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The Atmosphere: Part 3: Unsaturated convection

The Atmosphere: Part 3: Unsaturated convection. Composition / Structure Radiative transfer Vertical and latitudinal heat transport Atmospheric circulation Climate modeling. Suggested further reading: Hartmann, Global Physical Climatology (Academic Press, 1994).

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The Atmosphere: Part 3: Unsaturated convection

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  1. The Atmosphere: Part 3: Unsaturated convection • Composition / Structure • Radiative transfer • Vertical and latitudinal heat transport • Atmospheric circulation • Climate modeling Suggested further reading: Hartmann, Global Physical Climatology (Academic Press, 1994)

  2. Full calculation of radiative equilibrium stratosphere about right tropospheric lapse rate too large tropopause too cold surface much too warm

  3. Atmospheric energy balance

  4. Hydrostatic balance

  5. Pressure and density profiles in a compressible atmosphere gas constant for dry air R = 287 J kg-1K-1 hydrostatic balance perfect gas law Isothermal atmosphere More generally, H=H(z)and

  6. Pressure and density profiles in a compressible atmosphere hydrostatic balance perfect gas law (T=237K) Isothermal atmosphere More generally, H=H(z)and

  7. ConvectionI: Incompressible fluid, no condensation T and ρ are conserved under adiabatic displacement stable unstable

  8. Thermodynamics of dry air Cp = 1005 J kg-1K-1

  9. Thermodynamics of dry air Cp = 1005 J kg-1K-1 specific entropy

  10. Thermodynamics of dry air Cp = 1005 J kg-1K-1 p0 = 1000 hPa κ = R/cp = 2/7 (diatomic ideal gas) specific entropy potential temperature (+ constant)

  11. Thermodynamics of dry air Cp = 1005 J kg-1K-1 p0 = 1000 hPa κ = R/cp = 2/7 (diatomic ideal gas) specific entropy potential temperature (+ constant) Adiabatic processes : θ is conserved under adiabatic displacement (N. B. θ=Tat p =p0= 1000 hPa)

  12. ConvectionII: Compressible ideal gas, no condensation adiabatic displacement

  13. ConvectionII: Compressible ideal gas, no condensation adiabatic displacement hydrostatic balance

  14. ConvectionII: Compressible ideal gas, no condensation adiabatic displacement hydrostatic balance Following displaced parcel — adiabatic lapse rate

  15. ConvectionII: Compressible ideal gas, no condensation adiabatic displacement hydrostatic balance Following displaced parcel — adiabatic lapse rate unstable stable

  16. ConvectionII: Compressible ideal gas, no condensation adiabatic displacement hydrostatic balance Following displaced parcel — adiabatic lapse rate unstable stable

  17. Stability of RadiativeEquilibrium Profile • Radiative equilibrium is unstable in the • troposphere radiative equilibrium solution -10 K/km

  18. Effects of convection Model aircraft observations in an unsaturated convective region (Renno & Williams)

  19. Effects of convection radiative-convective equilibrium

  20. Effects of convection radiative-convective equilibrium STRATOSPHERE TROPOSPHERE

  21. Radiative-Convective Equilibrium • Radiative equilibrium is unstable in the • troposphere • Re-calculate equilibrium subject to the constraint that tropospheric stability is rendered neutral by convection. radiative equilibrium solution -10 K/km

  22. Radiative-convective equilibrium(unsaturated) • Better, but: • surface still too warm • tropopause still too cold

  23. Moist convection Above a thin boundary layer, most atmospheric convection involves phase change of water: condensation releases latent heat

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