Global Patterns of Atmospheric Heating and Circulation
Global patterns of atmospheric heating and circulation are explained using the three cell model. There are three cells, namely the Polar cell, the Ferrell cell and the Hadley cell. These cells regulate the heating and circulation behaviors. The Hadley cell which is responsible for the trade winds operates latitudes between the equator and 300. The polar cell is responsible for the easterlies in the polar regions and operates between the 600 and 900 latitudes. The Ferrell Cell operates between the 300 and 600 latitudes. The earth’s rotation is also a factor that affects the global patterns of atmospheric heating and circulation. Heat circulation ensures that thermal energy reaches all the parts of the earth and is responsible for the different climatic characteristics in the different regions of the world (Satoh, 2014).
When the earth surface and its atmosphere are heated, precipitation patterns are influenced. The sun heats the air around the equator. This causes it to expand and rise. As it rises, it grows colder. As the air rises, cloud form. The clouds then produce heavy rain as is characteristic of the tropical environment. Eventually, the air at the equator stops rising and begins to spread towards the north and the south. The air at higher altitudes is dry as the moisture it held previously has fallen as rain. As the air flows to the north and south, it sinks back closer to the surface of the earth due to increase in densities. As it continues to spread it absorbs moisture from the lands, it passes through making deserts out of these lands (Richardson, 2014).
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Temperature and precipitation are plotted on different scales. 10C is seen to be operational to 20mm of rainfall or precipitation. For tropical rain forests receive higher amounts of rainfall. As a result, the scale for precipitation represented for these regions is compressed. In this case, 10 C is equivalent to 200mm of rainfall (Satoh, 2014).
What contrivances yield high rainfall in the tropics?
The Hadley cell is the phenomena used to describe the mechanism that leads to the production of high precipitation in the tropics. Trade wind patterns bring humid and warm air from the two hemispheres. The air meets at the tropical convergence zone. Since the air carries large amounts of moisture, clouds are formed causing high amounts of precipitation. The Hadley cell is the cycling caused by cloudy and rainy weather around the equator regions.
What mechanisms produce high precipitation at temperate latitude?
In temperate regions, as air increases in mass and starts to rise, moisture is picked up from the desert regions in lower altitudes. The air then condenses as it continues to rise, forming clouds that produce abundant precipitation in temperate regions.
What mechanisms yield little rainfall in the tropics?
Temperature is greatly dependent on the temperature in the air. When the air temperature is high, it holds larger amounts of moisture and vice versa. The tropics are warm and hold large amounts of moisture but cannot lose it until they interact with cold winds. As a result, the tropics receive low amounts of rainfall unless they interact with cold winds from the mountains. Low precipitation can also occur as a result of the warm moist winds being blocked by the cold winds in the mountain regions. The cold air from the mountain regions forces precipitation to occur on the mountain side leaving the other tropical regions dry (Satoh, 2014).
Extremely Periodic Precipitation in The Tropical Dry Forest and Tropical Savanna Biomes
The global pressure system has a significant influence on the precipitation pattern of various regions in the globe. The biomes of the tropical dry forests and savannahs match their climatic regions in characteristic. The tropical dry forests are located north and south of the equator. As a result, these forests experience more variations in weather and climate than the tropical rain forests. Tropical dry forests experience both wet and dry seasons, unlike rainforests that have constant rainfall in large quantities. Just like the tropical dry forests, the tropical savannahs also experience both rainy and dry season. Instead of trees, however, the regions majorly comprise of grasslands (Richardson, 2014).
There is a region of the earth that receives the most direct sunlight at any given time. This region is known as the Inter-Tropical Convergence Zone (ITCZ). The ITCZ region receives a lot of sunlight and heat causing the air to increase in mass and to rise. The pressure in the air also drops. A characteristic of the ITCZ region is low pressure. As discussed, warm air can hold more moisture than cold air. As the air in the ITCZ rises, it becomes colder. The moist air then begins to condense forming clouds that cause the high levels of precipitation in the region.
The ITCZ is therefore greatly responsible for the wet seasons in the tropical regions. The tropics receive high amounts of rainfall in the summer when the sun is directly above the region causing hot and humid air. Because the ITCZ is located in the areas receiving direct sunlight, in the summer it is located in the tropics. During these warm months, the hot moist air rises, colliding with the colder air which leads to condensation and eventually, precipitation. As the ITCZ moves, it affects the precipitation patterns (Richardson, 2014).
In the areas where the sun is not directly overhead, the pressure in the air remains high. As a result, the air cannot rise, and clouds are not formed. These areas do not produce rain. These areas are referred to as Doldrums and are responsible for the dry seasons in the tropical dry forests and Savannahs. The doldrums are located south and north of the ITCZ and move seasonally parallel (Satoh, 2014).
Additionally, because of their geographical locations, the dry, tropical forests are under the ITCZ for longer periods of time than the savannahs. The savannahs are located in the northern hemisphere, in the north of the tropical dry forests. The rain in the savannah regions is not only seasonal but in lower quantities than the wet tropical regions. During the low-sun, the regions experience dry seasons. As a result, the geographical location is also a major contributing factor to the amount of precipitation in the Savannah and the dry forests. Other factors that affect rainfall in these regions include shadows as well as ocean currents carrying with them moisture. These factors affect dry tropical rain forests that are further away from the equator. The tropical rain forests are located along the equator and therefore experience rainfall in high amount throughout the year (Satoh, 2014).
References
Richardson, D. (2014, February 1). General Circulation Models. Retrieved January 1, 2015, from http://www.aip.org/history/climate/GCM.htm
Satoh, M. (2014). Atmospheric circulation dynamics and general circulation models . Berlin: Springer.
