Colorful Arc Above Pilesgrove, New Jersey
September 09, 2009
The photo above showing a wondrous circumhorizontal arc (CHA), or possibly an infralateral arc, was captured above Pilesgrove, New Jersey on August 7, 2009. These comely swatches look like they’re painted on the sky. When only small fragments of cirrus clouds are lit up by the refraction of sunlight, it’s often hard to positively identify certain arcs. In order for CHAs to form, sunlight must enter a vertical side face of similarly oriented, hexagonal, plate-shaped ice crystals and exit through the lower, horizontal basal face. They’re only observed when the Sun is high in the sky, which means during summer and near midday in the mid-latitudes. Still, if you keep an eye to the sky, and perhaps eat lunch outdoors, you’ll spy these beauties on occasion.