Climate ZonesThe worldwide system of winds, which transports warm and cold air very great distances away from the source regions, influences significantly the climates of the world. This worldwide wind system is called the general circulation of the atmosphere, and it gives rise to the Earth's climate zones. Although the changing of the seasons and the positions of large oceans and continental landmasses affect these climate zones, they provide a general approximation to the different types of climate seen on Earth. The Earth's general circulation arises as a result of the temperature difference between the equator and the poles. This latitudinal temperature gradient produces atmospheric pressure differences which generate winds that transport the equatorial heat north and south to higher latitudes. The Earth's rotation however, deflects the northerly and southerly components of this atmospheric circulation, by means of the Coriolis force, clockwise in the Northern Hemisphere and anticlockwise in the Southern Hemisphere. Thus, global winds tend to be more easterly and westerly rather than northerly and southerly. A number of climate zones or belts can be traced between the equator and the pole in each hemisphere. Centred roughly on the equator is the tropical or equatorial zone, a belt of relatively low atmospheric pressure and heavy rainfall associated with thunderstorms, due to the rising air. Historically, the zone became known to sailors as the Doldrums because, with the very light winds, ships would often spend many weeks stuck at sea. |
