What is ROSSBY WAVE? What does ROSSBY WAVE mean? ROSSBY WAVE meaning, definition & explanation

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What is ROSSBY WAVE? What does ROSSBY WAVE mean? ROSSBY WAVE meaning - ROSSBY WAVE definition - ROSSBY WAVE explanation. Source: Wikipedia.org article, adapted under https://creativecommons.org/licenses/by-sa/3.0/ license. Rossby waves, also known as planetary waves, are a natural phenomenon in the atmosphere and oceans of planets that largely owe their properties to rotation. Rossby waves are a subset of inertial waves. Atmospheric Rossby waves on Earth are giant meanders in high-altitude winds that have a major influence on weather. These Rossby waves are associated with pressure systems and the jet stream. Oceanic Rossby waves move along the thermocline: the boundary between the warm upper layer and the cold deeper part of the ocean. Atmospheric Rossby waves are the result of conservation of potential vorticity and are influenced by the Coriolis force and pressure gradient. A fluid, on the Earth, that moves toward the pole will deviate toward the east; a fluid moving toward the equator will deviate toward the west (true in either hemisphere). The deviations are caused by the Coriolis force and conservation of potential vorticity which leads to changes of relative vorticity. This is analogous to conservation of angular momentum in mechanics. In planetary atmospheres, including Earth, Rossby waves are due to the variation in the Coriolis effect with latitude. The waves were first identified in the Earth's atmosphere in 1939 by Carl-Gustaf Arvid Rossby who went on to explain their motion. One can identify a terrestrial Rossby wave as its phase velocity, marked by its wave crest, always has a westward component. However, the collected set of Rossby waves may appear to move in either direction with what is known as its group velocity. In general, shorter waves have an eastward group velocity and long waves a westward group velocity. The terms "barotropic" and "baroclinic", are used to distinguish the vertical structure of Rossby waves. Barotropic Rossby waves do not vary in the vertical, and have the fastest propagation speeds. The baroclinic wave modes are slower, with speeds of only a few centimeters per second or less. Most investigations of Rossby waves has been done on those in Earth's atmosphere. Rossby waves in the Earth's atmosphere are easy to observe as (usually 4-6) large-scale meanders of the jet stream. When these deviations become very pronounced, masses of cold or warm air detach, and become low strength anticyclones and cyclones, respectively, and are responsible for day-to-day weather patterns at mid-latitudes. Rossby waves may be partly responsible for the fact that eastern continental edges, such as the Northeast United States and Eastern Canada, are colder than Western Europe at the same latitudes. Oceanic Rossby waves are large-scale waves within an ocean basin. They have a low amplitude, on the order of centimetres (at the surface) to metres (at the thermocline), compared to a very long wavelength, on the order of hundreds of kilometres of atmospheric Rossby waves. They may take months to cross an ocean basin. They gain momentum from wind stress at the ocean surface layer and are thought to communicate climatic changes due to variability in forcing, due to both the wind and buoyancy. Both barotropic and baroclinic waves cause variations of the sea surface height, although the length of the waves made them difficult to detect until the advent of satellite altimetry. Satellite observations have confirmed the existence of oceanic Rossby waves.