Pa-share dito idol toink
A 22° halo is a halo, one type of optical phenomenon, forming a circle 22° around the sun, or occasionally the moon (also called a moon ring or winter halo). It forms as sunlight is refracted in millions of randomly oriented hexagonal ice crystals suspended in the atmosphere. The halo is large; the radius is roughly the size of an outstretched hand at arms length.As light passes through the 60° apex angle of the hexagonal ice prisms it is deflected twice resulting in deviation angles ranging from 22° to 50°. The angle of minimum deviation is almost 22° (or more specifically 21.84° on average; 21.54° for red light and 22.37° for blue light). This wavelength-dependent variation in refraction causes the inner edge of the circle to be reddish while the outer edge is bluish. As no light is refracted at angles smaller than 22° the sky is darker inside the halo. A 22° halo may be visible on as many as 100 days per year.
source:
http://en.wikipedia.org/wiki/22%c2%b0_halo In the summer, the presence of such ice crystals indicates the presence of stratospheric cirrus clouds, which can indicate an approaching cold front and strong lines of thunderstorms ahead of that front. As the cold air behind the cold front displaces summer heat, the temperature can drop so quickly that spring or summer heat can be followed by a flash freeze. This combination has led to the folklore that a ring around the moon indicates bad weather to come. The halo is not a 100% reliable predictor, but its presence does come close to the reliability of many 7-day forecasts.
Brightness does not itself correlate with the probability of bad weather, since there can be many different reasons for increased or decreased brightness, many of them having nothing whatsoever to do with atmospheric conditions. In contrast, the solidity of the ring indicates that large ice crystals are evenly scattered through a large section of sky, which suggests that a similarly large portion of land below is in for a serious storm.
source:
http://www.sciences360.com/index.php/the-cause-of-the-ring-around-the-moon-15554/ http://www.flickr.com/photos/prodigi/11929247394/ Lunar halo day 1 - Jan 13
http://www.flickr.com/photos/prodigi/11960385864/ Day 2
Timelapse:
VIDEO
