Two basic Recommendations dealing with refractivity.
Rec. P.453 gives the basic formulae and also global maps of refractivity and refractivity gradients. The latest version of Rec also gives other parameters such as duct thickness and duct heights.
Rec. P.834 addresses how refractivity influences radiowave propagation, e.g.
ray bending – which will cause a change in apparent elevation angle to a satellite
effective radio path length which differs from the geometrical path length
considerations of the conditions governing the entry and exit of energy in ducts.
