| A temperature inversion is a thin layer of the atmosphere where the decrease
in temperature with height is much less than normal (or in extreme cases, the temperature
increases with height). An inversion, also called a "stable" air layer, acts like a lid,
keeping normal convective overturning of the atmosphere
from penetrating through the inversion. This can cause several weather-related effects.
One is the trapping of pollutants below the inversion, allowing them to build up. If the
sky is very hazy, or is sunsets are very red, there is likely an inversion somewhere in the
lower atmosphere. This happens more frequently in high pressure zones, where the gradual
sinking of air in the high pressure dome typically
causes an inversion to form at the base of a sinking layer of air. Another effect is making
clouds spread out and take on a flattened appearance. Still another effect is to prevent
thunderstorms from forming. Even in an air mass that is hot and humid in the lowest layers,
thunderstorms will be prevented if an inversion is keeping this air from rising.
The opposite of a temperature inversion is an unstable air layer.
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