Rainbow Feather Cloud

On my way back to work after lunch today, I looked out the window and saw this feathery wisp of cloud with a clear rainbow pattern running from red at the the top to violet in the middle, then turning plain white below.

Feathery cirrus cloud banded from red to violet.

As I drove south, the colors moved down the cloud, disappearing entirely by the time I got back. By the time I could safely snap a photo, it was already more or less midway down the cloud.

I believe it’s a fragment of a circumhorizon arc, judging by the description:

Look for a circumhorizon arc near to noon near to the summer solstice when the sun is very high in the sky (higher than 58°). It lies well below the sun — twice as far from it (two hand spans) as the 22º halo.

The arc is a very large halo and is close to, and parallel to the horizon. Usually only fragments are visible where there happen to be cirrus clouds.

We’re still 2 months from the summer solstice, but it was 12:38 PM DST (half an hour before true noon), and the sun was apparently near 70.6° high. (The site is aimed at UK visitors, after all.) It also looked too far away from the sun to be part of the 22º halo, plus of course the colors were more well-defined.

This also points out the should-be-obvious fact that ice crystals can still form in the upper atmosphere even when it’s warm — say, 90°F — on the ground, so there’s no need to limit halo-hunting to winter.

I recommend checking out Atmospheric Optics’ additional pictures of circumhorizon arcs, most of which are more complete than this one. Some of them quite spectacular and must have been really impressive to see live.

Update: I spotted and photographed a much larger and more solid arc in May 2010.

8 thoughts on “Rainbow Feather Cloud

  1. David

    About 3:00 pm 12/25/08 here in Wichita, Ks my wife and I saw this phenomenon while walking our pom. The effect was very pronounced through our sun glasses and was so faint without them that we may not have noticed it otherwise. The colors were so dramatic they looked so surreal and lasted for about 15 – 20 minutes. The most prominent at first were the reds and oranges turning to bright yellow with greens blue and purple, unbelievable. This is the first time we have ever seen this phenomenon making this a very special Christmas Day.

    Reply
  2. Wendy

    We saw a rainbow like this while riding a motorcycle down a country road outside of Marysville Ohio on August 7. It was beautiful and very large. we pulled over to take a photo.

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  3. Frank

    Iw as over in Promised land State Park, PA today and seen a rainbow ball in the sky on a group of clouds. really neat changed color and intensity, lasted about 15 minutes

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  4. Kelson Post author

    I couldn’t get a decent picture this time, but I saw another very faint fragment of this arc today. This time the sky was really hazy, but again a wisp of cloud was drifting at just the right position.

    The weird thing: I saw it at around the same time of day, close to the same time of year, in the same direction, and from the same stretch of road as this one! (A road that I don’t frequent at lunchtime, that’s for sure!)

    When I got back to work and got out of the car, there was also a nice, full-circle halo. I did get pictures of that, which I’ll post tonight if I have time. Edit: here it is.

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  5. lisa

    i saw a rainbow ball in dartford in england 22nd of august it was beside the sun it wasnt dispersed or around any cloud formation it was a warm sunny day with no clouds im curious as to what this was as i have never seen one before and found it very odd and eery

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