Turbulent sea-like formation could be first new cloud type in 50 years
Image: An undulatus aspirates cloud over Burnie in Tasmania, Australia.
Credit: Gary McArthur

As founder of the US Cloud Appreciation Society, Gavin Pretor-Pinney has seen a lot of clouds. In fact, he’s seen hundreds of thousands of them, thanks to the members of the public who post photos of every kind on the Cloud Appreciation Society website every day, from serious storm clouds and big, fluffy cumulus clouds, to thin, wispy cirrus formations streaked across a clear blue sky.

Soon after launching the site in 2005, Pretor-Pinney noticed an increasing number of images being posted by the public that didn’t look like any type of cloud that had ever been classified. At least one of these images would pop up on the website every six months. "They struck me as being rather different from the normal undulates clouds,” he told Michael Zelenko at the Verge, referring to these dark clouds’ wavelike formation. "They were more turbulent, more confused - as if you were underneath the water looking up toward the surface when the sea is particularly disturbed and chaotic.” 

Pretor-Pinney wondered if these clouds warranted the first addition to the official scientific cloud classification system in 50 years, and became determined to find out.

Cloud classification goes all the way back to 1802, when British pharmacist Luke Howard first presented his paper, "On the modification of clouds”, in which many of the classifications we use today were first proposed, including cirrus, cumulus, stratus, and Nimbus. Almost a hundred years later, the colossal International Cloud Atlas was published, organising all known cloud types into four levels of classification, under which they’re grouped into a genre, species, and variety, sort of like how animals and plants are scientifically classified. This book is now the global standard for cloud classification, and since 1975, when the last edition was published, there has not been a significant change or addition to the classification system of clouds.

"Fortunately, the World Meteorological Organization is currently in the process of preparing the first new edition of the International Cloud Atlas in four decades. Finally, the Atlas will be available online - the clouds are coming to the cloud,” says Zelenko.

So Pretor-Pinney is now working on getting his new cloud type - which he’s named undulatus asperates - into the next edition of the International Cloud Atlas. On the advice of England’s Royal Meteorological Society, Pretor-Pinney collaborated with a graduate student at the University of Reading in the UK to publish the dissertation, "Asperatus: the Application of Cloud Classification to a Suggested New Cloud Type”, which he used to strengthen his case when he first approached the editors recently

While the editors have yet to officially commit to adding this new type of cloud to the next edition of their cloud atlas, they've gone so far as to propose an official definition for it, which is recited by Zelenko at the Verge

"A formation made up of well-defined, wavelike structures in the underside of the cloud, more chaotic and with less horizontal organization than undulatus. Asperatus is characterised by localized waves in the cloud base, either smooth or dappled with smaller features, sometimes descending into sharp points, as if viewing a roughened sea surface from below. Varying levels of illumination and thickness of cloud can lead to dramatic visual effects."

The fact that undulates aspirates now has its own formal definition means there’s a pretty good chance it’s going to end up in the International Cloud Atlas in a few years' time, and it's all thanks to Pretor-Pinney's one-man mission to make it happen.

Head to the Verge to see more amazing images of undulates aspirates, and watch this mind-blowing timelapse video to see it churn like an angry sea:

Source: The Verge