Fluctuations of the GPS signals on the tangential paths in the lower terrestrial atmosphere: Influence of the small-scale structure

The small-scale structure of the refractivity distribution due to water vapor density fluctuations in the terrestrial troposphere and lower stratosphere is modeled. Propagation of the signals in the troposphere and lower stratosphere are numerically simulated on the basis of the parabolic equation of diffraction and for occultation geometry. Fluctuations of the signal amplitude on the tangential paths due to small-scale inhomogeneities of the atmospheric refractivity are estimated.