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RADIATION . Insolation . in tercepted sol ar radi ation. Earth intercepts 0.0000000005 of the sun’s radiation. Solar constant amount of radiation received at the top of the atmosphere (on a plane surface perpendicular to sun’s rays) = 1372 Watts/m 2

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Solar constant

amount of radiation received at the top of the atmosphere (on a plane surface perpendicular to sun’s rays)

= 1372 Watts/m2

(reduced by half by the time it reaches surface of earth)

energy per unit area
energy per unit area

amount of energy received at earth’s surface per unit of area (square meter, square inch, etc.)


surface receives more energy per unit area (more concentrated) when the sun’s rays are vertical (direct)

less energy per unit area (less concentrated) when sun’s rays are oblique(slanted)

Earth, sun, everything! radiates energy
    • tropical zonesreceive more energy than they radiate
    • polar zonesradiate more energy than they receive
    • excess heat transfer:
      • ocean currents, winds
Sun’s energy from atomic fusion: hydrogen atoms fused into helium atoms
    • lost mass converted to energy
Electromagnetic radiation (EMR)
    • travels at speed of light

(93 million miles in 8.5 minutes)

    • travels in waves

Wavelength: size of wave

electromagnetic spectrum
electromagnetic spectrum
  • “ruler” to measure different types of energy
solar sun vs terrestrial earth radiation
Solar (Sun) vs. Terrestrial (Earth) Radiation:
  • sun’s SHORTWAVE :
    • gamma , X-ray, UV, visible, infrared
  • earth’s LONGWAVE :
    • infrared
absorption of radiation in the atmosphere
Absorption of radiation in the atmosphere:
  • Shortwave absorbers:
      • ozone, water vapor
  • Longwave absorbers:
      • water vapor, carbon dioxide, ozone
  • “The atmosphere is relatively transparent to shortwave radiation and opaque to longwave radiation”
types of heat energy
Types of heat energy
  • Sensible heat
      • thermometer
  • Latent heat
      • released or stored in a phase change
First Law of Thermodynamics:
      • energy cannot be created or destroyed, but can be:



energy transfer mechanisms
Energy Transfer Mechanisms:
  • Conduction
      • energy transmitted within a substance by collision of molecules
  • Convection
      • vertical motion of energy from one place to another through physical motion of air
energy budget balance
Energy Budget/Balance
  • Exchange of energy between the sun, the earth, and the atmosphere
    • balance between incoming and outgoing
radiation entering the atmosphere can be:
  • absorbed
      • transformed, re-emitted
  • reflected
      • “albedo” : percentage of incoming radiation that is reflected;
      • earth/atmosphere albedo = 31 %
the balancing act
The Balancing Act
  • 95+48 = 143
  • energy leaves surface as:
    • radiation
    • latent heat (evaporation)
    • sensible heat (conduction)
  • losses: 114+23+7= 144
greenhouse effect
Greenhouse Effect
  • atmosphere admits most shortwave; absorbs and counterradiates longwave
  • allows average surface temperature to be 59oF rather than - 4oF