Don't let clouds pass you by

WMO wants you to capture those moments

The World Meteorological Organization is asking scientists and amateur sky watchers to spend some time with their heads, and cameras, in the clouds.

Since 1939, the Geneva, Switzerland-based organization has published an International Cloud Atlas to help ensure uniform cloud classification standards and descriptions. But the atlas hasn’t been updated since 1987, and a lot in the world has changed since then – notably the advent of the Internet and digital imagery.

So WMO has embarked on a project to update the atlas for the 21st century. The goal is to infuse the atlas with sharper images, a new glossary, descriptions, and, as part of a Web-based edition, time-lapse images and videos. The WMO is calling for submissions by professional meteorologists and others.

A hole-punch cloud or Fallstreak Hole
A fallstreak hole cloud, also known as a hole punch cloud or sky punch cloud, dominates the sky over Hong Kong. (Photo by Lee Tse-cheung.)

"We want observers and enthusiasts everywhere in the world to have correct, consistent names describing the clouds they see," said Steve Cohn, an NCAR scientist and chair of the WMO committee of cloud experts overseeing the project. "It’s similar in concept to the classification schemes for the animal and plant kingdoms."

Cohn isn’t a cloud expert, but he’s been active in WMO and was chosen committee chair based on his management experience at NCAR.  While he still might look at clouds primarily for their beauty, he is enthusiastic about the scientific reasons for updating the atlas.

"It’s important for meteorologists around the world to have standard terms to describe clouds and cloud features, and it’s important too for storm spotters, forecasters, and others who need to communicate what they see," he said.

The updated atlas won’t just define scientific terms; it also will list and describe some commonly used regional and local terms, such as "Table Top" clouds, a term used for the lenticular clouds that settle over Table Mountain in Cape Town, South Africa.

Cirrus uncinus or "mares' tails"
Cirrus uncinus or mares' tails cloud above southeast England. (Photo by Richard Griffith.)

Clouds are also formed from human activities, such as condensation around industrial smokestacks and aircraft contrails. Images of these special clouds will be included as well, since they are valuable to researchers who study Earth’s radiation budget and climate science.

Cohn noted that the atlas includes observable phenomena other than clouds, such as lightning, haze, halos, St. Elmo’s Fire (plasma created by a coronal discharge), and even mirages.

Is WMO expecting to see new kinds of clouds? Well, just a few months ago, the Cloud Appreciation Society submitted "asperitas" (which means roughness in Latin) for consideration as a new cloud type.

WMO considered the wavelike structures of the cloud’s underside to be more chaotic than the undulatus cloud variety, but still generally associated with what are called stratiform clouds. So it was decided to include "asperitas" as a new cloud "supplementary feature." As part of a Cloud Appreciation Society competition, the WMO committee recently selected a photograph of an asperitas cloud by a photographer in Tasmania, Australia, to be included in the updated atlas.

Now, it’s time for cloud aficonados out there to submit their images  . . .

(For more cloud images, see Bob Henson's blog from Weather Undergound.)

Jeff Smith, science writer and public information officer