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Radiative transfer to space affected by atmosphere?

  1. Mar 5, 2008 #1

    Mapes

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    I'm trying to model radiation losses from a flat surface facing the sky at night. If we ignore radiative absorption/emission in the atmosphere, the heat flux is the well-known

    [tex]Q=\epsilon\sigma(T_s^4-T_\infty^4)[/tex]

    where we have the emissivity, the S-B constant, the temperature of the surface, and where I would think [itex]T_\infty[/itex] is the effective temperature of outer space, 3K.

    How does the presence of the atmosphere affect this model? How have other researchers dealt with this complication?
     
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  3. Mar 5, 2008 #2

    russ_watters

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    The IR transparency of the atmosphere is dependent on humidity. It would be a significant complication. I suppose you could get a reasonable estimate based on the view of earth down from the top: http://www.goes.noaa.gov/ECIR4.html

    With a known surface temperature and a measured temperature through the atmosphere, you can estimate the effect of sky transparency.
     
  4. Mar 6, 2008 #3

    Andy Resnick

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    It's pretty easy: the emissivity is a function of wavelength. Becasue of conservation of energy, the emissivity = absoprtion. The heat transfer equation simply turns into an integral over wavelength.

    The atmospheric absoprtion depends on pretty much everything, there's good computational models (LOWTRAN/MODTRAN/HITRAN) out there, some of which are public domain.
     
  5. Mar 6, 2008 #4

    GT1

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    On most of the heat transfer calculations I've seen the sky temperature on a clear night was taken as 230K.
     
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