Worldwide Extreme Weather Resulting from Sudden Stratospheric Warming

I’ve not written a climate diary for quite some time, and since this hasn’t been blogged yet, I thought I’d give it a stab. The title graphic is the 2-meter (standard surface air) Temperature departure from a 1979 — 2010 climatology for Asia and surrounding regions. The temperatures corresponding to the color shadings is at the bottom of the graphic, and it shows 2-m T’s of up to 24^oC (~43^oF) above normal. As you are probably aware, similar negative temperature departures have taken place in the Great Plains, Southern Plains (especially TX) and Midwest, during the climax of a 2 week cold wave that ended over the weekend. The electric and other utility problems resulting from greed, in combination with the cold wave, have been well-documented elsewhere.

I’ll document some of the extremes around the world in the rest of this entry, and suggest a connection not only to the sudden stratospheric warming (SSW) but to global warming as well.

Northern Hemisphere extremes during February 2021

polar vortex and jet stream

SSWs result from complex processes involving propagation of a particular type of tropical wave vertically into the stratosphere, then moving poleward. This warms the polar stratosphere, weakens and ultimately breaks down the polar vortex. Pieces of it, along with the associated arctic air, move into the mid-latitudes (and even subtropical latitudes, as we saw in south TX earlier this month). The polar jet stream responds by becoming more “wavy” than normal. These waves tend to move more slowly, so the more extreme weather often persists for longer periods of time than normal.

The graphic below illustrates this, at the altitude of the mean steering currents for movement of weather systems. Where the shading is blue, the atmosphere beneath is colder than normal. These are the pieces of the polar vortex which have shifted to lower latitudes after the SSW and disruption of that vortex. With the anomalously meandering jet stream, we can also see areas that are dark red, marking warmer than normal temperatures from the steering level to the surface. Note in particular the warm area from central Europe into the Arctic Ocean, reaching the North Pole. The air is somewhat warmer than normal over central and eastern Asia as well.

Impact of Breakdown of the Polar Vortex

Warmth

Some of the specifics related to the graphic above include some truly astounding records. For example, Beijing recorded a temperature of 25.6^oC (78^oF) or 5.8^oC (10^oF) above the previous record; this on the day after its earliest 20^oC (68^oF) on record. South Korea saw a warmest temperature yesterday of 24.9^oC (77^oF).

Extreme warmth hasn’t been limited to Asia. Central Europe has had record warmth as well, with a February record for warmth set for Lichtenstein 21.9^oC (72^oF). In Germany, record monthly temperatures were set at a number of locations on 21 February (warmest of which was 20.1^oC (68^oF)). On 22 February, Hamburg, Germany reached 21.1^oC (70^oF), the warmest ever for meteorological winter (Dec.-Feb.) at that location.

Cold

In the meantime, cold air drove south into northeastern Europe and central North America. Along with the North American extreme cold discussed elsewhere, the first -50^oC (-58^oF) since January 2017 occurred on 22 February in European Russia.

variability

Extreme excursions of the jet stream has also resulted in highly variable temperatures. This example from Gottingen, Germany is for February 2021 month to date. The average high and low are plotted with solid black lines, one above the other. Actual daily maximum and minimum temperatures are shown as red and blue lines, respectively, with departures from normal highs and lows shown as red and blue bars. The difference between the extreme low (on the 14th) and high (on the 21st) is about 38^oC (~68^oF), and results from anomalous southward (cold) and northward (warm) meanderings of the jet stream.

A similar temperature roller coaster shows up for the central U.S. This example is from Dallas-Fort Worth (DFW) airport for February 2021 to date. From a -2^oF minimum on the 16th, the 21st had a maximum temperature of 74^oF, an increase of 76^oF in 5 days.

ARE SSWs Affected by a Warming Climate?

Study of SSWs in the context of global warming has concentrated on both the frequency of SSWs and on how SSWs will manifest as extreme weather in the future. While more work needs to be done in this area, preliminary findings have been presented. This is a growing area of research.

SSW Extreme weather events superimposed onto a warming climate

Independent of SSWs, the warming climate has increased the amount of water vapor in the atmosphere, which in turn has increased the precipitation potential of extratropical cyclones. In the winter, this has manifested as heavier snowstorms. If we superimpose SSWs on a warming climate, we might not expect more extreme cold but likely heavier snow and ice storms. This would result in more economic and social disruption than in the past.  

frequency OF SSW

SSWs result from complex processes involving interactions between the tropical troposphere and the polar stratosphere. While the process is not fully understood, climate models suggest that the tropical phenomena that forces SSWs will be stronger in a warming climate, resulting in more frequent SSWs.