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Brief, beautiful circumzenithal arc

Circumzenithal arcs are sometimes referred to as “upside-down rainbows” or “a smile in the sky.”

View larger. | Photo by Amanda Cross.

View larger. | Circumzenithal arc captured September 16, 2015 by Amanda Cross.

Amanda Cross in Lancashire, UK, submitted these photos to EarthSky. They show the beautiful sky phenomenon known as a circumzenithal arc. Amanda wrote:

Sun halo spotted on the school run, dashed home for camera then the circumzenithal arc appeared above, smiling. Worth dashing home for! Smiling in the sky, upside down rainbow :)

Only lasted 10 minutes then it was gone, brief but beautiful.

Canon 600D & fisheye lens

Thank you, Amanda.

Photo by Amanda Cross.

Photo by Amanda Cross.

Les Cowley of the great website Atmospheric Optics says of these graceful and colorful arcs:

The circumzenithal arc, CZA, is the most beautiful of all the halos. The first sighting is always a surprise, an ethereal rainbow fled from its watery origins and wrapped improbably about the zenith …

Look straight up near to the zenith [overhead point in your sky] when the sun if fairly low and especially if sundogs are visible. The center of the bow always sunwards and red is on the outside.

Les says that the most ideal time to see a circumzenithal arc is when the sun is at a height of 22 degrees in the sky. Look here to see Les Cowley’s illustration of the various kinds of halo phenomena, related to circumzenithal arcs.

Bottom line: Photo from September, 2015 – Lancashire, UK – of a circumzenithal arc. They’re sometimes called upside-down rainbows, or “a smile in the sky.”

Deborah Byrd

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