What are inversions?

In the troposphere, the lowest layer of the atmosphere that reaches the earth’s surface, temperature typically declines with altitude. This rough estimation of temperature with height doesn’t always fit the situation due to weather, terrain, and solar radiation. Anomalies in the the lowest layer of the atmosphere occur when temperatures increase with height due to these factors. These anomalies are called inversions.

When cooler, higher density air, is in place under warm, less dense air the atmosphere can behave much differently than expected. These differences include poor air dispersion, light winds, and fog

Forward to: using the the Mesonet to detect inversions

How do surface inversions develop?

Due to solar radiation, inversions often occur at night at the surface of the earth. These inversions develop through the following process:

Figure 1. Development of the mixed layer that creates upward motion and good dispersion on a sunny day.
Figure 2. Breakdown of afternoon mixing/vertical motion and development/maturity of a surface inversion at night.
Figure 3. Idealized diagram of an inversion temperature profile, height, intensity, and subsequent air motion due to density stratification (Enz et al. 2014)

Keep in mind, this is an idealized situation. Typically there are many other factors at play besides sun. Some other factors that need considered consist of: clouds, winds, and time of the year.

What factors need consideration?

Inversions are most typical at night as previously described. However, they can also develop during particular weather and are sometimes more impactful based upon conditions, seasons, and time of day.


Figure 4. Trapped longwave radiation overnight will act as a lid and keep temperatures warmer throughout the profile. This will usually act as an inhibitor to inversion development.



What are inversion impacts?

Inversions have a substantial impact on the dispersion of particles as well as surface temperature. This has a resulting influence on smoke, spraying, and weather forecasting.




Using the mesonet to determine presence of an inversion.

In 2017, Kansas Mesonet has began an update to add the ability to detect the presence of inversions. This is done by adding a second temperature sensor at another height above the ground. We have done this at all our tower stations and added it at 10m (30 feet) above the ground. The difference between the 2m (6 feet) and 10m (30 feet) sensors will indicate the presence of an inversion as well as low level stability. Keep in mind, inversions often differ greatly over very small distances. These observations provide a small snapshot of regional conditions but aren’t necessarily representative at your location. When viewing the inversion data here: mesonet.ksu.edu/agriculture/inversion the following dataimplies:

How can you tell in the field if an inversion is present?

More times than not, there is no simple way to determine the presence of an inversion. You absolutely must take temperature measurements at two different heights to determine the change in temperature with height.

Occasionally, there are some visual indicators of an inversion. A few of these are:


Enz, J. W.; Hofman, V., and Thostenson, A. 2014. Air Temperature Inversions: Causes, Characteristics and Potential Effects on Pesticide Spray Drift. AE-1705. NDSU Extension Service publication.

Hunt, E. D., J. B. Basara, and C. R. Morgan, 2007: Significant inversions and rapid in situ cooling at a well-sited Oklahoma mesonet station. J. Appl. Meteor. Climatol., 46, 353–367, doi:10.1175/JAM2467.1.