Fire cloud

Contributed by
Jul 6, 2006
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Bad Reader Eric sent me a note about an email going around about a very pretty atmospheric phenomenon called, in the email, a "fire rainbow". It's actually called a circumhorizontal arc. It's caused by sunlight refracting through ice crystals in the air, much like rainbows and haloes.

The Snopes page linked above quotes an email going around saying this is "THE RAREST OF ALL NATURALLY OCCURING ATMOSPHERIC PHENOMENA" (yes, the original email was shouting). I don't think that's true, since I've seen this several times. I think the Parry arc is rarer; I've only seen one twice in my life. Ironically, one was when I was in grad school at the University of Virginia during a big football game; the arc formed a giant "V" in the sky, which we all got a kick out of-- though not so much the football team, which was humiliated by Georgia Tech. So much for omens in the sky!