Brunt-Väisälä frequency

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

: N equiv sqrt{frac{g}{ heta}frac{d heta}{dz, where heta is potential temperature, g is the local acceleration of gravity, and z is geometric height.

In the ocean where salinity is important, or in fresh water lakes near freezing, where density is not a linear function of temperature,

: N equiv sqrt{-frac{g}{ ho}frac{d ho}{dz, where ho, the potential density, depends on both temperature and salinity.

Context

The concept derives from Newton's Second Law when applied to a fluid parcel in the presence of a backgroundstratification (in which the density changes in the vertical). The parcel, perturbed vertically from itsstarting position, experiences a vertical acceleration. If the acceleration is back towards the initialposition, the stratification is said to be stable and the parcel oscillates vertically. In this case, N2>0 and the frequency of oscillation is given by N. If the acceleration is away from the initial position (N2<0), the stratification is unstable. In this case, overturning or convection generally ensues.

The Brunt-Väisälä frequency relates to internal gravity waves and provides a useful description of atmospheric and oceanic stability.


Wikimedia Foundation. 2010.

Look at other dictionaries:

  • Brunt — is a common surname:*Chris Brunt, West Bromwich Albion football player *Daryl Brunt, contestant on the third season of Canadian Idol *David Brunt, British meteorologist *Dominic Brunt, English actor *Hugh Brunt, British Composer, Conductor and… …   Wikipedia

  • David Brunt — Sir David Brunt KBE (17 June 1886 – 5 February 1965)[1] was a Welsh meteorologist. Contents 1 Early life 2 Career 3 Honours and Awards …   Wikipedia

  • Internal wave — Internal waves are gravity waves that oscillate within, rather than on the surface of, a fluid medium. They arise from perturbations to hydrostatic equilibrium, where balance is maintained between the force of gravity and the buoyant restoring… …   Wikipedia

  • Buoyancy — The forces at work in buoyancy In physics, buoyancy (  / …   Wikipedia

  • Richardson number — The Richardson number is named after Lewis Fry Richardson (1881 ndash; 1953). It is the dimensionless number that expresses the ratio of potential to kinetic energy [Modellers will be more familiar with the reciprocal of the square root of the… …   Wikipedia

  • Potential temperature — The potential temperature of a parcel of fluid at pressure P is the temperature that the parcel would acquire if adiabatically brought to a standard reference pressure P {0}, usually 1000 millibars. The potential temperature is denoted heta and,… …   Wikipedia

  • Rossby radius of deformation — In atmospheric dynamics and oceanography, the Rossby radius of deformation is the length scale at which rotational effects become as important as buoyancy effects in the evolution of the flow about some disturbance. : L {R} equiv frac{NH}{f {0,… …   Wikipedia

  • BVF — Biovail Corporation International (Business » NYSE Symbols) * Bua, Fiji (Regional » Airport Codes) * Brunt Vaisala Frequency (Academic & Science » Physics) …   Abbreviations dictionary


Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.