Simulating the Impact of Refractive Transverse Gradients Resulting From a Severe Troposphere Weather Event on GPS Signal Propagation

In this study, the effects of transverse refractive gradients in the ionosphere and in the lower atmosphere on GPS signal paths for both ground-based receivers and receivers on board low Earth orbital satellites are examined. A three-dimensional numerical ray tracing technique, based on geometrical optics, together with the models of the ionosphere, lower atmosphere, and magnetic field, are used to simulate GPS signal propagation. The average transverse refractive gradients were determined from a tropospheric storm event over Melbourne, Australia, on 6th of March, 2010. The traditional GPS ionospheric and atmospheric retrieval methods assume spherical stratification of the refractivity in the atmosphere and typically do not take into consideration the transverse refractivity gradients acting on the GPS signals. The transverse displacements of the GPS signal paths are calculated for both ground-based stations and for low Earth orbit radio occultation paths.