Undulatus Asperatus | By Phil Plait | October 11, 2014

I think someone opened one of the seven seals.
Photo by Agathman / wikimedia commons

I think someone opened one of the seven seals.
Photo by Agathman / wikimedia commons

I have been known, over the course of the past few years, to post pictures of the odd cloud or two. And I do mean odd. Sometimes they’re photos I’ve taken myself (and some of which have been very difficult to identify), sometimes they’re from machines in space, and sometimes from humans in space.

Still, I’m not a cloud chaser per se; you won’t see me hopping in my car and driving hundreds of kilometers to spy a weird cloud formation someone tweeted about, for example. On the other hand, if someone were to tell me they saw something like this nearby, well, I’d think pretty hard about getting my car keys and going for a look-see.

I have been known, over the course of the past few years, to post pictures of the odd cloud or two. And I do mean odd. Sometimes they’re photos I’ve taken myself (and some of which have been very difficult to identify), sometimes they’re from machines in space, and sometimes from humans in space.

Still, I’m not a cloud chaser per se; you won’t see me hopping in my car and driving hundreds of kilometers to spy a weird cloud formation someone tweeted about, for example. On the other hand, if someone were to tell me they saw something like this nearby, well, I’d think pretty hard about getting my car keys and going for a look-see.

Those are undulatus asperatus (agitated or turbulent wave) clouds, a type of cloud that is starting to get consideration as a wholly new category. From what I can tell, they are formed when there’s rising air that creates wide-spread cloud cover, together with wind shear that blows across the rising air. This can set up gravity waves, where air moves up and down as buoyancy and gravity battle it out, creating long rippling waves that carry the clouds up and down.

You can find out more about this on Slate’s Atlas Obscura blog. I urge everyone to bookmark that blog; it is always a fascinating tour of the weirder and wonderfuller places on our planet.

And let me leave you with this simply jaw-dropping video of undulatus asperatus in action. Make it high-def and full screen, because seriously: Holy wow.

http://www.slate.com/blogs/bad_astronomy/2014/10/11/undulatus_asperatus_a_new_category_of_cloud.html

Phil Plait writes Slate’s Bad Astronomy blog and is an astronomer, public speaker, science evangelizer, and author of Death From the Skies!  

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