A polar vortex (also known as a polar cyclone, polar low, or a circumpolar whirl ) is a persistent, large-scale cyclone located near either of a planet’s geographical poles. On Earth, the polar vortices are located in the middle and upper troposphere and the stratosphere.
They surround the polar highs and lie in the wake of the polar front. These cold-core low-pressure areas strengthen in the winter and weaken in the summer due to their reliance upon the temperature differential between the equator and the poles. They usually span less than 1,000 kilometers (620 miles) in which the air is circulating in a counter-clockwise fashion (in the northern hemisphere). As with other cyclones, their rotation is caused by the Coriolis effect.