Global Atmospheric Heating and Circulation - Essay Example

Global Atmospheric Heating and Circulation Introduction Atmospheric heating refers to the heating of the earth’s surface and air by the sun. This heating is mostly at the equator where the son is hottest and leads to circulation of air over the earth’s surface. Atmospheric circulation of air refers to the movement of air due to unequal heating by the sun. This movement is normally in large scale but in a relatively smaller scale in the oceans (Biasutti, 2014). Global atmospheric heating and circulation ensures the transfer and distribution of heat from the Tropical regions to the Polar Regions. Atmospheric circulation was maybe vertical or horizontal whereby, Vertical circulation occurs when occurs when air is heated and rises above to be replaced by cooler air from the top. Horizontal circulation occurs when air moves from high-pressure areas where it is denser to low pressure areas where it is less dense. The horizontal winds follow curved trajectories from the rotation of the earth. A good example to explain this is the sea winds. During the day, the earth heats faster than the ocean causing air above the earth to rise vertically and is replaced by air above the sea which travels horizontally towards the earth ("Unit 2: Atmosphere",2015). Each hemisphere has three cells that are Hadley cell, Ferrel cell and Polar cell. A cell is a space in which air circulates through the entire depth of the troposphere ("Global circulation patterns"). The Hadley cells extend from the equator to the south and north hemispheres. The trade winds from the northern and southern hemisphere blow within the Hadley cells. They form the Inter-Tropical Convergence Zone (ITCZ) (Biasutti, 2014).The Ferrell cell are located in the middle. Here air converges at low altitudes and ascends along the boundaries between cool polar air and warm subtropical air giving some regions such as the United Kingdom unstable weather. This cell moves in opposite direction with the Hadley cell and the Polar cell (Biasutti, 2014). The polar cell is normally found in the poles. It is the smallest and the weakest. The cold, dense air that descends at the poles causes high pressure. The Coriolis force that is exerted by the rotation of the earth is strongest at this pole and causes the moving air to deflect Unit 2: Atmosphere. (2015).Thermal heating leads to expansion of air and as a result, it rises from the surface of the earth and is replaced by cool air. This is because warm air is lighter than cool air. As it rises, it carries along with it moisture from the earth’s surface since warm air holds more moisture than cold air. The cooling effect of the air, as it rises, makes it condense to form clouds. The clouds produce heavy rainfall that is normally experienced with the tropics.After losing the moisture through rainfall, the air becomes light and moves to the Polar Regions either to the north or south. In the Polar Regions, the air is cooled to the low temperatures there leading to an increase in its density. This then triggers the horizontal movement of air due to the increased pressures of air in the tropics. Mechanisms that produce high precipitation in the tropics Precipitation refers the falling of any products of water resulting from its condensation. Different mechanisms produce high precipitation in the tropics that include convergence, convection, adiabatic cooling and the collision and coalescence of air containing moisture. Convergence occurs when warm and moist air moving horizontally from the hemispheres collide at the inter-tropical convergence zone (ITCZ) (Met Office, 2014) The forces then causes the air to rise as it cannot be displaced either downwards or side-ways. As the air rises, it cools down due to forming clouds that produce heavy precipitation in the tropical regions. Convection is the heating of the earth by the sun leading to the rise of air upward. The air that rises is replaced by cooler air and the process continues. The rising air carries moisture with it that condenses to form clouds and precipitation occurs. Adiabatic cooling of air occurs as it rises due to lesser pressure. The atmospheric pressure increases with depth of air. As the air is heated, it rises therefore reducing the depth and the atmospheric pressure. This causes cooling and high precipitation occurs (Met Office, 2014). Mechanisms produce high precipitation at temperate latitudes The suns heat over the equator causing the air to expand and rise. The air cools as it rises and forms clouds that produce heavy rains in the tropical dry forests. This then ceases to last, and the air spreads to the north and south poles. The air becomes dense as it cools in these poles therefore causing it to flow over deserts as it picks moisture. It condenses to form clouds that collide to produce abundant precipitation in the template regions. Mechanisms produce low precipitation in the tropics The tropics are warmer due to the suns heat being applied directly over the equator. The warmer the air, the greater its ability to hold moisture. The air only loses this moisture after it interacts with colder air, which is usually at mountains. This interaction causes the exchange of air between the mountains and the tropics leading to increasing the temperature of the air and moisture content. The result is the formation of clouds that are carried away by the wind to the mountain. The clouds hit the mountain leading to precipitation. This blockage of the clouds by the mountain lead to low precipitation on the leeward side of the tropics since all the moisture carried by the wind is shed on the windward side of the mountain (Biasutti, 2014). The rotation of the earth around the sun is maintained throughout the earth’s orbit. The rays of the sun are therefore concentrated at various points leading to the different seasons experienced. The heating of the earth’s surface and atmosphere drives the heating and circulation of the atmosphere influencing patterns of precipitation. The ITCZ point gets the most direct sunrays at any given point in time. This is because of its central location on the earth’s surface making the sun’s rays to be directly focused at this point (Met Office, 2014)This makes the air be warm and rise, holding more moisture. The rising of the air leads to the reduction in pressure and, therefore, the adiabatic effect cools the air. It reaches its dew point and condenses to form clouds that lead to precipitation in the tropics including the forests and savannah. Conclusion Global heating and circulation is important in determining the weather variations in the regions of the world. A thorough understanding of the process can, therefore, help explain the different climatic conditions affecting various parts of the earth. This can help predict weather patterns such as expected high rainfall and prepare before they occur References Biasutti, M., Battisti, D., & Sarachik, E. (2004).Mechanisms Controlling the Annual Cycle of Precipitation in the Tropical Atlantic Sector in an Atmospheric GCM. Journal of Climate, 17, 4708-4723. Met Office (2014) Global circulation patterns: Retrieved March 4, 2015, from http://www.metoffice.gov.uk/learning/learn-about-the-weather/how-weather-works/global-circulation-patterns. Unit 2: Atmosphere (2015). Retrieved March 4, 2015, from . Read More