then condenses into a cloud as it cools. The cloud is less dense than the air below it. While some clouds look light and fluffy, a cumulus or thunderstorm cloud can weigh about as much as 100 elephants, though its mass and water content depend on its dimensions. In a smaller cloud only a few tens of meters tall and wide that won’t imminently precipitate, that weight doesn't always translate to much water. "If I took all the water out of that cloud, it would probably not even fill a gallon jug," Miller said.

A rare type of iridescent, shining cloud that was forecast to become much more common and visible this summer has, so far, failed to live up to the hype — and the increasingly volatile sun may be to blame.

Noctilucent clouds (NLCs), or night-shining clouds, are a type of mesospheric cloud. As the name suggests, mesospheric clouds form in the mesosphere, the third layer of Earth's atmosphere, which stretches between 31 and 50 miles (50 and 80 kilometers) above Earth's surface. NLCs are created when atmospheric water vapor freezes into ice crystals that stick to particles of atmospheric dust left behind by meteor showers and volcanic eruptions. 

The colorful clouds — which are normally electric blue but can also be silver, orange or red — typically form near the upper boundary of the mesosphere in latitudes adjacent to polar regions. As a result, they continue to reflect sunlight when the sun is positioned just below the horizon before sunrise or after sunset, which is what makes the clouds shine against the dark sky.

Related: Ultra-rare 'rainbow clouds' light up the Arctic Circle like auroras in stunning new photos

In early June, Live Science reported that the main NLC season — which covers June and July, as well as parts of August — was well underway. Based on the previous year's NLC season, which was the most impressive in 15 years, experts at the time had forecast another strong show this year.

So far, however, NLCs have failed to turn up as frequently or spectacularly as scientists initially predicted, according to Spaceweather.com. The absence of NLCs is likely linked to an increase in solar activity as the sun approaches the explosive peak in its roughly 11-year cycle, which is melting the colorful clouds as they form, experts told Live Science. 

Unusually weak NLCs 

Astrophotographer Ruslan Merzlyakov has been photographing NLCs near his home in Jutland, Denmark, since 2013. This year, he has been particularly disappointed by the lack of quality shots he has been able to capture.

"Some seasons produce more NLCs than others, but in general, it is possible to experience them almost every night," Merzlyakov told Live Science. "But this year I have only seen them twice," he said, adding that both displays were extremely weak and "nearly not worth photographing."

Unfortunately, the lack of NLCs has coincided with a technical malfunction in NASA's Aeronomy of Ice in the Mesosphere (AIM) satellite, the main device used to monitor NLCs. The spacecraft has been offline since March after its battery overloaded, and it may not fully recharge until next year. 

"AIM is the only satellite dedicated to making high-resolution observations of mesospheric clouds," Cora Randall, an atmospheric scientist at the University of Colorado Boulder, told Live Science. "So without AIM, we no longer have the ability to track the clouds and their structure with high precision."

However, ground-based instruments, which collect less-precise data than AIM but still provide a general overview of NLC trends, show that NLCs have been much rarer this year. "The NLC season started relatively late this year, and there have been fewer NLC sightings," Randall confirmed. 

Approaching solar maximum 

Historically, the appearance of NLCs has been closely tied to the solar cycle. In general, NLCs become more common during the solar minimum, when the sun is at its calmest, than during the solar maximum, when solar activity peaks and solar storms frequently bash into Earth, Randall said.

NLCs are less common during the solar maximum because higher levels of solar radiation warms the upper atmosphere, making it harder for water vapor to freeze, Randall said. The increase in radiation can also destroy water vapor in the atmosphere, meaning there is less vapor to form clouds, she added.  

When the current solar cycle began in late 2019, scientists predicted that the solar maximum would likely arrive in 2025 and be comparable to the previous maximum, which was underwhelming compared with past solar peaks. However, Live Science recently reported that the explosive peak could arrive sooner — and be more extreme — than initially expected.

Related: 10 signs the sun is gearing up for its explosive peak — the solar maximum

"I think that the lack of NLCs is a sign that we're approaching solar maximum," Randall said. However, other, unrelated factors — such as atmospheric waves, ripples in the atmosphere that can disrupt cloud formation — could be to blame, she added.

The thermosphere, the atmospheric layer that sits above the mesosphere, has already reached its highest temperature in more than 20 years, which is another strong hint that the solar cycle is fast approaching and is preventing NLCs from forming.  

The lack of NLCs has been "very surprising," Merzlyakov said. "Even though I knew that NLCs are highly linked to the solar cycle [and we are approaching the solar maximum], I was still not expecting this season to be this poor."

If the solar maximum is right around the corner, it could limit how many NLCs form in the near future. "I think it is likely that NLC seasons will be weaker than average over the next few years," Randall said.

A scientist recently snapped a series of shining arcs and halos of light surrounding the sun in the sky above the U.K., including an exceptionally rare ring of light that circled the entire sky.

Alan Fitzsimmons, an astronomer at Queen's University Belfast in Northern Ireland, captured the unusual light show above Belfast's Botanic Gardens on May 28. The display lasted around 30 minutes, Fitzsimmons told Live Science.

Some of the bizarre glowing rays were also spotted across other parts of Northern Ireland, as well as in northern England and Scotland, according to Spaceweather.com.

The arcs and halos are caused by millions of tiny, perfectly positioned ice crystals in the upper atmosphere, which often accompany thin cirrus clouds, Fitzsimmons said. "If the winds are very uniform up there, the hexagonal-shaped crystals align," he added. "This allows the sunlight refracting through them to combine, just as light refracts through a prism, producing arcs and circles of sunlight."

Related: Photographers capture the exact moment a gargantuan storm blasts out of the sun during a total solar eclipse

Fitzsimmons' image includes at least three different confirmed optical phenomena: a 22-degree halo, the large circle surrounding the sun; a pair of "sundogs," the bright points on each side of the 22-degree halo; and a complete parhelic circle, the line that bisects the circle, which also forms a full circle around the entire sky. 

A full parhelic circle is very rare because it requires at least five internal reflections from millions of individual ice crystals, all catching sunbeams simultaneously, according to Spaceweather.com.

The images also may include features of a circumscribed halo and a supralateral arc, which form the "eyelids" above and below the 22-degree halo, according to Spaceweather.com.

The parhelic circle is the rarest and most "impressive feature" in the image, Fitzsimmons said. It is something he has seen only a couple of times before, he added. But the other phenomena are more common than most people realize.

"The sun can be quite bright when they [the phenomena] are visible, so to notice them, you need to block out the sun with your thumb or a tree," Fitzsimmons said. "But anytime it's sunny with high-altitude wispy clouds, it's worth taking a look to see if there is a halo or maybe something more."

On May 30, a photographer in Finland also caught a shot of a rainbow-colored ring of light, known as a pollen corona, surrounding the sun. These rings, which are created by light scattering off of pollen grains in the air, are also hard to spot unless part of the sun's light has been blocked out.

Tiny atmospheric ice crystals can also create a range of other weird visual phenomena, such as polar stratospheric clouds, which shine like rainbows in the Arctic, and night-shining clouds (also called noctilucent clouds), which will become more visible to people in the Northern Hemisphere during June and July.

Look up an hour or two after sunset and before sunrise over the next few months and you may see ethereal blue, silver or golden streaks in the Northern Hemisphere's northern skies. 

Called noctilucent clouds (meaning "night-shining" clouds in Latin) or NLCs, these strange-looking patterns in the sky are the highest, driest, coldest and rarest clouds on Earth, according to a 2018 study of the phenomenon. 

These shimmering, night-shining clouds appear in the mesosphere — a layer of Earth's atmosphere above the stratosphere and below the thermosphere, about 47 to 53 miles (76 to 85 kilometers) above Earth's surface. Sometimes dubbed "space clouds," NLCs form just below the invisible boundary where Earth's atmosphere ends and outer space begins, roughly 62 miles (100 km) above the planet's surface, according to NASA. 

Related: How much does a cloud weigh?

NLCs occur when water vapor freezes into ice crystals that cling to dust and particles left by falling meteors high in the atmosphere, which reflect sunlight. The peak season for observing NLCs from the Northern Hemisphere is around the summer solstice in late June through the end of July, when they're most easily visible from about 50 to 70 degrees north latitude, according to Windy. However, some NLCs have already been spotted this month in colder, northern regions like Denmark, according to Spaceweather.com.

NLC sightings were at a 15-year high last summer, according to the Washington Post. Sightings have become more frequent in recent years and at lower latitudes, possibly because climate change generates more water vapor in the atmosphere as a result of increased atmospheric methane, according to NOAA.

For the best chance to see some NLCs in the evening, you'll need a good view low to the northern horizon as the stars begin to shine in late twilight. It's typical to see displays in the bottom 20 to 25 degrees of the northern sky, according to Sky & Telescope. Naked eye viewing is the best way to find noctilucent clouds, but with a pair of the best binoculars for stargazing, you'll get a fabulous close-up of the structure of one of the summer's most elusive and impressive sky sights. 

Even if you don't crave the adrenaline rush of adventure sports, perhaps, while flying on an airplane, you've wondered what it might be like to reach out and touch the clouds. Or, during a particularly bumpy descent, maybe you've been thankful to be inside the cabin and not out on the wing.

So what would it be like to pass through those clouds, as skydivers do, exposed to the elements?

This experience of falling through a cloud will vary depending on the cloud type, your protective gear and the weather conditions, which collectively result in conditions that can leave you soaking wet, freezing, or even unconscious, according to current and historical accounts.

Related: Why don't hurricanes form at the equator?

Clouds form when water molecules condense around particles in the air, called aerosols, and the nature of those particles affects the type and size of the resulting clouds. But according to Marilé Colón Robles, an atmospheric scientist at the NASA Langley Research Center in Virginia who studies clouds, "not every aerosol is created equal."

Certain natural aerosols, such as dust, typically prompt the formation of ice particles, while sea spray precipitates water molecules. Scientists have also experimented with seeding the atmosphere with artificially-introduced aerosols, including silver or lead iodide, to generate bright, dense clouds that reflect incoming solar radiation away from Earth or induce rain and snow.

Because skydivers jump from an altitude of 13,000 feet (4,000 meters), they're most likely to encounter stratus and cumulus clouds — the thick blanket of an overcast day and the pillowy, flat-bottomed clouds that mark an otherwise sunny afternoon, respectively. Both types are made up mostly of water molecules, and when they occur at elevations higher than 6,500 feet (1,980 meters), they're called altostratus and altocumulus clouds to designate their position in the atmosphere.

