A measure of the tendency of air to move upward or downward
within the atmosphere, generating turbulence. The atmosphere may be more or less turbulent at any given time, depending on the amount of incoming solar radiation as well as other factors. Meteorologists have defined six atmospheric stability classes, from A to F, each representing a different degree of turbulence in the atmosphere. When moderate to strong incoming solarradiation heats air near the ground, causing it to rise and generating large eddies, the atmosphere is considered unstable.

Unstable conditions are associated with atmospheric stability classes A and B (air has a strong tendency to move up or down, and the atmosphere is more turbulent). When solar radiation is
relatively weak or absent, air near the surface has a reduced tendency to rise and less turbulence develops. In this case, the atmosphere is considered stable, the wind is weak, and the stability class would be E or F. Stability classes D and C represent conditions of more neutral stability (moderately turbulent).Neutral conditions are associated with relatively strong windspeeds and moderate solar radiation.