A refraction effect that causes distant objects to appear compressed vertically. It occurs when the lowermost layer of air has a markedly lower density than higher layers, i.e. when it is considerably warmer. Rays of light from the bottom of an object are subject to much greater refraction than normal and appear to come from higher in the sky. Higher rays are less affected. The opposite effect is known as towering. See also mirage.
Subjects: Meteorology and Climatology.