Radiative transfer to space affected by atmosphere?

In summary: This is a simplification that ignores the atmospheric absorption and emission. Some researchers have used more sophisticated models, such as LOWTRAN, MODTRAN, and HITRAN, which take into account atmospheric absorption. These models have shown that the atmospheric absorption can vary depending on factors such as humidity. However, for a rough estimate, one can use the Earth's view from space to determine the sky temperature. Overall, the heat transfer equation becomes an integral over wavelength due to the conservation of energy principle.
  • #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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  • #2
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.
 
  • #3
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.
 
  • #4
Mapes said:
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?

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

1. What is radiative transfer to space affected by atmosphere?

Radiative transfer refers to the transfer of energy in the form of electromagnetic radiation. In the case of Earth, this transfer of energy is affected by the atmosphere, as it absorbs, scatters, and reflects incoming solar radiation before it can reach space.

2. How does the atmosphere affect the amount of radiation reaching space?

The atmosphere plays a crucial role in regulating the amount of radiation that reaches space. It absorbs and scatters a significant portion of the incoming solar radiation, resulting in less energy reaching the upper layers of the atmosphere and ultimately escaping into space.

3. Which atmospheric gases are responsible for the absorption and scattering of radiation?

The main atmospheric gases responsible for the absorption and scattering of radiation are water vapor, carbon dioxide, methane, and ozone. These gases are known as greenhouse gases and play a crucial role in regulating Earth's temperature.

4. How does the amount of greenhouse gases in the atmosphere affect radiative transfer to space?

The more greenhouse gases there are in the atmosphere, the more radiation will be absorbed and scattered, resulting in less energy reaching space. This phenomenon is known as the greenhouse effect and is responsible for keeping Earth's temperature within a habitable range.

5. How does human activity impact radiative transfer to space affected by atmosphere?

Human activities, such as burning fossil fuels and deforestation, have significantly increased the levels of greenhouse gases in the atmosphere. This has amplified the greenhouse effect and is contributing to the warming of Earth's climate, also known as global warming.

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