Fire Rainbows – Rare Cloud Phenomenon
A rare “fire rainbow” appeared in the sky over South Carolina on Sunday evening.
Social media eagerly shared images of the fire rainbow, which appeared in wispy clouds over Isle of Palms, S.C. Some people on Twitter said the rainbow looked like angel’s wings, while others likened it to a whale tale.
For a fire rainbow to appear, the sun must be at an altitude of at least 58 degrees above the horizon. In order to produce the rainbow colors, the sun’s rays must enter the ice crystals at a precise angle to give the prism effect of the color spectrum.
“Fire Rainbows” are neither fire, nor rainbows, but are so called because of their brilliant pastel colors and flame like appearance. A circumhorizontal arc is an optical phenomenon – an ice-halo formed by the refraction of sun- or moonlight in plate-shaped ice crystals suspended in the atmosphere. These are typically found in cirrus or cirrostratus clouds. In its full form, the arc has the appearance of a large, brightly spectrum-coloured band running parallel to the horizon, located below the Sun or Moon.