Mini Mirage

Dave Pike imaged this scene in the Scottish Highlands.

A narrow band of the distant hillside appears strongly miraged where rays from it graze the nearby snowy slope.

The snow surface has radiatively cooled overnight and has in turn cooled air close to it. The mirage is produced by refraction across the temperature gradients between the cold air and warmer air above.

We have in effect a mini superior mirage or even a Fata Morgana.

Image ©Dave Pike, shown with permission
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Formation of a classical superior mirage.

A ray ‘A’ from low down on the distant hillside can be strongly refracted across temperature (air density) gradients between the cold and warmer air.  It appears to the eye to come from above the real object.   Rays leaving farther up the hillside can reach the eye directly ‘B’ or by refraction at the cold-warm air boundary ‘C’.   the result is an inverted image of the hillside.   Extra refraction ‘D’ gives an erect image above the inverted one.

The Scottish hillside mirage is hard to disentangle.  Parts are inverted and others erect.   Mirages like this approach the appearance of a Fata Morgana.