September 23rd, 2008

total eclipse

Circumzenithal Arc

Someone posted about the circumhorizontal arc last week and we had some nice threads about rainbows and sun dogs and sun pillars and the like. Well, how about the circumzenithal arc, also known as the upside down rainbow?

upside down rainbow

In case you ever wondered where the other side of the rainbow was! This phenomenon is caused by light reflecting back up into the sky (versus diffracting downward, as in a rainbow) when it hits high altitude ice crystals. Read more.
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