Circumhorizontal Arc Above Arlington Heights, Illinois

October 13, 2006

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Provided by: Dale Hugo
Summary authors & editors: Dale Hugo, Jim Foster

The above photo shows a handsome circumhorizontal arc taken from Arlington Heights, Chicago, Illinois, just after noon local time, on July 22, 2006. Circumhorizontal arcs can only be seen when the Sun is high in the sky, and are thus typically seen in the summer months at mid latitudes. Sunlight entering though the vertical side faces of similarly aligned ice crystals that compose cirrus clouds (shown above) and exiting through their lower horizontal basal faces, produce these arcs. Though it faded rather quickly, I wonder how many other people in this land of 8 million people witnessed this splendid arc?

Photo details: Fuji camera, FinePix2800 Zoom, hand held from my backyard deck, looking south-southeast (toward Chicago), arc was approximately 30 degrees above the horizon.

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