Smiling rainbow

Beth Curran of the Village of Greenwood Lake saw this spectacular site from her backyard last Sunday morning. "It was so vibrant and looked to us like a smiling rainbow," she said. With a little research she found out that it was what scientists call a circumzenithal arc, an optical phenomenon similar in appearance to a rainbow. It arises from refraction of sunlight through horizontally-oriented ice crystals, generally in cirrus clouds, rather than from raindrops. Generally, it forms no more than one-quarter of a circle centered on the zenith and on the same side as the sun. Its colors are from blue on the inside to red on the outside of the arc. It is one of the brightest and most colorful halos because there is much less color overlap in its formation. Photo by Beth Curran