Thursday, March 31, 2011

SunDogs @ Sunset in St. Stephen - March 31st

The atmospheric phenomenon, known as a sundog is similar in shape to the natural sun. A sundog can also look like a comet, and always appears beside the sun. It's not unusual to see two sundogs, one on each side of the sun. The scientific name for them is parhelia, from the Greek words "para" (meaning "next to"} and "helios" (meaning "sun"). 
Sundogs are usually seen at sunrise and sunset, when the sun is close to the horizon.  They are created when sunlight reflects off or refracts through the tiny ice crystals in cirrus or cirrostratus clouds - the clouds that look like white bands or patches of fleece.  When sunlight refracts or passes through horizontally-shaped ice crystals it bends the light the same way a prism does, producing a spectrum of colours which fan out to create a crisp, bright sundog. The part of the sundog closest to the sun is red, gradually fading to pale blue on the side furthest from the sun. Sunlight reflecting off an ice crystal will produce a white sundog. 

Ice fog and ground level cloud known as diamond dust will also cause sundogs to appear. A similar effect is caused by a bright moon, with the obvious name "moon dog". Sdogs can occur about ten times a year in any given area.                                                                                                           The appearance of sundogs and other atmospheric phenomena like arcs, haloes and rings often means that rain or snow will fall within the next 18 to 36 hours.