Ryan Katchmar, a Utah-based skydiving instructor with more than 10,000 jumps to his name, stressed that people should not skydive through clouds intentionally. If you can't see where you're going, there's no way to track potential hazards, including other skydivers or aircraft. But, he told Live Science, it does sometimes happen. "While we will try to dodge our way through clouds, sometimes you miss your window" and end up passing through, Katchmar said. 

"Sometimes it doesn't feel like anything," he added. "You go into a white room, and then you pop out the bottom. But if they're dark, thick or dense clouds, it'll feel like a bit of a speed bump, and you'll come out soaking wet." He likened the sensation to how the air feels in very humid regions, "but cool and refreshing."

Katchmar has also encountered unexpectedly cold conditions, such as hail pinging off of his goggles. For this reason, jumpers often cover up to avoid exposure injuries. On a recent jump in Utah, as Katchmar was filming another skydiver, he noticed that the woman's nose and cheekbones were turning white as the divers fell. "When we went through the cloud, ice formed on us," he said.

The most extreme cases of skydiving in poor weather have involved thunderstorms. Inside a storm cloud, warm air can rise at speeds of over 100 mph (160 km/h), but at high elevations, those particles feel the pull of gravity and descend as rain or hail. Plus, most lightning that occurs during storms strikes within or between clouds, Colón Robles told Live Science. "So, in addition to being launched into space, you'll be in the mecca of all the lightning strikes," she said.

Only two people are known to have survived such a trip through a lightning storm-bearing cloud. In 1959, U.S. Lt. Col. William Henry Rankin ejected from his fighter jet in rough weather and spent 40 minutes being churned around inside a storm cloud — suffering frostbite and nearly drowning — before being spit out a few hundred feet from the ground and crash-landing into a tree. Decades later, in 2007, German paraglider Ewa Wiśnierska was unintentionally sucked into a thunderhead while training for the paragliding world championship. She lost consciousness due to a lack of oxygen and landed several hours later about 37 miles (60 km) away.

If you have no interest in experiencing terminal velocity for yourself, there's another way you can move through a cloud, simply by walking. "Fog is a stratus type cloud, just on the ground," Colón Robles said. That cool, dense air gives you a taste of what skydivers face as they plummet toward Earth.

NASA's Curiosity rover recently snapped a stunning shot of dazzling "sun rays" shining through unusually high clouds during a Martian sunset. It is the first time sun rays have been clearly visible on the Red Planet. 

Curiosity captured the new image on Feb. 2 as part of a series of twilight cloud surveys that have been ongoing since January and will end in mid March. The photo, which is a panorama comprising 28 individual images, was shared by the Curiosity rover's Twitter page on March 6. 

"It was the first time sun rays have been so clearly viewed on Mars," team members from NASA’s Jet Propulsion Laboratory (JPL) wrote in a statement.

Sun rays, also known as crepuscular rays, occur when sunlight shines through gaps in the clouds during sunsets or sunrises when the sun is below the horizon. The rays are most visible on Earth in hazy conditions, when the light scatters off smoke, dust and other particles in the atmosphere, according to the U.K. Met Office. Although the dazzling beams appear to converge at a point beyond the cloud, they actually run near-parallel to one another.

Martian clouds, which are mostly made from ice crystals of both water and carbon dioxide, normally hover no more than 37 miles (60 kilometers) above the ground. But the clouds in the new image are estimated to be much higher, which is likely why this unusual phenomenon became visible to the rover, JPL representatives wrote.

Related: Detecting life on Mars may be 'impossible' with current NASA rovers, new study warns 

On Earth, sun rays normally appear red or yellow because the sunlight passes through around 40 times more air than it does when shining directly from above at midday, according to the Met Office. This means more light gets scattered by the air, known as Rayleigh scattering. As the light scatters, longer wavelengths of light that produce colors such as blue and green get scattered the most, so the light that reaches our eyes appears predominantly yellow and red.    

On Mars, the sun rays have a much more white color because the Red Planet has a very thin atmosphere, which means sunlight doesn't scatter as much as on Earth. This is why Martian sunsets often have a blue-ish glow. 

On Jan. 27, Curiosity also snapped a picture of a "feather-shaped iridescent cloud" during another one of its twilight cloud surveys. This was similar to a series of rainbow-colored clouds that recently shone in the skies above the Arctic. The rainbow clouds, known as polar stratospheric clouds, only form on Earth during unusually cold conditions when clouds form at higher altitudes than normal, which enables them to scatter strong sunlight as the surrounding skies darken. This suggests that Mars' clouds remained unusually high in the time period between the two photos being taken. 

Spotting strangely colored clouds and sunsets helps planetary scientists learn exactly what the clouds are made of and understand more about Mars' limited atmosphere.

"By looking at color transitions, we're seeing particle size changing across the cloud," Mark Lemmon, an atmospheric scientist at Space Science Institute who has worked on the Curiosity rover, said in the statement. "That tells us about the way the cloud is evolving and how its particles are changing size over time."

The dark skies in the Arctic Circle recently shone with ethereal multi-colored light. But this jaw-dropping spectacle was not caused by auroras. Instead, the iridescent rainbows were caused by clouds of tiny ice crystals floating higher in the atmosphere than is normally possible.

The clouds, known as polar stratospheric clouds (PSC), only form when the lower stratosphere reaches temperatures below minus 114 degrees Fahrenheit (minus 81 degrees Celsius). Normally, clouds do not form in the stratosphere because it is too dry, but at these extremely low temperatures "widely-spaced water molecules begin to coalesce into tiny ice crystals" that form into clouds, Spaceweather.com reported. This means PSCs can form much higher up than normal clouds, between 9.3 and 15.5 miles (15 to 25 kilometers) above the ground. 

As sunlight shines through these crystal clouds, it gets scattered, creating multiple different wavelengths of light, which has inspired the PSCs nickname, "rainbow clouds."  Due to the extreme altitude of the clouds sunlight can hit the crystals and scatter above an observer even if the sun is beyond the horizon, which is when these clouds appear brightest. 

On Jan. 25, extreme freezing conditions in the stratosphere allowed for a rare outbreak of PSCs across the Arctic Circle, including Iceland, Norway and Finland, according to Spaceweather.com. Amateur photographer Jónína Guðrún Óskarsdóttir captured a stunning shot of the vibrant clouds above the peak of Mount Jökultindur in Iceland and photographer Fredrik Broms took a series of snaps of the colorful lights above Kvaløya near Tromsø in Norway.

Related: Solar storm smashes hole in Earth's magnetosphere, triggering extremely rare pink auroras

There are two types of PSCs: Type I, which are made from a mix of ice crystals and nitric acid, which produces less spectacular colors and may be linked to the formation of ozone holes; and Type II, which are composed of pure ice crystals and produce more vivid colors. The ones that recently formed over the Arctic were Type II.

Type II PSCs are often referred to as nacreous clouds because their iridescent hues can sometimes resemble nacre, also known as mother of pearl, which is produced in the shells of some mollusks. However, they are much rarer than Type I clouds.

Type II clouds typically occur no more than two or three times a year in the Arctic, normally during the colder winter months, according to Spacewaether.com. However, experts believe that both types of PSCs could occur more often in the future as climate change creates more extreme weather, which could have a knock-on impact on the ozone layer if more Type I clouds can form, according to NASA.

Due to their intense colors, nacreous clouds are often confused with the northern lights, or aurora borealis, in the Arctic. These more common phenomena occur when highly energetic particles emitted by the sun travel down the magnetic field lines of Earth's magnetosphere.  

When you're flying in an airplane above a blanket of clouds, the pillars of white and gray look soft, fluffy and lighter than air. But don't be fooled — those bouncy-looking clouds are much, much heavier than they appear.

So just how much does a cloud weigh? And how do you weigh a cloud? We asked the experts to find out.

Clouds are composed mainly of air and millions of tiny water droplets, which form when water condenses around a "seed" particle. Seed particles can be anything from nitric acid to vapors released by trees, but they are generally very tiny.

There are a couple of ways to measure the weight of a cloud. The first is to weigh the water vapor that composes it — and to do that, "you need to know something about the dimensions of the cloud," Armin Sorooshian, a hydrologist at the University of Arizona, told Live Science. You also have to know how densely packed the droplets are. 

Related: Why do nuclear bombs form mushroom clouds?

Several years ago, Margaret LeMone, an atmospheric scientist at the National Center for Atmospheric Research in Boulder, Colorado, wondered about the weight of the water in an average cumulus cloud. So she did the math. First, she measured the size of a cloud's shadow and estimated its height, assuming a roughly cubic shape. Clouds are not typically cube shaped, but cumulus clouds are frequently about as tall as they are wide, so this assumption helped streamline the volume calculation. Then, based on prior research, she estimated the density of water droplets at around 1/2 gram per cubic meter. "I came up with around 550 tons [499 metric tons] of water," LeMone said. 

That's approximately the weight of 100 elephants suspended above your head. "It's really impressive," Soroohsian said.

Of course, different types of clouds have different weights. For example, "cirrus clouds are much lighter, because they have far less water per unit volume," LeMone told Live Science. And cumulonimbus clouds (the dark thunderheads you see just before a storm) tend to be much heavier. 

However, "the entire volume of the cloud is not just the droplets; there's air, too," Sorooshian said. If someone wanted to take LeMone's calculations a step further, they could factor in the weight of the air between each droplet.

But if clouds are so heavy, why don't they fall down? For one thing, "the droplets are so small that they don't fall very fast," LeMone said. The average water droplet in a cloud is roughly 1 million times smaller than a raindrop — about the size ratio of Earth to the sun. High-altitude wind currents blow these tiny droplets along, keeping them in the air for much longer than if they were static.

Heat convection also helps keep the drops aloft. "A cloud is actually less dense than the air directly below it," Sorooshian said. As warm air (and warm water) rises, it becomes more buoyant than the cold air (and cold water) beneath it, like a layer of foam on top of a latte. 

Of course, clouds can be said to "fall" in the form of rain. When cloud droplets cool and condense into one another, they grow, eventually becoming so heavy that they plummet to Earth. Although a raindrop is much bigger than a cloud droplet, each raindrop is still only 0.08 inch (2 millimeters) in diameter, according to the University Center for Atmospheric Research. Those small drops spread out the weight enough that 550 tons of water doesn't crash down on your head all at once. 

