In 2017 the Kansas Mesonet underwent an upgrade that included adding a second 30-foot (10 meters) high temperature/humidity sensor to tower stations (Figure 1). This upgrade coincides with the already existing 6-foot (2 meters) temperature humidity sensor. With temperature measurements at different heights, the Mesonet is able to provide a small vertical profile of the lower atmosphere. This lowest layer provides great insight into the vertical mixing occurring over land which has substantial impact on smoke dispersal, spraying results, and temperature forecasting.
Figure 1. All 30-feet towers measure temperatures at 30 feet and observe inversions on the Kansas Mesonet.
What are inversions?
In the troposphere, the lowest layer of the atmosphere that reaches the earth’s surface, temperature typically declines as altitude increases. This rough estimation of temperature with height doesn’t always fit the situation due to weather, terrain, and solar radiation. Anomalies in 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.
Using the Mesonet to determine presence of an inversion:
The difference between the 2-meter (2m) and 10-meter (10m) 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 data implies:
Figure 2. Data from August 30, 2017 at 9:00 pm. Strong inversions (values >5) are in place across much of western Kansas with weak to moderate inversions across central and eastern Kansas.
View data here: http://mesonet.k-state.edu/agriculture/inversion/
How can you tell in the field if an inversion is present?
More often 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 indicators are:
Want to learn more about inversions?
Visit the Mesonet Inversion page here: http://mesonet.k-state.edu/about/inversion/
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.
Christopher Redmond, Weather Data Library/Mesonet Manager
Mary Knapp, Weather Data Library
Dallas Peterson, Weed Management Specialist
Curtis Thompson, Extension Agronomy State Leader and Weed Management Specialist