Atmospheric circulation may be a very large-scale movement of the air where thermal energy is disseminated on the earth surface. These changes in atmospheric circulation from year to year are due to some factors. Several of these factors are tropical cells, and other pressure systems and mid-latitude depressions.
Global Atmospheric Circulation may be a result of the heating of the Earth by the produced energy from the Sun; nevertheless, this heat may be unevenly distributed transversely on the surface of the earth. Tropical and Equatorial regions receive a large amount of solar energy than the Polar Regions and the mid-latitudes. The tropics receive a large amount of heat radiation than what they end up emitting. On the contrary, the Polar Regions receive less heat radiation than what they release. If the tropics never emitted any heat transfers to the Polar Regions, the tropics would become hotter and consequently, the Polar Regions would maintain its coldness. This latitudinal heat-imbalance may be the reason that causes the circulation of the oceans and the atmosphere. Approximately 60 percent of heat energy is re-distributed about the earth by this atmospheric circulation and the ocean currents re-distribute approximately 40 percent (Vera, 2004).
Heat may be transferred in one way by a single cell of circulation to the poles from the equator the air moves towards the poles from the tropics and vice versa. This single circulation cell model was at first proposed by Hadley, in the 1700's. With the Hadley Cell, the low latitude air moves to the direction of the Equator and heats up. Whilst, the temperature increases the air goes up vertically and move towards the pole in the atmosphere upper. This may be the reason for the cells that control the sub-tropic and the tropics climates. The Ferrell cell is the second form of cell involved with circulation and atmospheric heating. This may be an atmospheric circulation mid-latitude cell. The air moves pole-wards towards the east near the facade and equator-ward at higher levels, in a westerly direction (Vera, 2004). Finally, the third cell linked to atmospheric circulation and heating may be the Polar Cell. With Polar Cell, the heat increases and spreads out in the direction of the poles. The air then sinks, when the air is circulating above the poles and a polar high is formed. At the surface, the air extends out from the polar-high and consequently, the surface winds become easterly in the polar cells (www.biology-forums.com).
The tropical savanna biomes and the tropical dry forest are located at the subtropical and tropical latitudes. Per year, these regions a lot of rain measured in centimeters. Savannas may be the tropical typical description of the “temperate grasslands”. A good number of the savannas may be caused by climatic patterns where there may be a strong season of dryness for a considerable part of the year. Huge tracks of the savanna may also be found in Australia, South America, and India. The annual rainfall of a savanna may be between 50.8 cm to 127 cm of rain annually and may be intense in one season in the same year (Savanna). In these biomes, the rationale that the rainy season comes during the period warmer months in the year may be due to the location of the sun and the humid hot air. At some stage in the warmer months, the hot humid air goes up and off the surface of the earth and collides with cooler air from above and consequently turning into rain. In the warmer months, the warm air may be required create the rain and for this process to occur.
References
Savanna. (n.d).Retrieved on Feb 4, 2013; from, www.blueplanetbiomes.org/savanna.htm
Vera, S., (2004). Weather Basic: Global Atmospheric circulation. Hungarian Meteorological
Service. Retrieved on Feb 4, 2013; from, www.atmosphere.mpg.de/enid/3sj.html
www.biology-forums.com. (2012) Describe global patterns of atmospheric heating and
circulation. What mechanisms. Retrieved on Feb 4, 2013; from,
www.biology
forums.com/index.php?topic=9910.0
