Atmospheric oxygen and particularly atmospheric water vapour cause a minor level of attenuation of satellite signals. The effects generally increase with frequency and are greatest near lines in the absorption spectra for each molecule. The line of most interest normally is the water absorption line at 22.3 GHz.
The amount of absorption will depend on the humidity (water vapour concentration) and the elevation angle.
The graphs below show the effect and give some idea of its magnitude.
Figure 21: Graph showing specific attenuation for atmospheric oxygen and water vapour as a function of frequency [Ref 9].
Figure 22: Graph showing total atmospheric attenuation as a function of frequency and elevation angle, E [Ref 2].
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