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Lecture 3 IOPs: Absorption physics and absorbing materials
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Lecture 3 IOPs: Absorption physics and absorbing materials

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  1. Lecture 3IOPs: Absorption physics and absorbing materials Collin Roesler 3 July 2007

  2. Lecture Overview • Overview of the electromagnetic spectrum • What is absorption? • Who are the absorbers? • Impacts on ocean color

  3. Electromagnetic Spectrum • Charged particles create electric fields (oscillation between +,-) • When a charged particle moves, it creates a magnetic field • The electromagnetic field oscillates as the energy propagates • the range of oscillation frequencies is described by the EM spectrum http://wps.prenhall.com/wps/media/objects/610/625137/Chaisson

  4. http://aeon.physics.weber.edu/jca/PHSX1030/Images/blackbody.jpghttp://aeon.physics.weber.edu/jca/PHSX1030/Images/blackbody.jpg Black body radiation • Any object with a temperature >0 K emits electromagnetic radiation • The spectrum of that emission depends upon the temperature (Planck’s Law) • As T , emitted energy  (Stefan-Boltzman’s Law), and the frequency of emitted energy  (shorter wavelengths) • As T , the l of maximal emission  (Wein’s Law) • Energy contained in a packet of EM radiation (e.g. visible photon)  with  wavelength

  5. So the sun, at ~5800 K, emits primarily visible radiation (light), most of which penetrates the atmosphere

  6. Light Penetration

  7. What is absorption? • since electromagnetic radiation is energy propagation, when materials absorb radiation, they absorb energy • what happens to the molecule depends upon the wavelength (frequency)

  8. MICROWAVE Interactions between energy and matter

  9. The amount of energy required to move an electron to another orbital shell is quantized interatomic distance 400 450 500 550 600 650 700

  10. quantized energy states interatomic distance 400 450 500 550 600 650 700

  11. quantized vibrational states interatomic distance 400 450 500 550 600 650 700

  12. http://www.mie.utoronto.ca/labs The chlorophyll a molecule has two higher energy orbital shells associated with the energy equivalent of a blue (443 nm) and a red (676 nm) photon

  13. Example of absorption spectra for three environments all have strong red absorption but variable blue absorption

  14. Absorbing matter Ideally… aT = aw + Sadissolved compounds + Saparticles

  15. Absorbing matter Practically… aT = aw + aCDM + af + aCOPM + aCIPM water chromophoric dissolved matter phytoplankton (in vivo pigments) chromophoric organic particulate matter (not pigments) chromophoric inorganic particulate matter (minerals)

  16. Absorbing Components:Water variations are methodological

  17. Temperature 30oC 5oC Pegau and Zaneveld 1993 Limnol Oceanogr. Absorbing Components:Water natural variations

  18. Salinity Pegau etal. 1997 Appl.Opt. Absorbing Components:Water natural variations

  19. Kirk 1983 Carder et al. 1989 L&O Absorbing Components:Chromophoric Dissolved Matter aCDM(l) = aCDM(lo) exp(-S (l-lo))

  20. Equatorial Pacific S=0.014 S 0.01 0.02 S=0.011 Carder et al. 1989 L&O Simeon et al. 2003 JGR Absorbing Components:Chromophoric Dissolved Matter aCDM(l) = aCDM(lo) exp(-S (l-lo))

  21. Species 1989 L&O Roesler et al. 1989 L&O Absorbing Components:Phytoplankton Individual cells

  22. Pigment Packaging impact on absorption Morel and Bricaud 1981 DSR Absorbing Components:Phytoplankton

  23. Absorbing Components:other protists heterotrophic bacteria ciliates and flagellates cytochrome 412 Morel and Ahn 1990 JMR

  24. JMR Iturriaga and Siegel 1989 L&O Absorbing Components:organic detrital particles

  25. Patterson et al. 1977 JGR Absorbing Components:inorganic particles Babin and Stramski 2003

  26. To model the impacts of absorbing constituents…add them up

  27. More on absorption • CDOM absorption methods • Lecture today • Lab today • Phytoplankton absorption • Lecture Thursday • Particulate absorption methods • Lecture Thursday • Lab Thursday