Geography is the study of the Earth and its lands, features, inhabitants, and phenomena. It is a vast topic considering the enormous diverse objects in this world. Apart from land, geography also studies about the seas or oceans, atmosphere, climate, wind etc. It also deals with the living and nonliving things in this world. Geography can be divided into many subcategories; but the major subsidiary fields in geography are human geography and physical geography. Human geography deals largely on the human behavior and interactions with the environment like how space is created, viewed and managed by humans as well as the influence humans have on the space they occupy whereas physical geography examines the natural environment and how the climate, vegetation & life, soil, water, and landforms are produced and interact. The interactions with human geography and physical geography resulted in a third field of geography called environmental geography which combines physical and human geography and looks at the interactions between the environment and humans. This paper mainly concentrates on physical geography and some of its topics such as General circulation of the atmosphere, Land and water contrasts, Trade winds, Atmosphere-Ocean Interactions, El Nino, Tectonism etc.
General circulation of the atmosphere
Atmospheric circulation is the large-scale movement of air through which thermal energy is distributed on the surface of the Earth. When, one part of air is hot up, cool air from other parts will move towards the hot region, in order to keep the balance of atmospheric temperature. Atmospheric circulation varies from month to month and year to year, even though the basic climate structure remains almost constant. However, minor changes can occur regionally and hence it is difficult to predict the weather beyond certain limits because of the changes in wind directions, speed from one moment to the next and from one location to the next.
Climate and general circulation of the atmosphere are related to energy balance and transport processes. The energy balance is balanced when averaged over a year. In other words, “when averaged over a latitude band, incoming radiation is a surplus in the tropics and deficit of radiation is found in the polar regions due the outgoing terrestrial radiation being larger than the absorbed solar radiation” (General Circulation of the Atmosphere, n. d). When energy surplus or deficit occurs in different regions of the globe, atmospheric and oceanic transport processes distribute the energy equally around the earth with the help of atmospheric winds and ocean currents.
Land and water contrasts
Land heats and cools faster and more intensely than water and hence the continental locations have a larger seasonal temperature range than maritime locations. During the day, the land heats more rapidly which result in sea breeze moving from sea to land whereas at night land cools which result in creating a land breeze that blows toward the water from the land. Water is a transparent medium whereas land is opaque. Moreover, water allows sun light to penetrate to depth and hence the surface layers would be cooler compared to an opaque object like land. Land surface will always have more heat energy compared to the water surface. A cooler water surface may contribute to the cooler air above the water surface compared to the land surface.
When radiant energy is absorbed by land, most of the net radiation is used for sensible heat transfer or ground heat transfer, only small amounts are used for latent heat transfer. As sensible heat transfer into the air is the dominant heat transfer, air temperatures increase over the land. Over water, much of the net radiation is used for evaporation. With little energy used for sensible heat transfer, air over water remains cooler than that over land.
The trade winds are found in tropics within the lower portion of the Earth’s atmosphere. It blows mainly from the northeast in the Northern Hemisphere and from the southeast in the Southern Hemisphere. It occurs normally during the winter when the Arctic oscillation is in its warm phase. The trade winds helped ship captains to cross the world’s oceans when the technologies were moderate. In fact the name trade winds were given because of its ability to quickly propel trading ships across the ocean. “In the Northern Hemisphere, the trade winds blow from the northeast and are known as the Northeast Trade Winds; in the Southern Hemisphere, the winds blow from the southeast and are called the Southeast Trade Winds” (Rosenberg, 2010)
Ocean-atmosphere interaction is an important factor in earth’s climate system. Oceans and atmosphere have lot of connections between them. Energy transfer occurs while oceans and the atmosphere constantly interact with each other. Five major ocean-atmosphere oscillations have been recognized currently: “the North Atlantic, the Arctic, the Pacific Decadal, the El Niño-Southern, and the Antarctic Polar Wave. Each of these interactions has profound effects on weather and climate” (Ocean-atmosphere interaction, 2010). Population increase and industrial developments are affecting the Ocean-atmosphere interaction drastically and hence the energy transfer between these entities is not taking place properly at place.
El Ninoor Southern Oscillation is the abnormal warming of surface ocean waters in the eastern tropical Pacific. El Ninois “the see-saw pattern of reversing surface air pressure between the eastern and western tropical Pacific; when the surface pressure is high in the eastern tropical Pacific it is low in the western tropical Pacific, and vice-versa” (El Nino – and What is the Southern Oscillation Anyway?, 2003). Ecuador and Peru are two countries which are affected mostly by the EL Nino. It occurs mostly between January and March and in some years the atmospheric temperature remains high for a prolonged period. Ocean warming beyond the normal limits can impact the ocean life and the fishing industries in Peru and Ecuador badly.
The following illustrations will give better idea about El Nino.Normal Conditions (Non El Nino)
El Nino Conditions
The exact reason for the formation of El Nino is still unknown to the scientists. However, it is assumed that El Nino can cause drastic climate changes and many people believe that El Nino was responsible for the 1993 Mississippi and 1995 California floods, drought conditions in South America, Africa, Australia etc. If El Nino causes problems to some parts of the world, it saves another part of the world. For example, it is believed that El Nino is behind the reduced serious storms such as hurricanes in the North Atlantic.
Tectonism is the faulting or folding or other deformation of the outer layer of a planet. It happens very slowly, on the scale of millions of years. Tectonic activity is caused by heat loss; all the terrestrial planets passed through a molten (or nearly molten) stage early in their development and they have been cooling ever since (Tectonism, n. d) .
Tectonism is common in large and hot planets like Venus, Earth, and Mars. Earth is one of the prominent planets which are undergoing Tectonism from its evolution onwards. Earth is still so hot in its interiors because of its larger size and its inner parts are extremely hot and enormous amount of energy is suppressed at this inner parts. Moreover these inner parts are moving or sliding and its continued movement causes the earth’s surface to deform.
Earth has lot of unique characteristics compared to other planets. Its outer surface or the lithosphere is divided into several rigid plates which can move or slide. Sometimes these plates move toward each other and in some other cases they move away from each other. These uneven movements of plates may result in volcanic eruptions and earthquakes.