Gravity wave
The term gravity waves is used in oceanology , meteorology and planetology for waves whose propagation is dominated by the acceleration of gravity . They have nothing to do with gravitational waves , which are an entirely different phenomenon.
There are basically two types of gravity waves:
- External gravity waves propagate along the interface between two fluids . One mechanism of formation of external gravity waves is the Kelvin-Helmholtz instability .
- Internal gravity waves occur within a medium with continuous, stable stratification. If the amount of the density gradient does not have a pronounced maximum, the energy of the wave can be distributed over a depth range that is large compared to the wavelength .
Examples
Lee waves behind mountain ridges or island mountains are stationary internal waves. See also Mountain Wave Project .
![](https://upload.wikimedia.org/wikipedia/commons/thumb/0/08/Messina-waves-image.jpg/220px-Messina-waves-image.jpg)
Gravity waves south of the Strait of Messina
The same effect occurs in lakes and seas, for example at river mouths or when flowing over obstacles.
Water waves are mostly gravity waves, but see capillary waves .