### Brunt-Väisälä frequency

**(buoyancy frequency)**
(natural frequency of buoyancy waves)

The **Brunt-Väisälä frequency**
(or **buoyancy frequency**)
is a characteristic frequency of buoyancy waves in
a stratified fluid, specifically the frequency of
the oscillation caused by a vertical displacement of a
parcel of fluid within a still body of fluid whose
density varies with depth,
lying stably within a gravitational field.
The concept is used in meteorology
and other sciences and applies to stars and planet
atmospheres. It is defined as:

N² = -(G/ρ_{0}) ∂ρ/∂z

- N - Brunt-Väisälä frequency.
- z - depth.
- ρ - density of the fluid (a function of z).
- ρ
_{0} - density at the point of disturbance.
- G - gravitational constant.

(*atmosphere,fluid dynamics*)
http://en.wikipedia.org/wiki/Brunt-Vaisala_frequency

**Referenced by:**

zonal flow

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