By all the news accumulating around Polar vortex, you must be thinking that it is something which is responsible for the teeth-cluttering, mind-boggling, and water-freezing cold by which Midwest and Northeast America are suffering currently.
The atmospheric phenomenon of Polar Vortex, however, is no ice-monster that takes a round of the earth once in a while and freezes everything. It, in fact, is something that saves the earth from the extremely cold winds.
By definition, Polar Vortex is a system of high-level winds, known as jet-stream, surrounding the cold air of Arctic. These winds form a boundary, thus preventing the northern hemisphere from freezing.
One such Polar Vortex is also there, surrounding the freezing air of Antarctica and protecting the Southern Hemisphere.
See the recent image released by NASA, explaining the Polar Vortex. The colours represent the regional variation in the temperature.
In winters, when the North Pole and the South Pole get really cold (temperature as low as minus 79 degree Celsius), there emerges a great contrast in the temperature and pressure of the regions far away from the Poles. This cause the formation of spinning cyclones. The cyclones containing the cold winds move from the Troposphere to Stratosphere, and further beyond to Mesosphere.
The Polar Vortex is more intense in the Sothern Hemisphere and is north, it swirls around Canada's Baffin Island and a point in northeast Siberia. It also encloses North America, Greenland, Europe and Asia.
Now, you must be wondering that how and why news reports are holding the Polar Vortex responsible for the chilling winters in America right now.
It is because the boundaries of these protective winds are quite irregular and once in a while, they break down. Consequently, the powerful and chilly winds hit us, taking the temperature to extreme low.