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Language of the Energy Cycle: The Electromagnetic Spectrum

Language of the Energy Cycle: The Electromagnetic Spectrum. Energy. Wavelength l. Speed of light = wavelength ( l ) x frequency = 3 x 10 8 m/s in vacuum Wavenumber = 1/ wavelength ( cm -1 ) Frequency in GHz (1 Hz = sec –1 ). 620 K. 380 K.

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Language of the Energy Cycle: The Electromagnetic Spectrum

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  1. Language of the Energy Cycle:The Electromagnetic Spectrum Energy Wavelength l • Speed of light = wavelength (l) x frequency = 3 x 108 m/s in vacuum • Wavenumber = 1/ wavelength ( cm-1) • Frequency in GHz (1 Hz = sec –1)

  2. 620 K 380 K 1.Power Source: Blackbody Radiation Planck’s Law: The amount and spectrum of radiation emitted by a blackbody is uniquely determined by its temperature Max Planck (1858 – 1947) Nobel Prize 1918 Emission from warm bodies peak at short wavelengths wavelength

  3. Sun at 6000K; peak emission at 0.5 mm Solar Spectrum = Shortwave spectrum =visible spectrum:

  4. CO2 O3 H2O Terrestrial Spectrum = Longwave Spectrum = Infrared Spectrum = Thermal Spectrum:Sahara Desert on Nimbus 4 Satellite Theoretical Planck curves: Earth ~300K, peak emission ~15 mm

  5. Sun Earth High energy Short wavelength / high frequency Emitted at high T Electromagnetic Spectrum

  6. 2. What happens to the radiation in the atm? n1symmetric O O C C n2 bending 15 mm O O n2asymmetric 4.3 mm O C O Vibrational Modes for CO2 Greenhouse effect: Radiation at specific wavelengths excite CO2 into higher energy states: energy is “absorbed” by the CO2 molecules

  7. O O O H O H H H C H N O N H Nitrous oxide methane Other Greenhouse Gases water ozone

  8. Absorption Transmission Atmosphere: Characteristic Absorption/Transmission for different atm molecules for l: 0-15 µm

  9. Earth Spectrum Incoming from Sun: High energy, short wavelength 0.5 mm Outgoing from Earth Low energy Long wavelength 20 mm 10 mm

  10. Shortwave Longwave 100 CO2, H2O, GHG 50 Earth’s Energy Balance

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