(CNN) — Looking up, you might be thinking you're under a roiling, stormy sea.
But what you're looking at is a unique and breathtaking meteorological phenomenon. And today, World Meteorological Day, it's being officially recognized: asperitas cloud.
"Asperitas is characterized 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."
What's in a name?
In 2006, the Cloud Appreciation Society, a group of weather enthusiasts based in the UK, received the first images of the distinctive cloud from Cedar Rapids, Iowa. A few years later, they proposed the cloud be included in the atlas. That would be a huge coup since the atlas is widely used to train meteorologists from the time it was first published in the late 19th century.
"When we know the name of something, we began to know it in a different way and when we began to know it, we began to care about it," Gavin Pretor-Pinney said at a World Meteorological Day ceremony in Geneva.
A big deal
Adding a new cloud type is rare. The World Meteorological Organization had not updated the atlas in 30 years, until now.
"It is a classic example of citizen science, in which observations by the general public, enabled by the technology of smartphones and the Internet, have influenced the development this most official of classification systems," a news release on the Society's website reads.
Alongside the striking cloud formations, a few other classifications have been added to the new edition. Some of them are "volutus," a roll cloud, "contrail," a vapour trail that is sometimes produces by airplanes and more common phenomena like rainbows, halos and hailstones, according to the foreword of the atlas.