International Cloud Atlas

Cloud of the Day – International Cloud Atlas

The International Cloud Atlas has recently published a new edition, the first in thirty years. The 2017 edition is only the fifth one, with the first coming out in 1939, so it’s pretty special. The International Cloud Atlas is a product of the World Meteorological Organization, an agency of the United Nations. The Atlas takes much the same approach as I do in their definition of what is a “cloud.” In my Cloud of the Day series I have included many things that aren’t strictly clouds, such as rainbows, haloes and sprites. The Atlas collects them all under the umbrella of meteors. So we have hydrometeors — meteors composed of water — that include things other than clouds, such as fog and rain. And there are photometeors, that are made by light, such as rainbows, etc . Electrometeors include auroras and Saint Elmo’s fire. There are even lithometeors, made of dry particles, like dust and haze. I don’t feel quite so bad now. If the UN can do it, who am I to cavil?

The existing classifications have been reviewed and all have been retained. Several new, formal cloud classifications have been introduced. These include one new species (volutus), five new supplementary features (asperitas, cauda, cavum, fluctus and murus), and one new accessory cloud (flumen). The species floccus has been formally recognized as being able to occur in association with stratocumulus. The separate section on Special Clouds has been removed, and the cloud and meteor types previously discussed within this section have been integrated into the cloud classification scheme as cataractagenitus, flammagenitus, homogenitus, silvagenitus, and homomutatus.

This edition of the International Cloud Atlas includes new additions, including one you might remember seeing here when it hadn’t yet been accepted as a unique type. I wrote about it as asperatus, but they’ve changed the spelling to asperitas. This cloud was championed by the Cloud Appreciation Society, a collection of enthusiastic amateurs, and great photographers.

Photo credit – NASA – PD

Enjoy this fresh edition of the International Cloud Atlas. It has a searchable image gallery.


About arjaybe

Jim has fought forest fires and controlled traffic in the air and on the sea. Now he writes stories.
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4 Responses to International Cloud Atlas

  1. Very interesting! I have had a couple of my cloud images showcased on the Cloud Appreciation Society website. Being an amateur astronomer, I was not particularly fond of clouds. But being a serious photographer too, I decided to adopt the “lemons to lemonade” mindset and photograph interesting clouds whenever the opportunity arose. That way I always have something interesting to do in my spare time.

    • arjaybe says:

      I’ve featured your sites here before haven’t I, Ralph. I’d gladly put up some of your cloud shots if you’d like that.


      • Ralph A. Croning says:

        I do believe the first I heard of Green Comet is when you posted a cloud image of mine – mammatus? I will go through my archives and see what else I can come up with.

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