Weather Conditions. Weather conditions that affect smoke formation include temperature
gradient, humidity, precipitation, and cloud cover. There are three types of temperature gradients that
affect smoke screens: inversion (stable), neutral (moderately stable, favorable, or moderately unstable),
and lapse (unstable). The effects are shown in Figure 10. An estimate of temperature gradient
conditions is used to predict the stability of air. Temperature gradients are measured by subtracting the
air temperature 0.5 meters above the ground surface from the air temperature 4.0 meters above the
surface. With logistical limitations, smoke can be produced under any temperature gradient condition.
Figure 10. Effects of temperature gradients on smoke.