Differential equations, Parabolic Numerical solutions 12 Differential equations, Elliptic 5 Mathematical models 5 Tropospheric radio wave propagation 5 Evolution equations 3 Finite element method 3 Galerkin methods 2 Lyapunov stability 2 Manifolds (Mathematics) 2 Pseudodifferential operators 2 Singularities (Mathematics) 2 Sobolev spaces 2 Spectral theory (Mathematics) 2 Attractors (Mathematics) 1 Curves, Algebraic 1 Geometric analysis 1 Hamilton-Jacobi equations 1