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15 Billowing Facts About Clouds

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Cumulus clouds dot the afternoon sky. Image credit: Melynda Huskey, Flickr //CC BY-NC 2.0

Clouds are incredible. Their endless shapes can add beauty to a sunny afternoon or terror to a day marked by tragedy. When you look at how diverse these billowing formations of atmospheric water are, it’s easy to forget that they’re just that—atmospheric water. Even so, there’s much more to clouds than meets the eye. Here are 15 interesting tidbits about these mainstays of everyday life.

1. THEY'RE NOT WEIGHTLESS.

Clouds look like they weigh little more than a tuft of cotton, but they’re heavier than they look. Your average cumulus (fair weather) cloud can weigh more than a million pounds, and a vivacious thunderstorm can pack billions (if not trillions) of pounds of water in one tiny part of the sky. Yet, all of that weight seems effortlessly suspended in the air. It’s both a little unsettling and, at the same time, awesome to think about.

2. CIRRUS CLOUDS ARE MADE OF ICE.

Wispy cirrus clouds fill the sky near sunset. Image credit: Dennis Mersereau

While most clouds we see are made up of tiny liquid water droplets, there is one common type of cloud that’s made of ice: cirrus. These clouds are collections of ice crystals that form in the upper levels of the atmosphere when water vapor deposits onto tiny particles like dust or smoke. Strong winds then shred these clouds apart, giving them their iconic wispy appearance.

3. VIRGA DOES A DISAPPEARING ACT BEFORE IT REACHES THE GROUND.

Virga falls from the clouds at sunset. Image credit: Bryce Bradford, Flickr // CC-BY-NC-ND 2.0

Another phenomenon that’s often mistaken for a cirrus cloud is something called “virga,” or precipitation that evaporates before reaching the ground. The great thing about virga is that it’s both cool to look at and won’t ruin your day; it’s an indication that the lower and middle levels of the atmosphere are very dry—usually too dry to rain or snow.

4. CONTRAILS BEGIN WITH HOT, MOIST JET EXHAUST.

Contrails lingering in the sky on a day with high upper-level humidity. Image credit: Mark Robinson, Flickr // CC BY-NC 2.0

While most clouds form from natural processes, some can occur as a result of human activities. The best example of this is a condensation trail, commonly known as a contrail for short. Contrails form from an airplane’s hot, moist jet exhaust condensing in the extremely cold air of the upper atmosphere. These cirrus clouds can immediately dissipate or linger for hours depending on how much moisture is present.

5. FEAR THE SUPERCELL.

The rotating updraft of a supercell looms over the horizon. Image credit: Niccolò Ubalducci, Flickr // CC BY-NC-ND 2.0

Most thunderstorms are uneventful, but a tiny percentage of them can grow strong enough that they rage for hours and produce unimaginable horror. These storms, known as supercells, are characterized by a rotating updraft that powers them like an engine. In addition to their enormous hail and monstrous tornadoes, supercells are known for their incredible appearance. The most striking part of a supercell is the rotating updraft, which looks like a column that stretches from the horizon to the heavens.

6. ANVIL CLOUDS ARE THE BEAUTIFUL RESULT OF A COLLISION.

An overshooting top towers over an anvil in an intense thunderstorm in Kansas in June 2009. Image credit: Jeff Slater, Flickr // CC BY-NC 2.0

One of the most impressive sights that fills the sky near a thunderstorm is a thin, flat cloud that covers an area miles around like an umbrella. This is known as an anvil cloud, and it occurs when a thunderstorm’s updraft hits the tropopause, usually the point at which air is neutrally buoyant and it can no longer rise on its own. The air hits this layer like a ceiling, spreading out in all directions and forming this beautiful feature.

7. IF YOU SEE AN OVERSHOOTING TOP, TAKE COVER.

Sometimes, though, an updraft will be so strong that some of the rising air shoots straight through the tropopause and continues soaring hundreds (if not thousands) of feet above the top of the thunderstorm. This creates an overshooting top, a cloud that looks like a dome on an intense thunderstorm. If you see an overshooting top on an approaching storm, it’s a good idea to take shelter, because it’s going to be a doozy.

