The use of GPS signals to estimate turbulence intensity in the troposphere and stratosphere

A methodology for estimating turbulence intensity and location from GPS-to-aircraft and GPS-to-LEO (Low Earth orbiting satellites) occultations is presented. The NexGen concept for using these measurements is to incorporate them in the Graphical Turbulence Guidance Nowcast (GTGN) product. This product is currently under development at NCAR, under the sponsorship of the FAA's Aviation Weather Research Program. GTGN will become operational for the NexGen IOC. In this paper it will be shown that measuring turbulence from GPS signals is feasible, and so it is hoped that these data can be used in a future version of GTGN.

The theoretical underpinnings for this problem are taken from weak-scattering theory for electromagnetic wave propagation in random media. These techniques are modified to deal with a transmitter and receiver moving relative to each other, as well as considering the more realistic situation of a defined patch of turbulence. The standard approaches in the literature are based upon space-filling turbulence (i.e., between the transmitter and receiver), or an infinitely thin screen. A simulation method is then used to evaluate the performance of estimators to calculate the intensity and location of the turbulence. Results from real GPS-COSMIC links will be presented to show that the methodology works with real-world data.