So, the next time you see a happy little cloud passing overhead, just remember: 100 elephants. And thank your lucky stars for heat convection.

An unusual cloud formation, known locally as a "Levanter," was recently captured in exquisite detail as it appeared to flow off the peak of the Rock of Gibraltar, a monolithic peak located in the British overseas territory of the same name in southern Europe.

The Gibraltar Met Office captured the new time-lapse video on Aug. 24 on the runway at Gibraltar International Airport and shared the breathtaking scene on Twitter. In the sped-up footage, the billowing cloud appears to form out of thin air around the peak of the 1,398-foot-tall (426 meters) Rock of Gibraltar, which is home to Europe's only wild monkey population, a group of around 300 Barbary macaques (Macaca sylvanus), according to the Gibraltar tourism website.  

The bizarre formation is known as a "banner cloud," which is a type of orographic cloud, meaning it is created due to the shape of the land below it, according to the U.K. Met Office. Banner clouds are birthed when strong winds blow moisture-rich air against a hill or mountain, forcing the air to lift toward the peak. As the air reaches the summit, it cools down, causing the water vapor to condense into a cloud, which either hangs, stationary, around the peak or, in the case of the new video, gets blown away by the wind, according to the Met Office. 

The Rock of Gibraltar is well suited to spawning banner clouds because it catches a regularly occurring wind known as the Levant, an easterly gust that blows westward through the Strait of Gibraltar, off southern Spain. Locals have, therefore, nicknamed the cloud formations "Levanters."

Related: Striking bull's-eye-shaped clouds form above erupting La Palma volcano 

There is no publicly available data on how rare Levanter clouds are in Gibraltar nor when they are most likely to form, but the Levant wind is most prevalent between June and October, according to the Royal Meteorological Society in the U.K. However, when the Levant wind forms from a southeasterly direction instead of a more common northeasterly origin, its gusts are normally dry and do not contain the necessary moisture needed to create banner clouds, according to MeteoGib, a private Gibraltar-based weather company.

But the Levanter clouds do come around often enough to inspire some comical cloud spotting: In recent times, locals have taken to social media to share funny images of Levanter clouds overlaid with doodles to depict what animals the banner clouds look like as they hang over the Rock of Gibraltar, some of which were tweeted by MeteoGib on Aug. 20.

Levanter clouds can also create contrasting climatic conditions on either side of the Rock of Gibraltar. During summer, Levanter clouds can act as a kind of lid that traps hot humid air on the Western side of the mountain for several days, which can aggravate conditions such as asthma and arthritis, according to MeteoGib. 

In the 1800s, the humid conditions caused by a Levanter were blamed for an outbreak of yellow fever. However, later research showed the real culprits were mosquitoes, which would have struggled to fly around in such humid conditions, meaning this particular Levanter actually may have stopped the spread of the disease and saved lives, according to MeteoGib.  

Originally published on Live Science.

One of the world's most dangerous volcanoes, Mount Vesuvius, appears to "peer up" into the sky through an eerily circular hole in the clouds in this striking satellite image.

The Operational Land Imager onboard the Landsat-8 satellite snapped the photo, which was released Jan. 10 by NASA's Earth Observatory. The volcano's summit caldera — a large bowl-like depression that forms when a volcano erupts and collapses — is clearly visible in the new image, as well as a section of large mountainous ridge to the north, which is a remnant of Mount Somma — an ancient volcano that once stood in the same spot as Mount Vesuvius, before the newer volcano's cone grew from it's center. 

Mount Vesuvius is a stratovolcano, meaning that its cone is built from accumulating layers of lava and ash from previous eruptions. It is part of the Campanian volcanic arc, a string of volcanoes in Italy that sits on a boundary between tectonic plates, where the African plate is being subducted beneath the Eurasian plate. It is made up of multiple active, dormant and extinct volcanoes both on land and underwater, including Mount Etna in Sicily, which began erupting again in February 2021, Live Science previously reported.

Related: 10 times volcanoes blew our minds in 2021

Vesuvius' most famous eruption simultaneously destroyed and preserved the Roman city of Pompeii, as well as the neighboring town Herculaneum, in A.D. 79. However, lava flows from its most recent eruption in 1944 destroyed the nearby village of San Sebastiano. In total, Mount Vesuvius has had eight major eruptions in the last 17,000 years, based on geological analysis of the layers of lava surrounding it, according to the Earth Observatory. 

Despite remaining calm since its last eruption, Mount Vesuvius is still classified as an active volcano and occasionally experiences shaking from belowground earthquake activity and gas venting from its summit. It is regarded as one of the most dangerous volcanoes on the planet because any future eruption has the potential to destroy Naples, an Italian city located 7.5 miles (12 kilometers) northwest of the volcano, which is home to more than 3 million people.

In 2011, a study published in the journal Nature described Mount Vesuvius as "Europe's ticking time bomb." 

The Landsat-8 satellite responsible for capturing the image is run by both NASA and the U.S. Geological Survey.

Originally published on Live Science.

New satellite images have revealed a stunning pattern of concentric cloud rings, resembling a bull's-eye, that was formed by the continued eruption of the volcano on La Palma in Spain's Canary Islands. 

The La Cumbre Vieja volcano, meaning "The Old Summit" in Spanish, has been erupting since Sept. 19 for the first time in more than 50 years, Live Science previously reported. The eruption has forced thousands of locals to evacuate as massive lava flows, which were visible from space, burned through farmland, roads and houses on the southwestern part of the island. 

Now, satellite images captured Oct. 1 by the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard NASA's Aqua satellite show a peculiar bull's-eye-shaped cloud formation above La Palma. Together, the volcano's eruption plume — a mixture of ash, smoke, water vapor and other volcanic gases — and a rare atmospheric disturbance led to the circular pattern, according to NASA's Earth Observatory. 

Related: The world's five most active volcanoes

Normally, a volcano's eruption plume rises straight up into the stratosphere — the second layer of the atmosphere, which extends from about 4 to 12 miles (6 to 19 kilometers) above Earth's surface to 31 miles (50 km) — forming a towering column of cloud and ash. This happens because hot air and gases rise above colder ones and the atmospheric air temperature decreases with altitude, creating a sort of invisible elevator that the plume can ride up. 

However, a rare phenomenon known as a temperature inversion meant that a temporary elevated layer of hot air acted like a lid, trapping the volcano's plume in the troposphere — the first layer of the atmosphere right above Earth's surface — at an altitude of 3.3 miles (5.3 km). That lidforced the plume outward horizontally, according to the Earth Observatory. The trapped plume ended up creating concentric rings because of the natural ebbs and flows in the intensity of volcanic activity, which created a sort of pulse in the emissions given off by the volcano.

This unique process was also caught on camera by the Izaña Atmospheric Research Center, based on Tenerife (another Canary Island), and can be seen in a mesmerizing time-lapse video shared on Twitter.

The official name for this type of concentric cloud formation is a gravity wave, according to the National Weather Service. However, the formation has nothing to do with gravity and is completely separate from the ripples in space-time called gravitational waves.

Though experts initially thought the eruption would last only a few days, La Cumbre Vieja continues to spew lava and gases. 

Originally published on Live Science.

Earth is reflecting less light as its climate continues to change, new research suggests.

A beautiful phenomenon connects climate and brightness: clouds. Clouds are a notoriously complicated piece of the climate puzzle — scientists struggle to model how clouds will respond to climate change and how those responses in turn will shape the future climate. But the scientists behind the new study think that the reflectivity finding hinges on the dynamics of clouds over the Pacific Ocean.

The research relies on two decades' worth of observations of a phenomenon called "earthshine," which is the light that Earth reflects onto the surface of the dark side of the moon, combined with satellite observations of Earth's reflectivity, or albedo, and the sun's brightness.

Related: The top 10 views of Earth from space

Different features on Earth reflect different amounts of light: the oceans very little, land about twice as much. Meanwhile, clouds reflect about half the sunlight that hits them, and snow and ice reflect the majority of light they receive.

Scientists at Big Bear Solar Observatory in Southern California have been studying how earthshine fluctuates since 1998, looking for changes at time scales from daily to decadal. (The researchers note that these measurements are only relative and call for more robust observations, perhaps even from cubesats or a lunar observatory.)

In the new research, scientists combined that data with observations from NASA’s Clouds and the Earth’s Radiant Energy System (CERES) project, which has been operating since 1997 with instruments on a host of NASA and National Oceanic and Atmospheric Administration (NOAA) satellites.

The researchers pulled together the two datasets to get a sense of whether and how Earth's brightness has been changing. Over the full two-decade span, the amount of light Earth reflected dropped about 0.5% — or about half a watt less light per square meter. (One square meter is a little less than 11 square feet.) Most of the change comes in the last three years of the earthshine data set, which the researchers analyzed through 2017; the CERES data continues until 2019 and shows an even starker decline at its end.

And during that time, the researchers determined, the brightness of the sun — which went through two periods of maximum activity and one quiet period during the course of the study — didn't meaningfully connect to the dip in reflectance. So a change in the amount of light Earth is reflecting must come from a change in Earth itself, the scientists reasoned.

In particular, the CERES data noted a loss of bright low-altitude clouds over the eastern Pacific Ocean, off the west coast of the Americas, where scientists are also registering stark temperature increases at the ocean surface.

And because light not reflected out to space is trapped in the Earth system, the change in brightness also has implications for the future of climate, potentially increasing the pace of human-caused climate change.

The research is described in a paper published Aug. 29 in the journal Geophysical Research Letters.

Email Meghan Bartels at mbartels@space.com or follow her on Twitter @meghanbartels. Follow us on Twitter @Spacedotcom and on Facebook.

A NASA-funded study is giving scientists insight into how "night-shining clouds" form in the upper atmosphere — and the role that growing space traffic plays in the phenomenon.

Scientists have known about these high-flying clouds since at least the late 1800s — well before the space age that launched in 1957. Newer research, however, shows that these clouds tend to form in high-altitude areas with abundant water vapor, such as what is produced after modern-day rocket launches.

The polar mesospheric clouds (PMCs), as the clouds are formally called, are collections of ice crystals usually found over the north or south poles during the late spring and summer. They're easiest to spot at twilight when the sun shines on them from just below Earth's horizon.

