Dicamba Details – 5
Temperature Inversions Make Evening Applications Risky
By Emily Unglesbee | May 1, 2018
ROCKVILLE, Md. (DTN) — New research on temperature inversions is changing recommendations for how applicators can safely apply dicamba this year.
A temperature inversion occurs when a cool air mass — and any particles in it — become trapped near the ground for hours until the air warms and disperses.
New research suggests that inversions are most likely to set up in the afternoon and evening hours, not mornings, and the air doesn’t have to be dead calm for them to develop. Most importantly, scientists from Missouri have shown they can trap pesticide particles in the air for many hours after application.
This latest information comes from weather stations and monitoring networks set up in Missouri and North Dakota, which are measuring inversions around the clock and bringing scientists up to date on how they affect pesticide applications.
DTN checked in with experts from both states for the new details on inversions and how dicamba applicators can avoid them in 2018….
…KNOW THE SIGNS
At least one company, Innoquest, is selling a handheld device to measure temperature inversions in the field, but there are other good indicators that an inversion is underway.
Use all your senses, Thostenson said.
Dust clouds, or even odors nearby can tell an interesting story. Is the dust behind that pick-up truck rising slowly and hanging in the air, or drifting along in the breeze but not dissipating quickly? Can you smell the neighbor’s chickens more than usual? If so, the cool air mass of an inversion could be trapping those particles near the ground.
Inversions also distort both light and sound waves, which can change how your surroundings look and sound. Does that tree line loom larger than usual? Did you catch the whistle of a train you don’t normally hear?
“A wind break can look much taller than it is because of an inversion, and the same can occur with mountains or hillsides,” Thostenson explained. “The cool temperatures near the ground can also distort sound waves and they project out farther so all noises will project farther, too.”
Beware of calm or lightly breezy afternoons with less than 25% cloud cover. In contrast, wet, stormy weather or high humidity can make inversions far less likely, Thostenson added.
“Moisture in the atmosphere is a gigantic buffering mechanism,” he explained. “The more moisture there is, the slower temperatures will move in either direction.”