Mirage Near Cascais, Portugal

November 13, 2005


Provided and copyright by: Filipe Alves
Summary authors & editors: Filipe Alves; Jim Foster

This photo showing a superior mirage was taken on September 4, 2005 from near Cascais, Portugal toward the cliffs of Cabo Espichel (approximately 40 km distant). Note that the refracted image of the cliff edge is here greatly exaggerated. Superior mirages occur when the temperature lapse rate near the surface is less than what would be normally expected. Thus, a ray of light traveling through the air will be bent or refracted downward, and so the object in question appears above its true position. Though the air temperature was very warm on this day (in excess of 30 degrees C), a very shallow layer of fog enveloped the sea. This resulted in a temperature inversion -- a layer of warm air overlying a shallow layer of cooler fog.

Photo details: Canon 300D camera, 600 mm lens.

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