This example shows a common temperature profile in Los Angeles, where there is a temperature inversion aloft (aloft = above the ground).

A demonstration of how the inversion prevents vertical mixing. Note that:

• In the neutrally stable air underneath the inversion base (the air could also be unstable, but we're making it neutral in this example), the air parcels are able to mix in the vertical direction. The air parcel starting at the ground drifts upward (slowly) due to atmospheric turbulence (the neutral stability does not prevent this motion, nor does it suppress it) and expands adiabatically as it is pushed upward.
• The environmental lapse rate in the inversion layer is negative, which definitely makes it less than the positive 10°C/km for the adiabatic lapse rate, hence the atmosphere within the inversion layer (the region above the inverstion base) is stable.
• As the air parcel is forced above the inversion base and into the inversion layer, it loses some more temperature at the adiabatic lapse rate. However, in this region the environment gains temperature with increasing altitude, making the air parcel much colder than the surrounding air.
• The restoring force that makes a lifted parcel go back down is proportional to the difference between the parcel and environmental temperature; as the parcel is lifted higher, the difference grows rapidly, producing a very strong restoring force and preventing any significant convection.

Thus, pollution released at the ground can mix upward in this example until it reaches the inversion base, and then its upward mixing is strongly inhibited. If the inversion base is close to the ground, then the pollution is confined to a small volume of air next to the ground, resulting in high pollution concentrations.