The Radio Refractive Index of Air

This is a tutorial paper. The derivation of the classical Debye expression for the radio refractive index is reviewed. Recent determinations of the constants in this expression are reviewed and the conclusion reached that differences between constants are small compared with the error in using standard meteorological data in the formula. The various transformations of refractive index data are discussed as a natural result of the model assumed for its height distribution. The effect of the use of the various units is illustrated by examples drawn from radio climatology and the refraction of radio waves.