Polar vortex refers to a large cyclonic air circulation over and near the poles. This is caused by very cold poles and relatively warmer regions in lower latitudes causing great pressure difference. Due to this pressure difference warm air circulates at speeds of 200-400 km per hour and encapsulates a low pressure very cold air mass at poles.The vortex has its base in troposphere and extends to mesosphere.When seen from higher up it may look like an eclipse.The northern pole vortex has two centres while the southern pole vertex has only one centre.
It protects Canada and parts of U.S.A. from exposure to very cold air from poles. But, at times as recently evidenced in winters of 2014 the vortex gets distorted and weakened. Then the temp. falls reaching even upto -80 degree celsius with resultant disruption of life and damage.
It has been claimed recently that climate change and melting of arctic ice has weakening influence on Polar vortex. This is proposed to be caused by decrease in pressure gradient between poles and lower warmer latitudes resulting in weak cover of warm winds and changes in shape of vortex.
