Watch Temperature Inversions Prior to Herbicide Treatments

How often do temperature inversions occur in west Tennessee? Recent research funded by the United Soybean Board designed to study low level inversions has had some interesting results.

We set up two weather stations that measure temperature at 18, 66 and 120 inches above the soil. One of these stations was placed on the crest of a hill, and the other was set up about a mile away in a creek bottom between a field of corn and a field of soybeans on the UT Martin farm. The weather station in the bottom was 40 feet less in elevation than the one located on the hill.


In the month of June, there were 18 temperature inversions measured on the hill and 22 inversions documented in the creek bottom. The temperature inversions for both locations typically, though not always, started between 5:00 to 6:00 in the evening. What was interesting is that the temperature inversion measured on the hill often dissipated early in the morning (4:00 to 6:00 am), while the inversions in the bottom would often linger until 8:00 am or later.

UT Martin meteorologist Dr. Mark Simpson, who is consulting on this project, thought that topography would have an impact on low level inversions. Indeed, this research would suggest that topography can effect both the frequency and intensity of low level inversions.

I know when it comes to temperature inversions, most producers have moved from being happily ignorant they even exist to really trying to watch for them. Indeed, many of the applicators I have visited with this spring have, on more than one occasion, made the comment that they would wait for the wind to start to pick up to spray. Based on this data, a good field to start with in the morning would be one that has some elevation, and then move to the bottoms later to utilize time the most efficiently.

Finally a question I have from looking at his data is “Are the apps that predict inversions taking into account topography?” I do not know the answer to that. But based on this data. topography needs to be a variable when predicting temperature inversions.