Lake Wanapitei Sundogs
September 08, 2005
These spectacular sundogs or parhelia appeared in mid-morning on December 26, 2004 (Boxing Day), above Lake Wanapitei, Ontario, Canada. The photo was taken by Blaine Nicholls. Slowly falling, hexagonal plate ice crystals, associated with thin cirrus clouds refracted and dispersed sunlight from the relatively low Sun (16 degrees elevation), giving rise to these astounding "dogs." For sundogs to occur, as they fall the plate shaped ice crystals, which are larger than 0.03 mm (0.0012" -- about a third of the thickness of a human hair), need to be aligned with their flat faces horizontal.
Also visible here are sections of the much fainter parhelic circle. One arc of this circle appears as a faint glowing band that connects the two sundogs with the Sun, while two other segments emerge as bright horizontal outward extensions to the sundogs. The same hexagonal plate ice that produced the parhelia also reflected sunlight to form the colorless parhelic circle.
Today marks the 5th anniversary of the Earth Science Picture of the Day! We owe a big "Thank You" to our contributors and faithful readers.Related Links: