The Tricellular Model is a simplified explanation of how atmospheric circulation patterns give rise to distinct weather and climatic conditions at various latitudes. It is based upon the premise of differential heating of the Earth's surface. The basic elements of this theory include:
- The intense heating at the Equator resulting in low pressure and the development of a band of clouds in an area called the Doldrums , leading to the development of the Inter Tropical Convergence Zone (ITCZ)
- Air rising at the this zone begins to drift to higher latitudes where it is cooler in an effort to equalize temperature variance but cools and becomes denser in the process, forcing it to sink at around 30 degreees North and South of the Equator.
- The first loop is completed as the sinking air then moves laterally back towards the Equator, owing to pressure gradient differences (air moving form higher to lower pressure areas). this is called the Hadley Cell.
- Some sunken air continues along the Earth's surface northwards towards the Poles until around 60 degrees N and S where it meets even colder Polar air migrating south (in the Northern Hemiphere). Temperature differences causes the warmer air coming from the tropics to rise over this cold air at a meeting known a front. Some of this rising air begins to head back towards the Equator until it cools and sinks at around 30 degrees N and S, closing the second loop called the Ferrell Cell.
- Meanwhile, cold Polar air moving laterally across the land towards the lower latitudes warms up and rises at the pole-ward boundary of the Ferrell Cell at 60 degrees. At a certain altitude this warmer air begins to migrate to the higher latitudes again until it cools and sinks at the Poles, thus completing the Polar Cell.
Click to view the You Tube video that explains the Tricellular Model.
Another crucial mechanism by which heat is redistributed around the Earth is by ocean circulation or ocean currents. Click on the arrow to view the slides on the Prezi presentation below based on the Thermohaline conveyor and its effect on Earth's climate.
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