Circumzenithal Arc Photographed in UK

[xocet]

A nice photograph of a circumzenithal arc accompanies this story. Unfortunately, the explanation of the phenomenon is given as "sunlight bouncing off ice crystals...."

'Rare' upside down rainbow spotted in Wiltshire
19 May 2014 Last updated at 07:04 ET

A "rare" upside down rainbow has been spotted in the sky over Wiltshire.
The circumzenithal arc, or Bravais' arc, was photographed at Bowood Golf Club near Calne early on Saturday.

Created by sunlight bouncing off ice crystals high in the atmosphere, it is hard to spot inverted rainbows as they appear so high in the sky.

A Met Office spokesman said: "They are seen relatively rarely in the UK but the more defined they are, the rarer they are."

The phenomenon or "smile in the sky" only occurs when thin wispy cirrus clouds - made of ice crystals - are at a specific angle to the sun, according to the Met Office.

...

http://www.bbc.com/news/uk-england-wiltshire-27466519

A better explanation would have explicitly mentioned or illustrated the refraction of light and not implied reflection. Here is a site that provides a such an explanation of this phenomenon along with several others:

Circumzenithal Arc

The CZA is produced by oriented plate crystals, the same crystals that form sundogs.

Downcoming sunrays enter the uppermost horizontal face and leave through a vertical side face.

The refraction of rays nearly parallel rays through faces inclined at 90° produces very pure and well separated prismatic colours. The colours of the circumzenithal arc are purer than those of the rainbow.

...

http://www.atoptics.co.uk/halo/czaform.htm

This site is a nice one, but the description of the colors that are produced as "purer" and "well separated" is straying far into the subjective unless there is some quantitative measure of color purity and separation of which I am unaware.

[Fred Sanders]

1. Diamonds In the Sky: A Parhelic Circle

http://www.atoptics.co.uk/halo/parcirc.htm

[2naSalit]

2. That's pretty neat.

Usually when I see those, several in a year, they are joined with a full circle around the sun with cardinal points often extending spikes. Can't post any pics here but I have also seen a horizontal rainbow with no noticeable arc, seen that three times in my entire life. And then I have seen "snowbows" made when snow is falling and once I saw a rainbow illuminated by the full moon... a "moonbow"?

These are interesting, those in the OP and the links above, quite unique and fascinating.

[shenmue]

3. Yeah!

Wow.

[Duppers]

4. pic

[2naSalit]

5. But.. what if...

it's a crop circle looking for a place to land?

[defacto7]

6. Maybe God changed his mind

and will send a flood after all.

[Javaman]

7. AHHHH! it's the end of the world!!!