Cloud Shadow Band

August 08, 2011

KAScott_20110630_4347pano-1

Photographer: Ken Scott; Ken's Web site
Illustration: David Lynch
Summary Author: Ken Scott; David Lynch

August 2011 Earth Science Picture of the Day Viewer's Choice

Earlier this summer I was watching some amazing clouds and cloud shadows over the West Arm of Grand Traverse Bay of Lake Michigan near Traverse City, Michigan, when I suddenly noticed the bow-shaped shadow pictured above. This shaded arc is a large shadow of the cloud on the right. According to David Lynch, lead author of "Color and Light in Nature," the arcing is a consequence of perspective and theCsphere wide angle of the sky covered by the shadow (almost 180 degrees) as well as its position close to the horizon. The illustration (right) shows the celestial sphere with the shadow of the cloud (like Ken's picture) colored in. On the wide angled photo, note both the crepuscular rays to the right of the shadowed arc and the anticrepuscular rays to the left of the arc. Photo taken on June 30, 2011.

Photo details: Camera Maker: FUJIFILM; Camera Model: FinePix HS20EXR; Focal Length: 4.2mm; Aperture: f/3.2; Exposure Time: 0.0091 s (1/110); ISO equiv: 100; Exposure Bias: -0.67 EV; Metering Mode: Matrix; Exposure: aperture priority (semi-auto); White Balance: Auto; Light Source: Unknown; Flash Fired: No (enforced); Orientation: Normal.