The Fata Morgana is a complex optical phenomenon in the atmosphere, consisting of several forms of mirage, in which distant objects are seen many times and with various rapidly changing distortions. Fata Morganas occur when several alternating layers of air of different density are formed in the lower layers of the atmosphere, capable of giving mirror reflections. As a result real objects appear on the horizon or above it, as several distorted images, overlapping one another and rapidly changing in time, which creates a fanciful picture of fata-morgan. Contrary to popular belief, they are not only seen in the desert but often seen in Polar regions above large sheets of ice, having a uniformly cold temperature.

The name is Italian, but comes from the Arthurian sorceress Morgan le Fay, from a belief that appearances often seen in the Strait of Messina, were created by her witchcraft to lure sailors to their deaths.

More Info: en.wikipedia.org