earth’s global energy balance overview electromagnetic radiation –radiation and temperature...

Download Earth’s Global Energy Balance Overview Electromagnetic Radiation –Radiation and temperature –Solar Radiation –Longwave radiation from the Earth –Global

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  • Slide 1
  • Earths Global Energy Balance Overview Electromagnetic Radiation Radiation and temperature Solar Radiation Longwave radiation from the Earth Global radiation balance Geographic Variations in Energy Flow Insolation over the globe Net radiation, latitude and energy balance Sensible and latent heat transfer Electromagnetic Radiation Radiation and temperature Solar Radiation Longwave radiation from the Earth Global radiation balance Geographic Variations in Energy Flow Insolation over the globe Net radiation, latitude and energy balance Sensible and latent heat transfer
  • Slide 2
  • The global energy system Solar energy losses in the atmosphere Albedo Counterradiation and the greenhouse effect Global energy budgets of the atmosphere & surface Climate & global change The global energy system Solar energy losses in the atmosphere Albedo Counterradiation and the greenhouse effect Global energy budgets of the atmosphere & surface Climate & global change Overview
  • Slide 3
  • What is light?
  • Slide 4
  • Light is an Electromagnetic Wave & a Particle Photons: pieces of light, each with precise wavelength, frequency, and energy. Our eyes recognize frequency (or wavelength) as color!
  • Slide 5
  • Photons Photons are little packets of energy. The energy carried by each photon depends on its frequency (color) Blue light carries more energy per photon than red light.
  • Slide 6
  • Electromagnetic Spectrum
  • Slide 7
  • Electromagnetic Radiation Energy constantly emitted from every surface Can be in many different forms, e.g. light or heat Energy constantly emitted from every surface Can be in many different forms, e.g. light or heat
  • Slide 8
  • What happens when light gets absorbed?
  • Slide 9
  • What causes the atmosphere to be opaque?
  • Slide 10
  • Solar Radiation Shortwave Radiation from Sun (dark purple) Absorption of UV by O 3 Absorption by CO 2 and water vapor (H 2 O) shown as valleys Longwave Radiation from Earth (dark red) Much absorbed by CO 2 & H 2 O
  • Slide 11
  • Scattering Solar radiation can be scattered by atmosphere Deflected off a molecule, cloud droplet, or particle May go up toward space, or down toward Earth Scattering most prevalent in blue wavelengths Thus, clear, blue skies Some solar radiation goes directly to surface Called transmission Solar radiation arrives as 0.3m to 3m wavelengths This is shortwave radiation Solar radiation can be scattered by atmosphere Deflected off a molecule, cloud droplet, or particle May go up toward space, or down toward Earth Scattering most prevalent in blue wavelengths Thus, clear, blue skies Some solar radiation goes directly to surface Called transmission Solar radiation arrives as 0.3m to 3m wavelengths This is shortwave radiation
  • Slide 12
  • Remember you live on a rotating sphere
  • Slide 13
  • Geographic Variation in Solar Energy Insolation Incoming solar radiation More intense where sun angle is highest Less intense with lower sun angle Same energy spread over a larger area Insolation Incoming solar radiation More intense where sun angle is highest Less intense with lower sun angle Same energy spread over a larger area
  • Slide 14
  • Insolation Daily insolation avg radiation total in 24 hours Depends on : Sun angle higher sun angle greater insolation Length of day higher latitudes get long summer days Annual insolation avg radiation total for year Also depends on sun angle and length of day Both of these determined by latitude So, latitude determines annual insolation Daily insolation avg radiation total in 24 hours Depends on : Sun angle higher sun angle greater insolation Length of day higher latitudes get long summer days Annual insolation avg radiation total for year Also depends on sun angle and length of day Both of these determined by latitude So, latitude determines annual insolation
  • Slide 15
  • Net Radiation Energy not usually balanced at any location Net Radiation - Difference between incoming and outgoing radiation Between 40N and 40S, incoming > outgoing Creates energy surplus Poleward of 40N & S, outgoing > incoming Creates energy deficit Deficit = Surplus, so net radiation for Earth = 0 Energy not usually balanced at any location Net Radiation - Difference between incoming and outgoing radiation Between 40N and 40S, incoming > outgoing Creates energy surplus Poleward of 40N & S, outgoing > incoming Creates energy deficit Deficit = Surplus, so net radiation for Earth = 0
