The circulation of air near the tropics is called Hadley cells named after George Hadley, the scientist. Between 23.5 degrees latitude south and north, i.e., in the tropics the air rises having been heated. As it meets the tropopause it fans out while at about thirty degrees south and north a great part of this air drops back towards the ground. When it drops it removes air while to complete the cycle the removed air returns back towards the equator.
From thirty to sixty degrees north and south similar circulation known as Ferrel cells occur while in the polar regions polar Hadley cells flow.
But a straight north-south direction these air-flows do not follow and that is interesting enough. What is known as Coriolis effect is due to the earth's rotation. In the Northern and the Southern Hemisphere any fluid or object that moves freely seems to turn to the left or right respectively to the direction of motion. Since Gustavo-Gaspard de Coriolis first identified it in 1835 the Curiolis effect is named after him.
To an area of low pressure air tends to flow but deflection of air in this case is due to the Coriolis effect. By creating a circular movement, or a cyclonic flow an equilibrium it establishes ultimately. In the Northern Hemisphere air flows in a counter-clockwise direction in low pressure areas while in the Southern Hemisphere the direction is clockwise. But around high pressure areas the air flow is just the reverse to it.
Had there been no rotation of the earth the pressure would have been equalized fast since air flow of air would be quick and along straight lines. At the equator the Coriolis effect is precisely zero. For this reason, on the equator cyclones hardly occur or travel to the same. Most logically at the poles Coriolic effect reaches its maximum.
