APOD: When Rainbows Smile (2022 Mar 11)

[APOD Robot]

When Rainbows Smile

Explanation: /24/]Want to see a rainbow smile? Look near the zenith (straight up) when the sun is low in the sky and you might. This example of an ice halo known as a circumzenithal arc was captured above a palm tree top from Ragusa, Sicily on February 24. The vividly colorful arcs are often called smiling rainbows because of their upside down curvature and colors. For circumzenithal arcs the zenith is at the center and red is on the outside, compared to rainbows whose arcs bend toward the horizon after a downpour. True rainbows are formed by water droplets refracting the sunlight to produce a spectrum of colors, though. Circumzenithal arcs are the product of refraction and reflection in flat hexagonal ice crystals, like the ice crystals that create sundogs, formed in high thin clouds.

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[Chris Peterson]

Off my deck a few years ago, in context with some other common halos.
_

Click to view full size image

[De58te]

Hmm. I wonder why smiling rainbows are usually described as curved arcs, rather than described as curved bow shaped? Rainarcs anyone?

[XgeoX]

Stunning pic Chris.
Thanks for sharing!

Eric

[orin stepanek]

ArcoCircumzenitale_1024c.jpg

Today's APOD= A-OK!
I have seen circular rainbows from the spray of my garden hose!

[NCTom]

Beautiful picture, Chris. Out of curiosity, how long would the conditions last for those arcs to remain as they are? Seconds, minutes?

[Chris Peterson]

Beautiful picture, Chris. Out of curiosity, how long would the conditions last for those arcs to remain as they are? Seconds, minutes?

IIRC, the arcs that day were around for a good hour. They kind of come and go in intensity at the thin clouds pass through.

[Fred the Cat]

Quite the juxaposition; cold weather and a palm tree!

But it makes me smile.

[MarkBour]

Wow, I've never seen one of these before. The "refraction and reflection" linked article says "The circumzenithal arc, or 'smile in the sky' is fairly common but is rarely seen." I wonder if there is any weather data that could help one to know when such a wonder is more likely to appear.

[Chris Peterson]

Wow, I've never seen one of these before. The "refraction and reflection" linked article says "The circumzenithal arc, or 'smile in the sky' is fairly common but is rarely seen." I wonder if there is any weather data that could help one to know when such a wonder is more likely to appear.

I see them all the time. All you need is those thin ice clouds, which are common enough in most places in the winter. The reason they are rarely seen is probably the same reason so many common astronomical things are rarely seen: most people just don't look up very much. If you can see sundogs or the usual halo around the Sun, there's a good chance there's also a circumzenithal arc high in the sky above it.