Index of Refraction of Atmosphere for Radio Waves

Theorem
The index of refraction of the atmosphere of Earth for radio waves of frequency less than $3 \times 10^{10} \, \mathrm {Hz}$ is given by:


 * $\paren {n - 1} 10^6 = \dfrac {77 \cdotp 6} t \paren {p + \dfrac {4810 e} t}$

where:
 * $n$ denotes the index of refraction of the atmosphere
 * $t$ denotes the temperature in kelvin
 * $p$ denotes the total atmospheric pressure in millibars
 * $e$ denotes the water vapor partial pressure in millibars.