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Tue Jul 23, 2013, 11:00 AM

A Rare Look at an Iridescent Cloud

The photo was taken in Noida, India.

Iridescent clouds, known as "fire rainbows" or "rainbow clouds," occur when sunlight diffracts off water droplets in the atmosphere. And the recipe for these heavenly sights is actually pretty simple.

Like common cloud-to-ground rainbows, iridescent clouds usually accompany thunderstorms. According to atmospheric phenomena expert Les Cowley, they often appear in the late afternoon, on very hot and humid days. This stems from the fact that most rainbow clouds form on top of cumulus clouds—the fluffy cotton-ball-shaped clouds we often see in children's drawings.

"What happens is that the cumulus cloud, boiling upwards, pushes the air layers above it higher and higher," Cowley explained. "As the air gets pushed upwards, it expands and cools. And sometimes moisture in that air suddenly condenses into tiny droplets to form a cap cloud."


I had never heard of a rainbow cloud before. At 67 years of age, I learn something new everyday! It's fun.

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Reply A Rare Look at an Iridescent Cloud (Original post)
Little Star Jul 2013 OP
napoleon_in_rags Jul 2013 #1

Response to Little Star (Original post)

Tue Jul 23, 2013, 05:28 PM

1. Cool! I saw one of these once, right after Fukashima. Scared the bejeebus out of me.

Now I now what it was.

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