No, this isn’t an upside-down rainbow, and the photographer hasn’t faked the picture. It’s an unusual phenomenon caused by sunlight shining through a thin, invisible screen of tiny ice crystals high in the sky and has nothing at all to do with the rain.
Andrew G. Saffas, a Concord artist and photographer, saw the colorful arc at 3:51 p.m. on a beautiful day recently when a slight rain had fallen in the morning. He thought it was a rainbow, created by raindrops refracting sunlight the way glass prisms refract any bright beam of light.
Instead, what Saffas saw was what scientists call a circumzenithal arc, according to physicist Joe Jordan, a former NASA space scientist at the Ames Research Center in Mountain View, who is now director of the Sky Power Institute in Santa Cruz, which promotes solar power and other alternative fuels.