Central Campus Air Quality Model (CCAQM) Instructions
Height and Inversions
height is the height of vertical mixing of air and suspended
particles above the ground. This height is determined by the
observation of the atmospheric temperature profile. A parcel of air
rising from the surface of the Earth will rise at a given rate
(called the dry-adiabatic lapse rate). As long as the parcel of air
is warmer than the ambient temperature, it will continue to rise.
However, once it becomes colder than the temperature of the
environment, it will slow down and eventually stop. It is at this
junction where the temperature of the parcel crosses the curve
denoting the vertical environmental temperature profile determines
the mixing height.
are a result of the vertical temperature profile of air.
Temperature normally decreases as altitude increases in the
troposphere (at an average rate of 1°C per 100 meters). However, an
increase of temperature as altitude increases can occur and is
called an inversion. Thus, the colder air layer is below the warmer
air, resulting in a stable temperature profile that restricts
vertical mixing. Because of the restricted mixing volumes of air
due to the inversion, pollution becomes stagnant and does not
Los Angeles is
a prime example of a location that is prone to inversions. Thus, in
this location, pollution does not dissipate, causing large amounts
of smog and air pollution.
Inversions affect plume rise. On the left there
is no inversion present, while the inversion is above the stack in
the figure on the right