CAMBRIDGE AS GEOGRAPHY REVISION: ATMOSPHERE AND WEATHER - 2.2 THE GLOBAL ENERGY BUDGETS
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The document discusses key concepts related to the atmosphere and weather, including terms such as anticyclones, the Coriolis effect, and insolation. It explains the energy budget of the earth, including the greenhouse effect and variations in temperature and pressure across latitudes. The document also covers ocean currents and their influence on global temperature patterns, alongside the general circulation model of atmospheric movement.
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CAMBRIDGE AS GEOGRAPHY REVISION: ATMOSPHERE AND WEATHER - 2.2 THE GLOBAL ENERGY BUDGETS
- 2. KEYTERMSANDDEFINITIONS Anticyclone is a high-pressure system. Aspect is the direction in which a slope faces. In the northern hemisphere a slope with a southerly aspect receives more sunshine than other slopes and is therefore better suited for growing crops. Continentality is a climate characteristic of a continental area (i.e. a long way from the sea), having very hot summers, very cold winters and low rainfall. Coriolis effect is an effect that causes any body that moves freely with respect to the rotating Earth to veer to the right in the northern hemisphere and to the left in the southern hemisphere.
- 3. KEYTERMSANDDEFINITIONS El Niño is an anomalous warming of surface waters in the eastern equatorial Pacific Ocean linked with climatic disturbances throughout the world. Frontal rainfall is the rain formed when warm air is forced to rise over denser cold air when two different air masses meet at a front.
- 4. KEYTERMSANDDEFINITIONS General Circulation Model is a model of the general circulation of atmosphere based on convection. In the most simple case, cells of warm air rise at the equator and descend at the poles. In fact, there are three such cells in each hemisphere. The first two of these consist of air that rises at the equator and sinks at the tropics; the second two exist at the mid-latitudes where the air from the sub-tropics flows towards the cold air masses of the third pair of cells circulating from the two polar regions.
- 6. KEYTERMSANDDEFINITIONS Insolation is the amount of incoming solar radiation (heat energy from the Sun) that reaches the Earth’s surface. Insolation varies with season and latitude, being greatest at the equator and least at the poles. Jet streams are narrow, fast-flowing currents of air found near the tropopause. The major jet streams are meandering westerly winds. The main jet streams in each hemisphere are the polar jets, which are associated with the polar front, at around 8–11 km above sea level, and the higher and weaker subtropical jets at around 11–16 km height.
- 7. KEYTERMSANDDEFINITIONS Pressure (air) refers to the pressure at any point on the Earth’s surface that is due to the weight of the air above it; it decreases as altitude increases. At sea level the average pressure is 1013 millibars. Areas of relatively high pressure are called anticyclones; areas of low pressure are called depressions. Prevailing wind is the direction from which the wind most commonly blows in a locality. In north-western Europe, for example, the prevailing wind is south-westerly, blowing from the Atlantic Ocean in the south west and bringing moist conditions.
- 9. KEYTERMSANDDEFINITIONS Thermohaline circulation (THC) is also known as the ocean conveyor belt, and is a deep water ocean convection current that moves cold water at depth from polar areas towards the equator, while at the same time transferring warm waters from tropical and sub-tropical areas to the mid latitudes. The North Atlantic Drift is part of the thermohaline circulation.
- 10. TOPICSUMMARY The atmosphere is an open energy system receiving energy from both Sun and Earth. Incoming solar radiation is referred to as insolation. Radiation is the emission of electromagnetic waves such as X-ray, short- and long-wave. Convection is the transfer of heat by the movement of a gas or liquid. Conduction is the transfer of heat by contact. Very hot bodies such as the Sun emit short-wave radiation, whereas cold bodies such as the Earth emit long-wave radiation.
- 11. TOPICSUMMARY The atmosphere is largely heated from below. Most of the incoming short-wave radiation is let through, but the outgoing long-wave radiation is trapped by CO2. This is known as the greenhouse effect. There are important large-scale east–west temperature zones. These patterns reflect the general decrease of insolation from the equator to the poles. Sea-level pressure conditions show marked differences between the hemispheres. In the northern hemisphere (NH) there are greater seasonal contrasts, whereas in the southern hemisphere (SH) much simpler average conditions exist. On a global scale, latitude is the most important factor determining temperature.
- 12. TOPICSUMMARY The specific heat capacity is the amount of heat needed to raise the temperature of a body by 1 °C. There are important differences between the heating and cooling of water. The effect of ocean currents on temperatures depends upon whether the current is cold or warm. Vertical air motion is important on a local scale, whereas horizontal motion (wind) is important at many scales, from small-scale eddies to global wind systems. The driving force is the pressure gradient, i.e. the difference in pressure between any two points. Air blows from high pressure to low pressure. The general circulation model is a model that links low latitude and high latitude circulation of winds.
- 14. ADDITIONALWORK 1. Describe and explain seasonal variations in surface pressure belts. 2. Outline the main factors that affect global temperature patterns. 3. Describe and explain the factors affecting air movement. 4. Briefly explain the general circulation model.
- 15. SUGGESTEDWEBSITES http://earthguide.ucsd.edu/earthguide/diagrams/energybalance/ind ex.html for an animated diagram of the global energy budget. www.ace.mmu.ac.uk/resources/gcc/1-2-4.html for the energy budget of the atmosphere. www.cgd.ucar.edu/cas/Trenberth/trenberth.papers/TrenberthScienc ePerspectives-1.pdf for an article on recent changes to the Earth’s energy budget. http://openlearn.open.ac.uk/mod/oucontent/view.php?id=397952&s ection=1.1.4 provides an overview of the Earth’s energy budget.