Lecture 3 IOPs: Absorption physics and absorbing materials Collin Roesler 3 July 2007.
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Transcript of Lecture 3 IOPs: Absorption physics and absorbing materials Collin Roesler 3 July 2007.
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Lecture 3IOPs: Absorption physics and
absorbing materials
Collin Roesler3 July 2007
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Lecture Overview
• Overview of the electromagnetic spectrum
• What is absorption?• Who are the absorbers?• Impacts on ocean color
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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
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Black body radiation
http://aeon.physics.weber.edu/jca/PHSX1030/Images/blackbody.jpg
• 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 of maximal emission (Wein’s Law)
• Energy contained in a packet of EM radiation (e.g. visible photon) with wavelength
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So the sun, at ~5800 K, emits primarily visible radiation (light),
most of which penetrates the atmosphere
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Light Penetration
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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)
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Interactions between energy and matter
MICROWAVE
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The amount of energy required to move an electron to another orbital shell is
quantized
400 450 500 550 600 650 700
interatomic distance
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quantized energy states
400 450 500 550 600 650 700
interatomic distance
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quantized vibrational states
interatomic distance
400 450 500 550 600 650 700
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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
http://www.mie.utoronto.ca/labs
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Example of absorption spectra for three environments
0
0.2
0.4
0.6
0.8
400 500 600 700
Wavelength (nm)
abso
rpti
on (
m-1)
open ocean
coastal
estuarine
all have strong red absorption
but variable blue absorption
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Absorbing matter
aT = aw + adissolved compounds + aparticles
Ideally…
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Absorbing matter
waterchromophoric dissolved matterphytoplankton (in vivo pigments)chromophoric organic particulate matter (not pigments)chromophoric inorganic particulate matter (minerals)
aT = aw + aCDM + a + aCOPM + aCIPM
Practically…
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Absorbing Components:Water
variations are methodological
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Absorbing Components:Water
natural variations
Pegau and Zaneveld 1993 Limnol Oceanogr.
Temperature
5oC
30oC
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Absorbing Components:Water
natural variations
Pegau etal. 1997 Appl.Opt.
Salinity
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Absorbing Components:Chromophoric Dissolved Matter
aCDM() = aCDM(o) exp(-S (-o))
Kirk 1983Carder et al. 1989 L&O
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Absorbing Components:Chromophoric Dissolved Matter
aCDM() = aCDM(o) exp(-S (-o))
Carder et al. 1989 L&O
S0.01
0.02
S=0.014
S=0.011
Simeon et al. 2003 JGR
Equatorial Pacific
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Absorbing Components:Phytoplankton
1989 L&O
Individual cells
Roesler et al. 1989 L&O
Species
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Absorbing Components:Phytoplankton
Pigment Packaging impact on absorption
Morel and Bricaud 1981 DSR
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Absorbing Components:other protists
Morel and Ahn 1990 JMR
heterotrophic bacteriaciliates and flagellates
cytochrome 412
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Absorbing Components:organic detrital particles
Iturriaga and Siegel 1989 L&OJMR
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Absorbing Components:inorganic particles
Babin and Stramski 2003Patterson et al. 1977 JGR
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To model the impacts of absorbing constituents…add them up
0
0.2
0.4
0.6
0.8
400 500 600 700
Wavelength (nm)
abso
rpti
on (
m-1)
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More on absorption
• CDOM absorption methods– Lecture today– Lab today
• Phytoplankton absorption– Lecture Thursday
• Particulate absorption methods– Lecture Thursday– Lab Thursday