Circumhorizontal Arc Over Phoenix
August 12, 2004
The photo above of an ethereal circumhorizontal arc was captured over downtown Phoenix, Arizona on June 23, 2004. Like the more commonly observed circumzenithal arc, the circumhorizontal arc is formed by similarly oriented ice crystals. In the case of the circumhorizontal arc, sunlight enters though a vertical side face of an ice crystal and exits through the lower horizontal basal face. See also yesterday's "picture of the day." Even in the hub of a city, the sky can often be rewarding if you just look up -- best not to do so when crossing the street.