Photos: Magnificent night views of the heavens in America's dark sky parks

"What has attracted a lot of interest in these clouds is their sensitivity — they're occurring just on the edge of viability in the upper atmosphere, where it's incredibly dry and incredibly cold," lead author Richard Collins, a space physicist at the University of Alaska, Fairbanks, said in a statement. "They're a very sensitive indicator of changes in the upper atmosphere — changes in temperature and/or changes in water vapor."

Collins and his team followed the origin story of PMCs using NASA's Super Soaker mission, which used a small suborbital rocket that flew to space from Alaska. Water vapor from such launches, the study suggests, can lower the temperature in the immediate region and create a shiny cloud. Team members found this even happens in January during the toughest conditions in the Arctic — when PMCs don't typically form.

"We wanted to make sure to avoid mixing artificially created and naturally occurring PMCs. That way, we could be confident that any PMC we observed was attributable to the Super Soaker experiment," Irfan Azeem, a space physicist at Astra in Colorado and principal investigator of the Super Soaker mission, said in the same statement. 

After the rocket launched on Jan. 26, 2018, from the Poker Flat research range near Fairbanks, it flew to 53 miles (85 kilometers) in altitude and deliberately released 485 lbs. (219 kilograms) of water packed into a canister. Just 18 seconds later, ground-based laser radar picked up the signature of a PMC.

The team also put their results into a model to estimate how PMCs formed. The model suggested that the water from Super Soaker must have cooled the air dramatically, by about 45 degrees Fahrenheit (25 degrees Celsius). "We don't have direct temperature measurements of the cloud, but we can infer that temperature change based on what we think is required for the cloud to form," Collins said.

While this experiment threw water vapor into the air with a canister, water vapor is a common byproduct of satellites and rocket launches — such as with the space shuttle that flew from NASA's Kennedy Space Center between 1981 and 2011. One launch of the space shuttle spurred 20% of PMC ice mass observed in a season, the team members said in their statement.

"As the water vapor freezes, it turns into ice crystals. But those ice crystals absorb heat even better than water in vapor form. As the ice crystals heat up, they eventually sublimate back into vapor, and the cycle repeats," NASA added in the statement.

The effects of space traffic should be monitored and if rocket launches increase dramatically, the researchers urge that PMCs should be further modeled to understand what happens in an artificial environment. (More space traffic is a reality already, and may accelerate with the launch of more cubesats and small satellites in the coming years.)

A paper based on the team's work was published Feb. 1 in the Journal of Geophysical Research: Space Physics.

Follow Elizabeth Howell on Twitter @howellspace. Follow us on Twitter @Spacedotcom and on Facebook. 

A ghostly white saucer hovers over the peaks of El Chaltén in southern Argentina. As wind thrashes the nearby clouds, the saucer remains fixed above the craggy summit, anchored in the sky like a mothership surveying the hills below.

It's not aliens. (Sorry … it's never aliens). It's just a friendly neighborhood "UFO cloud" — better known in meteorological circles as a standing lenticular cloud.

This eerie weather phenomenon is relatively common in mountainous regions like El Chaltén, or the Rocky Mountains in the U.S., where high-speed winds ricochet over a tall peak, creating a distinct lens- or saucer-shaped cloud formation high in the sky. Still, photographer Francisco Javier Negroni Rodriguez — whose photo above is a finalist in the Royal Meteorological Society's (RMS) 2020 Weather Photographer of the Year contest — had to wait the better part of a day to capture the cloud in its mysterious glory.

Related: Gallery: Reading the clouds

"An hour before taking this photograph I was walking along the trails that surround the beautiful rock formation … [but] the day was very cloudy. Apparently, luck was not with me on this adventure," Negroni Rodriguez told the RMS. "Only for a moment, the clouds allowed me to see El Chaltén — and to my surprise, there was a spectacular and brilliant lenticular cloud with a beautiful and perfect figure that I had never seen."

This type of cloud forms when strong wind blows into the side of a mountain, skyscraper or other tall obstruction, according to the National Weather Service. The mountain deflects the wind, forcing it into a wave that crests over the mountaintop, dips down on the other side, then rises up again. In the upward-moving parts of the wave, the air cools until it condenses into clouds. When the air descends again on the downward-moving side of the wave, the cloud evaporates. The result is a spooky, stationary cloud perched atop the crest of the wave, sculpted into a saucer shape by the wind constantly rising and falling within it.

Negroni Rodriguez's photo joins 25 other finalists in the RMS contest, which is co-sponsored by AccuWeather. While the alien cloud was not one of the three grand-prize winners announced on Oct. 17, it nevertheless rose to the top of more than 7,700 entries, according to the RMS. To see some of the other stunning finalists — including the big winners — click through this gallery. 

Originally published on Live Science.

The Southern Ocean is a vast band of open water that encircles the entire planet between Antarctica and the Southern Hemisphere landmasses. It is the cloudiest place on Earth, and the amount of sunlight that reflects off or passes through those clouds plays a surprisingly important role in global climate. It affects weather patterns, ocean currents, Antarctic sea ice cover, sea surface temperature and even rainfall in the tropics.

But due to how remote the Southern Ocean is, there have been very few actual studies of the clouds there. Because of this lack of data, computer models that simulate present and future climates overpredict how much sunlight reaches the ocean surface compared to what satellites actually observe. The main reason for this inaccuracy is due to how the models simulate clouds, but nobody knew exactly why the clouds were off. For the models to run correctly, researchers needed to understand how the clouds were being formed.

To discover what is actually happening in clouds over the Southern Ocean, a small army of atmospheric scientists, including us, went to find out how and when clouds form in this remote part of the world. What we found was surprising — unlike the Northern Hemisphere oceans, the air we sampled over the Southern Ocean contained almost no particles from land. This means the clouds might be different from those above other oceans, and we can use this knowledge to help improve the climate models.

Ice clouds and liquid clouds

Clouds are made of tiny water droplets or ice crystals, or often a mixture of the two. These form on small particles in the air. The type of particle plays a big role in determining whether a liquid droplet or ice crystal forms. These particles can be natural — like sea spray, pollen, dust or even bacteria — or from human sources like cars, stoves, power plants and so on.

To the untrained eye, an ice cloud and a liquid cloud look much the same, but they have very different properties. Ice clouds reflect less sunlight, precipitate more and don't last as long as liquid clouds. It matters to the weather — and to climate models — what kinds of clouds are around.

Climate models tend to predict too many ice clouds over the Southern Ocean and not enough liquid clouds when compared to satellite readings. But satellite measurements around the poles are hard to make and less accurate than other regions, so we wanted to collect direct evidence of how many liquid clouds are actually present and determine why there were more than the models predict.

This was the mystery: Why are there more liquid clouds than the models think there are? To solve it, we needed to know what kinds of particles are floating around in the atmosphere around Antarctica.

Before we went down there, we had a few clues.

Previous modeling studies have suggested that the ice–forming particles found over the Southern Ocean may be very different from those found in the Northern Hemisphere. Dust is a great ice cloud seeder, but due to the lack of dusty land sources in the Southern Hemisphere, some scientists have hypothesized that other types of particles might be driving ice cloud formation over the Southern Ocean.

Since most models are based on data from the Northern Hemisphere, if the particles in the atmosphere were somehow different in the Southern Hemisphere, that might explain the errors.

Bacterial maps

It's hard to directly measure the composition of particles over the Southern Ocean — there simply aren't very many particles around. So, to help us track down what is inside the clouds, we used an indirect approach: the bacteria in the air.

The atmosphere is full of microorganisms that are carried hundreds to thousands of kilometers on air currents before returning to Earth. These bacteria are like airborne license plates, they are unique and tell you where the car — or air — came from. Since scientists know where most bacteria live, it's possible to look at the microbes in an air sample and determine where that air came from. And once you know that, you can predict where the particles in the air came from as well - the same place the bacteria usually live.

In order to sample airborne bacteria in this remote ocean region, one of us headed out on the Australian Marine National Facility's R/V Investigator for a six-week expedition. The weather was unruly and the waves were often white-capped, but for one to two days at a time, we sucked air from the bow of the ship through a filter that caught the airborne particles and bacteria. We then froze the filters to keep the bacterial DNA intact.

Ocean bacteria alone

In most ocean regions around the world, especially in the Northern Hemisphere where there is a lot of land, the air contains both marine and terrestrial particles. That's what we expected to find down south.

With the frozen filters safely back at our lab in Colorado, we extracted DNA from the bacteria and sequenced it to determine what species we had caught. Much to our surprise, the bacteria were essentially all marine species that live in the Southern Ocean. We found almost no land-based bacteria.

If the bacteria were from the ocean, then so were the cloud-forming particles. This was the answer we were looking for.

Ice nucleating particles are very rare in seawater and marine particles are very good at forming liquid clouds. With mostly marine-based particles in the air, we'd expect the clouds to mostly be made of liquid droplets, which is what we observed. Since most models treat clouds in this region the same way they do clouds in the dustier Northern Hemisphere, it's no wonder the models were off.

Going forward

Now that we know the summertime Southern Ocean clouds are being formed from purely marine particles, we need to figure out if the same is true in other seasons and at higher altitudes. The larger project, which involved planes as well as ships, has given atmospheric scientists a much better idea of the clouds both close to the ocean surface and high up in the atmosphere. The climate modelers among us are already incorporating these new data into their models and will hopefully have results to share soon.

Discovering that the airborne particles over the Southern Ocean are mostly coming from the ocean is a remarkable finding. It not only improves global climate models, it also means we confirmed the Southern Ocean is one of the most environmentally pristine regions on Earth — a place that has probably changed very little due to human activities. Our work will hopefully improve climate models, but has also given researchers a baseline for what a truly pristine marine environment looks like.

[You're smart and curious about the world. So are The Conversation's authors and editors. You can get our highlights each weekend.]

• 16 Times Antarctica revealed its awesomeness in 2019
• Images of melt: Earth's vanishing ice
• The reality of climate change: 10 myths busted

A person lounging on a patch of grass dreaming up images in the clouds will typically have only the familiar puffs and streaks to work with. But a satellite passing overhead can see an entirely different canvas. 

On Jan. 29, an instrument on NASA's Aqua satellite captured a photo of cloud forms that look like bursting fuzzballs near the west coast of Australia, according to NASA's Earth Observatory, which released the image Friday (Feb. 7). These fuzzballs, or actinoform clouds, are impossible to see from the ground, because they are just so big, sometimes stretching as far as 180 miles (300 kilometers) across, which is a little over the width of Florida.

