Supralateral Arc, Parhelion and Contrails

December 02, 2010

Photographer: Lisa Gonnelli
Summary Author: Lisa Gonnelli; Jim Foster

The photo above shows a sky clotted with contrails and a colorful arc at far left that is likely a piece of a supralateral arc. These sprightly strips of sky form when columnar ice crystals, found in in cirrus type clouds, are similarly aligned. Sunlight passes through the side and basal (end) faces of the columns. Supralateral arcs are only visible at solar altitudes below 32 degrees. Their shape changes dramatically with changes in solar altitude. Note also the bright left parhelion (sundog) at lower center. It's located 22 degrees from the Sun itself (behind the tree to the right) and at the same solar elevation. It's no wonder why sundogs are also referred to as mock suns. Photo taken on November 22, 2010.

Photo Details: Camera: OLYMPUS E-500; Focal Length: 17.0mm; Aperture: f/7.1; Exposure Time: 0.0063 s (1/160); ISO equiv: 100.