The upper mirage.

The air is warmed at the Earth surface and its temperature falls with the height. But if above the layer of the cool air there is a warmer one (taken by the south winds) and deeply rarefied air, a transition between them is very sharp, then refraction is greatly increasing. The light beams coming from the objects on the Earth, draw a kind of an arch and return back down, sometimes tens or hundreds kilometres from the origin. Then we can observe the "rising horizon" or upper mirage.

The upper mirages are seen in the sea before storm. Perhaps they bear the legends about the ships-phantoms.

  Back.