week 2 notes
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This 10 page Class Notes was uploaded by Paige Notetaker on Thursday January 14, 2016. The Class Notes belongs to GEOG 1111 at University of Georgia taught by Hopkins in Fall 2015. Since its upload, it has received 215 views. For similar materials see Intro to Physical Geography in Geography at University of Georgia.
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Date Created: 01/14/16
Geography notes- Lecture 5 RADIATION/ENERGY BALANCE ENERGY is the ability or capacity to do work on some form of matter. Potential energy is the energy of an object prior to it being released as free energy, commonly called the energy at rest. Kinetic energy is the free energy of motion or action. Heat energy is the kinetic energy generated by all the motion of molecules. It is measured as the sum total of all molecular motion of an object. Radiant energy is the energy transferred as electromagnetic waves by all objects with a Tº > 0ºK (-273ºC or absolute zero). * Energy follows the Laws of Thermodynamics: First Law of Thermodynamics: In all physical & chemical changes energy is neither created nor destroyed, but it may be converted from one form to another. (Law of Conservation of Energy) Second Law of Thermodynamics: When energy is changed from one form to another, some of the useful energy is always degraded to lower-quality, more dispersed, less useful energy. Properties of Radiant Energy or Radiation: * Light, heat, radio, X-rays, etc. are all part of the electromagnetic spectrum or radiation. * All objects with a Tº > 0ºK emit radiation with the amount of energy emitted dependent on the Tº of the object. * Hotter objects emit more total energy than cooler objects and the hotter the emitting body, the shorter the wavelength * The Sun's maximum energy is radiated at .5 micrometers & its Tº = 6000º K (5700° C or 10,300° F). This Solar Radiation is also called Shortwave (SW) Radiation. * The Earth's maximum energy is radiated at 10 micrometers & its Tº = 300ºK (15° C or 59° F). This Terrestrial Radiation is also called Longwave (LW) Radiation. SOLAR RADIATION: * Shortwave (SW) radiation is designated as those wavelengths of the electromagnetic spectrum which are ~1 micron and smaller. * Visible light is in the wavelengths from .4 microns (violet) to .7 microns (red). The Sun emits wavelengths from about ~.2 to 8 micrometers. * As it passes through Earth’s atmosphere, it may be scattered, reﬂected, or absorbed, or reach the surface. This affect the transfer of this radiant energy to other forms, both within the atmosphere and at the ground surface. Scattering is the process of incoming solar radiation (SW) being redirected from its original path by particles in the atmosphere * Gas molecules scatter blue & violet SW better than longer waves waves such as red or orange which affects the sky color we see. * Some of this is redirected back into space and that energy is lost to the Earth. Reﬂection is the process whereby a surface turns back a portion of the radiation that strikes it. It essentially “bounces-off” the object. * Radiation follows the Law of Reﬂection which states that the angle of incidence (incoming) = the angle of reﬂection (outgoing). Albedo is the term to describe the % of radiation reﬂected off a surface compared to the incident radiation striking it. * TheAlbedo of a surface/object will vary dependent on its composition, color, roughness and the sun angle. * Approximately 31% of all incoming SW from the Sun is reﬂected back to space, so the average planetaryAlbedo is 31. and this again this is lost energy. * Other examples: thick clouds 70-80, thin clouds 30-50, fresh snow 80-85, old snow 50-60, forest 5-10, grass 20-25, dry earth 15-25, water 3-5 (high sun altitude) to 50-80 (low sun altitude) Absorption is the process whereby some of the energy of incoming SW radiation is transferred into the object being struck. This energy is transferred as (changed to) heat energy, as it increases the internal molecular motion of the object/substance. * Since heat energy is increasing in the object, so will the temperature of the substance/ object increase. * Substances in the atmosphere with high absorptive characteristics for SW include O2, O3, & H2O, however, overall the atmosphere is a poor absorber of incoming SW. Absorption is the opposite of reﬂection. * So, of the 100% of incoming radiation from the Sun that hits the top of the atmosphere: ** ~45% reaches the Earth’s surface and is absorbed ** ~24% is absorbed by the atmosphere (clouds, gases, dust) ** ~31% is loss to space by reﬂection & scattering TERRESTRIALRADIATION: * Longwave (LW) radiation is designated as those wavelengths of the electromagnetic spectrum which are ~1 micron and larger. * Earth emits radiant energy at wavelengths generally in the 1-30 micrometers range or in the infrared portion of the spectrum. * It can be scattered, reﬂected and absorbed, and CO & H 2 are 2 very good absorbers of these wavelengths. * Water vapor absorbs 5X what all the other gases do * Some of the LW radiation emitted by the Earth is thus “trapped” by these and other gasses in the atmosphere. This process is commonly called the Greenhouse Effect and what heats the lower atmosphere and thus the Earth. * This Greenhouse Effect causes the atmosphere to be heated from the ground up as the LW radiation is "bounced" back & forth between the atmosphere (clouds, dust, and Greenhouse Gasses) & the ground. * This helps to keep the Earth's average Tº some 35º C warmer than it would be otherwise. with Greenhouse Gasses without them 15ºC (59ºF) -18ºC (0ºF) *The actual process of warming the atmosphere is a little more complicated than the simple Greenhouse Effect. The basic Greenhouse Effect does not incorporate the effect of air moving vertically (convection) or horizontally (advection or wind) and thus a more accurate term is the Atmospheric Effect. *The process of Global Warming is basically an enhanced Greenhouse Effect, or what I like to call, the Greenhouse Effect on “Overload” Geography notes- lecture 6 HEAT energy is measured as the total kinetic energy of all the atoms & molecules of an object or substance. (Remember temperature is the average kinetic energy.) Acalorie is the term which refers to the heat required to raise the Tº of 1 gram of water by 1ºC. Heat is often measured in calorie units. Heat Transfer is by 3 primary mechanisms: Conduction, Convection, Radiation Conduction is the process of transferring heat through matter molecule by molecule. This is done by direct contact & transfer from one molecule to the next. EX: Heat one end of a metal rod and some of that energy will be passed molecule by molecule to the other end. * Some substances will more easily transfer heat via conduction than others, solids (most metals) for example, and these are known as conductors of heat. Substances which are poor transferors of heat (air for example) are known as insulators. * As heat energy ﬂows thru a substance, it will ﬂow from an area of higher Tº toward an area of lower Tº. * An important mechanism for heating the Earth’s surface (the ground) and the air in contact with the surface, but not high into the atmosphere. Convection is the process of transferring heat through matter by mass movement of material within the substance.Aportion of the material is heated and in mass moves thru the substance. EX: As water in a pan is heated on a stove, a small portion at the bottom of the pan is heated and in mass moves toward the top of the pan. * This is the most important mechanism of heat transfer in the atmosphere. This transfer of energy from the surface up into the atmosphere is comprised of 2 processes or methods, Sensible Heat Flux & Latent Heat Flux * Sensible heat ﬂux is the process of transferring energy using the dry components/molecules of the air (O2, CO2, N2, etc.). * Latent heat ﬂux is the process of transferring energy using water vapor molecules or the processes of evaporation and condensation. ** Latent heat is the heat energy added to a substance without changing the temperature of the substance, BUT changing the state of the substance (solid to liquid to gas, etc.) EX: It takes a speciﬁc amount of calories (energy) to raise the temperature of a molecule of substance, but then an additional amount to change it from a solid to a liquid, or a liquid to a gas. The molecules will store this energy and then release it when changing from a gas to a liquid, or a liquid to a solid. Radiation is the wavelike transfer of energy. EX: the use of UV radiation, visible light, infrared radiation, etc. EARTH’S HEAT BUDGET refers to how the Earth system balances the energy of incoming (solar or SW) radiation with outgoing (terrestrial or LW) radiation. It also encompasses all the various pathways and types of energy involved within the Earth system. * If there was no balance of incoming and outgoing energy, then Earth would be too cold or too hot. Q* = net radiation = (SW↓ - SW↑) + (LW↓ - LW↑) = incoming ( ↓ ) minus outgoing ( ↑ ) Q* = Q G H + LE ground sensible latent heat heat heat ﬂux ﬂux ﬂux (conduction) (dry convection) (evaporation/condensation) * This balance involves both a temporal (over time) and spatial (over an area/space) component. It will vary with time periods (daily, monthly, annually, etc.) and in different areas of the Earth. ** day vs. night, summer vs. winter ** tropics vs. polar regions * There exists a horizontal (spatial) imbalance of energy over the Earth’s surface which leads to a surplus in the tropics and a deﬁcit at the poles. The Earth system prefers a status of equilibrium, so it tries to balance this imbalance. * Energy is redistributed by moving excess energy from one place to another across the Earth’s surface. Fluids are the most efﬁcient method to do this and the two primary ﬂuids on the Earth are water and air. Energy is thus moved via: Atmospheric circulation (winds) & Oceanic circulation (currents) * Most heat transfer takes place between 30º - 50º latitude N & S (the Mid-Latitudes) & a large portion of the stormy weather we receive in the U.S. is attributable to this transfer of heat energy. * Q LE is most important in the humid tropics. * Q SH is most important in the arid tropics. Geography notes- Lecture 7 TEMPERATURE (T°): is measured as the average kinetic energy of the atoms and molecules of an object or substance. (Remember heat is the total kinetic energy.) * When the atoms of a substance or object are moving faster this means greater kinetic energy, which means the substance will have a higher Tº. * Tº is NOT heat such that the amount of HEAT energy in one object or substance may be different than another, but they have the same temperature. EX: An 8 oz. glass of water and a ﬁlled bath tub can have the same Tº, but will not have the same amount of