Several Storm Station viewers spotted vivid, rainbow-like features in the sky on Thursday, despite completely dry conditions. These colorful displays were atmospheric optical phenomena created as sunlight filtered through passing high clouds composed of ice crystals.

Todd Cattano captured one such feature in Norwood known as a circumzenithal arc (see above). Often described as an “upside-down rainbow” or “smile in the sky,” these form when sunlight strikes the horizontal top face of plate-shaped ice crystals high up in the sky. The light enters the crystal, bends, and exits through a side face at a sharp 90 angle toward the ground, casting a brilliant band of colors.

Others captured a related phenomenon known as a sun dog. Sun dogs appear as bright, colored patches flanking the sun at a 22° angle. They form similarly when sunlight passes through ice crystals and gets bent, or refracted, toward the eye. Stacey Bracey (right) captured one near LSU, while Gaynell Haslett (left) spotted another in Livingston Parish.

While both features resemble traditional rainbows, the science behind them is distinct: true rainbows require sunlight passing through liquid raindrops, whereas arcs and sun dogs rely entirely on the precise geometry of ice crystals suspended in the upper atmosphere.

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