Not by Rainbow Alone: Fogbow, Moonbow, Dewbow and Other Miracles of Nature

A rare white fogbow was spotted in Scotland on November 20 by photographer Melvin Nicholson.
A fogbow, sometimes called a white rainbow or even a ghost bow, forms in the same way that a rainbow does: the refraction of sunlight in water droplets in the air creates a multicolored arc. The difference is in the droplets are in fog and so the colors are kept out.

A moonbow, also known as a lunar rainbow, is produced by moonlight rather than sunlight.

This optical rainbow-like effect is created by the dewdrops that reflect and disperse sunlight, producing all the colors in the visible spectrum.

This optical phenomenon belongs to the family of ice halos formed by the refraction of the sun or moonlight in plate-shaped ice crystals suspended in the atmosphere. It runs parallel to the horizon, far below the Sun or Moon. Red is the uppermost color.

The circumzenithal arc, also called an upside-down rainbow and “a smile in the sky,” is an optical phenomenon similar in appearance to a rainbow, but belonging to the family of halos arising from refraction of sunlight through ice crystals, generally in cirrus or cirrostratus clouds, rather than from raindrops. Red is the bottom color.

Iridescent clouds are a diffraction phenomenon caused by small water droplets or small ice crystals individually scattering light. Larger ice crystals produce halos. The occurrence of colors in a cloud is similar to those seen in oil films on puddles.