Temperature inversions — Introduction


What Is A Temperature Inversion?

Many decades ago researchers examined how the temperature of our atmosphere changes with distance up from the surface of the earth.  Data were collected from locations throughout the world.  The data were averaged over the years and over the locations.  This led to a “standard” model for the behavior of our atmosphere. 

 

In particular, it led to the conclusion that generally the temperature of the air in the troposphere drops as the altitude above the earth’s surface increases.  The standard rate for the decline is about 6.5°C per kilometer increase in altitude. 

 

For example, if the air temperature is 15°C at some specific location, the air temperature would be 8.5°C 1000 meters directly overhead.  That sort of behavior of air temperature is considered the normal behavior.

 

When a temperature inversion occurs, the air gets warmer with increasing altitude instead of getting colder.  The temperature for some distance up through the atmosphere is “inverted” from normal.  The inversion exists over a limited range of altitudes.  At even higher altitudes in the troposphere, the temperature eventually resumes its normal decline with increasing height.

 

Temperature inversions occur commonly across the earth.  There are multiple conditions that can produce them.  The mechanisms that cause a band of air to have a temperature inversion can be put into three groups:

  1. Mechanisms that cool the band of air from below to a temperature that is lower than that at the top of the band;
  2. Mechanisms that warm the band of air from above to a temperature that is higher than the temperature of the air at the bottom of the band; and
  3. Mechanisms that transport warm/cold air into a region where it slides over/under existing air that initially was not temperature inverted.

A well known example of the first mechanism occurs commonly at night (especially in the desert) when the surface of the earth radiates infrared radiation into space and cools the earth’s surface.  In turn, the earth’s surface cools the air near it, making it cooler than the air above it.

 

An example of the second category occurs when a band of air from higher up in the atmosphere sinks and, as it does so, the increased pressure it experiences warms the air.

 

The last category of inversion involves a process called advection Air is “advected” from outside the local region into the local air system.  Weather fronts are examples of this occurrence. 

In cold fronts, cold air slides under warmer air, creating an inversion.  Warm fronts, on the other hand, occur when warm air overruns colder air below.  In the advection inversions, it is necessary that the air coming into the local environment be sufficiently different in temperature that it can disrupt the local state of temperature distribution.  Advection inversions are one of the more popular possible explanations for the mysterious Marfa lights.

Inversions are discussed in greater detail on the links below.