  • Slide 16
  • Poleward Heat Transport Surplus energy moves toward poles (deficit regions) Carried by: Warm, moist air Warm sea water Tropical cyclones Poleward heat transport is driving force behind: Global atmospheric circulation Weather systems Ocean currents
  • Slide 17
  • Why are there seasons? The Earth is tilted 23.5 from it orbital plane Combine tilt with orbit Northern hemisphere gets more direct Sun part of year (northern summer) Southern hemisphere gets more direct Sun part of year (northern winter) Tilt & orbit create seasons, not distance to Sun
  • Slide 18
  • Northern Summer
  • Slide 19
  • Northern Winter
  • Slide 20
  • Solstices & Equinoxes
  • Slide 21
  • Path of the Sun in the Sky June solstice: Sun rises north of east & sets north of west Peaks at 73.5 above horizon at noon 15 hours of daylight Highest daily insolation of year 40 North
  • Slide 22
  • DateNoon Sun Angle DaylightDaily Insolation June Solstice73.515 hrs460 W/m 2 Dec. Solstice26.59 hrs160 W/m 2 Equinoxes5012 hrs350 W/m 2 Path of the Sun in the Sky (40 North)
  • Slide 23
  • DateNoon Sun Angle DaylightDaily Insolation June Solstice66.512 hrs~400 W/m 2 Dec. Solstice66.512 hrs~400 W/m 2 Equinoxes9012 hrs440 W/m 2 Path of the Sun in the Sky (Equator)
  • Slide 24
  • DateNoon Sun Angle DaylightDaily Insolation June Solstice23.524 hrs500 W/m 2 Dec. SolsticeNo Sun0 hrs0 W/m 2 EquinoxesHorizon12 hrs~0 W/m 2 Path of the Sun in the Sky (North Pole)
  • Slide 25
  • Daily Insolation through the Year Yearly change in insolation greatest toward poles In Arctic & Antarctic Circles, Sun is below horizon part of year At Equator, 2 maxs & 2 mins for daily insolation At equinoxes & solstices Between tropics, also 2 maxs & 2 mins per year Yearly insolation change important to climate Insolation at equinox
  • Slide 26
  • Annual Insolation by Latitude Tilted Earth shown as red line Equator greatest annual insolation Considerable insolation at highest latitudes Untilted Earth (blue line) Equator greatest annual insolation Highest latitudes little insolation Big changes in climate Very cold pole Massive poleward heat transport
  • Slide 27
  • Heat Transfer: Surplus energy is transported in two forms Sensible Heat can be felt & measured Transferred by conduction (touching surface) Transferred by convection (carried by rising air) Example: Moving air masses Latent Heat cannot be felt or measured Stored as molecular motion when water changes phase Absorbed in evaporation, melting, and sublimation Released in condensation, freezing, and deposition Very important form of heat transfer over long distances Example: Storm systems, hurricanes Sensible Heat can be felt & measured Transferred by conduction (touching surface) Transferred by convection (carried by rising air) Example: Moving air masses Latent Heat cannot be felt or measured Stored as molecular motion when water changes phase Absorbed in evaporation, melting, and sublimation Released in condensation, freezing, and deposition Very important form of heat transfer over long distances Example: Storm systems, hurricanes Conduction Convection Latent heat absorbed in evaporation
  • Slide 28
  • Solar energy losses in the atmosphere Scattering due to: Gas molecules Dust or other particles O 2, O 3, & H 2 O most important absorbers of insolation Global avg 49% of insolation makes it to surface
  • Slide 29
  • Once at the surface what happens? Albedo Proportion of shortwave radiation reflected Shown as a proportion (0-1) Examples: Snowfield 0.45-0.85 Black pavement 0.03 Clouds 0.30-0.60 Water (calm, high angle 0.02), (low angle 0.80) Avg for Earth and atmosphere 0.29- 0.34 Proportion of shortwave radiation reflected Shown as a proportion (0-1) Examples: Snowfield 0.45-0.85 Black pavement 0.03 Clouds 0.30-0.60 Water (calm, high angle 0.02), (low angle 0.80) Avg for Earth and atmosphere 0.29- 0.34
  • Slide 30
  • So what happens to all the energy absorbed by these various processes? Counterradiation heat absorbed by atmosphere reflected down to surface A energy radiated to space from surface B energy from surface absorbed by atmosphere C energy radiated to space from atmosphere D Counterradiation
  • Slide 31
  • Part of Counterradiation is the Greenhouse Effect Longwave radiation absorbed & re-radiated to surface by atmosphere Lower atmosphere acts like blanket Longwave radiation absorbed & re-radiated to surface by atmosphere Lower atmosphere acts like blanket
  • Slide 32
  • Global Energy Budget Energy balanced for each level: surface, atmosphere,

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