Kelvin wave

Summary

A Kelvin wave is a wave in a rotating fluid that is trapped against a boundary, such as a coastline. It can also be trapped against the equator, where the Coriolis parameter changes sign. The velocity across the boundary is zero. Along the boundary the wave moves like a non-rotating gravity wave, at speed $\sqrt{gH}$ in a layer of depth $H$. Its amplitude decays away from the boundary over a Rossby radius of deformation. Kelvin waves carry tides along coasts and play a central role in the dynamics of El Niño.