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WEATHER U: Reason for rainbow-soaked cloud

Larry Burt reached for his camera when he saw this stunning cloud in the sky. It was noon on Monday and he was looking southward from his property in Lower Onslow, N.S. He was curious about it and so were many others who happened to see the optical phenomenon.
Larry Burt reached for his camera when he saw this stunning cloud in the sky. It was noon on Monday and he was looking southward from his property in Lower Onslow, N.S. He was curious about it and so were many others who happened to see the optical phenomenon. - Contributed

On Monday, many of you were treated to a fairly rare optical phenomenon. The first photo I saw was taken around noon near Truro, N.S. Before long, my mailbox was filling up with lovely photos of iridescent clouds. They were spotted from Truro to Inverness Beach, Cape Breton.

Cloud iridescence is a fairly rare phenomenon usually seen in altocumulus or high cirrus-type clouds. The lovely display can also be described as cloud irisation; that term comes from Iris, who was the ancient Greek goddess of the rainbow.

When parts of clouds are thin and have similar-sized droplets or ice crystals, diffraction splits the incoming light into stunning colours. The colours are quite similar to those seen in soap bubbles or oil on the road after a rain and usually found in random patches or bands.

It’s not accurate to say that these clouds are rare, but rarely are they quite as vivid as they were on Monday, and therefore, they often go unnoticed.

Because the cloud irisation is usually found in the vicinity of the sun, it can be hard to see. It’s never a good idea to stare directly into the sun, so the best way to see an iridescent cloud is to block the sun with your hand and have a look that way.

It’s fun to look up, but always remember to protect your eyes!



Cindy Day is the chief meteorologist for SaltWire Network.

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