# Internal gravity wave

From AMS Glossary

## internal gravity wave

(

*Also called*internal waves, gravity waves.) A wave that propagates in density-stratified fluid under the influence of buoyancy forces.The dispersion relation is given by frequency in which

*N*is the buoyancy frequency and*k*_{h}is the horizontal component of the wavenumber vector**k**. For all wavenumbers, internal gravity waves have frequency smaller than*N*. Their group velocity is perpendicular to the phase velocity such that the vertical component of the group velocity is opposite in sign to the vertical component of the phase velocity.