Brunt-Väisälä frequency

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In atmospheric dynamics and oceanography, the Brunt-Väisälä frequency, or buoyancy frequency, is the frequency at which a vertically displaced parcel will oscillate within a statically stable environment.

, where θ is potential temperature, g is the local acceleration of gravity, and z is geometric height.

[edit] Context

Dynamical processes to which the Brunt frequency apply are adiabatic and embedded in a buoyantly stable, continuously stratified, hydrostatic fluid. Parcels that are vertically perturbed are accelerated back to their initial position by a restoring buoyancy force.

In a statically unstable environment, vertically displaced fluid parcels do not oscillate, but instead continue to move in the direction of their initial displacement.