Circumhorizontal Arc above Norfolk, Virginia
May 11, 2009
This stunning photo showing a magical circumhorizontal arc was taken approximately 1:00 p.m. on August 25, 2008 from Norfolk, Virginia. It was visible for at least 30 minutes, allowing me to return to the office to get my camera. These gorgeous arcs are on occasion called fire rainbows, but except for their attention getting color, they have little to do with rainbows. They’re caused by the refraction of sunlight through similarly aligned, hexagonal ice crystals, most often found in cirrus type clouds. Sunlight enters through a vertical side face and exits through the lower horizontal basal face. Circumhorizontal arcs can only be seen when the Sun is greater than 57 degrees above the horizon. This limits their visibility to late spring and summer in the mid latitudes.