Actinoform clouds have arms called "actiniae" that reach out in all directions, but the clouds can take on various shapes, such as a more leaf-like structure, according to the Earth Observatory. The clouds sometimes appear to be lined up and sometimes scattered about the sky, as they are in this new image.

Related: See photos of amazing cloud formations

These types of clouds typically form relatively lower in the atmosphere, around 6,600 feet (2,000 meters) high, in an area usually dominated by stratocumulus clouds, those superpuffy and thick clouds. "This scene is interesting because it's a little to the north of the typical stratocumulus region to the west of Australia," Michael Garay, a cloud researcher at NASA's Jet Propulsion Laboratory, told the Earth Observatory.

Actinoform clouds were first captured by NASA’s Television Infrared Observation Satellite V in 1962, but not much is known about how they form; previously, scientists saw a link between actinoform cloud formation and the use of aerosols, according to the observatory. But in this case, the clouds over Australia were found to be so far from land that it's difficult to point to aerosols as the cause, Garay said. 

These clouds can linger for up to 72 hours and typically release some raindrops on the daydreamers below.

• 7 ways the Earth changes in the blink of an eye
• Earth from above: 101 stunning images from orbit
• Earth pictures: Iconic images of Earth from space

Originally published on Live Science.

Rippling gravity waves in the sky are usually invisible, but a satellite recently caught a rare glimpse of the phenomenon off the coast of northwestern Australia.

In the images, captured Oct. 21, air moves away from land and over the ocean, and rows of curved white lines emerge, like ripples do in disturbed water. Those thin white bands are clouds forming on the crests of atmospheric gravity waves, according to the Australian meteorology site Weatherzone, which tweeted an animation of the satellite view on Oct. 22. 

Gravity waves appear following atmospheric disturbances; in this case, storms in the area produced cold air — which is denser than the warm air over land, Weatherzone says. Interaction between cool and warm air agitated the atmosphere, and the ripples that formed are gravity's way of restoring that lost equilibrium.

Related: Gorgeous Gravity Waves Intersect Near Africa (Photo)

Unlike gravitational waves — theoretical ripples in space-time, proposed by Einstein's  theory of general relativity — gravity waves are a physical phenomenon. It's easy to picture the physical appearance of gravity waves in liquid: Think of ocean waves, or the ripples that form in a pond after you drop a pebble in the water. While we usually can't see gravity waves in the atmosphere, they behave in the same way that liquids do when they're disturbed, according to the National Oceanic and Atmospheric Administration (NOAA). 

Atmospheric gravity waves take shape from the push and pull between gravity and buoyancy; when air is perturbed, gravity pulls the air down and the air's buoyancy pushes it back up. In some cases, when there is enough moisture in the air, water condensation creates white vapor outlines along the crests of the oscillating air waves; the white lines dissipate as the air sinks into troughs. 

When that happens, the waves' rippling lines are visible to satellites — such as Japan's geostationary weather satellite Himawari-8, which captured the images featured on Weatherzone.

A large, brownish dust plume carried over the ocean from the Australian coast was also visible in the satellite images, making the ripples even easier to spot, the Australian Broadcasting Corp. (ABC) reported.

• Infographic: Earth's Atmosphere Top to Bottom
• The Mysterious Physics of 7 Everyday Things
• 6 Weird Facts About Gravity

Originally published on Live Science.

Look up from the Red Planet on the right morning, and you might see a blue sky. All year round, wispy blue clouds of ice form in the Martian atmosphere, hovering between 18 and 37 miles (30 and 60 kilometers) above the planet's surface. There, they streak across the sky like the feathery cirrus clouds we see so often on Earth.

Decades after rovers like the Mars Pathfinder snapped the first pics of these alien clouds, astronomers still struggle to explain them. To form a cloud, airborne ice or water molecules need something solid to condense onto — a fleck of sea salt, maybe, or some stray dust tossed up on the wind. Scientists long assumed that bits of surface dust lofted into the Martian atmosphere might be the source of the planet's icy blue clouds. But a new study published today (June 17) in the journal Nature Geoscience argued that this might not be the case.

A more likely culprit, the study authors said, is pulverized meteorites. [Photo Gallery: Images of Martian Meteorites]

The hypothesis goes like this: Every day, 2 to 3 tons of screeching space rocks slam into the Martian atmosphere and break apart. All those midair collisions leave a lot of dust — or "meteoric smoke," as the study authors call it — hanging around the Martian sky. And that dust might just be enough to turn trace amounts of water vapor in the atmosphere into fragile, icy clouds.

To find out if this meteor-based cloud system is possible, the researchers ran multiple computer simulations of how particles flow through the Martian atmosphere. Clouds formed at the correct altitudes only when meteorites threw sufficient amounts of dust into the sky, the researchers found. When there were no meteorites, there were no clouds.

The team's work also showed that the meteor clouds of Mars had a noticeable effect on the planet's climate. At certain times of year, ice clouds in the Martian sky increased temperatures by up to 18 degrees Fahrenheit (10 degrees Celsius) in the upper atmosphere, the model predicted. If that's the case, tiny flecks of dust from other worlds may profoundly affect weather on Mars and even our own planet.

"We're used to thinking of Earth, Mars and other bodies as these really self-contained planets that determine their own climates," lead study author Victoria Hartwick, a graduate student in the University of Colorado's Department of Atmospheric and Ocean Sciences, said in a statement. "But climate isn't independent of the surrounding solar system."

• 5 Mars Myths and Misconceptions
• Fallen Stars: A Gallery of Famous Meteorites
• The 5 Strangest Meteorites in History

Originally published on Live Science.

BOSTON — The Arctic is melting. The first ice-free summer is coming. The whole melting process is speeding up the warming of the entire Earth. And every autumn, a layer of extra clouds are forming over the ice-thinning Arctic that — researchers now believe — are speeding that melting up.

In a talk here March 4 at the March meeting of the American Physical Society, Ariel Morrison, an atmospheric scientist at the University of Colorado, Boulder, presented research that for the first time offered a clear answer as to how the melting Arctic is changing its clouds, and how those clouds in turn are changing the Arctic. It was originally published in the journal JGR Atmospheres Dec. 10, 2018.

"Right now, there's about a 20-year estimate: Between the 2040s and the 2060s, we're expecting to see the first ice-free summer," Morrison told Live Science. "This moves that toward the earlier end of the estimates." [On Ice: Stunning Images of Canadian Arctic]

Modeling how clouds impact the Arctic is complicated because they have two different effects: They reflect light back into space before it can hit the ground, and they act like a blanket that traps heat from escaping from the planet's surface into space. The first effect cools the ground, and the second warms it up.

When the sun is out, every cloud does dual duty: reflecting incoming light back into space, and reflecting radiating heat back toward the ground. So it can be difficult to know whether, in any given situation, clouds are doing more to warm the surface or keep it cool.

Until Morrison's research, scientists weren't sure if the changing cloud situation in the Arctic was speeding or slowing melting overall. There were just too many factors involved.

Clouds are also famously difficult to study in climate science in general. And in the Arctic, matters are further complicated by the vast, ice-free North Atlantic Ocean that has lots of cloud cover in the sky but no sea ice due to the warm underwater currents that keep the ocean's surface above the freezing point. Morrison developed a "mask" that cut out all the noisy, unnecessary extra data from the North Atlantic so she could target regions where the clouds were actually relevant to melting.

Once she narrowed down the model to target the clouds she was focused on, Morrison found that the melting Arctic isn't dramatically changing the reflective, cooling effect of clouds. In the summer, most clouds in the Arctic form from moisture that flows through the atmosphere from warmer southern latitudes. So the yearly increase in open water in the Arctic doesn't have a big effect on total cloudiness during the months when clouds are most crucial to reflecting light back into space.

"If we had found that summer clouds were responding to sea-ice loss — so you melt some ice, a cloud forms on top of it — then clouds would have this negative feedback with sea ice," she said.

In other words, as sea ice melted, clouds would do more to cool the Arctic.

But it turns out, the summer melt has no significant impact on clouds.

However, Morrison found, things are different in the fall. During those months, it turns out, the skies above patches of open water are much more likely to be cloudy. And those clouds do much more to trap heat than to reflect light into space.

"It's very, very seasonal in the Arctic," Morrison said. "Because the Arctic only has sunlight for about six months out of the year, and it's strongest in the middle of the summer. So only in the middle of the summer, only in the middle of July, do clouds have this cooling effect, because they're reflecting away more [light] than they're [trapping]."

The rest of the year, more clouds means more heat. And during the fall, less ice also seems to mean more clouds. So as the Arctic melts, it's effectively covering itself in a seasonal blanket that makes that melting happen even faster.

Morrison said she hopes her research will, in the future, factor in to Arctic climate models, so they can more precisely plot out the future of the quickly warming region.

• Images of Melt: Earth's Vanishing Ice
• In Photos: The Vanishing Ice of Baffin Island
• Collapsing Beauty: Image of Antarctica's Larsen Ice Shelf

Editor's note: This article was corrected at 10:24 am EST on March 11, 2019 to reflect that Morrison's work had already been through peer review and been published, contrary to what was originally stated.

Originally published on Live Science.

If humanity pumps enough carbon dioxide into the atmosphere, one of Earth's most important types of cloud could go extinct. And if the stratocumulus clouds — those puffy, low rolls of vapor that blanket much of the planet at any given moment — disappear, Earth's temperature could climb sharply and radically, to heights not predicted in current climate models.

That's the conclusion of a paper published today (Feb. 25) in the journal Nature Geoscience and described in detail by Natalie Wolchover for Quanta Magazine.

As Wolchover explained, clouds have long been one of the great uncertainties of climate models. Clouds are complicated, small and fast-changing. Computer models that easily capture the complexity and detail of most climate systems just aren't powerful enough to predict worldwide shifts in cloud behavior. [7 Ways the Earth Changes in the Blink of an Eye]

But clouds are important. They dye a wide swath of the atmosphere white, as seen from space, reflecting sunlight away from Earth's surface. And stratocumulus clouds are an important part of that picture; they're those white blankets you might have seen as you looked out the window of an airplane, rolling out below you and hiding the ground. Researchers suspect that certain sudden, past jumps in temperature may have been caused by changes to clouds like these.

