Chapter 4 Atmosphere and Surface Energy PDF

Chapter 4 Lecture Geosystems 9th Edition Chapter 4: Atmosphere and Surface Energy...

Chapter 4 Lecture Geosystems 9th Edition Chapter 4: Atmosphere and Surface Energy Balances Ms Hodgkinson [email protected] © 2015 Pearson Education, Inc.  Learning Objectives Define energy and heat. Explain four types of heat transfer: radiation, conduction, convection, and advection. Identify alternative pathways for solar energy on its way through the troposphere to Earth’s surface—transmission, scattering, refraction, and absorption. Review the concept of albedo (reflectivity) and how it relates to urban heat islands Analyze the effect of clouds and aerosols on atmospheric heating and cooling. Explain the greenhouse concept as it applies to Earth. Plot typical daily radiation and temperature curves for Earth’s surface —including the daily temperature lag. Explain the urban heat island/city climate concept. © 2015 Pearson Education, Inc.  Energy Pathways and Principles Insolation or incoming solar radiation is the single energy input driving the earth-atmosphere system. It is not, however, equal at all surfaces across the globe. © 2015 Pearson Education, Inc. © 2015 Pearson Education, Inc.  Energy Pathways © 2015 Pearson Education, Inc.  Annual Mean Insolation at Earth’s Surface © 2015 Pearson Education, Inc.  Methods of Heat Transfer Heat energy can be transferred in a number of ways through the earth's atmosphere, land and water Four types of heat transfer: radiation, conduction, convection, and advection. Radiation refers to the transfer of heat in electromagnetic waves such as the waves from the sun to the earth or from a stove top plate. Light + Heat. The hotter the substance, the shorter the wavelengths emitted. © 2015 Pearson Education, Inc.  Heat Transfer Radiation: energy traveling through air or space Convection: energy transferred by vertical movement Conduction: molecule-to-molecule transfer (from higher temperature to lower temperature) Advection: horizontally dominant movement © 2015 Pearson Education, Inc. © 2015 Pearson Education, Inc.  Types of Heat Heat is the flow of kinetic energy between molecules and from one body to another resulting from a temperature difference between them. Two types of heat energy – Sensible heat can be ‘sensed’ by humans as temperature because it comes from the kinetic energy of molecular motion – Sensible heat is the back-and-forth transfer between air and surface through convection and conduction – Latent heat is ‘hidden heat’ is the energy gained or lost when a substance changes from one state to another © 2015 Pearson Education, Inc.  Sensible Heat Flux Sensible heat can be ‘sensed’ by humans as temperature because it comes from the kinetic energy of molecular motion Sensible heat flux is the back-and-forth transfer between air and surface in turbulent eddies through convection and conduction. © 2015 Pearson Education, Inc.  Ground Heat Flux Ground heat flux is the energy that flows into or out of the ground surface by conduction. Heat and energy re-radiated © 2015 Pearson Education, Inc.  Latent Heat Flux Latent heat flux is the energy that is stored in water vapor as water evaporates. Water absorbs large quantities of this latent heat as it changes state to water vapor, thus removing this heat energy from the surface. © 2015 Pearson Education, Inc.  Energy transfer in the atmosphere Scattering: insolation interacts with particles, changing direction of light’s movement, without altering its wavelengths. Diffuse radiation is the incoming energy that reaches the earth’s surface after scattering occurs (waves travel in different directions). Opposite of direct radiation when it travels in a straight line to the earth. Rayleigh scattering rule: The shorter the wavelength, the greater the scattering; the longer the wavelength, the less the scattering. The wavelength of blue light is less than red light. Think of a rainbow – from blue (short) to red (long) Blue sky, red sunrise, and red sunset © 2015 Pearson Education, Inc.  Dispersion of light © 2015 Pearson Education, Inc.  Transmission and Absorption Transmission refers to the passage of shortwave and longwave energy through the atmosphere or water. Absorption is the assimilation of radiation by molecules of matter and its conversion from one form of energy to another. CO2 and water vapor absorb solar radiation and longwave radiation. © 2015 Pearson Education, Inc.  Refraction Change in speed and direction of light as light passes from one medium to another © 2015 Pearson Education, Inc.  Refraction and Rainbow © 2015 Pearson Education, Inc. © 2015 Pearson Education, Inc. © 2015 Pearson Education, Inc.  