Pigeon Lake Wave Clouds

July 16, 2006


Provided by: John A. Adam, Old Dominion University
Summary authors & editors: John A. Adam

The lens like clouds in this picture were formed over Pigeon Mountain, in Dead Man's Flats, near Canmore, Alberta, about ten kilometers from the entrance to the beautiful Banff National Park. Note also (i) the single crepuscular shadow band caused by one of the clouds, and (ii) the "silver lining," most evident in the leftmost cloud, a result of light diffraction at the cloud edges. Such wave clouds (more accurately called orographic or wind-driven lenticular clouds) are commonly formed when stable air is forced to rise over hills and mountains, as was the case on this day. They can also form in the crests of standing gravity waves, sometimes several at a time are visible.

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