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Environmental Physics: Climate Dynamics aspects Arnaud Czaja Space & Atmospheric Physics

Environmental Physics: Climate Dynamics aspects Arnaud Czaja Space & Atmospheric Physics. Overview (Lectures #7-14). Greenhouse effect (#7, i.e. today) Water Vapour feedback (#8) Cooling mechanisms for the planet (#9) Climate models (#10) + MATLAB session Climate timescales (#11)

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Environmental Physics: Climate Dynamics aspects Arnaud Czaja Space & Atmospheric Physics

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  1. Environmental Physics:Climate Dynamics aspectsArnaud CzajaSpace & Atmospheric Physics

  2. Overview (Lectures #7-14) • Greenhouse effect (#7, i.e. today) • Water Vapour feedback (#8) • Cooling mechanisms for the planet (#9) • Climate models (#10) + MATLAB session • Climate timescales (#11) • Climate sensitivity (#12) • Modes of climate variability (#13) • Discussion of a hot Topic (#14)

  3. Atmosphere Extra Tropics Ocean Tropics Our own EP Climate Model!

  4. Atmosphere Extra Tropics Ocean Tropics Our own EP Climate Model! (i) Use of model is not mandatory and thus the model is not examinable (ii) MATLAB session on Thursday Feb 7 (5-6pm) (come if you wish, this is not mandatory)

  5. Lecture 7The Greenhouse effect

  6. Lecture 7The Greenhouse effect Student: Oh yeah! It’s the trapping of radiation by the atmosphere

  7. Lecture 7The Greenhouse effect Lecturer: Let’s be a bit more precise!!

  8. 7.1 Motivation:Observations of Earth from Space

  9. Total radiation seen by a satellite NB: Photon energy is the main form of energy exchanged between the earth and space (GERB project in Space & Atmospheric Physics)

  10. SW LW + Long wavelength photons (emitted by the Earth) Short wavelength photons (reflected from the Sun)

  11. Terrestrial radiation λ≈10-20μm 1 erg s-1 cm-2 = 10-3 W m-2

  12. Solar radiation λ≈0.2-1μm Sun radiation

  13. To zero order… • Solar photons are absorbed by the atmosphere (clouds, water vapour, ozone) • …but much less so than are the terrestrial photons. • This is because of the atmospheric composition, with tri-atomic molecules efficient at interacting with λ≈10-20μm photons (“greenhouse absorbers”).

  14. Atmospheric composition (fraction of total molecules) N2 Main Greenhouse gas (GHG) is Water vapour (variable ≈1%) O2 CO2 NB: 1ppmv = 1 molecule out of a million 1ppbv = 1 molecule out of a billion

  15. What is meant by variable H2O… Low level enthalpy Upper tropospheric RH on April 27, 1999 3.5 0 100 2.5

  16. 7.3 Observations of the greenhouse effect (G)

  17. 180 Observed Greenhouse effect 50 50 Water vapour content 10 303 Sea surface temperature 273 NB: All are annual mean data (from Held & Soden, 2000)

  18. Solar spectrum Lean (1991) [adapted by Lockwood] 28 May 2003 Imperial College London 20

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