22º Halo

Morning exercise over and I was mellowing out in the garden after lunch when I noticed this halo around the sun. It’s a sundog I thought remembering something I read somewhere. Why is it I don’t know what I was doing two days ago yet an insignificant fact from twenty years ago pops into mind? Anyway my memory proved wrong as it turned out not to be a sundog but a similar solar phenomena called a “22º Halo”, a rather boring name. 22º Halos are formed by the refraction of sunlight in ice crystals in clouds in the upper atmosphere. The ice crystals are found in cirrus or cirrostratus clouds and are hexagonal in shape. Cirrus and cirrostratus clouds may foretell the approach of a warm front and a deterioration of the weather.

Sundogs are formed by the same mechanism but are concentrated areas of light either side of the sun (at 3 and 9 o’clock positions). They are rarer than 22º Halos which are actually quite common but rarely noticed.


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