waves are absorbed in the atmosphere according to wavelength. Two compounds are responsible for the majority of
signal absorption: oxygen (O2
) and water vapor (H2
Here is the official document by the International Telecommunications Union that contains very detailed data.
Recommendation ITU-R P.676-9
Attenuation by atmospheric gases
P Series Radiowave propagation
The first peak occurs at 22 GHz due to water, and the second at 63 GHz due to oxygen. The actual amount of water
vapor and oxygen in the atmosphere normally declines with an increase in altitude because of the decrease in
pressure, so these graphs apply from sea level to around 1 km altitude.
Total attenuation through the
atmosphere at any frequency through unobstructed atmosphere is the sum of free space
, attenuation caused by oxygen absorption and attenuation caused by water vapor absorption. Rain
attenuation, when present adds an additional element. For a chart of sunlight power density in the visible light
and infrared / ultraviolet region of the electromagnetic spectrum, click
This chart was generated from frequency / attenuation data points picked off of a published
Atmospheric Attenuation Chart
that were entered into Excel and plotted.