(1/n) An unprecedented wave-2 event has been unfolding in the Southern Hemisphere polar stratosphere, with all-time record amplitudes of wave-2 during a time of year that is often quiet in the SH #polarvortex.
(2/n) The wave-2 signature can clearly be seen in total column ozone; this is the time of year when the ozone hole is typically just beginning to form.

1-How will the stratospheric #polarvortex respond to #climate change? Bottom line: we have no idea. A 🧵on a new paper out by Alexey Karpechko, @HillaA1, me, @Domeisen_D, @Marlene_Climate, @zd1awrence, E. Manzini, @michaelsigmond, @IslaSimpson4, and Z. Wu: agupubs.onlinelibrary.wiley.com/doi/10.1029/20… 2- There is no agreement across #CMIP6 models in the magnitude or even sign of the polar vortex response to climate change, though the magnitude of any individual model response tends to increase with the magnitude of climate warming.

(1/n) One measure I pay close attention to in winter is the "eddy heat flux". What does that mean? Eddy heat flux is basically referring to the heat transported from the tropics to the poles by weather fronts (otherwise, the tropics would be much hotter and the poles colder!). (2/n) Mathematically, it’s defined as v’T’, where the prime is a deviation from the zonal-mean, v is meridional wind, and T is temperature. Usually it’s averaged over the mid-latitudes.