Geography 1111 Lecture 5 & 6 Notes 8-19
Geography 1111 Lecture 5 & 6 Notes 8-19 GEOG 1111
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This 7 page Class Notes was uploaded by Bridget Notetaker on Monday August 22, 2016. The Class Notes belongs to GEOG 1111 at University of Georgia taught by Hopkins in Fall 2016. Since its upload, it has received 43 views. For similar materials see Intro to Physical Geography in Geography at University of Georgia.
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Date Created: 08/22/16
Geography 1111 Lecture 5 Notes Radiation/Energy Balance: o Energy: the ability or capacity to do work on some form of matter Potential Energy: the energy of an object prior to it being released as free energy Commonly called the energy at rest Kinetic Energy: the free energy of motion or action Heat Energy: the kinetic energy generated by the motion of molecules Measured as the sum total of all molecular motion of an object Radiant Energy: the energy transferred as electromagnetic waves by all objects with a temperature > 0°K (-273°C or absolute zero) Energy follows the Laws of Thermodynamics: First Law of Thermodynamics: In all physical and 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 o 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 temperature > 0°K emit radiation with the amount of energy emitted dependent on the temperature 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 and its temperature = 6,000°K (5,700°C or 10,300°F) This Solar Radiation is also called Shortwave (SW) Radiation The Earth’s maximum energy is radiated at 10 micrometers and its temperature = 300°K (15°C or 59°F) This Terrestrial Radiation is also called Longwave (LW) Radiation o Solar Radiation: SW Radiation is designed 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 is passes through the Earth’s atmosphere, it may be scattered, reflected, or absorbed to reach the surface This affects the transfer of radiant energy to other forms, both within the atmosphere and at the ground surface Scattering: gas molecules scatter blue and violet SW better than longer waves such as red or orange which affects the sky color we see o Some of this is redirected back into space and that energy is lost to the Earth Reflection: the process whereby a surface turns back a portion of the radiation that strikes it It essentially bounces off the object o Radiation follows the Law of Reflection which states that the angle of incidence (incoming) = the angle of reflection (outgoing) Albedo: the term to describe the percent of radiation reflected off a surface compared to the incident radiation striking it o The Albedo of a surface/object will vary dependent on its composition, color, roughness and the Sun angle o Approximately 31% of all incoming SW from the Sun is reflected back to space This means that the average planetary Albedo is 31 and is lost energy o 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: the process whereby some of the energy of incoming SW radiation is transferred into the object being struck o This energy transferred as (changed to) heat energy, as it increases the internal molecular motion or the object/substance o Since heat energy is increasing in the object, so will the temperature of the substance/object increase o Substances in the atmosphere with high absorptive characteristics for SW include O2, O3, and H2O However, overall the atmosphere is a poor absorber of incoming SW o Opposite of reflection 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 lost to space by reflection and scattering Terrestrial Radiation: 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, or absorbed and CO2 and H2O are very good absorbers of these wavelengths Water vapor absorbs 5x what all other gases do Some of the LW radiation emitted by the Earth is thus “trapped” by these and other gasses in the atmosphere o This process is commonly called the Greenhouse Effect and what heats the lower atmosphere and thus the Earth This GH Effect causes the atmosphere to be heated from the ground up and the LW radiation is “bounced” back and forth between the atmosphere (clouds, dust, and Greenhouse Gasses) and the ground This helps to keep the Earth’s average temperature some 35°C warmer than it would be otherwise o With GH gasses: 15°C o Without GH gasses: -18°C o The actual process of warming the atmosphere is a little more complicated than the simple GH Effect The basic GH 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 idea of Global Warming is basically an enhanced Greenhouse Effect aka the Greenhouse Effect on ‘Overload’ Geography 1111 Lecture 6 Notes Global Energy/Heat Balance o Heat: A calorie is the term which refers to the heat required to raise the temperature of 1 gram of water by 1°C Heat is often measured in calorie units Heat Transfer by 3 primary mechanisms: 1. Conduction: the process of transferring heat energy through matter molecule by molecule This is done by direct contact and transfer from one molecule to the next o 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 (ex: air) are known as insulators o As heat energy flows thru a substance, it will flow from an area of higher temperature toward an area of lower temperature o Ex: Heat one end of a metal rod and some of that energy will be passed molecule by molecule to the other end 2. Convection: the process of transferring heat through matter by mass movement of material within the substance. A portion of the material is heated and in mass moves thru the substance o 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 o 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 1. Sensible Heat Flux: the process of transferring energy using the dry components/molecules of the air (O2, C02, N2, etc.) 2. Latent Heat Flux: the process of evaporation and condensation o Latent Heat: 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.) o 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: the wavelike transfer of energy o 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 o 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 o Q* = net radiation = (SW↓ - SW↑) + (LW↓ - LW↑) = incoming ( ↓ ) minus outgoing ( ↑ ) o Q* = Q + Q + Q G H LE ground sensible latent heat heat heat flux flux flux (conduction) (dry convection) (evaporation/condensation) o This balance involves both a temporal (over time) and spatial (over an area/space) component It will vary with time period (daily, monthly, annually, etc.) and in different areas of the Earth Day vs. night, summer vs. winter, tropics vs. polar regions o There exists a horizontal (spatial) imbalance of energy over the Earth’s surface which leads to a surplus in the tropics and deficit at the poles The Earth system prefers a status of equilibrium, so it tries to balance the imbalance o 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 thus and the two primary fluids on Earth are water and air o Energy is thus moved via Atmospheric circulation (winds) and Oceanic circulation (currents) o Most heat transfer takes place between 30° to 50° latitude N and S (the Mid-Latitudes) and a large portion of the stormy weather we receive in the U.S. is attributable to this transfer of heat energy QLEs the most important in the humid tropics QSHs most important in the arid tropics
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