Fire Rainbow

| March 26, 2008 @ 2:31 pm | 10 Replies

Thanks Jean Watson for these images… she writes:

“I know fire rainbows are rare but I truly believe these pictures are of one that occurred over our catfish farm on Aug 13, 2007. Please let me know what you think.”

The technical name for this is a circumhorizontal arc (CHA). It is a halo or an optical phenomenon similar in appearance to a horizontal rainbow, but in contrast caused by the refraction of light through the ice crystals in cirrus clouds. It occurs only when the sun is high in the sky, at least 58° above the horizon, and can only occur in the presences of cirrus clouds. It can thus not be observed at locations north of 55°N, except occasionally from mountains.

The phenomenon is quite rare because the ice crystals must be aligned horizontally to refract the high sun. The arc is formed as light rays enter the horizontally-oriented flat hexagonal crystals through a vertical side face and exit through the horizontal bottom face. It is the 90° inclination that produces the well-separated rainbow-like colours and, if the crystal alignment is just right, makes the entire cirrus cloud shine like a flaming rainbow. (CHA description from Wikipedia)

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James Spann is one of the most recognized and trusted television meteorologists in the industry. He holds the AMS CCM designation and television seals from the AMS and NWA. He is a past winner of the Broadcast Meteorologist of the Year from both professional organizations.

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