Air Atmospheric Stability Effects on Spray Drift

Results from two field studies are used to show the effects of atmospheric stability on drifting spray. Deposits sampled in the adjacent field, downwind from an orchard, were a factor of 3-4 higher during stable conditions than during unstable conditions. Lidar scans of drifting plumes over a forest-corn field edge are used to show the dispersion characteristics of spray material during stable and unstable regimes. In unstable conditions, the small droplets disperse rapidly upward into the atmospheric boundary layer, while during stable conditions the drifting material does not disperse but moves slowly away from the spray site and stays near the ground.