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Published byAlfred Shaw Modified over 9 years ago
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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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Full calculation of radiative equilibrium surface much too warm tropopause too cold stratosphere about right tropospheric lapse rate too large
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Atmospheric energy balance
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Hydrostatic balance
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Pressure and density profiles in a compressible atmosphere hydrostatic balance perfect gas law Isothermal atmosphere More generally, H=H(z) and gas constant for dry air R = 287 J kg -1 K -1
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Pressure and density profiles in a compressible atmosphere hydrostatic balance perfect gas law Isothermal atmosphere More generally, H=H(z) and (T=237K)
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Convection I: Incompressible fluid, no condensation T and ρ are conserved under adiabatic displacement stable unstable
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Thermodynamics of dry air C p = 1005 J kg -1 K -1
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Thermodynamics of dry air C p = 1005 J kg -1 K -1 specific entropy
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Thermodynamics of dry air C p = 1005 J kg -1 K -1 p 0 = 1000 hPa κ = R/c p = 2/7 (diatomic ideal gas) potential temperature (+ constant) specific entropy
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Thermodynamics of dry air C p = 1005 J kg -1 K -1 p 0 = 1000 hPa κ = R/c p = 2/7 (diatomic ideal gas) potential temperature Adiabatic processes : θ is conserved under adiabatic displacement (N. B. θ=T at p =p 0 = 1000 hPa) (+ constant) specific entropy
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Convection II: Compressible ideal gas, no condensation adiabatic displacement
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Convection II: Compressible ideal gas, no condensation hydrostatic balance adiabatic displacement
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Convection II: Compressible ideal gas, no condensation hydrostatic balance adiabatic displacement — adiabatic lapse rate Following displaced parcel
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Convection II: Compressible ideal gas, no condensation hydrostatic balance adiabatic displacement — adiabatic lapse rate Following displaced parcel unstable stable
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Convection II: Compressible ideal gas, no condensation hydrostatic balance adiabatic displacement — adiabatic lapse rate Following displaced parcel unstable stable
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Stability of Radiative Equilibrium Profile Radiative equilibrium is unstable in the troposphere -10 K/km radiative equilibrium solution
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Effects of convection Model aircraft observations in an unsaturated convective region (Renno & Williams)
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Effects of convection radiative-convective equilibrium
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Effects of convection radiative-convective equilibrium TROPOSPHERE STRATOSPHERE
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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. -10 K/km radiative equilibrium solution
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Radiative-convective equilibrium (unsaturated) Better, but: surface still too warm tropopause still too cold
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Moist convection Above a thin boundary layer, most atmospheric convection involves phase change of water: condensation releases latent heat
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