They are often bright white; they can be grey or even quite dark, but how about pastel-shaded clouds?
I didn’t see them, but many did. By early afternoon, I had received several lovely photos of a pretty pastel cloud. While the attached photo was being taken in Wolfville, the intriguing cloud was being admired over New Minas.
Ruby Brooks writes, "Hi Cindy. I saw these beautiful rainbow clouds in the sky in New Minas just minutes ago and thought you might enjoy them. They are truly beautiful. The pictures truly don't do them justice."
That is very often the case when you’re dealing with an optical phenomenon. This one is known as “cloud iridescence” - a fairly rare phenomenon usually seen in altocumulus or high cirrus-type clouds. The colours in the cloud are similar to those seen in soap bubbles or oil on the road after a rain. The lovely display can also be described as cloud irisation; that term comes from Iris, the Greek personification of the rainbow.
Here’s what happens:
When parts of clouds are thin and have similar-sized droplets, diffraction can make them shine with stunning colours. These colours are often found in random patches or bands. Iridescence is usually seen in the edge of a cloud that is forming; that’s where the droplets will have a similar history and therefore a similar size.
Because this iridescence is normally quite close to the sun, it’s often hard to see. It’s never a good idea to stare directly at the sun, so the best way to see an iridescent cloud is to place the sun behind a foreground object, like a building or a large tree, or even just behind your hand.
Look up, but always remember to protect your eyes!
If you see something unusual overhead and would like to know more about it, grab a photo if you can, and drop me a line at [email protected].
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Cindy Day is the chief meteorologist for SaltWire Network
