Update on Last Week’s Strange Clouds

July 26, 2005 at 1:42 am | Posted in Uncategorized | Leave a comment

Sundogs and haloes are rather common. But what we saw last Thursday was entirely different. And I was having trouble coming up with a compelling answer as to what might have caused those strange colorful clouds.

So I wrote Les Cowley, an expert in atmospheric optical phenomena. I sent him some of our viewers’ amazing photographs. And he finally gave me a definitive answer to what those strange clouds were:
“The colors are fragments of an ice halo called a circumhorizon arc. The arc is formed by sunlight refracted through horizontal hexagonal plate shaped ice crystals in high cirrus cloud.
More about circumhorizon arcs at:
http://www.sundog.clara.co.uk/halo/cha.htm
They can only be seen in summer around noon when the sun is very high in the sky.
Les Cowley
Atmospheric Optics”

I knew the photos couldn’t be of a circumzenithal arc, because the sun was too high in the sky for that to be possible. I have to admit, I had never before even heard of a circumhorizon arc. But we finally have an answer. And I learned something new! So check out the link that Les gave us, and learn more for yourselves.

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