Circumzenithal arc over Prestatyn, Wales
© Stuart Prince
This rare upside-down rainbow was snapped in the skies over Prestatyn by aviation photographer Stuart Prince.

The circumzenithal arc, sometimes known as Bravais' arc, is a type of Halo.

Stuart, 50, said: "It is rarely seen as the conditions have to be just right and is formed when light reflects off ice crystals."

Stuart, who photographs aircraft around the world - including North Korea - added: "It was such a beautiful sky that afternoon. I looked up and was amazed to see the smile in the sky overhead.

"I was just about to walk my boxer dog Ben to Prestatyn beach when i saw the arc."

Grahame Madge, a Met Office spokesman, said: "Circumzenithal arcs are more popularly known as 'upside-down' rainbows. They occur much higher in the atmosphere than rainbows and they are created when sunlight refracts through ice crystals in high-altitude cirrus clouds. Rainbows are created by water droplets, rather than ice.

"These upside-down rainbows are actually quite frequent, but they're not always visible at ground level if other, lower-level, cloud hides their shy beauty from view."