Atmospheric Phenomena

Rainbows and Other Colorful Phenomena

How is a corona different from a halo?

As with a corona or anticorona, haloes are created by light passing through clouds of ice crystals. Coronas, when they have some color to them, are reddish on the outside of the ring and bluish on the inside, while haloes are red on the inside and blue on the outside. Coronas tend to be formed when altostratus clouds are present, while haloes occur with cirrostratus clouds in the air. A halo’s radius extends at a 22-degree angle from the Moon or Sun, but on rare occasions subtends at 46 degrees; coronas have smaller angular diameters than haloes. Because the cirrostratus clouds causing haloes contain icy crystals that could lead to rain, folklore about the sighting of haloes correctly concluded that haloes may predict oncoming rain.


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