Reflection Reflection is a portion of arriving radiation that bounces directly back into space without being absorbed or performing any work. © 2015 Pearson Education, Inc.  Albedo Albedo is the percentage of insolation that is reflected – 0% is total absorption; 100% is total reflectance. Smooth surface (High albedo) versus rough surface (low albedo) Light color surface (high albedo) versus dark color surface (low albedo) Albedo of water surface varies with Sun altitude – low angles = high albedo vs high angle = low. © 2015 Pearson Education, Inc. © 2015 Pearson Education, Inc.  Reflection and Albedo © 2015 Pearson Education, Inc.  The Greenhouse Effect and Atmospheric Warming Earth emits energy back to the sun as longwave radiation. Some of this radiation is absorbed by CO2, H2O, CO2, CH4, NO and CFC’s in the lower atmosphere and reradiated back to earth. This process affects the heating of earth’s atmosphere. The Greenhouse Effect works in a similar way © 2015 Pearson Education, Inc.  The Greenhouse Effect and Atmospheric Warming Atmosphere absorbs heat energy. A real greenhouse traps heat inside. Atmosphere delays transfer of heat from Earth into space. © 2015 Pearson Education, Inc.  The Greenhouse Effect and Atmospheric Warming The gases associated with this process are collectively termed greenhouse gases Atmosphere absorbs heat energy. A real greenhouse traps heat inside. Atmosphere delays transfer of heat from Earth into space. Higher CO2 levels are creating a stronger Greenhouse effect © 2015 Pearson Education, Inc.  Daily Radiation Patterns The Sun provides constant heat throughout the day, especially during peak hours. However, after sunset, time is needed to cool down. This is due to the fact that solar radiation is absorbed into the ground and releases infrared heat into the air. The lag is due to the fact that heating of the air occurs, not from the sun's rays passing through, but from heating of the ground and infrared radiation leaving the ground in the form of heat. This process takes some time, and it is also the reason it does not get chilly immediately after sunset.....there is residual warmth in the ground being radiated into the air producing some residual heating even after the sun has set. © 2015 Pearson Education, Inc.  Daily Radiation Patterns © 2015 Pearson Education, Inc. © 2015 Pearson Education, Inc.  According to the World Resources Institute Climate Analysis Indicator Tool (WRI CAIT), South Africa’s GHG profile is dominated by emissions from the energy sector, which accounted for 84% of South Africa’s total emissions in 2012. Of this, 60% of energy emissions were due to electricity and heat, 15% to manufacturing and construction, 12% to transportation, and 12% to other energy subsectors. © 2015 Pearson Education, Inc.  Agriculture is the second highest emitting sector and contributes 7% of total GHGs, of which 42% is due to enteric fermentation, 33% to manure left on pasture, and 25% to other agriculture subsectors. © 2015 Pearson Education, Inc. © 2015 Pearson Education, Inc. © 2015 Pearson Education, Inc. © 2015 Pearson Education, Inc.  Urban Heat Island An urban heat island, or UHI, is a metropolitan area that's a lot warmer than the rural areas surrounding it. (you may be more familiar with the concept “City Climates”) An urban heat island occurs when a city experiences much warmer temperatures than nearby rural areas. The difference in temperature between urban and less- developed rural areas has to do with how well the surfaces in each environment absorb and hold heat. Building materials are usually very good at insulating, or holding in heat. This insulation makes the areas around buildings warmer. © 2015 Pearson Education, Inc. Urban Heat Island  Summary of Chapter 4 Solar energy through the troposphere to Earth’s surface undergoes transmission, scattering, diffusion, and reflection. Albedo is the reflective quality of a surface. Blue sky, red sunrise, and red sunset are due to scattering. Conduction is the molecule-to-molecule transfer of energy. Convection is the energy transfer by vertical movement. Advection is the energy transfer by horizontal movement. Net radiation is the balance of all radiation at Earth’s surface. Net radiation is expended from a non-vegetated surface through three pathways: sensible heat flux, which is the heat energy transfer between air and surface; latent heat of evaporation, which is the energy stored in water vapor as water evaporates; and ground heat flux, which is the energy flows into or out of the ground surface by conduction. © 2015 Pearson Education, Inc.  End of Chapter 4 Online class test on Chapter 4 open Due Monday © 2015 Pearson Education, Inc.