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15 Billowing Facts About Clouds

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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Department Of Classics, University Of Cincinnati
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Stones, Bones, and Wrecks
Ancient Poop Contains First Evidence of Parasites Described by Hippocrates
Department Of Classics, University Of Cincinnati
Department Of Classics, University Of Cincinnati

The long-held mystery of Hippocrates and the parasitic worms has finally been solved, and it’s all thanks to a few samples of ancient poop.

Researchers don’t know much about the parasites that plagued the Greeks thousands of years ago, and what they do know is largely from the Hippocratic Corpus, the medical texts that the father of medicine and his students put together between the 4th and 3rd centuries BCE. Modern historians have spent years trying to figure out which diseases and parasites Hippocrates and his followers were referring to in their writing, relying solely on their descriptions to guess at what ailments the ancient Greeks might have suffered from. Now, they finally have concrete evidence of the existence of some of the intestinal worms Hippocrates mentioned, Helmins strongyle and Ascaris.

As part of a study in the Journal of Archaeological Science: Reports, an international group of researchers analyzed the ancient remains of feces in 25 prehistoric burials on the Greek island of Kea to determine what parasites the people were carrying when they died. Using microscopes, they looked at the soil (formed by the decomposed poop) found on the pelvic bones of skeletons dating back to the Neolithic, Bronze, and Roman periods.

A roundworm egg under the microscope
A roundworm egg
Elsevier

Around 16 percent of the burials they studied contained evidence of parasites. In these ancient fecal samples, they found the eggs of two different parasitic species. In the soil taken from the skeletons dating back to the Neolithic period, they found whipworm eggs, and in the soil taken from the Bronze Age skeletons, roundworm.

With this information, researchers deduced that what Hippocrates called the Helmins strongyle worm was probably what modern doctors would call roundworm. The Ascaris worm probably referred to two different parasites, they conclude, known today as pinworm (which was not found in this analysis) and whipworm (pictured below).

Whipworm under a microscope
A whipworm egg
Elsevier

Though historians already hypothesized that Hippocrates's patients on Kea had roundworm, the Ascaris finding comes as a particular surprise. Previous research based solely on Hippocrates’s writing rather than physical evidence suggested that what he called Ascaris was probably a pinworm, and another worm he mentioned, Helmins plateia, was probably a tapeworm. But the current research didn’t turn up any evidence of either of those two worms. Instead of pinworm eggs, the researchers found whipworm, another worm that’s similarly small and round. (Pinworms may very well have existed in ancient Greece, the researchers caution, since evidence of their fragile eggs could easily have been lost to time.) The soil analysis has already changed what we know about the intestinal woes of the ancient Greeks of Kea.

More importantly, this study provides the earliest evidence of ancient Greece’s parasitic worm population, proving yet again that ancient poop is one of the world’s most important scientific resources.

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Arctic Temperatures are Rising So Fast, They're Confusing the Hell Out of Computers
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This past year was a brutal one for northern Alaska, which saw temperatures that soared above what was normal month after month. But you wouldn't know that by looking at the numbers from the weather station at Utqiaġvik, Alaska. That's because the recent heat was so unusual for the area that computers marked the data as incorrect and failed to report it for the entirety of 2017, leaving a hole in the records of the Climate Monitoring group at the National Centers for Environmental Information (NCEI), according to the Huffington Post.

The weather station in the northernmost tip of Alaska has been measuring temperatures for nearly a century. A computer system there is programed to recognize if the data has been influenced by artificial forces: Perhaps one of the instruments isn't working correctly, or something is making the immediate area unnaturally hot or cold. In these cases, the computer edits out the anomalies so they don't affect the rest of the data.

But climate change has complicated this failsafe. Temperatures have been so abnormally high that the Utqiaġvik station erroneously removed all its data for 2017 and part of 2016. A look at the region's weather history explains why the computers might have sensed a mistake: The average yearly temperature for the era between 2000 and 2017 has gone up by 1.9°F from that of the era between 1979 and 1999. Break it down by month and the numbers are even more alarming: The average temperature increase is 7.8°F for October, 6.9°F for November, and 4.7°F for December.

"In the context of a changing climate, the Arctic is changing more rapidly than the rest of the planet," Deke Arndt, chief of NOAA's Climate Monitoring Branch, wrote for climate.gov. The higher temperatures rise, the faster Arctic sea ice melts. Arctic sea ice acts as a mirror that reflects the Sun's rays back into space, and without that barrier, the sea absorbs more heat from the Sun and speeds up the warming process. “Utqiaġvik, as one of a precious few fairly long-term observing sites in the American Arctic, is often referenced as an embodiment of rapid Arctic change,” Arndt wrote.

As temperatures continue to grow faster than computers are used to, scientists will have to adjust their algorithms in response. The team at NCEI plans to have the Utqiaġvik station ready to record our changing climate once again within the next few months.

[h/t Huffington Post]

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