Asperitas - A New Cloud Type
Mike Grandmaison, June 18, 2017 at 6:02 PM

It is no wonder I could not identify the type of cloud shown above that I made a few years ago until just recently. That's because the World Meteorological Organization (WMO) only lately classified it as Asperitas, 1 of 11 new cloud types the WMO added in March of 2017 to their International Cloud Atlas. This is the first update that the Atlas has received in 30 years.


Asperitas (formerly known as Undulatus asperatus) was first observed back in 2006 by a member of the amateur cloud-spotting group in Cedar Creeks, Iowa who sent a photograph of the unusual cloud to Gavin Pretor-Pinney, president of the Cloud Appreciation Society in London, England. After receiving more similar photos, the new cloud type was proposed but only recognized 9 years later this past spring on World Meteorological Day.


I first witnessed these dark, storm-like clouds as I drove into Sault Ste Marie, Ontario around dinner time on May 25, 2008. I was immediately taken aback by the unusual, somewhat apocalyptic formation that appeared like rippling waves. The Asperitas clouds covered the entire sky (360 degrees!) and I had never in my life seen anything like that before. I expected a severe storm to materialize as we were adjacent Lake Superior but nothing happened. In fact, the distinctive, but relatively rare cloud formation almost always dissipates without a storm forming.


As is typically the case, I tend to process most of my RAW images only a few years after I make them, sometimes not until years later! In this instance, it took me more than 2 years to process this image after coming across this series of images I made while working on my Ontario book, which was published in the spring of 2015. The caption which accompanied the image on page 128 read: 'Menacing storm clouds, Sault Ste Marie'. Now, I would write: 'Menacing Asperitas clouds, Sault Ste Marie'.