For the new research, scientists modeled just a small patch of sky using a supercomputer. They found that if carbon dioxide (CO2) levels reach about 1,200 parts per million (ppm) in the atmosphere, stratocumulus clouds break up. That's a very high carbon dioxide concentration. Right now, levels have climbed past 410 ppm — already a dangerous shift from the 280 ppm that prevailed before the industrial revolution.

But humans put more and more CO2 into the atmosphere every year. If current trends continue, Earth could reach 1,200 ppm within 100 to 150 years. This could happen if our society doesn't follow through on any of its commitments to reduce emissions, Wolchover reported. And even if it does, the result would be another 14 degrees Fahrenheit (8 degrees Celsius) of heat added to the global average, on top of the dangerous changes already underway due to greenhouse gases.

That's an enormous change, and it goes beyond predictions of worldwide ice melt and catastrophic sea-level rise. The last time our planet was that warm, crocodiles swam in the Arctic and the region around the equator was "scorched" and "mostly lifeless," according to Wolchover.

And once the stratocumulus clouds are gone, Wolchover reported, they likely wouldn't reappear until atmospheric carbon dioxide levels dropped below where they are currently.

There's still some uncertainty in the data, however; and it hasn't been replicated. The 1,200-ppm figure could shift up or down as scientists look into the issue further.

But whether or not humans kill off stratocumulus clouds or not, this study highlights the many factors in climate change we don't yet understand.

• Album: Reading the Clouds
• Reality of Climate Change: 10 Myths Busted
• Image Gallery: Extraordinary Environmental Art

Originally published on Live Science.

A mysterious chemical cloud descended on beaches in England on Sunday (Aug. 27), according to news reports, and authorities are puzzling over what caused it and why it sickened more than 100 people.

As the cryptic cloud fogged up the shoreline, several beaches in East Sussex were evacuated and residents were advised to close their windows and doors, The Independent reported yesterday (Aug. 28).

The chemical composition of the cloud is not clear. "What it was, it smelled like burnt plastic," Bob Jefferey, a deputy launching authority at the Royal National Lifeboat Institution Eastbourne division told The Guardian.

One beachgoer tweeted, "Some sort of chemical incident at Birling Gap, eyes are streaming and there's a strong smell of chlorine in the air."

Another beachgoer told The Guardian that doctors who treated her said she had been exposed to ammonia.

Authorities are still investigating where the cloud came from.

"Neither the gas nor its source have been established, but agencies are continuing to investigate and have not ruled out either on-shore or off-shore locations, although it does appear that it did sweep in from the sea driven by on-shore breezes," the Sussex police said, according to The Independent.

It's unlikely, however, that the cloud drifted across the English Channel from France, the Sussex police said. (Chemical clouds have drifted across the English Channel from Europe in the past, but British officials said Sunday's weather would not have caused this, according to The Independent.)

Jay Merrell, a weather forecaster from the U.K.'s national weather service, said the cloud may have been caused by a ship offshore, but added that nothing conclusive had been proved, according to the Associated Press.

By Monday, the cloud had mostly dissipated, The Guardian reported. 

Originally published on Live Science.

Rotating winds paint the sky with a series of cotton-candy spirals in a new satellite image over the South Atlantic.

The spirals are properly known as von Kármán vortices, according to NASA's Earth Observatory, which released the stunning satellite shot this week. The mechanism that creates clouds like these is fairly simple. Wind moving at just the right speed flows into a blunt object — in this case, the island of Tristan da Cunha — and separates into two distinct flows, which rotate in opposite directions. The rotating air sculpts water vapor in the air into a line of spirals.

NASA's Landsat-8 satellite captured this false-color image on June 25, 2017, using its Operational Land Imager instrument. The candy color of the clouds is artificial, better to differentiate cloud from sea in the image.

A month earlier, the Suomi NPP satellite captured a similar view in an entirely different spot. A second image released by NASA's Earth Observatory shows von Kármán vortices in their true color. In this image, taken May 24, vortices twirl away from Guadalupe Island off the coast of Baja California, Mexico.

The vortices are a frequent subject of satellite glamor shots. In May 2016, a satellite captured an image of the cloud swirls created by wind hitting Mawson Peak on Heard Island in the Indian Ocean. In 2012, the vortices popped up behind St. Helena, a volcanic island in the South Pacific. They even made another appearance by Guadalupe Island that year, accompanied by a double rainbow.

Wind and land often combine to create impressive cloud formations. Coastal breezes can cause low, tube-shaped clouds called "roll clouds," which are almost always associated with thunderstorm downdrafts above dry land. Some wind patterns create not spirals on the lee side of islands, but stripes. These so-called "gravity waves" look like ripples in the sky. 

Tristan da Cuhna is known as the most remote inhabited island on the planet. ("Inhabited" is a limited term — fewer than 300 people call the island home.) St. Helena, that other vortice-generating island, is the closest land mass, 1,510 miles (2,430 kilometers) away, according to tristandacunha.org. The island's closest land mass that could not itself be described as "remote" is South Africa, 1,750 miles (2,816 km) away.

Original article on Live Science. 

A curling tongue of clouds reaches out to taste the Iberian Peninsula in a new satellite image.

The striking shot comes courtesy the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite and NASA's Earth Observatory, which released the image Tuesday (July 25). It shows a cyclone, or low-pressure system, off the coast of Portugal. The system produced little to no rain, but pulled dry air from over the land into an atmospheric dance with moist ocean air, forming a spiral, Peter Knippertz, a meteorologist at the Karlsruhe Institute of Technology in Germany, told the Earth Observatory.

Knippertz told the Earth Observatory that this weather pattern on July 16 occurred during a heat wave, when Portugal and Spain were experiencing temperatures above 100 degrees Fahrenheit (40 degrees Celsius). The heat contributed to the temperature difference between the continent and the ocean.

The conjunction of land and water often gives rise to strange and beautiful cloud formations. In 2015, the MODIS instrument on NASA's Aqua satellite (Terra's sister satellite) captured sweeping cirrus clouds off the coast of Chile, sculpted by swift winds in the upper atmosphere. Gravity wave clouds often form off coastlines, as in this 2016 shot off of West Africa; in this instance, dry, cool nighttime air from the desert buoyed moist ocean air upward into the atmosphere, where it condensed, dropped under the influence of gravity, hit the rising dry air and rose again, creating the wave-like pattern.

Off Alaska, ocean winds sometimes sculpt clouds into parallel "streets." And marine upwelling that brings frigid water from deep in the Pacific Ocean up to the surface causes frequent bumpy fog off the coast of Peru when water vapor in the air condenses on contact with the cold ocean surface.

Original article on Live Science. 

A NASA sounding rocket launched early this morning and lit up the skies over the U.S. East Coast with colorful clouds, ringing in an early July Fourth celebration.

The launch of the Terrier-Improved Malemute two-stage sounding rocket had been repeatedly rescheduled, but the rocket finally got its chance at 4:25 a.m. EDT (0825 GMT) today (June 29). The rocket lifted off from NASA's Wallops Flight Facility in Virginia, and its flight lasted about 8 minutes.

About 4 to 6 minutes into takeoff, 10 canisters released barium, strontium and cupric oxide, which interacted with each other to form colorful vapor. Scientists could use the red and blue-green artificial clouds that formed to track the movement of particles in Earth's ionosphere, which is in its upper atmosphere. They were visible along the mid-Atlantic coastline from North Carolina as far north as New York, and could be seen as far west as Charlottesville, Virginia, according to NASA. (NASA Wallops reported cloud views as far as Staten Island, NY and Outer Banks, NC.)

"Two-stage" refers to the method of rocket launch where the first stage achieves liftoff from Earth's surface, and those propellants are discarded soon after to reduce the weight of the rocket. At that moment, the second, upper stage fires to continue the journey. The word "sounding" is a borrowed nautical term meaning the rocket is intended to take measurements.

The ionosphere that the sounding rocket is looking to study is the layer of Earth's atmosphere that is ionized (hence the name) by solar and cosmic radiation. When an atom or molecule is called an ion, it simply means that the particle does not have the normal number of electrons — instead, it carries a negative or positive charge.

Editor's note: If you caught an amazing photo of the launch or artificial clouds and you'd like to share it with us and our partners for a story or image gallery, send images and comments in to managing editor Tariq Malik at spacephotos@space.com.

Follow Doris Elin Salazar on Twitter @salazar_elin. Follow us @Spacedotcom, Facebook and Google+. Original article on Space.com. 

Time-lapse images recently captured an incredible sight — a "tide" of clouds rolling into Arizona's Grand Canyon, in a rare phenomenon known as a total cloud inversion.

Thick, white clouds roil and churn in footage that was shot and edited into a video by filmmaker Harun Mehmedinovic. Titled "Kaibab Elegy," the film was published on Vimeo on May 14 and is part of the Skyglow video series and book project, documenting the impact of light pollution on the visibility of the night sky, and contrasting bright urban landscapes with wild spaces untouched by the shine of electric illumination. [Image Gallery: See Photos of Wild Cloud Formations]

Air temperature typically cools as it moves higher into Earth's atmosphere. But during an inversion event, a layer of warm air traps cool air and moisture closer to the ground, preventing it from dissipating as it normally would, according to the National Weather Service (NWS).

The phenomenon, also called a surface inversion, is most likely to form during winter months when the air near the ground cools quickly at night, while the air just above the surface stays warm. If winds are calm, the warm air can't mix with the cooler air below it, and the cooler air — which is already denser than the warm air — persists close to the ground; that cool air is particularly likely to get stuck if there are also high-pressure conditions in the area or topographical features such as mountains that can trap the cool air, the NWS explained.

When an inversion happens at the Grand Canyon, dense clouds can take shape, rolling through the basin like ocean waves. Seen in Mehmedinovic's time-lapse footage, the fast-moving clouds are so thick that they obscure all but the very lip of the vast canyon, as the sun sets and the sky fills with brilliant colors.

Skyglowproject.com: 'Kaibab Elegy' from Harun Mehmedinovic on Vimeo.

The National Park Service (NPS) documented a similar episode at the Grand Canyon on Dec. 11, 2014, sharing it on YouTube; in its video, a minute of time-lapse footage captures about 15 minutes of clouds advancing up the canyon walls and then retreating.

