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Biosphere/Atmosphere Interactions Biology 164/264. 2007 Joe Berry [email protected] Chris Field [email protected] Adam Wolf [email protected] Basic questions to be addressed by this course:.

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basic questions to be addressed by this course
Basic questions to be addressed by this course:
  • What are the major fluxes of energy and matter between the atmosphere and land ecosystems?
  • What determines the temperature of leaves, plants, soils, and ecosystems?
  • What controls rates of plant photosynthesis and transpiration?
  • How do atmospheric processes interact with ecosystem processes to control CO2 and water exchanges?
  • How do characteristics of the land surface influence the motions of the atmosphere?
  • How do characteristics of the land surface influence climate?
  • How do greenhouse gases exchanged by ecosystems influence climate?
  • How can we measure and model the exchanges of matter and energy from the leaf to the global scale?
mechanics
Mechanics
  • 2 lectures per week – TTh 11-11:50
    • Bio T 185
  • 1 lab per week – Tuesday 2-5
    • Carnegie Global Ecology (260 Panama Street)
  • 1 optional Matlab/problem session – Thursday 4-6
    • Carnegie Global Ecology (260 Panama Street)
  • Grading:
    • Bio 164:
      • Weekly problem/program 60%
      • Final project data analysis 20%
      • Class participation 10%
      • Labs (weekly data sets) 10%
    • Bio 264:
      • Weekly problem/program 40%
      • Final integrated program 20%
      • Final project data analysis 20%
      • Class participation 10%
      • Labs (weekly data sets) 10%
    • Problem/programs in Matlab
    • No midterm, no final, no papers
slide4
Labs
  • January 16
    • Principles of environmental sensors & data loggers
    • Radiation sensors
  • January 23
    • Environmental sensors – wind, humidity, soil moisture, water potential
  • January 30
    • Environmental sensors – CO2, water vapor
  • February 6
    • Leaf gas exchange
  • February 13
    • Leaves – fluorescence, spectral reflectance, isotope exchange
  • February 20
    • Canopy gas exchange – eddy flux hardware
  • February 27
    • Canopy gas exchange – environmental conditions at an eddy flux installation
  • March 6
    • Canopy gas exchange – vegetation status and fluxes at an eddy flux installation
  • March 13
    • Canopy gas exchange – setting up an eddy flux system
  • For each lab, each pair will be responsible for collecting, analyzing, and turning in a data set collected from at least one sensor or system
texts
Texts
  • Campbell, G. S. and J. M. Norman. 1998. An Introduction to Environmental Biophysics. Springer, New York. 286 pp. (core)
  • Hartmann, D. L. 1994. Global Physical Climatology. Academic Press, San Diego. 411 pp. (optional)
  • Stull, R. B. 2000. Meteorology for Scientists and Engineers. Brooks Cole, Pacific Grove. 503 pp. (optional)
  • Bonan, G. B. 2002. Ecological climatology: Concepts and applications. Cambridge University Press, New York. 678 pp. (optional)
slide7

What controls the temperature of the planet?

Heat-trapping or greenhouse gases trap thermal radiation on its way to space.

Energy in = Energy out + storage

what controls rates of photosynthesis
What controls rates of photosynthesis?

Annual weeds

Deciduous trees

Photosynthetic capacity

Evergreen sclerophylls

Leaf nitrogen

radiation
Radiation
  • All objects at temperatures above absolute zero emit radiation.
  • Photons carry a unique amount of energy that depends on wavelength
  • E = hc/l
  • Where h is Planck’s constant (6.63*10-34 Js), c is the speed of light (3*1010m s-1), and l is wavelength (m).
thermal radiation
Thermal Radiation
  • Stephan-Boltzmann Law
  • s = 5.67 * 10-8 W m-2 K-4
  • Earth approximates a black body at 288 K -- Emits 390 W m-2
  • Black body = emissivity () = 1
  • Note: the emissivity of plants is close to 1, but other objects can have very different values
absorptance and emissivity
Absorptance and Emissivity
  • Absorbed radition is proportional to absorptance
  • Emitted radiation in proportional to emissivity = absorptance
blackbody radiation
Blackbody radiation
  • Amount increases with T4
  • Wavelength of maximum proportional to 1/T
wien law
Wien Law
  • objects at 300k maximum emission at about 10 micrometers
solar energy
Solar energy
  • Solar output 3.84*1034 W
  • extra-atmosphere – the sun is close to a 5760 K black body
  • radiant emittance = 6.244*107 W m-2
  • most of the solar energy is in the range of 0.3 – 2.5 micrometers
  • about 50% is visible (0.4 – 0.7m) and about 50% is infrared (> 0.7m)
  • The solar (not so) constant
  • Integrating this emittance over the size of the sun and the distance to the earth leads to a radiation at the outside of the atmosphere of 1360 W m-2
  • Integrating over the spherical surface leads to an average radiation of about 342 W m-2
atmospheric transmission
Atmospheric transmission
  • Absorption
    • Average absorption by the atmosphere 62 W m-2
  • Scattering
    • Raleigh (small particle) – shortest wavelengths scattered preferentially out of the solar beam
    • Mie (large particle) – little wavelength dependence
    • Average reflected solar radiation by the atmosphere 77 W m-2
  • Effects of clouds
  • Scattering and reflectance
  • The greenhouse effect
    • Increased absorptance of thermal radiation means increased radiation directed back to the surface
    • Increased absorptance in the atm effectively increases the height at which the atmosphere is radiating back to space
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