RT Dissertation/Thesis T1 Application of Global Positioning System slant path delay data for mesoscale modelverification and four-dimensional variational assimilation A1 Zus,Florian WP 2011/01/11 AB Observation modeling is required in order to make use of slant path delay data, processed from ground-based Global Positioning System (GPS) measurements, for verification purposes and numerical weather prediction. A rigorous ray-tracing algorithm based on the Euler-Lagrange equation derived from Fermat's principle is developed to simulate the propagation of GPS radio signals in a mesoscale model. The ray-tracing algorithm is based on a finite difference scheme and allows the direct numerical simulation of GPS slant path delays. K1 GPS PP Hohenheim PB Kommunikations-, Informations- und Medienzentrum der Universität Hohenheim UL http://opus.uni-hohenheim.de/volltexte/2011/516