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Chapter 3 Atmospheric Radiative Transfer and Climate

Chapter 3 Atmospheric Radiative Transfer and Climate. Kiehl and Trenberth (1997). Energy Balance at the TOA (Ch. 2). Planetary albedo Outgoing longwave radiation (OLR) Net incoming radiation Movie of net incoming radiation Zonal mean net radiation at TOA.

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Chapter 3 Atmospheric Radiative Transfer and Climate

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  1. Chapter 3 Atmospheric Radiative Transfer and Climate Kiehl and Trenberth (1997)

  2. Energy Balance at the TOA (Ch. 2) Planetary albedo Outgoing longwave radiation (OLR) Net incoming radiation Movie of net incoming radiation Zonal mean net radiation at TOA

  3. Why do we global wind patterns (general circulation)? Unequal heating of tropics and poles

  4. General Circulation of the Atmosphere

  5. Radiative Forcing

  6. The greenhouse effect Solar radiation Long-wave radiation 236 Wm-2 236 Wm-2 Equivalent T = 255 K (-18ºC) 390 Wm-2 T = 288 K (+15ºC)

  7. Nuclear Configuration and Permanent Dipole Movement Symmetric, linear molecules (Both ends look the same) Nonlinear or bent Have pure rotation bands

  8. Vibrational Modes of Diatomic and Triatomic Molecules

  9. Nitrous Oxide Atmospheric Absorption Methane Solar radiation passes rather freely through earth's atmosphere, but earth's re-emitted longwave energy either fits through a narrow window or is absorbed by greenhouse gases and re-radiated toward earth. Ozone Absorption (100%) Water Vapor Carbon Dioxide UV IR Total Atmo Wavelength

  10. Spectra of outgoing radiation from Earth observed by IRIS on Nimbus 3

  11. Clouds and Radiation • 1. Cloud maps 2. Radiation plots Cloud forcing = cloudy – cloud-free NET = SW + LW

  12. Thermal equilibrium profiles

  13. The Enhanced greenhouse effect S L 236 236 S L 236 236 S L 236 236 S L 236 236 Solar (S) and longwave (L) radiation in Wm-2 at the top of the atmosphere T = -18°C CO2 x 2 + Feedbacks H2O (+60%) Ice/Albedo (+20%) Cloud? Ocean? CO2 x 2 CO2 x 2 TS = 15°C TS = 15°C DTS ~ 1.2K DTS ~ 2.5K

  14. The climate system

  15. The Development of Climate models, Past, Present and Future Late 1960s Early 1980s Mid 1990s Present day Late 2000s? Mid 1950s Atmosphere Atmosphere Atmosphere Atmosphere Atmosphere Atmosphere Land surface Land surface Land surface Land surface Land surface Ocean & sea-ice Ocean & sea-ice Ocean & sea-ice Ocean & sea-ice Sulphate aerosol Sulphate aerosol Sulphate aerosol Non-sulphate aerosol Non-sulphate aerosol Carbon cycle Carbon cycle Atmospheric chemistry Sulphur cycle model Non-sulphate aerosols Ocean & sea-ice model Off-line model development Strengthening colours denote improvements in models Land carbon cycle model Carbon cycle model Ocean carbon cycle model Atmospheric chemistry Atmospheric chemistry Modified based on John Houghton

  16. Coupled atmosphere / ocean climate model Radiation Atmosphere: Density Motion Water Heat Exchange of: Momentum Water Ocean: Density (inc. Salinity) Motion Sea Ice Land

  17. 30km 19 levels in atmosphere 2.5 lat 3.75 long THE HADLEYCENTRETHIRDCOUPLEDMODEL -HadCM3 1.25 1.25 20 levelsin ocean -5km

  18. Physical Feedbacks • Water vapour • Ice albedo • Clouds • Oceans • Ice sheets

  19. Cloud Radiation Feedback

  20. Cloud radiation feedback

  21. Global average change in T /C

  22. Model Estimates of Cloud Radiative Forcing with CO2 Doubling Cloud forcing = cloudy – cloud-free NET = SW + LW

  23. Effect of cloud feedback formulation on climate prediction • Feedback scheme Global Av Temp change,C for doubled CO2 • RH 5.3 • CW 2.8 • CWRP 1.9 • after Senior & Mitchell, Hadley Centre

  24. Net cloud forcing: January to July Hadley Centre

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