variance analysis numerical model 6 Analytical expressions 4 Computer simulation 4 Delta functions 4 El Nino-Southern Oscillation 4 GPS 4 Geometrical relations 4 Global positioning system 4 Gravitational effects 4 Gravity waves 4 High probability 4 Hydrodynamics 4 Line of Sight 4 Numerical simulation 4 Pacific Ocean 4 Radio occultations 4 Radio waves 4 Relative orientation 4 South America 4 Spherical symmetry 4 Wave amplitudes 4 Wave phase 4 Wave vector 4 Wavefronts 4 Waves 4 amplitude 4 computer simulation 4 gravity wave 4 marine ecosystem 4