9 21 15 Dr Frauenfeld Chapter 4 Atmosphere and Surface Energy Balance I Atmosphere and Surface Energy Balances a The sun provides the solar energy to heat the Earth s surface and atmosphere i Unevenly distributed in time and space b Transmission of energy is all the radiation that passes through the atmosphere i Both shortwave in and longwave out c Energy Pathways i Insolation Input all of the radiation that is received at Earth s surface 1 Direct vs Diffuse see picture above 2 Greatest in the tropics 180 220 W m2 3 Decreases poleward Midlatitudes 120 180 W m2 Poles 100 W m2 4 Not all insolation directly reaches the surface a Scattering Change only in the direction of light without altering wavelength i Results in diffuse radiation ii A greater of incoming radiation is scattered back to space iii Causes differences in color of the sky throughout the day color is also affected b Refraction Change in speed and direction of light i Occurs when light moves from one medium outer space to another by pollution atmosphere ii Adds approximately 8 minutes of sunlight 4 sunrise 4 sunset c Reflection Bouncing back of energy without being absorbed i Deflected away unchanged in the direction from which it came ii Reflective property Lightness of a surface is also known as Albedo a percentage of reflected insolation 0 no reflection and 100 all reflected 9 21 15 Dr Frauenfeld Darker surfaces lower albedo while lighter surfaces higher albedos MUST KNOW THAT THE AVERAGE ALBEDO OF EARTH IS 31 iii Varies with the season increase and decrease in snow cover iv Clouds cloud cover will reflect shortwave radiation cloud albedo effect which makes the Earth slightly cooler HOWEVER clouds also keep the longwave radiation from going into space cloud greenhouse effect which makes the Earth slightly warmer These are two opposite feedbacks 5 Everything that is not reflected is absorbed a Absorption is the assimilation of radiation by an object and converting it from one form of energy to another b 69 of insolation is absorbed i 45 ii 24 is absorbed by the surface land oceans is absorbed by the atmosphere gases dust clouds and ozone c After the shortwave radiation is absorbed it is converted into longwave radiation 9 21 15 Dr Frauenfeld d Earth Atmosphere Radiation Balance black boxes are s you need to know 31 is reflected 24 is absorbed by the atmosphere and 45 is absorbed by the surface 100 it is balanced II Mechanisms of Heat Transfer a Conduction i Molecule to molecule transfer b Convection Advection i Energy transferred by movement 1 Vertically Convection 2 Horizontally Advection ii Happens in the water and in the atmosphere 9 21 15 Dr Frauenfeld III Energy Balance at Earth s Surface Infrared is over 100 110 96 because of the Greenhouse Effect IV The Greenhouse Effect a Greenhouse gases in the atmosphere absorb longwave radiation i Water Vapor Carbon Dioxide Methane and others ii Delays energy loss back up to space similar to a greenhouse because glass lets solar radiation in but traps longwave radiation from going out b Keeps the globe at a comfortable temperature i Global temp would be 0 F 18 C but it is at 59 F 15 C because of the Greenhouse ii This happens naturally and is needed but humans are making it worse by producing Effect more carbon dioxide and methane c Clouds and the Greenhouse Effect i They play an important role Amount of clouds and also type and height of clouds determines whether clouds act as absorbers make the Earth warmer or reflectors make the Earth cooler 1 High clouds more trapping of longwave radiation Net Warming 2 Low clouds more reflection of shortwave radiation Net Cooling V a Daily Variability of Energy Balance Insolation peaks at noon i Total amount varies with the time of year and latitude b BUT the warmest part of the day is the mid afternoon 3 4 pm because temperature lags behind insolation i This is when insolation and emitted longwave radiation which is kept in the atmosphere due to the greenhouse effect are both high c Lowest temperature is right at sunrise because there has been no insolation for the longest time 9 21 15 Dr Frauenfeld VI Net Radiation SW and LW a Earth s surface receives shortwave SW and longwave LW radiation and loses b Net Radiation SW SW LW LW insolation albedo infrared infrared 9 21 15 c Global Net Radiation Dr Frauenfeld VII Variability of Net Radiation at the Surface a Net radiation is expended via i Latent Heat LE Dominant important most form 1 Latent or hidden 2 Heat transfer from evaporation to condensation of water 3 The process doesn t feel like a change in temperature that s why it s called latent 4 Also is creates cloud which affects the temperature after the fact so the effects are delayed ii Sensible Heat H 1 Heat you can sense feel 2 Transferred through conduction and convection iii Ground Heat G 1 Energy flow in and out of the ground via conduction 2 Only 1 m 3 ft down 3 Balanced on an annual basis b Global Latent Heat through water so oceans have the highest 9 21 15 Dr Frauenfeld c Global Sensible Heat dominant on land Values are much higher overall for LE d Radiation Budgets i El Mirage California hot desert dry location 35 N In the absence of water all energy will be expended through sensible heat 9 21 15 Dr Frauenfeld ii Pitt Meadows British Colombia moderate moist location 49 N Wet locations will expend energy through latent heat iii The Urban Environment 1 Acts like a desert little water so expends energy through sensible heat 2 Urban Heat Island Man made structures absorb more heat asphalt concrete steel etc 3 More pollution and byproducts acts like a greenhouse gas 9 21 15 Dr Frauenfeld VIII Net Radiation Balance a Earth Atmosphere system as a whole has a net radiation balance equilibrium b But there is a great latitudinal variability i Surplus in tropics ii Deficit in polar regions iii Perfectly balanced at approximately 36 latitude