A rainbow is always a welcome sight, especially in tough times like these. This particular ‘flat rainbow’ spotted in Mossel Bay yesterday [March 6], however, had many scratching their heads in confusion and wonder.

Photographer Amanda Walden captured a beautiful image of what appeared to be a rainbow over her home in Danabaai. However, the rainbow was without its arc, leaving Walden wondering why it appeared this way.

“I photographed this “flat rainbow” earlier today from my home in Danabay (Mosselbay),” Walden wrote in a Facebook post.” A cold front is moving through the area. Could somebody please explain why it isn’t arched like “normal” rainbows?”

Credit: Amanda Walden

A rainbow happens when light hits water droplets and reflect, refract and disperse against them. The light reflects off the back of the droplet and leaves through the front, back towards the rainbow and causing a spectrum of light in the sky. They always appear in the section of sky directly opposite the sun.

One Facebook user suggests that since the picture was taken while a cold front was moving through the area, it is possible that the image captures an optical phenomenon known as a circumhorizontal arc.

This phenomenon shows a near-horizon arc that extends parallel to the horizon, and only occurs when elevation of the light source is more than 58°. Sunlight enters through horizontally-oriented, flat, hexagonal ice crystals in the air through a vertical side face and leaves through the near horizontal bottom face. Because of the angle at which the sunlight hits the crystals, it leaves a much more angular light refraction.

Another Facebook user suggests that it’s a combination of the angle of the sun and the sea spray being very low and whipped up from the wind that caused the rainbow to take on this appearance.

Whatever the reason, this is quite the spectacular sight!

Picture: Amanda Walden

Article written by