For background, I was on a tour coming back from Ballestas Islands just off of Peru, around 11:00 a.m., no rain (it's a desert area), sky was partly cloudy. The phenomenon stayed a couple of minutes. As we progressed, the colours merged to a strand of amber.

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[–] 48 points 11 months ago (12 children)

Cloud iridescence! . Typical with thin high atmosphere clouds. When very small ice crystals or water droplets form the cloud they can diffract the light from the sun, causing an interference pattern to form. Not entirely dissimilar from an oil slick.

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  • [–] [S] 11 points 11 months ago (7 children)

    Thanks a bunch. Are they more common in hot countries? Never seen them in Canada.

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  • [–] 16 points 11 months ago* (last edited 11 months ago) (3 children)

    Am Canadian. Have seen them. It's more about altitude than lattitude.

    Edit: Spend a little bit of every day looking at the sky. Day or night, it's often magnificent.

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  • [–] 5 points 11 months ago (3 children)

    Super interesting that this is an entirely different mechanism from a rainbow.

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  • [–] 1 point 11 months ago (2 children)

    The way they are describing it isn't entirely accurate.

    It's not an interference pattern, it's basic refraction. And since each wavelength of incoming "white" light is refracted slightly different, you get the rainbow display

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  • [–] 1 point 11 months ago (1 child)

    You are correct! I think the use of the word "diffraction" is a bit confusing because "diffraction patterns" are an interference effect.

    So is this any different than a rainbow? The path of light must be at least different since rainbows only occur in the opposite direction of the Sun.

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  • [–] 6 points 11 months ago* (last edited 11 months ago) (6 children)
  • [–] 4 points 11 months ago (2 children)

    Sun dogs are refraction, and these clouds are diffraction

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  • [–] 2 points 11 months ago