Thursday, 2 September 2010

Sun Dog

Sun Dogs are rather common, but usually missed or overlooked. Yesterday, as the sun began to set behind the houses of our estate, we were treated to the sight of this phenomenon in the clear skies. Evenings are usually the best time of day to see Sun Dogs as the brightness of the sun, when higher in the sky, can obscure the Sun Dogs altogether. So, what are Sun Dogs? Well, are you sitting comfortably? Then I shall begin....
Sun Dogs are patches of refracted light, often coloured like diminutive rainbows, in the sky on either side of and at the same height as the sun. There are usually two - one on each side of the sun - and they are at an angle of 22° from the sun. Sun Dogs are formed by tiny, flat, hexagonal ice crystals which form the very high, whispy Cirrus clouds, seen in these pictures. These crystals act like minute prisms, splitting the sunlight into the familiar 'rainbow' colours. The principal is much the same as raindrops refracting sunlight to produce a rainbow in the lower atmosphere, but this happens at much higher altitudes, where the air is very much colder. Quite beautiful and so tenuous.
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