Inversion layers over water often create mirages

A wonderfully beautiful picture taken on the outskirts of the Atacma Desert shows a Geminids meteor falling in a perfectly dark sky above the apparently daylight landscape surrounding the La Silla Observatory (Chile). The picture, appearing to show a night sky in the daytime, is difficult to believe is not two separate images. Alas, the image’s unusual characteristic is possible because of an “inversion layer” located slightly above the 7,900 foot observatory.

An “inversion” is an unusual deviation from the normal atmospheric properties that vary with altitude. Normally the air within the lower atmosphere (called the troposphere) near the surface of the Earth is warmer than the air above it. This occurs because the lower atmosphere is heated from solar radiation striking the Earth’s surface. Given enough air pressure, this expected condition can change – the normal temperature is inverted so that the air is colder near the surface of the Earth. The condition typically occurs near warm fronts, along ocean coasts, or near mountains and results in the areas below the inversion being “murky” or clouded while the areas above the inversion point are perfectly clear. Inversion conditions often create unusual vistas and can even create a mirage!

Check out the pictorial gallery below for more interesting examples of inversion layers.


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