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Atmospheres. Take a weather class for details (870:021) But until then… Physical Principles Structure Characteristics Origin/Evolution. Hydrostatic Equilibrium P=change in pressure G=Constant M=planet mass z=height r =density. Ideal Gas Law  =Constant T=Temperature (K)

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atmospheres
Atmospheres
  • Take a weather class for details (870:021)
  • But until then…
    • Physical Principles
    • Structure
    • Characteristics
    • Origin/Evolution
atmospheric physics
Hydrostatic Equilibrium

P=change in pressure

G=Constant

M=planet mass

z=height

r=density

Ideal Gas Law

=Constant

T=Temperature (K)

m=mean molecular weight

Atmospheric Physics
slide3
Combine them to get Pressure Scale Height (H)

(height needed for pressure to drop e )

Assume isothermal atmosphere

(good temperature assumption…?)

slide4
What influences the Temperature?
    • Sun
    • Internal energy sources – re-radiated light
    • Chemical reactions – change opacity
    • Clouds/haze – change opacity, latent heat
    • Volcanoes/Geysers
    • Oxidation/Sedimentation
    • Biogenic, Anthropogenic processes
  • Temperature structures not all the same
slide5
Localized temperature influences
  • Distance from Sun
  • Albedo
  • Angle of the Sun
  • Rotation rate
  • Non-blackbody aspects - emissivity
slide6
Solar heating – assuming sun over equator

T = Surface temperature

Fsun= Solar Constant

(1360 W/m2)

A = albedo

f = latitude

e = emissivity

s = constant

a = distance from Sun

atmosphere structures
Atmosphere Structures
  • Troposphere
  • Tropopause
  • Stratosphere
  • Statopause
  • Mesosphere
  • Mesopause
  • Thermosphere
  • Thermopause/Exobase
  • Exosphere
wimpy atmospheres
Wimpy Atmospheres
  • Mercury
    • O, Na, He, K, H, Ca, Xe, Kr, CO2, H2O, Ar
    • P=10-15 bar, T=100-700 K
  • Moon
    • H, He, Ar, Na, K
    • P=10-15 bar, T=120-380 K
  • Pluto –
    • N2, CO, CH4, ethane
    • P=6.5x10-6 – 2.4x10-5bar, T=53 K
  • Triton –
    • N2, CH4
    • P=1.4x10-5bar, T=40 K
  • Io – SO2, SO
  • Enceladus – N, CO2, CH4
atmospheric motions
Atmospheric Motions
  • Circulation Patterns
    • Thermal Tidal Winds
    • Condensation Winds
    • Hadley Circulation
    • Pressure gradients
    • Rotation (Coriolis effect)
origin
Origin
  • Where do atmospheres come from?
    • Why are they different?
      • Origins different (location)
      • Gravity - escape
      • Chemical reactions – Photodissociation/Recombination

CH4 + H2O ↔ CO + 3H2

2NH3↔ N2 + 3H2

H2S + 2H2O ↔ SO2 + 3H2

Etc.

      • Plus Ar, Kr, Xe in solar amounts – NOT!
      • Outgassing
earth s atmospheric history
Earth’s Atmospheric History
  • Past was hotter
  • Early Greenhouse effect (H2O, CO2, CH4, NH3)
  • CO2 cycles through a system
    • Weathering
    • Carbonate minerals
    • Volcanism
  • Oxygen – life, dissociation of H2O
mars atmospheric history
Mars Atmospheric History
  • Thicker in the past (Noachian era)
  • Atmosphere ~ 1 bar, T ~ 300 K
  • Rich in CO2, H2O
  • CO2 lost through
    • Weathering
    • Adsorption into regolith
    • Condensation
    • Impacts
  • No water, no CO2 cycling
  • No volcanism, no CO2 cycling
  • Why no water?
venus atmosphere history
Venus Atmosphere History
  • Very little H2O – Why?
  • D/H ratio is high!
  • Lost to space? No… Runaway greenhouse!
    • Outgassing
    • more water in atmosphere
    • more green house effect
    • No CONDENSATION!