baroclinic instability

In fluid dynamics, the baroclinity (sometimes called baroclinicity) is a measure of the stratification in a fluid. A baroclinic atmosphere is one for which the density depends on both the temperature and the pressure; contrast this with barotropic atmosphere, for which the density depends only on the pressure. In atmospheric terms, the barotropic zones of the Earth are generally found in the central lattitudes, or tropics, whereas the baroclinic areas are generally found in the mid-lattitude/polar regions.
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