A Whirlpool in the Stratosphere above Antarctica

What I have visualized here is the relative vorticity at 10hPa (~30km) developing over a full year taken from the Global Forecast Model (GFS). You can imagine the relative vorticity as the rotation of air masses. In this animation, blueish colors represent a clockwise spinning while redish colors represent an anti-clockwise spinning of air. During January-February-March a giant stratospheric whirlpool develops over Antarctica which appearance still puzzles colleagues and myself. In a similar fashion we observe such a whirlpool around August in the northern hemisphere. Watch also the beautiful dynamics of the polar night jet in winter!

Comment:

While this stratospheric whirlpool was puzzling us for about a year, we could finally tell that it is NOT A REAL FEATURE of the atmosphere but arises due to model initialization and/or data assimilation increments.