A ring or arc of light encircling the sun or moon, produced when light refracts and reflects through millions of tiny, randomly oriented ice crystals suspended in high cirrus or cirrostratus clouds. The most common form, the 22-degree halo, appears as a pale white or faintly colored circle at a fixed angular distance from the light source, and its appearance has long been read as a folk sign of approaching rain or snow as cirrus clouds often precede a warm front.
Facts
Identification
Distinguishing AppearanceAny of a variety of bright circles or arcs centered on the sun or moon, caused by refraction or reflection of light by ice crystals, showing prismatic coloration from red inside to blue outside 1 Sources
1. Glossary, NOAA National Weather Service
Glossary entry for haloQuote, Glossary entry for halo
Any of a variety of bright circles or arcs centered on the sun or moon, caused by the refraction or reflection of light by ice crystals suspended in the earth's atmosphere and exhibiting prismatic coloration ranging from red inside to blue outside.
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