Gravity wave

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Ocean wave

Wave clouds over Theresa, Wisconsin, USA

Atmospheric gravity waves as seen from space. [1]

For the different concept in general relativity, see gravitational radiation.

In fluid dynamics, gravity waves, are waves generated in a fluid medium or at the interface between two mediums (e.g. the atmosphere or ocean) which has the restoring force of gravity or buoyancy.

When a fluid parcel is displaced on an interface or internally to a region with a different density, gravity restores the parcel toward equilibrium resulting in an oscillation about the equilibrium state. Gravity waves on an air-sea interface are called surface gravity waves or surface waves while internal gravity waves are called internal waves. Ocean waves and tsunamis are examples of gravity waves.

[edit] Atmosphere dynamics on Earth

Since the fluid is a continuous medium, a traveling disturbance will result. In the earth's atmosphere, gravity waves are important for transferring momentum from the troposphere to the mesosphere. Gravity waves are generated in the troposphere by frontal systems or by airflow over mountains. At first waves propagate through the atmosphere without affecting its mean velocity. But as the waves reach more rarefied air at higher altitudes, their amplitude increases, and nonlinear effects cause the waves to break, transferring their momentum to the mean flow.