Blue Springs, Missouri Circumhorizontal Arc

Provided and copyright by: Tammy Chamberland
Summary authors & editors: Jim Foster, Tammy Chamberland

This coquettish circumhorizontal arc formed in the afternoon of July 9 over Blue Springs, Missouri. Ice crystals in cirrus clouds produce these colorful arcs. To form this "fire rainbow," the Sun has to be at least 58 degrees above the horizon. Sunlight enters the vertical side faces of ice crystals and exits through their lower horizontal basal face. On this summer's day, building cumulus clouds conceal the higher level cirrus clouds, making the alluring strip of sky all the more mysterious.