Iridescence

Iridescence (or iris) is a phenomenon that causes clouds to acquire unusual colors. It is rarely noticed because it occurs very close to the sun (rarely occurs far from the sun).

Iridescence is most often observed in Cumulus, Cirrocumulus, Altocumulus and lenticularis clouds, and very rarely in Cirrus clouds.

Iridescence is seen mostly at the edges of clouds or in transparent clouds, and newly formed clouds (such as pileus) produce a brighter and more colorful iridescence. When a thin cloud has droplets of similar size and to a large extent, iridescence takes the form of a central bright disk around the sun or moon, surrounded by one or more colored rings; It's the corona.

Iridescence is formed by the interaction of sunlight with water droplets or, in rarer cases, ice crystals within a cloud. This interaction is called light diffraction. This phenomenon, along with Cirrocumulus clouds, may indicate approaching thunderstorms.