Nowadays this mirage is so common we almost don't think about it. Inferior mirages occur when the air close to the surface is much warmer than that above it. Thus the desert mirage is an inferior mirage. Skylight passing through this air is bent by refraction so that it appears to be coming from a source below the horizon. The superior mirage forms above the horizon and is seen where warm air overlies cold air, a condition known as a temperature inversion .
Superior mirages can be quite common over cold water and snow surfaces.
Here in Victoria, British Columbia, the colder waters surrounding Vancouver Island provide ideal conditions for superior mirage viewing. Most often they are evident through an apparent increase in the height of the Olympic Mountains to the south. There are several areas approaching the city core where the Olympics appear to tower to great heights, a disappointment to those tourists who rush to the shoreline only to find much smaller mountains rising across the strait. Superior mirages can distort the horizon or bring images of topography located below the horizon into view. Superior mirages may also invert an image.