Sudden, `explosive' warming of the Arctic lower stratosphere during the polar night was first reported in the early 50s by Richard Scherhag of the Free University of Berlin. It was not until the early 70s that a theory by Taroh Matsuno was broadly accepted as describing the essential cause of warming. Details, of course, remain contentious. Modern, high resolution reanalysis products such as MERRA reveal these events in remarkable detail, and will undoubtedly prove invaluable for resolving questions about their dynamics. In the mean time, however, they're great for making animations.

I'll spend some time reviewing the theory and dynamics of sudden warmings, illustrated by real events from MERRA. I'll also discuss their common, if somewhat problematic, classification into vortex displacements and splits, and whether that sheds any light on the details of what's going on.