Circumzenithal Arc Over New Jersey

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

The photo above featuring a showy circumzenithal arc (cza) was captured over Pilesgrove, New Jersey on October 12, 2008. I noticed it reclining well above the Sun at approximately during 7:15 a.m. (Eastern Daylight Time). Sunrise at this time of year occurs in front of my house, so this cza was fairly easy to observe. Czas are high in the sky when the Sun is less than 32 degrees above the horizon and are most vibrant when the Sun is positioned about 22 degrees above the horizon. Plate-shaped, hexagonal ice crystals in cirrus type clouds are responsible for their formation. Sunlight enters the upper horizontal basal face and departs through one of the vertical side faces.