Climate Physics and Chemistry Role of the Atmosphere in Climate Ways by which the atmosphere influences climate: • Strong effects on radiative transfer, including filtering of ultraviolet radiation • Large advective and convective heat transfer • Main driver of ocean circulation • Important role in biogeochemical cycles Atmospheric Composition Gas Name Nitrogen Chemical Formula N2 Percent Volume 78.08% Oxygen O2 20.95% *Water H2O 0 to 4% Argon Ar 0.93% CO2 0.0360% Neon Ne 0.0018% Helium He 0.0005% *Methane CH4 0.00017% Hydrogen H2 0.00005% N2O 0.00003% O3 0.000004% *Carbon Dioxide *Nitrous Oxide *Ozone * variable gases 100000 Thermosphere 90000 Mesopause 80000 Altitude (meters) 70000 60000 Mesosphere Stratopause 50000 40000 30000 Stratosphere 20000 Tropopause 10000 Troposphere 0 -100 -80 -60 -40 Temperature oC -20 0 20 Figures removed due to copyright restrictions. See Figure 1.6 and Figure 1.7 in Hartmann, Dennis L. Global Physical Climatology. Reading, MA: Academic Press, p.411. ISBN: 0123285305. Elements of Thermal Balance: Solar Radiation • Luminosity: 3.9 x 1026 J s-1 = 6.4 x 107 Wm-2 at top of photosphere • Mean distance from earth: 1.5 x 1011 m • Flux density at mean radius of earth L − 2 0 = 1370 Wm S ≡ 0 2 4π d Stefan-Boltzmann Equation: F =σ T 4 − 8 − − 2 4 σ =5.67×10 Wm K Sun: → 7 − 4 2 σ T =6.4×10 Wm T 6,000 K Disposition of Solar Radiation:   2 Total absorbed solar radiation = S 1 − a  π r 0 p p a ≡ planetary albedo ( 30% ) p Total surface area = 4π r 2 p S Absorption per unit area = 0 1 − a  p 4  Absorption by clouds, atmosphere, and surface Terrestrial Radiation: Effective emission temperature: S σ T 4 ≡ 0 1 − a  e 4  p Earth: T = 255 K = − 18°C e Observed average surface temperature = 288K = 15°C Highly Reduced Model • Transparent to solar radiation • Opaque to infrared radiation • Blackbody emission from surface and each layer Radiative Equilibrium: Top of Atmosphere: S   4 4 0 σT = 1− a  = σT  A p e 4  → TA = Te Surface: S0 4 σ Ts = σ TA + (1 − a p ) = 2σ Te 4 4 4 1 → Ts = 2 4 Te = 303 K Surface temperature too large because: • Real atmosphere is not opaque • Heat transported by convection as well as by radiation Figures removed due to copyright restrictions. See Figures in Hartmann, Dennis L. Global Physical Climatology. Reading, MA: Academic Press, p.411. ISBN: 0123285305. 6 4 Ocean Transport Atmosphere Transport Total Transport petaWatts 2 0 -2 -4 -6 -90 -60 -30 0 30 60 Latitude Heat Transport by Oceans and Atmosphere 90