“Polar Vortex and its Effects”

The mild winters in the northern regions of the hemisphere which are particularly south of the Arctic circle have led to the decrease in the energy consumption by the people.

What is Polar Vortex?

• 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.
• The polar vortex extends from the tropopause (the dividing line between the stratosphere and troposphere) through the stratosphere and into the mesosphere (above 50 km). Low values of ozone and cold temperatures are associated with the air inside the vortex.
• The term "vortex" refers to the counter-clockwise flow of air that helps keep the colder air near the Poles.
• Many times during winter in the northern hemisphere, the polar vortex will expand, sending cold air southward with the jet stream.
• Often when the polar vortex is strong, temperatures are mild in the mid-latitudes across the Eastern US and Northern Eurasia; and when the vortex is weak, temperatures tend to be cold across the Eastern US and northern Europe and Asia.

What is Strong Polar Vortex?                     

• The strong polar vortex is the more common state of the vortex which creates strong low pressure in the Arctic region.
• Because of the pressure difference between the Arctic and mid-latitudes, air flows into low pressure and this confines the cold air to high latitudes closer to the Arctic.
• Therefore it is often mild across the Eastern US, Europe and East Asia during winters when the polar vortex is strong.
• During strong polar vortex, the airflow is fast and in a direction from west to east.
• Low pressure in the Arctic region is referred to as the positive phase of the Arctic Oscillation (AO), which is also known as the North Atlantic Oscillation (NAO).

Weak polar vortex                                 

• Occasionally, the polar vortex is disrupted and weakens, due to wave energy propagating upward from the lower atmosphere.
• When this happens, the stratosphere warms sharply in an event known as sudden stratospheric warming, in just a few days, miles above the Earth’s surface.
• The warming weakens the polar vortex, shifting its location somewhat south of the pole or, in some instances, ‘splitting’ the vortex up into ‘sister vortices’.
• The split higher up in the atmosphere can give rise to both, sudden and delayed effects, much of which involves declining temperatures and extreme winter weather in the eastern US along with northern and western Europe.
  

Is global warming responsible for the weakening of polar vortex?

• It is being hypothesised that the weakening of polar vortex is a result of global warming. Warming leads to melting of polar ice during summer months. The melting ice warms the Arctic Ocean and the heat is radiated back to the atmosphere.
• In the absence of global warming, there used to be a substantial difference between the temperatures at the poles and in the mid-latitudes.
• As more and more ice melts in the coming years, more such events can be expected. But very little research on this is available as ice melting is a recent phenomenon.
• IPCC (Intergovernmental Panel on Climate Change) report says that the polar vortex is expected to become smaller in the coming years.