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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 l.jpg
Atmospheres

  • Take a weather class for details (870:021)

  • But until then…

    • Physical Principles

    • Structure

    • Characteristics

    • Origin/Evolution


Atmospheric physics l.jpg

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


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Combine them to get Pressure Scale Height (H)

(height needed for pressure to drop e )

Assume isothermal atmosphere

(good temperature assumption…?)


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  • 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


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Localized temperature influences

  • Distance from Sun

  • Albedo

  • Angle of the Sun

  • Rotation rate

  • Non-blackbody aspects - emissivity


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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 l.jpg
Atmosphere Structures

  • Troposphere

  • Tropopause

  • Stratosphere

  • Statopause

  • Mesosphere

  • Mesopause

  • Thermosphere

  • Thermopause/Exobase

  • Exosphere









Wimpy atmospheres l.jpg
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 l.jpg
Atmospheric Motions

  • Circulation Patterns

    • Thermal Tidal Winds

    • Condensation Winds

    • Hadley Circulation

    • Pressure gradients

    • Rotation (Coriolis effect)



Origin l.jpg
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 l.jpg
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 l.jpg
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 l.jpg
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!


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