in which the image
of distant objects is displaced downward.
Because the displacement increases with distance, a horizontal surface, such as that of a body of water, desert
, or road, appears to bend downward and one's perception is that of being on top of an inverted bowl or possibly on a planet with a very much smaller radius. Indeed, the downward bending surface results in an (optical) horizon
that can be very much closer to the observer than in the absence of a mirage. Sinking is an example of an inferior mirage
. The opposite of sinking is looming
. Sinking occurs when the concave side of light
rays from a distant object is up, and this in turn occurs when the refractive index
of the atmosphere
increases with height. This only happens near a surface when the heat flux
is upward and so the temperature
gradient decreases with height. This is common over a warm surface (such as might occur over sun-warmed ground or a lake at night). Sinking is often accompanied by a two-image inferior mirage. Compare stooping
Copyright 2022 American Meteorological Society (AMS). For permission to reuse any portion of this work, please contact email@example.com. Any use of material in this work that is determined to be “fair use” under Section 107 of the U.S. Copyright Act (17 U.S. Code § 107) or that satisfies the conditions specified in Section 108 of the U.S.Copyright Act (17 USC § 108) does not require AMS’s permission. Republication, systematic reproduction, posting in electronic form, such as on a website or in a searchable database, or other uses of this material, except as exempted by the above statement, require written permission or a license from AMS. Additional details are provided in the AMS Copyright Policy statement.