And that's a lot of space to fill — the Grand Canyon extends for 277 miles (433 kilometers) in length, is 10 miles (16 km) wide and has a depth of about 1 mile (1.6 km), according to the NPS.

But inversions don't just create dramatic cloud displays — in populated areas, they can also dramatically affect air quality by trapping pollution. When a "lid" of warm air covers a region, particularly in a valley, airborne pollutants from industry, traffic and furnaces can collect in a miasma of smog, the NWS explained.

Original article on Live Science.

A dramatically turbulent cloud formation called asperitas and the bizarrely cylindrical roll cloud are among the newest additions to the international handbook for cloud identification.

The World Meteorological Organization has released a new, digitized version of its "International Cloud Atlas," the global reference book for meteorologists and skywatchers alike. It's the first update for the atlas since 1987 and the first version to be fully web-based. The release also marks a red-letter day for amateur enthusiasts in the Cloud Appreciation Society, who get the satisfaction of seeing the asperitas cloud that they discovered become an official scientific category.

"It is a new classification of cloud, with a chaotic, turbulent appearance, that was proposed by the Cloud Appreciation Society back in 2008, based on photographs sent to us from members all around the world," the organization posted on its blog. "It is a classic example of citizen science, in which observations by the general public, enabled by the technology of smartphones and the Internet, have influenced the development of this most official of classification systems." [Gallery: The Craziest Clouds Ever]

Clouds 101

The cloud atlas' classification system is not for the faint of heart. There are 10 basic "genera" of clouds, most of the names of which would be familiar to schoolchildren: cirrus, cirrocumulus, cirrostratus, altocumulus, altostratus, nimbostratus, stratocumulus, stratus, cumulus and cumulonimbus.

Within each genera are species, which describe the internal structure of the shape of clouds. A lenticularis cloud, for example, is a flattened pancake shape that looks a bit like a giant UFO. Each type of cloud can only have one species, but the same species types are present in multiple different genera of clouds.

Next, the classification system includes varieties of clouds, which describe the clouds' transparency and arrangement. A single cloud can have multiple varieties, except in the case of opacus (opaque) clouds varieties and translucidus (translucent) varieties, which are mutually exclusive: One doesn't let any sun through, and the other does. [See Photos of a Various Cloud Types]

Thus, a standard cloud identification might look something like "altocumulus stratiformis translucidus perlucidus undulates" — an altocumulus cloud arranged in a thin sheet (stratiformis) that is translucent to sunlight, has small gaps allowing blue sky to show through (perlucidus) and which has wavy features (undulates).     

New forms

The cloud atlas update doesn't alter any of the basic classifications for clouds, but it does add several new twists. The roll cloud, known as the volutus, is defined as a new species of cloud. These horizontal, cylindrical clouds form where descending cold air pushes warm, moist air upward. Under the right wind conditions, the atmospheric turbulence condenses into a tubular cloud that seems to roll across the sky. 

The atlas also adds five new "supplementary features" to its classification system. Supplementary features are unusual parts of, or attachments to, clouds. The wave-like undulations of the undersides of clouds, dubbed "asperitas," are among these new features. Another is "cavum," known colloquially as a hole-punch cloud because the cloud has a large circular gap through which the sky can be seen. A "cauda" is a horizontal feature that extends like a tail from a cloud. "Fluctus" features are wave formations that look like something a cartoon surfer would ride; they're commonly known as Kelvin-Helmholtz waves and are caused by wind shear. Finally, "murus" features, or wall clouds, are familiar to any storm chaser for their role in the formation of tornadoes.

The other main changes to the atlas are the addition of a new accessory cloud, or a cloud that accompanies another, larger cloud, and the establishment of five new special clouds, which describe unusual cloud formation circumstances. The new accessory cloud type is called "flumen" and describes a low cloud associated with severe supercell storms.

The five new special clouds are: cataractagenitus, describing clouds that develop from the spray of large waterfalls; flammagenitus, describing clouds formed under the influence of wildfires; homogenitus, describing clouds formed by human activities, such as airplane contrails; silvagenitus, describing clouds formed under the influence of moisture from respiring trees; and homomutatus, describing clouds originally made by humans that gradually transform into more natural-looking forms, like a contrail that eventually spreads in the wind.

The cloud atlas is available online and will be official unveiled today (March 23) for World Meteorological Day.

Original article on Live Science. 

In an unexpected first, researchers have discovered ammonia in Earth's lowest atmospheric layer, a new study said.

The detected ammonia was most concentrated in the upper layer of the troposphere above India and China, countries that have experienced population and economic booms in recent years. The gas (NH3) is most likely coming from livestock farming and fertilization in those countries, the researchers said.

Plants and crops need ammonia to grow, but too much of it can harm the environment and human health. However, the newly detected ammonia may have an unexpected silver lining: The gas is involved in cloud formation, so it may act as a cooling agent and help compensate for the human-caused greenhouse gas effect, the researchers said. [Infographic: Earth's Atmosphere Top to Bottom]

Now that researchers are aware of the ammonia, they can incorporate it into models assessing and predicting climate change, the researchers added.

The troposphere

The troposphere reaches from 4 miles to 12 miles (7 to 20 kilometers) above sea level and includes up to 80 percent of Earth's atmosphere and weather phenomena.

During an investigation, a team of researchers from Germany, Colorado and Mexico collected satellite data from different regions of the upper troposphere between June 2002 and April 2012, and calculated the three-month averages of ammonia concentrations.

Surprisingly, they found atmospheric ammonia about 7.5 miles to 9.3 miles (12 to 15 km) above sea level in the same area and time period in which Asian summer monsoons happen. In this region — above north India and southeast China — the ammonia had a concentration of 33 pptv (33 ammonia molecules per trillion air molecules), the researchers found.

A thorough search failed to reveal ammonia at these levels during any other season or anywhere else on Earth, the scientists said.

"We have presented the first evidence of ammonia being present in Earth's upper troposphereabove 10 km [6.2 miles]," the researchers wrote in the study.

The discovery indicates that agricultural ammonia produced on Earth's surface can make its way into the troposphere, where it ends up in monsoons, the researchers said.

"Observations show that ammonia is not washed out completely when air ascends in monsoon circulation," the study's lead researcher, Michael Höpfner, the head of the Remote Sensing Using Aircraft and Balloons Group at the Institute of Meteorology and Climate Research at the Karlsruhe Institute of Technology in Germany, said in a statement. "Hence, it enters the upper troposphere from the boundary layer close to the ground, where the gas occurs at relatively high concentrations."

Cloud formation

Ammonia can act as an aerosol, or teensy particles suspended in the atmosphere. Aerosols often act as "cloud seeds" around which cloud droplets can form.  

Aerosols are the smallest particles known to contribute to cloud formation, and they also appear to influence the properties of existing clouds, the researchers said. For instance, aerosols can alter the size of cloud particles, changing how clouds reflect and absorb sunlight. This can lead to reduced visibility (haze) and redder sunrises and sunsets, according to NASA.

The finding shows that in addition to polluting local ecosystems, agricultural ammonia released in high concentrations can drive the formation of new clouds and alter the properties of existing clouds, the researchers said. [Gallery: Reading the Clouds]

In a strange twist, humans may rely on atmospheric ammonia to mitigate the human-induced effects of climate change. The accumulation of aerosols in the troposphere is thought to have a cooling effect, as clouds reflect the sun's energy. However, clouds can also trap heat released by Earth, which can warm the planet.

In a November study published in the journal Nature Communications, researchers found that ammonia released from guano (seabird poop) in the Arctic may influence cloud formation, leading to a slight cooling effect there.

The new study was published online Nov. 18 in the journal Atmospheric Chemistry and Physics.

Original article on Live Science.

Bird poop is a messy nuisance in the Arctic, but the droppings from seabirds actually have a beneficial effect: slightly cooling the region threatened by climate change, a new study finds. 

In short, chemical reactions that are set in motion by the bird droppings, or guano, change the properties of the clouds above, and make them more reflective, the researchers said.

"Clouds can actually reflect energy that's coming from the sun back to space, which is a cooling effect," said study co-lead researcher Betty Croft, a research associate in the Department of Physics and Atmospheric Science at Dalhousie University in Nova Scotia, Canada. [Images of Melt: Earth's Vanishing Ice]

However, Croft cautioned that although the newfound connection between bird droppings and summertime cooling is intriguing, it's minor and "not an effect that is going to counteract global warming."

Still, the researchers were surprised to learn that seabird excrement is likely a key player in the Arctic's climate, at least during the summer. Every year, usually between May and September, tens of millions of seabirds migrate to the Arctic to breed and raise their young, they said.

These seabirds eat seafood, which is chock-full of nitrogen, said study co-lead researcher Greg Wentworth, an atmospheric scientist with Alberta Environment and Parks, who did the research for his doctoral degree in chemistry at the University of Toronto.

A large portion of this nitrogen is defecated in the form of uric acid, Wentworth said. In the presence of water and oxygen, microbes can break down the uric acid into carbon dioxide and ammonia (gaseous nitrogen compound), he said.  

This ammonia is key. Once it enters the atmosphere, it can react with other gases — specifically, sulfuric acid and water vapor — and create atmospheric particles. These particles are very small, just a couple of nanometers in diameter (a nanometer is 1 billionth of a meter), Croft said. But as they grow larger — to at least 50 to 80 nanometers, the molecules "can act as the seeds for cloud droplet formation," she said.

These molecules do not form new clouds, Croft said. Rather, they affect existing clouds. As more of these newly formed atmospheric particles enter a cloud, then, so long as the water content in the cloud stays the same, the cloud will become more reflective, and "that's a cooling effect," Croft said.

Cloud caveats

However, the researchers have studied just one possible effect that guano can have on clouds. Although clouds can reflect the sun's energy, they can also trap energy released by the Earth, which can lead to a warming effect, the researchers said.

"There's a lot of work [that needs] to be done to understand the details before we could really understand what would be the overall effect [of the guano] in the climate system," Croft said.

But, now that researchers know that seabird guano plays a factor in climate cooling during the Arctic's summer months, it's more important than ever that people protect these migratory birds, the researchers said. [Quest for Survival: Photos of Incredible Animal Migrations]

"Given the accelerated rate of Arctic warming, seabird numbers and migratory patterns may change, altering the seabird-guano ammonia emissions in the Arctic," the researchers wrote in the study. "Thus, the relative importance of ammonia from seabird guano to the Arctic climate may be susceptible to future change."

