
.topic 20
Transparent whitish cloud veil of fibrous (hair-like) or smooth appearance, totally or partly covering the sky, and generally producing halo phenomena.


.topic 30
An optical phenomenon in the form of a ring, arc, pillar or bright spot, produced by the refraction of light by ice crystals suspened in the atmosphere (cirriform clouds, ice fog, etc.). This phenomenon, when formed by refraction of the light of the sun, may show colors, while a halo phenomenon produced by the light of the moon is always white.


