An upside down rainbow appeared in UK

Seen just a handful of times this stunning phenomena is known as the 'smile in the sky.'
Freak weather conditions created this reverse rainbow in Leicestershire where it was pictured by antique dealer William Freeman.
But while the sight looks like an upside-down rainbow, it is actually caused by light shining through tiny ice crystals in the clouds.

The reverse rainbow is caused by tiny ice crystals in the clouds

Rather than being caused by raindrops like normal rainbows, it is the result of freak atmospheric conditions, rarely seen outside the North and South Poles.

The upside down rainbow is much brighter than a 'normal' rainbow

But unlike a rainbow, the sky has to be clear of rain and low level clouds for a circumzenithal arc to be seen.

Relatively rare in Britain, the arc only appears when sunlight shines at a specific angle through a thin veil of wispy clouds at a height of around 20,000 to 25,000 feet.

At this altitude the cirrus clouds are made of tiny ice crystals.

A normal rainbow

Meteorologists say the clouds must be convex to the sun,with the ice particles lined up together in the right direction, to refract the light.
This results in the sunlight bouncing off the ice crystals high in the atmosphere, sending the light rays back up and bending the sunlight like a glass prism into a spectrum of colour.
The arc is generally only seen in the artic circle - and this is one of just a handful of instances where the arc has been spotted in the UK.
The 'rainbow'' is also much brighter and more concentrated than a rainfall rainbow. Rainbows are formed when sunlight is refracted in a raindrop.


But in a circumzenithal arc, the colours are in reverse order from a rainbow, with violet on the top and red at the bottom.
The arc usually vanishes quickly because the cirrus clouds containing the ice crystals shift their position.
Ice particles in high cirrus clouds occur all year round, but circumzenithal arcs are usually obscured by lower level clouds.