In this episode of the podcast, I have talked about “Polar Vortex” and Professor Darryn Waugh investigation on how polar vortices interact with the rest of the atmosphere, and the ways in which they can impact our weather.
Additional Info:
The strong circumpolar westerlies that define the stratospheric polar vortex maximize at around 60o latitude, from just above the tropopause (~100 hPa) into the mesosphere (above 1 hPa). The stratospheric vortex can also be defined by the coherent region of low geopotential height that is enclosed by the westerlies. The stratospheric polar vortex appears each winter as a consequence of the large-scale temperature gradients between mid-latitudes and the pole. It forms in fall when there is no solar heating in polar regions, strengthens during winter, and then breaks down as sunlight returns to the polar regions in spring, and the high latitude winds become weak easterlies. Every now and then, about every two winters, there is a strong warming of the stratosphere due to warmer air flowing in. Greenland and the North Atlantic, for example, are said to throw the vortex particularly out of balance with their warmth. The polar vortex stumbles — or rather squiggles — and air currents can assert themselves more frequently. This split causes temperatures in the stratosphere to rise by 60 to 80 degrees Celsius within a very short time. To put it more graphically, you can imagine a flying circle of pizza dough that is jerking through the air out of shape. In the worst case, the pizza (the vortex!) loses its shape completely or even splits. Then there is a lot of whirling up there, which also has an effect on the entire Northern Hemisphere: Arctic air provides for icy temperatures. This is exactly what happened on January 5, 2021, and will probably hit us again soon. Forecasters say we can expect the cold snap in mid to late January, and it could last in spurts into February. Again, key word: could.
The chemistry of the Antarctic polar vortex has created severe ozone depletion. The nitric acid in polar stratospheric clouds reacts with chlorofluorocarbons to form chlorine, which catalyzes the photochemical destruction of ozone. Chlorine concentrations build up during the polar winter, and the consequent ozone destruction is greatest when the sunlight returns in spring. These clouds can only form at temperatures below about −80 °C (−112 °F). Accordingly, the seasonal reduction of ozone levels over the Arctic is usually characterized as an "ozone dent", whereas the more severe ozone depletion over the Antarctic is considered an "ozone hole". That said, chemical ozone destruction in the 2011 Arctic polar vortex attained, for the first time, a level clearly identifiable as an Arctic "ozone hole".
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