March 07, 2011


Photographer: William Briscoe
Summary Authors: William Briscoe; Jim FosterMarch 2011 Earth Science Picture of the Day Viewer's Choice

The photo above shows a layer of mid-level clouds and their shadows as observed from an altitude of approximately 8,500 ft (2,590 m). It was taken flying east to west somewhere over the desert of southeastern California -- the camera is facing northwest. Note the thin beams of light filtering through the altocumulus cloud deck. From this perspective, the picture seems as if it could have been snapped by a scuba diver. Shadows from the clouds projected upon the desert floor look much like undulations in the sand in shallow water. In actuality, the dappled surface results from the interplay of nearly vertical sunbeams and cloud shadows -- crepuscular rays. The wavy appearance of the shadows is caused by uneven topography. Photo taken on October 12, 2007.

Photo Details: Camera Model: Canon EOS DIGITAL REBEL XTi; Focal Length: 34.0mm; Aperture: f/16.0; Exposure Time: 0.0020 s (1/500); ISO equiv: 400.