Inverted rainbow spotted in Oxfordshire

http://www.bbc.co.uk/news/uk-england-oxfordshire-34637103

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A couple sitting in their garden in Oxfordshire spotted a "rarely seen" inverted rainbow above their house.

Louise Longson photographed the circumzenithal arc and said: "It was like a smile in the sky."

Her husband Mark said: "They are rarely seen as atmospheric conditions have to be perfect."

The Met Office said the phenomenon occurs when thin wispy cirrus clouds made of ice crystals are at a specific angle to the sun

According to the Met Office website the rainbows, also known as Bravais' arc, are normally obscured by clouds as they appear high in the sky.

Described as "a type of halo", it says: "They are formed when sunlight refracts through horizontal ice crystals at such an angle, that the light enters the crystal through its flat top face and exits through a side prism face, causing the distinctive upside-down rainbow effect.

"Circumzenithal arcs are actually quite common as these types of clouds occur throughout the year, however we only sometimes see them as they are usually obscured by clouds underneath."

Mrs Longson, of Leafield, said: "It didn't last very long, we watched it fade away.

"It was about 10 minutes or so, then it was just gone.

"It was lovely, something I may never see again."