Circumhorizontal Arc Over Acadia National Park

October 06, 2008

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Provided: Barbara Kent Lawrence, Hamilton-Wenham GREEN
Summary Author: Barbara Kent Lawrence, Jim Foster

This strip of color apparently splashed across the sky was photographed at Great Head, Acadia National Park, in Maine on May 16, 2008. The time was a little before noon and for nearly twenty minutes we were able to observe this stunning circumhorizontal arc. In order for circumhorizontal arcs to form, sunlight must enter the vertical side faces of similarly oriented ice crystals and exit through their lower horizontal basal faces. Views of the sea, of rock formations and of dense forests usually grab one's attention in beautiful Acadia National Park; however, on this mid-spring day, the sky had no trouble competing with the surface. These colorful arcs are easier to see than many other arcs and halos since they’re often observed midway between the horizon and the zenith which is naturally where our eyes are directed when we look at the sky.