8. SHELF CLOUDS APPEAR IN SPRING AND SUMMER.

A shelf cloud precedes a thunderstorm in Sydney, Australia. Image credit: Andrea Schaffer, Flickr // CC BY 2.0

Shelf clouds are a common sight in an afternoon thunderstorm during the spring or summer. These formations roll across the horizon like a shelf or a wedge suspended just above the surface, immediately preceding heavy rain and wind. Shelf clouds form as a result of rain-cooled air descending from a thunderstorm and hugging the ground like a bubble. This creates an outflow boundary, which acts like a mini cold front scooping up warm air ahead of it. The shelf cloud forms at the ridge of the pool of cold air, creating a striking scene.

9. MAMMATUS CLOUDS MEAN A WILD RIDE.

Mammatus clouds produced by a nearby thunderstorm. Image credit: David Putz/Connie Sieh, Flickr // CC BY-NC-ND 2.0

If you ever encounter mammatus clouds, chances are you just experienced horrible weather or you’re about to go through a wild ride pretty soon. These numerous, bulbous protrusions hanging high in the sky beneath a deck of clouds look like the mammary glands of a cow or human, hence their name. These clouds are thought to form due to intense turbulence produced by the strong thunderstorm, leading to their smooth, bubbly appearance.

10. ROLL CLOUDS FORM THE LEAD EDGE OF A BOUNDARY YOU CAN'T SEE.

A roll cloud lumbers over Canyon, Texas. Image credit: Kenneth Cole Schneider, Flickr // CC-BY-NC-ND 2.0

Roll clouds are similar to shelf clouds, forming along the leading edge of a boundary like a sea breeze or cold front. Unlike shelf clouds, though, these formations aren’t attached to a neighboring deck of clouds, unspooling across the sky like a thick rope. They’re both unnerving and beautiful, but like almost every other cloud mentioned here, also completely harmless.

11. IRIDESCENCE IS STUNNING BUT RARE.

Cloud iridescence around the thin edges of a cumulus cloud. Image credit: Mike Lewinsky, Flickr // CC BY 2.0

Every once in a while, you might be able to look up at the clouds near the sun and see an abrupt smattering of colors mixed together like the sun reflecting off of an oily sheen on a puddle. This is called “iridescence,” and it’s somewhat rare. Cloud iridescence occurs when sunlight diffracts through water droplets or ice crystals in very thin clouds.

12. A SKY FULL OF IRIDESCENCE GIVES YOU NACREOUS CLOUDS.

Nacreous clouds over Oslo, Norway, in 2008. Image credit: Eirik Newth, Flickr // CC BY-NC 2.0

An even rarer sight is a deck of nacreous clouds, which is pretty much an entire sky full of iridescent clouds. Nacreous clouds are technically called “polar stratospheric clouds,” as they occur in the stratosphere (tens of thousands of feet above the cruising altitude for jets) and are most commonly seen near the poles as they require extremely cold temperatures to form.

13. NOCTILUCENT CLOUDS ARE THE HIGHEST IN OUR ATMOSPHERE.

Noctilucent clouds after sunset. Image credit: Jan Erik Paulsen, Flickr // CC BY 2.0

A distant cousin to the nacreous cloud is the noctilucent cloud, which are thin, wispy clouds that occur in the mesosphere dozens of miles above Earth’s surface. These clouds are the highest that form in our atmosphere, and they reflect a beautiful blue hue as they appear to glow against the dark night sky. These clouds are most common near the Arctic/Antarctic Circles, including parts of northern Canada, Scandinavia, and Russia. Rocket launches can also produce these vivid formations.

14. HALOS NEED THE ICE CRYSTALS IN CIRRUS CLOUDS TO FORM.

A halo around the Moon. Image credit: Nico Nieuwstraten, Flickr // CC BY-NC-ND 2.0

A halo is a spectacular sight that occurs when sunlight or moonlight scatters through the ice crystals that make up a thin layer of cirrus clouds covering the part of the sky directly between the observer and the celestial body. Most halos completely encircle the Sun or the Moon, but depending on the shape or size of the ice crystals, the halos can be partial, inverted, or appear on different sides of the sky.

