polar vortex

A large-scale cyclonic circulation in the lower stratosphere that flows west to east around a polar region. It is coupled to a vortex located below, in the mid and upper troposphere, whose dynamics are modulated by the upper one. On Earth we have the Arctic polar vortex and the Antarctic one, with the latter being more powerful and persistent than the Arctic one. Every so often, the stratospheric vortex of the Arctic region undergoes a breakup, brought about by episodes that have been dubbed sudden stratospheric warmings, caused by incursions of warm air associated with Rossby waves, which in the northern hemisphere sometimes reach great amplitudes. In the boreal summer, the Arctic polar vortex becomes notably blurred, and can even disappear.