Nozzle selection is a critical force in reducing drift. Temperature influences drift in other ways beyond its effect on evaporative loss of droplets. Pesticide volatility increases with increasing temperature. Temperature also influences atmospheric air turbulence, stability and inversions - all of which, in turn, affect drift. Atmospheric Stability Atmospheric stability is an important factor influencing drift.
Cool air tends to sink, displacing lower warm air and causing vertical mixing.
As a warm air layer rises, suspended droplets rise with it and dissipate into the upper layers by normal air turbulence and vertical mixing. Under these conditions, the opportunity for crop injury at any specific off target site is very small because the pesticide is dispersed and diluted into the atmosphere. However, other problems may arise when the atmosphere is very stable. Under stable conditions, a warm air layer at some distance overhead may become a blanket, holding down cooler air underneath. Particles suspended in the cool layer cannot move anywhere except laterally, possibly for several miles.