15. DIAMOND DUST ONLY APPEARS IN THE EXTREME COLD.

Diamond dust is extremely hard to photograph—the Sun creates a sun dog (a type of rainbow-tinted halo) in the diamond dust close to the ground in this picture. Image credit: Peter von Bagh, Flickr // CC BY 2.0

Fog is simply a stratus cloud that forms at the surface. Freezing fog is fog that forms when temperatures are below freezing, consisting of supercooled water droplets that don’t have a nucleus to allow them to freeze into ice crystals. Diamond dust, on the other hand, is fog that forms into ice crystals instead of water vapor. This rare event occurs when the air is so cold (usually below 0°F) that water vapor deposits onto tiny particles in the air, creating suspended ice crystals that float around like snow. Visibility usually doesn’t drop much during diamond dust events, leading to a phenomenon that looks like light snow falling on a brilliantly clear day.

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Space
Look Up! The Orionid Meteor Shower Peaks This Weekend
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Ethan Miller/Getty Images

October is always a great month for skywatching. If you missed the Draconids, the first meteor shower of the month, don't despair: the Orionids peak this weekend. It should be an especially stunning show this year, as the Moon will offer virtually no interference. If you've ever wanted to get into skywatching, this is your chance.

The Orionids is the second of two meteor showers caused by the debris field left by the comet Halley. (The other is the Eta Aquarids, which appear in May.) The showers are named for the constellation Orion, from which they seem to originate.

All the stars are lining up (so to speak) for this show. First, it's on the weekend, which means you can stay up late without feeling the burn at work the next day. Tonight, October 20, you'll be able to spot many meteors, and the shower peaks just after midnight tomorrow, October 21, leading into Sunday morning. Make a late-night picnic of the occasion, because it takes about an hour for your eyes to adjust to the darkness. Bring a blanket and a bottle of wine, lay out and take in the open skies, and let nature do the rest.

Second, the Moon, which was new only yesterday, is but a sliver in the evening sky, lacking the wattage to wash out the sky or conceal the faintest of meteors. If your skies are clear and light pollution low, this year you should be able to catch about 20 meteors an hour, which isn't a bad way to spend a date night.

If clouds interfere with your Orionids experience, don't fret. There will be two more meteor showers in November and the greatest of them all in December: the Geminids.

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science
11-Year-Old Creates a Better Way to Test for Lead in Water
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In the wake of the water crisis in Flint, Michigan, a Colorado middle schooler has invented a better way to test lead levels in water, as The Cut reports.

Gitanjali Rao, an 11-year-old seventh grader in Lone Tree, Colorado just won the 2017 Discovery Education 3M Young Scientist Challenge, taking home $25,000 for the water-quality testing device she invented, called Tethys.

Rao was inspired to create the device after watching Flint's water crisis unfold over the last few years. In 2014, after the city of Flint cut costs by switching water sources used for its tap water and failed to treat it properly, lead levels in the city's water skyrocketed. By 2015, researchers testing the water found that 40 percent of homes in the city had elevated lead levels in their water, and recommended the state declare Flint's water unsafe for drinking or cooking. In December of that year, the city declared a state of emergency. Researchers have found that the lead-poisoned water resulted in a "horrifyingly large" impact on fetal death rates as well as leading to a Legionnaires' disease outbreak that killed 12 people.

A close-up of the Tethys device

Rao's parents are engineers, and she watched them as they tried to test the lead in their own house, experiencing firsthand how complicated it could be. She spotted news of a cutting-edge technology for detecting hazardous substances on MIT's engineering department website (which she checks regularly just to see "if there's anything new," as ABC News reports) then set to work creating Tethys. The device works with carbon nanotube sensors to detect lead levels faster than other current techniques, sending the results to a smartphone app.

As one of 10 finalists for the Young Scientist Challenge, Rao spent the summer working with a 3M scientist to refine her device, then presented the prototype to a panel of judges from 3M and schools across the country.

The contamination crisis in Flint is still ongoing, and Rao's invention could have a significant impact. In March 2017, Flint officials cautioned that it could be as long as two more years until the city's tap water will be safe enough to drink without filtering. The state of Michigan now plans to replace water pipes leading to 18,000 households by 2020. Until then, residents using water filters could use a device like Tethys to make sure the water they're drinking is safe. Rao plans to put most of the $25,000 prize money back into her project with the hopes of making the device commercially available.

[h/t The Cut]

All images by Andy King, courtesy of the Discovery Education 3M Young Scientist Challenge.

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