“The Global Circulation can be described as the worldwidesystem of winds where the necessary transport of heat from tropical to polarlatitudes is accomplished,” (metoffice.gov.uk).These atmospheric heatingand circulation patterns are controlled by three cells of air flow between the Earth’spoles and the equator. These three cells are the Polar Cell, Ferrel Cell, andthe Hadley Cell. The polar celloriginates at lower latitudes, its warm air rises and move to higher altitudes,where the cooled air will descend due to the high pressure. The Ferrel cellswinds are complicated; it is a boomerang flow of air at high altitudes towardsthe tropics that join sinking air at lower latitudes near the Hadley cell.
Whenhumid and warm air from both hemispheres brought by trade winds joins in theIntertropical Convergence Zone the low-pressure areas move up to 30 degreeslatitude until it descends in high-pressure areas which then causes convectionin the atmosphere resulting in high precipitation in the tropics. This cyclingof winds is called Hadley cell.What mechanisms produce high precipitation in the tropics?High precipitation occurs in zones where there is thecontinual and rapid ascension of air masses. In the tropics, there is aconvergence of trade winds in the ITCZ which ascend due to the low pressure.Also, the evaporation rates are high. Thus, moist air rises as it cools. On theother hand, warm air is able to condense and hold more water leading to highprecipitation (Schumacher, 2003).
Whatmechanisms produce high precipitation at temperate latitude?It isat the temperate latitudes where the convergence of moist subtropical air andcold polar air causes forced condensation. Also, the region receives the mostintense sun radiation per unit area, thus, increased evaporation. Besides,the low-pressure system causes a rise in more air for precipitation. Cloudsbuild up due to the rising air that picks up moisture from the dry land atlower latitudes (Schumacher, 2003).Whatmechanisms produce low precipitation in the tropics?Intropical zone, low precipitation can occur as a result of warm, prevailingwinds being impeded by mountain ranges since the mountains force the moisturein those winds to come down on the mountainside that is blocking the winds asrain leaving the other side with low precipitation. When air rises moisture ispicked up from dry regions at lower latitudes it causes clouds to build upbringing a high amount of precipitation since precipitation is largely involvedwith temperature that means the lower the temperature the less moisture it canhold because it is very warm near the tropics the air moisture will have tointeract with colder weather in order to lose it.
Therefore causing theprecipitation to stay low. This levitation is known as rain shadow. The tropicaldry forests and savanna biomes are located in the Inter-Tropical Convergence Zone(ITCZ) where high precipitation is observed, due to the amount of sunlight nearthe equator. Tropical savannas are covered with grassland and a few scatteredtrees while tropical dry forests have more trees that are green during rainyseasons and withered in dry seasons.
The two biomes are usually warm throughoutthe year as the wind movement cause shifting of Inter Tropical Convergence Zone(ITCZ). The sunlight causes air to rise which causes the pressure to drop, andmakes the warm low-pressure air to rise and condenses into clouds highprecipitation occurs. The ITCZ shifts between Northern and Southern hemispherescausing seasonal variations in pressure and hence precipitation. In the dryseason, however, the ITCZ moves to the warm and dry trade winds flow to theother side of the equator.