Polar vortex

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    Chilly weather in Asia is due to the Polar vortex that brought extreme cold to the US recently.

    About  Polar vortex

    • The term “vortex” refers to the counter-clockwise flow of air that helps keep the colder air near the Poles. 
    • The polar vortex is a large area of low pressure and cold air surrounding both of the Earth’s poles. 
    • It always exists near the poles, but weakens in summer and strengthens in winter. 
    • Causes: The polar vortex is held in place by the Earth’s rotation and temperature differences between the Arctic and mid-latitudes. 
      • When those variations in temperatures grow, the polar vortex can shift south. 
        • This happens naturally, but scientists think that as the planet warms, shifts in the polar vortex are likely to become more frequent and pronounced.
    • Impacts: When the Arctic polar vortex is especially strong and stable, it encourages the polar jet stream, down in the troposphere, to shift northward. 
      •  When the vortex weakens, shifts, or splits (right globe), the polar jet stream often becomes extremely wavy, allowing warm air to flood into the Arctic and polar air to sink down into the mid-latitudes. 

    Image Courtesy: NOAA