The study was published online Tuesday (Nov. 15) in the journal Nature Communications.

Original article on Live Science.

A satellite image showing peculiar hexagonal clouds over the ocean area known as the Bermuda Triangle is prompting speculation about whether they may represent a recurring phenomenon responsible for decades of unexplained disappearances in the region.

The photo appeared in the Science Channel's "What on Earth"? series in a recent episode about the Bermuda Triangle, a loosely defined area bound on the west by the tip of Florida, to the south by Puerto Rico and to the north by Bermuda. In the image, oddly shaped cloud networks hovered above the triangle's western tip, off the coast of Florida, over the Bahamas. Seen from above, the clouds appeared to form six-sided outlines, like honeycombs, with hard edges. They range in size from 20 to 55 miles (32 to 89 kilometers) across, according to the Science Channel.

According to the Science Channel, similar cloud formations in the North Sea near the U.K. have been associated with so-called "air bombs" — powerful downdrafts of air that could overpower and destroy ships and airplanes. But even though the clouds over the North Sea and the Bahamas may look the same, they likely have different causes and interact with the ocean below in different ways, experts say. [Gallery: Lost in the Bermuda Triangle]

The image over the Bahamas was captured in 2002 by NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) instrument on the Terra satellite. The Science Channel described the hexagons as measuring approximately 20 to 55 miles across, and invited comparison to an image of a similar cloud configuration 4,500 miles (7,200 km) away, over the North Sea.

Randy Cerveny, a meteorologist at Arizona State University, told the Science Channel that the hexagonal shapes were signatures of "microbursts," rapid and highly focused blasts of downward-moving air that can generate sea-surface winds reaching nearly 100 mph (161 km/h) and ocean waves towering more than 40 feet (12 meters) high — which could certainly wreak havoc on the sea surface and any vessel on or near it.

According to the Science Channel, radar images of the North Sea clouds did reveal underlying wind gusts close to 100 mph. However, the episode did not present any evidence that similar winds battered the Atlantic Ocean under the hexagonal clouds seen over the Bahamas in 2002, saying only that "scientists believe" the same winds existed.

And meteorologist Kevin Corriveau told NBC News that the hexagonal shape of the Bermuda clouds did not display the distinctive signature of a microburst.

"You would normally have one large to extremely large thunderstorm that wouldn't have an opening in the middle," he said.

He explained that the weather patterns in the two areas were too different to allow comparisons between similar cloud shapes. Moreover, the peculiar formations in the Bahamas may have occurred because of erratic weather patterns created by small islands heating the air differently than the Florida coastline.

"I wouldn't say what we're seeing in the Bahamas is the exact same as in the North Sea," Corriveau said.

Honeycomb cloud networks are actually a regular occurrence under certain conditions in the mid-latitudes, according to NASA — they can take shape as part of a low-pressure system or cyclone when cold air masses move over warm water. And they can form as open-cell clouds — cloud outlines surrounding an empty space — or closed-cell clouds, which are solid shapes.

Since the 1940s, dozens of ships and airplanes have gone missing while traveling through the Bermuda Triangle. Disappearances were blamed on numerous implausible culprits, from the lost city of Atlantis to deep-sea methane blasts.

Equipment failure and human error are less dramatic explanations for vanished vessels in the Bermuda Triangle, but they are the most likely ones, experts say. "There is no evidence that mysterious disappearances occur with any greater frequency in the Bermuda Triangle than in any other large, well-traveled area of the ocean," the National Oceanic and Atmospheric Administration said in a statement.

Original article on Live Science.

Interlacing waves of clouds decorate the sky above the coast of Angola in a new satellite image.

The image, taken June 26 by an instrument on NASA's Terra satellite, highlights the atmospheric patterns off the coast of West Africa. The clouds are called gravity waves, which form as gravity and buoyancy try to balance each other out. (Gravity waves are different than gravitational waves, which are ripples in space-time.)

According to NASA's Earth Observatory, the culprit here is dry, cool air moving out of the nighttime Namib desert and over the ocean. This cool air pushes the humid and warm ocean air up (there's the buoyancy part of the equation). As the moisture rises and condenses to form clouds, gravity pushes it back down, where it hits the rising column of dry air and gets hoisted up again. (A similar push-and-pull occurs at the ocean's surface because of the interactions of wind and gravity.)

[See Photos of the Namib Desert's Fairy Circles]

The ripple-like clouds seen in this image represent the peaks of the gravity waves, where the moisture in the air condenses. The clear skies between the peaks are the troughs of the gravity waves.

On the day the Moderate Resolution Imaging Spectroradiometer on the Terra satellite captured this image, winds were creating gravity waves in all different directions, Bastiaan van Diedenhoven, who researches ice-containing clouds at NASA's Goddard Space Flight Center, told the Earth Observatory. The result was a complicated pattern of crisscrossing clouds curving across at least 620 miles (1,000 kilometers). These patterns are often seen off Angola and Namibia in the morning and early afternoon, van Diedenhoven told the Earth Observatory, and tend to be pushed out to sea as the day goes on.

Gravity waves may be important for commercial air travel. A study presented in 2012 at the annual meeting of the American Geophysical Union found that gravity waves can break against an aircraft just as ocean waves break against a beach, causing turbulence in otherwise clear skies.

Original article on Live Science.

Clouds might seem like a nuisance if you’re headed on a Sunday afternoon picnic. But put aside your personal biases for a second and consider this: clouds can also tell the story of life on earth.

That story has become a lot clearer thanks to new maps created by scientists that document a global year in the clouds in more intimate detail than ever before. The maps — a cloud atlas if you will — provide a fine-grained view of how clouds move around in our atmosphere and represent an important link between climate and ecological research. They’re also pretty easy on the eyes.

It turns out, England is indeed cloudy for most of the year while most of the Bay Area’s clouds show up in February. Adam Wilson, a researcher at the University of Buffalo who helped create the cloud atlas, joked that you could use the maps to settle bets between friends on who lives in the cloudiest place.

But beyond bets and bragging rights, Wilson said the maps also provide a tool for tracking life around the planet. It turns out that the different biomes of the world from deserts to mountains to cloud forests all have their own special patterns of clouds, patterns that can be instrumental to studying the patterns of life itself.

"I wasn’t expecting the signal of the biomes would stand out so stark globally," Wilson said. "The Mediterranean, southwest Africa, Australia, they all pop out as a totally different. That’s not scientifically amazing but seeing it for the first time in a map was just striking."

There have been other efforts to get fine-grained cloud data in the past, but they’ve been marred by being limited to the tropics or getting false positives of clouds in snowy areas. Wilson and colleagues at Yale created a new analysis of satellite data captured at a 1-kilometer resolution by NASA everyday for the past 15 years to shine a light on the cloudy skies.

The new data analysis helps bridge an big divide between the climate and ecology communities. Ecologists track plants and animals across the planet at very fine scale, sometimes looking at a few square feet of soil, but climate science often provides data at a much larger spatial scale. With the new dataset, ecologists' understanding of the climate factors that affect life has vastly expanded.

And because it’s satellite data, the majority of the globe is covered including places that might be lacking on-the-ground measurements like rainforests and deserts in developing countries. Those areas are also home to a number of threatened and endangered species that will face growing pressure from climate change.

“Having the best possible environmental data will lead to best species model distribution approach,” he said, noting that that modeling could in turn help inform management decisions.

Species distribution modeling incorporates a whole host of environmental data from climate to the type of soil on the ground to get a better view of where individual plants and animals live. Wilson and his colleagues recently authored a study that plugged the new cloud data into a model for two species and found it helped improved their range estimates.

“One thing that’s been a disconnect between the climate community and the ecological community is this gap in spatial resolution,” he said. “Using remote sensing like we’ve done that’s capable of directly observing cloud cover is how we can get down to fine spatial resolution.”

Climate change is expected to put more stress on plants and animals. That means decisions on how to manage them, what areas to conserve and whether and where to relocate threatened species will take on ever greater importance. The new data could help answer some of those pressing questions.

Because the data is publicly available, users beyond the ecological realm can also play around with it. Wilson told Vox there could be a whole host of applications in the solar industry, which perhaps not surprisingly has a lot invested in the sunny side equation.

You May Also Like: Global Warming Is Starving West Coast Waters of Oxygen Satellite Shows U.S. Has the Most Gas Flares in the World Climate Change is ‘Devastating’ The Great Barrier Reef Strong El Niño Helped Lower U.S. Heating Costs

Originally published on Climate Central.

You may not have seen it, but in July there was a large "A" written in the sky over the ocean near the Kamchatka Peninsula, in far-eastern Russia. In an image of this "A" that was snapped from space, the letter looks like it could have been made by an airplane that was using standard skywriting.

But actually, ships crossing the ocean were responsible for creating the streaky, white letter.  

The image of the A, published on Sunday (Dec. 27) on NASA's Earth Observatory website, shows how ocean-going ships produce a stream of exhaust gases that leaves tracks across the sky behind them, called ship tracks. A camera aboard NASA's Aqua satellite took the image on July 27. [Image Gallery: Sunrises and Sunsets]

Not only can ship tracks produce interesting imagery in the sky, but they can also give scientists the opportunity to see how exhaust fumes affect cloud formation over the ocean. Clouds over the ocean are influenced by fewer environmental factors than clouds that form over land, according to NASA's website.

NASA scientists who study climate have discovered that pollution from burning fossil fuels produces aerosols, which are solid, airborne particles that can change what clouds are made of and how they form. Aerosols influence cloud formation and come from many sources, including natural ones such as volcanic activity and algal blooms, according to NASA.

However, the aerosols from burned fossil fuels, such as sulfate particles, have built up in Earth's atmosphere over time and have actually made clouds brighter, leading them to reflect more solar radiation than they used to. While this may sound like a good thing in today's warming world, it is actually changing clouds in negative ways, such as stopping them from releasing water, and researchers don't yet understand how far the effect might go, according to a report from the Intergovernmental Panel on Climate Change (IPCC).

NASA researchers hope that by continuing to study ship tracks, they can help climate scientists gain more insight into how aerosols from burned fossil fuels affect cloud formation, and what any changes they observe mean for the climate going forward.

The image of the letter A was posted as part of NASA's Reading the ABCs from Space project.

Follow Elizabeth Newbern @liznewbern. Follow Live Science @livescience, Facebook & Google+. Original article on Live Science.