Atmospheric instability

Atmospheric instability is a state in which vertically displaced air continues to rise or sink rather than returning to its original level. It depends on how the surrounding air’s temperature changes with height.

Environmental lapse rate: The rate at which ambient air temperature changes with altitude. It sets the temperature profile against which a displaced air parcel is tested.
Stable atmosphere: An atmospheric state in which a vertically displaced parcel tends to return toward its original level. It is the direct opposite of instability’s self-amplifying parcel motion.
Atmospheric convection: Vertical heat and mass transport in the atmosphere driven by buoyancy. Instability supplies the buoyant motions that initiate convection.
Atmospheric stability: The tendency of the atmosphere to resist, permit, or amplify vertical displacement. Instability is one possible state within the broader stability framework.
Adiabatic lapse rate: The rate at which an unsaturated or saturated air parcel changes temperature as it rises or sinks without exchanging heat. It predicts a parcel’s temperature change during vertical displacement.
Conditional instability: Instability that occurs for saturated air parcels but not for unsaturated parcels. It explains why condensation can turn a capped parcel buoyant.
Thunderstorm: A storm produced by deep convective clouds, often accompanied by lightning and thunder. Strong instability can support the vigorous updrafts that build thunderstorms.
Inversion (meteorology): An atmospheric layer in which temperature increases with altitude instead of decreasing. An inversion commonly suppresses vertical motion and can cap unstable air below.
Buoyancy: The force on a body in a fluid caused by a difference in density between it and the surrounding fluid. Parcel buoyancy determines whether a displacement grows or is opposed.
Potential instability: Instability produced when a lifted layer becomes less stable after saturation, often because moisture varies with height. It describes instability generated by lifting an entire layer rather than one parcel.

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