heat energy because of different volumes. ** T° Scales: Celsius Fahrenheit Kelvin freezing pt of water 0° 32° 273° boiling pt of water 100° 212° 373° range 100° 180° 100° * 0°K = no molecular motion or absolute zero which = -273°C = -459° F * C° = (F° - 32°) x 5/9 F° = (C° x 9/5) + 32° K = C + 273 or C = K - 273 Isotherm: refers to a line on a map or chart which connects points of equal temperature Factors which Control T°s at the Earth's Surface Receipt of Solar Radiation refers to the amount of solar radiation a location receives. This is determined by the locations latitude. On an annual basis, lower latitudes (closer to 0º, the Equator) receive more solar radiation than higher latitudes. This is the primary control of temperatures at the Earth’s surface. Differential Heating of Land and Water Surfaces: ** Land surfaces cool and warm more quickly than water surfaces, and to lower and higher temperatures because: * Water is more transparent (SW can pass thru it), while land is opaque (thus SW does not pass thru it). Thus the solar energy striking the land only needs to transfer energy to the top portion of the ground, but it must try to ‘heat-up’a greater volume of water. * The speciﬁc heat of water is 3X greater than land. Speciﬁc heat is the heat needed to raise 1 gm of a substance 1 degree C. * Evaporation from water is greater than land, so energy is used to evaporate the water and not just raise the temperature * Water turbulence & movement causes water that has been heated to be replaced by cooler water that has to be heated. This movement will be both horizontal & vertical. SO, it takes more solar energy (sunlight) to heat up water than it does the same amount of land * Water thus has a moderating inﬂuence on T° such that average monthly T°s of a location near a large water body will not vary as much between summer and winter compared to a location far away from an ocean. * Inland locations show greater T° variation between winter and summer. This is the idea of continentality. Geographic Setting & Position refers to the temperature differences brought about by a location being on one side of a continent versus the other. * This is related to a locations relationship to wind patterns, and whether that wind is coming off a large water body or a large land surface. This is the idea of windward vs. leeward side of a continent. * Windward refers to the side/direction the wind is coming from, and Leeward refers to the side/direction the wind is going toward. * For NorthAmerica Windward is the West Coast (and thus the wind is coming off a water surface) and Leeward is the East Coast (and thus the wind is coming off a land surface). Ocean Currents * Will inﬂuence air temperatures of both the ocean area and adjoining land area where the current is located. * Warm currents will help keep the temperature higher than it would be without the current. This is especially true in winter. EX: Gulf Stream helps keep the British Isles a little warmer than they would be without it. * Cold currents will help keep the temperature lower than it would be without the current. This is especially true in summer. EX: California Current helps keep the U.S. west coast a little cooler than it would be without the current. * Ocean current patterns will also inﬂuence precipitation patterns. Elevation inﬂuences Tº simply because within the troposphere as elevation/altitude increases, Tº normally decreases. * Locations at higher elevations usually have lower average annual temperatures compared to lower locations Cloud Cover & Albedo affect surface temperatures by controlling the levels of solar and terrestrial radiation at the Earth’s surface. * Clouds trap-in terrestrial radiation keeping the surface warmer (Greenhouse Effect), but they will also reﬂect solar radiation coming in causing the surface to be cooler. Thus: cloudy day vs clear day; cloudy night vs clear night * Acloudy day is usually cooler than a clear day * Acloudy night is usually warmer than a clear night Worldwide T° Patterns * The variations in temperature seen across the Earth’s surface are controlled by the above factors, with one of the key factors being the proportion of land to water over the Earth's surface. The Southern Hemisphere has a higher percentage of water than does the Northern Hemisphere. * Southern Hemisphere: 81% water, 19% land * Tº variations & range are smaller. * Northern Hemisphere: 61% water, 39% land * Greater Tº variations over the land surfaces. * Greater winter time variations with latitude than summer. ** Coldest Tº's are usually over land at high latitudes in winter. EX: Siberia andAntarctica ** Warmest Tº's are usually in the tropical deserts in summer. EX: Sahara Wind Chill Temperature Index refers to the effect of wind and temperature on a person’s body which can lead to increased heat loss from the body and a lowering of body T°. The wind moves heat generated by the body away from the body, thus the body has to work harder to generate more heat. * Astronger wind = greater heat loss. * Can lead to hypothermia. Heat Index refers to the effect of humidity and temperature on a person’s body which can lead to an increase of body T°. High humidity (the amount of water vapor in the air) decreases the body’s ability to cool down by sweating, thus increasing the body T°. * Can lead to heat cramps, heat exhaustion, or heat stroke.
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