Upside-down rainbow in Salford
© Adam Davies
Settled skies and warm weather combined this week to produce a minor meteorological phenomenom: the 'upside-down rainbow'.

Adam Davies captured this image of the inverted coloured curve while sitting out in his garden in Sportside Avenue, Walkden. Known as a 'Bravias arc', it's not technically a rainbow as it's produced when light from the sun is refracted through ice crystals, rather than raindrops.

High up among the cirrus clouds, water droplets turn to ice. It's here where light refracts through tiny hexagonal ice crystals, which bends the wavelength of the light and makes it appear inverted to the human eye.

The spectrum of colours is only produced under special atmospheric conditions: when the air high up above us is relatively still, and when the sun is shining down at an angle less than 32 degrees from the horizon.

Comment: And it appears to be happening more often because part of the 'special atmospheric conditions' include increased particulates in the atmosphere, i.e. increased volcanic ash/dust and 'meteor smoke' debris left by meteor fireballs exploding in the atmosphere.

Adam used his HTC One M9 smartphone to capture the image. "You could also see a kind of halo ring effect around the sun - I've never seen it shining that bright before," he said.

Sun halo
© Adam Davies