Fata Morgana (mirage) - Observing A Fata Morgana

Observing A Fata Morgana

A Fata Morgana is most commonly seen in polar regions, especially over large sheets of ice which have a uniform low temperature. It can however be observed in almost any area. In polar regions the Fata Morgana phenomenon is observed on relatively cold days, however in deserts, over oceans, and over lakes, a Fata Morgana can be observed on hot days.

To generate the Fata Morgana phenomenon, the thermal inversion has to be strong enough that the curvature of the light rays within the inversion layer is stronger than the curvature of the Earth. Under these conditions, the rays bend and create arcs. An observer needs to be within or below an atmospheric duct in order to be able to see a Fata Morgana.

A Fata Morgana can be observed from any altitude within the Earth's atmosphere, from sea level up to mountain tops, and even including the view from airplanes.

A Fata Morgana can be described as a very complex superior mirage with more than three distorted erect and inverted images. Because of the constantly changing conditions of the atmosphere, a Fata Morgana can change in various ways within just a few seconds of time, including changing to become a straightforward superior mirage.

The sequential image here shows sixteen photographic frames of a mirage of the Farallon Islands as seen from San Francisco; the images were all taken on the same day.

In the first fourteen frames, elements of the Fata Morgana mirage display alternations of compressed and stretched zones. The last two frames were photographed few hours later, around sunset time. At that point in time, the air was cooler while the ocean was probably a little bit warmer, which caused the thermal inversion to be not as extreme as it was few hours before. A mirage was still present at that point, but it was not as complex as few hours before sunset: the mirage was no longer a Fata Morgana, but instead had become a simple superior mirage.

Fata Morgana mirages are visible to the naked eye, but in order to be able to see the detail within them, it is best to view them through binoculars, a telescope, or as is the case in the images here, through a telephoto lens.

Gabriel Gruber (1740–1805) and Tobias Gruber (1744–1806), who observed Fata Morgana above Lake Cerknica, were the first to study it in a laboratory setting.