Circumzenithal Arc Above Memphis
November 23, 2003
The above photo shows a classic circumzenithal arc gracing the skies above Memphis, Tennessee. On this winter's day (February 7, 2003), cirrus clouds, caught in the jet stream, were moving very rapidly west to east. Ice crystals in these clouds created this circumzenithal arc -- sunlight passes through the uppermost basal faces of hexagonal plate crystals and then exits through vertical side faces. In order to observe circumzenithal arcs, the Sun must be lower than about 32 degrees above the horizon.
This circumzenithal arc, as well as a pair of sundogs, kept flashing in and out of view in the time span of mere seconds, but the show went on for at least 30 minutes. The photo has been gently enhanced by the use of Micrografx Picture Publisher Version 8 to bring out the subtle colors in the arc.