Air Current Zones

Image from: "Figure 7.5 in The Atmosphere, 8th edition, Lutgens and Tarbuck, 8th edition, 2001."

In the atmosphere of planet Earth, circulating currents of air are divided into latitudinal zones called cells.

The Sun heats the atmosphere at the equator, causing warm air to rise from the surface of the Earth, resulting in a low pressure system equatorially. A current of surface air moves towards the equator from other latitudes to fill the low pressure. Due to the rotation of the Earth and the Coriolis effect, this wind takes an easterly direction at the equator, combining with the motion between the tropics and the equator to create a Northeasterly trade wind in the Northern Hemisphere and a Southeasterly trade wind in the Southern hemisphere. These atmospheric regions are the Hadley cells. Where the trade winds meet is the doldrums, where winds are weak.

At the North and South poles, cold air descends and travels along the surface towards less polar latitudes and in an Easterly direction before rising again at a subpolar latitude. These atmospheric regions are the polar cells.

At mid-latitudes between the polar and Hadley cells, Ferrel cells operate. At subtropical latitudes, air descends, creating a high pressure system. This air then moves near the surface of the Earth towards the subpolar latitudes and takes a Westerly turn. In the Northern hemisphere, Southwesterly winds result, while in the Southern hemisphere, Northwesterlies are formed.

Near the subpolar and subtropical boundaries between the zones there are jet streams.

The exact latitudes of the boundaries between the atmospheric cells vary with the seasons and features on the surface of the Earth, but approximately, the cells divide latitudinally the right angle of each quadrant into three portions by the equator, subtropical, subpolar, and polar, such that the angle of the total circle is divided into twelve sectors. Does this not imply that the dozenal base of numeration provides a natural division for angular measure of this planet Earth?

On other planets, the number of atmospheric zones can be different.

Reference
Atmospheric Circulation: http://www.ux1.eiu.edu/~cfjps/1400/circulation.html