A departure from the usual decrease of temperature with increasing altitude: Advectional inversion is a temperature reversal caused by cold air moving across a previously warmed up surface, causing the warm air to rise up above the cooler air below.

An atmospheric condition in which the air temperature rises with increasing altitude, holding surface air down and preventing dispersion of pollutants: Atmospheric inversion is a departure from the usual increase or decrease of an atmospheric property with altitude.

Atmospheric inversion usually refers to an increase in temperature with increasing altitude, which is a departure from the usual decrease of temperature with height.

In other words, atmospheric inversion is a reversal in the normal temperature lapse rate, the temperature rising with increased elevation instead of falling.

Usually within the lower atmosphere (the troposphere), the air near the surface of the Earth is warmer than the air above it, largely because the atmosphere is heated from below as solar radiation warms the Earth's surface, which in turn then warms the layer of the atmosphere directly above it.

A meteorological condition characterized by a temperature increase; rather than a decrease, with the altitude.

During a thermal inversion, air pollution can increase dramatically as a mass of cold air is held in place below a warmer mass of air.

The absence of air circulation prevents the pollution near the earth's surface from escaping.