An inferior mirage is a mirage of an object visible below that object. Usually the mirage is mirrored upside-down. Inferior mirages are very common on roads when the sun is shining; also in winter. The heating just over the road creates a steep temperature gradient and refraction of light rays upwards; so you look downwards (on the road) to see light coming from the sky, or the horizon. Hence the mirage causes the sky to be reflected on the road, and so it looks as if there is a reflecting water surface, because water surfaces are what we associate with reflections.

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