sudden stratospheric warming

A significant alteration of the stratospheric polar vortex as a consequence of the intrusion of a Rossby wave from the troposphere into the stratosphere (from bottom to top) and its "breaking" at the upper part of the polar vortex, which causes it to weaken. As a consequence, it shifts and/or fragments, entailing a significant displacement of cold air toward mid-latitudes and a highly anomalous warming of the air in the polar stratosphere. To refer to these events in the scientific literature, the acronym SSW ( Sudden Stratospheric Warming ) is used.