Lenticular Cloud Over the French Alps

August 17, 2014

Impressive orographic cloud

Photographer: Bernard Durand; Bernard's Web site
Summary Authors: Bernard Durand; Jim Foster

The photo above shows a sunlit orographic cloud that formed on the flanks of Mont Colombis, in the French Alps. This is a lenticular cloud (Altocumulus lenticularis) -- a mid-level, stationary wave cloud. When a layer of air near the surface is lifted by upslope winds and cools, lenticulars may appear on the lee side of a topographic feature, such as the French Alps. Because they form in wave crests (the top most portion of an undulating current of air), these saucer-shaped clouds seem to be nearly motionless with respect to the underlying terrain. Photo taken on July 10, 2014.
Photo details: Camera Model: Canon EOS 5D Mark II; Focal Length: 62.0mm; Aperture: f/5.6; Exposure Time: 0.0050 s (1/200); ISO equiv: 400.