Presentation is loading. Please wait.

Presentation is loading. Please wait.

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

Similar presentations


Presentation on theme: "Earth’s Global Energy Balance Overview Electromagnetic Radiation –Radiation and temperature –Solar Radiation –Longwave radiation from the Earth –Global."— Presentation transcript:

1 Earth’s 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

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

3 What is light?

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!

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.

6 Electromagnetic Spectrum

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

8 What happens when light gets absorbed?

9 What causes the atmosphere to be opaque?

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↑

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 0.3μm to 3μm 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 0.3μm to 3μm wavelengths –This is shortwave radiation

12 Remember you live on a rotating sphere

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

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

15 Net Radiation Energy not usually balanced at any location Net Radiation - Difference between incoming and outgoing radiation Between 40°N and 40°S, incoming > outgoing –Creates energy surplus Poleward of 40°N & 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 40°N and 40°S, incoming > outgoing –Creates energy surplus Poleward of 40°N & S, outgoing > incoming –Creates energy deficit Deficit = Surplus, so net radiation for Earth = 0

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

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

18 Northern Summer

19 Northern Winter

20 Solstices & Equinoxes

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

22 DateNoon Sun Angle DaylightDaily Insolation June Solstice73.5°15 hrs460 W/m 2 Dec. Solstice26.5°9 hrs160 W/m 2 Equinoxes50°12 hrs350 W/m 2 Path of the Sun in the Sky (40° North)

23 DateNoon Sun Angle DaylightDaily Insolation June Solstice66.5°12 hrs~400 W/m 2 Dec. Solstice66.5°12 hrs~400 W/m 2 Equinoxes90°12 hrs440 W/m 2 Path of the Sun in the Sky (Equator)

24 DateNoon Sun Angle DaylightDaily Insolation June Solstice23.5°24 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)

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

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

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

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

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

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

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

32 Global Energy Budget Energy balanced for each level: surface, atmosphere, & space

33 Climate & Global Change Quantifying human impacts on climate difficult Climate and society have complex relationship e.g., Industrial processes add CO 2 to atmosphere (warming) add aerosols to atmosphere (cooling)


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

Similar presentations


Ads by Google