Air at either pole moves in large-scale and persistent cyclones called the polar vortices. These vortices extend from the mid and upper-level troposphere in to the stratosphere. They enclose the polar highs, the regions of high atmospheric pressure around either pole, and lie in the wake of the polar fronts.Continue Reading
The vortices alternate in strength depending on the season in each hemisphere. They are generally larger and stronger in winter than they are in summer. Their size depends on the difference in temperature between the equator and the poles.
The temperature at the equator remains almost constant all year round, while the temperature at either pole depends on the Earth’s rotational tilt relative to the sun, which gives rise to seasons. In winter, the respective pole tilts away from the sun, leading to lower temperature. This causes the temperature difference between the pole and the equator to widen, leading to stronger and larger polar vortices.
The size of the polar vortices rarely exceeds 1,000 kilometers in diameter. Their rotational direction is flipped at either pole, due to the Coriolis force. The northern hemisphere polar vortex rotates counterclockwise, while the southern hemisphere vortex rotates clockwise. The foci of the northern polar vortex are often at Baffin Island Canada and Siberia.Learn more about Atmosphere