This animation shows the stratospheric polar vortex in the lower stratosphere as it evolves from 1 Oct 2020 through 7 Feb 2021. The quantity shown is called "Potential Vorticity", which is plotted on the 520 K isentropic surface, corresponding to about 20 km in altitude. In a very simple sense, potential vorticity is a dynamical fluid quantity that ties together conservation of mass and conservation of angular momentum in a fluid.
Potential vorticity is approximately conserved following the flow, meaning it behaves a bit like a "dye tracer" in water. The polar vortex in this animation is represented by the brightest (highest potential vorticity) region.
On January 5th, 2021, a sudden stratospheric warming began as the polar vortex was displaced off the pole and stretched in the middle stratosphere. In the lower stratosphere the polar vortex was actually stretched thin and torn apart multiple times going into February.
The stratospheric polar vortex has vertical structure too! Want to see what it looks like around 30 km instead? See this video: [ Ссылка ]
Do you prefer a shorter animation showing the polar vortex disturbances? See this video: [ Ссылка ]
