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Kirill Ignatyev via Flickr Creative Commons // CC BY-NC 2.0
Kirill Ignatyev via Flickr Creative Commons // CC BY-NC 2.0

Meet Asperitas, the Newest Addition to the Cloud Atlas

Kirill Ignatyev via Flickr Creative Commons // CC BY-NC 2.0
Kirill Ignatyev via Flickr Creative Commons // CC BY-NC 2.0

Cloud-spotters, rejoice! After years of lobbying, the World Meteorological Organization (WMO) has granted Asperitas formations a spot in the official cloud canon. The change is part of an update to the International Cloud Atlas released for World Meteorological Day on March 23.

The first iteration of the cloud atlas, published in the late 19th century, laid down the scientific standards for the monitoring and measurements of clouds and other meteorological phenomena. It formalized the system of taxonomy introduced by an amateur cloud-spotter in 1802, which mirrored the classification of plants and animals by sorting clouds into 10 major types, or genera, then splitting them further into varieties and species.

The last edition of the atlas was published in 1987. The clouds may not have changed since then, but the world has, and the WMO wants to keep up. The new edition will be all-online and include measurements and data from 191 different countries and territories. It will also feature one new species—the volutus, or tube-shaped cloud—and five supplementary features, including asperitas.

The inclusion of asperitas is a point of pride for Cloud Appreciation Society founder Gavin Pretor-Pinney, who says members have been sending in photos of asperitas-covered skies for more than a decade.

“Ever since we first noticed distinctive turbulent waves of cloud back in 2006 in images sent from Cedar Rapids, Iowa, US, we have argued that this formation did not easily fit within the existing naming system,” CAS noted on its website. “So we are very pleased that now, almost ten years later, asperitas is finally being accepted as an official classification by the World Meteorological Organisation.”

The taxonomy of clouds may sound fluffy to laypeople, but experts like WMO secretary-general Petteri Talaas take it very seriously. “If we want to forecast weather, we have to understand clouds,” he said in a statement. “If we want to model the climate system, we have to understand clouds. And if we want to predict the ability of water resources, we have to understand clouds.”

The theme of this year’s World Meteorological Day was—you guessed it—Understanding Clouds.

Spotted something spectacular? Check out the CAS website or the WMO’s submission guidelines to share it with the cloud-loving world.

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Weather Watch
Thanks to Desert Dust, Eastern Europe Is Covered in Orange Snow
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iStock

Certain areas of Eastern Europe are starting to look a bit like Mars. Over the last few days, snowy places like Sochi, Russia have experienced an unusual snowfall that coated mountains in orange powder, according to the BBC.

The orange snow was the result of winds blowing sand from the Sahara east to places like Moldova, Romania, Bulgaria, Ukraine, and Russia. The sand mixes with precipitation to form orange-tinted snow. According to the BBC, the phenomenon occurs semi-regularly, turning snow orange about once every five years, but this year is especially sandy. As a result, skiers are navigating slopes that look like they're from a different world, as you can see in the video below from The Guardian.

The Sahara rarely gets snow, but when it does, the landscape can look somewhat similar, as you can see in this image of the Atlas mountains in Morocco.

Instagram is currently filled with photos and videos from Eastern Europe featuring the odd-looking snow. Check out a few samples below.

[h/t BBC]

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Weather Watch
What Is Thundersnow?
Jessica Kourkounis, Getty Images
Jessica Kourkounis, Getty Images

The northeastern United States is dealing with its second major nor'easter in a week, with rain and heavy snow—and the associated power outages—cutting a path across the Mid-Atlantic and New England. But news of the adverse impacts of the snowstorm is being accompanied by an unusual buzzword: thundersnow. Thundersnow occurs during a thunderstorm that produces snow instead of rain. The mechanisms that produce rainy thunderstorms and snowy thunderstorms are largely the same, even if the air temperature is below freezing.

A band of snow can become strong enough to produce lightning through two processes known as convection and forcing. Convection occurs when an area of warm air quickly rises through cooler air above it. Convective snow is most common during lake effect snow events like those you’d find on Lake Ontario or Lake Erie, since the process requires extreme vertical temperature gradients that can result from bitterly cold air flowing over a warm body of water.

Forcing is slightly different. A strengthening low-pressure system involves fast, dynamic changes in the atmosphere, especially when one of these storm systems quickly gains strength. Such a fast-developing storm can cause large amounts of lift in the atmosphere, a process that forces air to swiftly rise like you’d see during convection. This creates intense bands of snow that can grow so strong that they produce thunder and lightning. This process is responsible for the thundersnow that occurs during blizzards and nor’easters, those powerful storms that regularly hit the eastern coast of the U.S. during the winter. Thundersnow can be pretty exciting—just ask The Weather Channel's Jim Cantore:

The name “thundersnow” can be a bit misleading. One of the most enjoyable things about a snowfall is how silent it is outside when there’s a thick blanket of snow on the ground. Snow absorbs sound waves so efficiently that you can usually only hear ambient noises immediately around where you’re standing. Snow muffles the sound of thunder for the same reason. Thunder that might be audible for many miles during a rainy thunderstorm might only be audible for a few thousand feet away from where the lightning struck. Unless the lightning strikes very close to where you are, you might only see a bright flash during thundersnow without ever hearing the thunder.

While thundersnow is a fascinating phenomenon to encounter, it does involve lightning, after all, and it’s just as dangerous as any other lightning bolt you’d see in a rainy thunderstorm. If you’re ever lucky enough to experience thundersnow, the event is best enjoyed indoors and out of harm’s way.

This piece originally ran in 2017.

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