The phenomenon of rainbow clouds - what are they and where can they be seen
The phenomenon of rainbow clouds - what are they and where can they be seen

Since rainbow clouds are quite a rare phenomenon, it is rather difficult to see them with your own eyes. And, in fact, even when such clouds hang directly overhead, not everyone will pay attention to them for one simple reason - they are in the sky in close proximity to the bright sun, so without dark glasses you can notice them in the sky almost impossible.

Rainbow Cloud in Ohio, Dublin City, May 2009

In order for rainbow clouds to form, a whole set of conditions is required at once. The sun must be 58 degrees or higher, cirrus clouds with plate-like ice crystals must already be present in the sky, and sunlight must penetrate the ice crystals at a certain angle.

Washington State, June 2006

In other words, heavy thunderclouds are never rainbow - they are too dense for that. But if in the “high” sky you can see individual “feathers” or “scraps” of clouds, then those that are closest to the shining sun have the opportunity to be painted in rainbow colors. Sometimes a rainbow even occurs in airplane condensation trails.

New Jersey, July 22, 2007

It is also important where the observer is located. Rainbow clouds cannot be seen if a person is located north of 55th parallel north latitude (that is, north of Denmark or north of the city of Omsk) or south of 55-1 parallel of south latitude (that is, in the Antarctic region).

Portugal, 2006

Another difficulty is that such clouds are in close proximity to the sun - 3-17 degrees from it. It is difficult to look at the sun, therefore it is possible to see a rainbow in such proximity to it only through dark eyes or with the help of smoked glass. Sometimes it happens that the sun is covered by another cloud, and the rainbow cloud becomes more visible and brighter. Sometimes the distance reaches 30 degrees - then the rainbow clouds are visible to the naked eye.

Arizona, 2009

So what are rainbow clouds? These are, in fact, the most ordinary clouds, just the light in them for the observer is refracted in the form of a spectrum. This refraction is called irisation. For its occurrence, you need the presence of cooled drops of water, which are on the verge of turning into ice crystals. This most often happens in mountainous areas - there the air is usually free of impurities, and water droplets in the clouds remain in a liquid state longer. It is through such drops that the light irides itself and a person on earth sees a rainbow.

Canada, July 3, 2001 New Mexico, USA, August 2004 Switzerland, June 2007 California, USA, June 2004 California, June 8, 2003

For what other clouds are, see our selection "20 photos of incredible sky".

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