Mirages in Canada have made cities appear in the sky!

When we speak of a mirage, we immediately think to the deserts, and yet mirages also occur in icy regions. Far from being hallucinations, mirages are very real optical phenomena since they can be photographed. On January 10, a meteorologist from Calgary, in the Canadian province of Alberta, was able to immortalize these appearances with spectacular shots. The buildings of Calgary appear distorted, stretched upwards: it is a superior mirage.

A temperature inversion that bends the light

These imaginary buildings in the sky actually stretch until called weather report, the “inversion layer”: the upper mirage, or “cold mirage”, occurs when theair close to the ground is much colder than that present at altitude. In the case of the Calgary mirages, the difference between these two air masses was 15°C that day. A phenomenon called inversion because, in a classic weather context, the air is warmer on the ground, and colder at altitude. The temperature inversions occur in mountainous areas, and more commonly in polar areas, above land, ice or sea. In this situation, the light rays projected by real objects (buildings, boat…) follow an upward and curved trajectory: the initial object is then deformed, stretched, and perceived as much larger. It sometimes appears offset from the actual object, and in some cases, reversed.

There are three categories of mirages in all: the upper mirage of cold regions, the lower mirage of hot regions which makes an object appear at an altitude lower than reality, and the Fata Morgana which combines several layers of inversions and gives appearances of superimposed objects.