Language of the Energy Cycle: The Electromagnetic Spectrum

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

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

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