Rossby waves

Rossby waves, also called planetary waves, are large-scale meanders in the jet stream and ocean currents that arise from the conservation of potential vorticity on a rotating sphere. Named after Carl-Gustaf Rossby, these waves are the primary mechanism by which the atmosphere and ocean redistribute heat and momentum across latitude, and their interaction with mean flows produces the atmospheric blocking patterns that govern mid-latitude weather persistence.

The wave dynamics depend on the meridional gradient of potential vorticity, which is steepened by the Earth's rotation and the temperature contrast between equator and pole. When this gradient weakens — as in Arctic amplification — the waves slow, amplify, and become more susceptible to wave-mean flow interaction that can lock them into persistent patterns. The zonal wavenumber of Rossby waves determines their propagation speed and their capacity to resonate with thermal forcing.