With the method provided by stratification theory, the properties of several important systems of quasilinear partial differential equations in hydrodynamics and atmospheric dynamics are discussed, these partial differential equations include: The Euler equation of describing inviscid compressible adiabatic fluid (call it equations setâ… );The motion equations of adiabatic dry atmosphere with turbulent viscosity but without consideration of turbulent dissipation and aerosol (call it equations setâ…¡);The anelastic equations set without consideration of turbulent viscosity (call it equations setâ…¢);The anelastic equations set with consideration of turbulent viscosity (call it equations setâ…£);The discussed properties involve: topological construction ; C kstability ; the well-posedness conditions of representative initial boundary value problem;the computation of analytical solution for analytic well-posed problem, and the solvability of ill-posed problem etc.. The main conclusions are obtained as follows:1. The equations setâ… ,â…¡,â…¢are C∞stable equations;and the equations setâ…£is C k( k≥2)unsteady equation.2. The C∞stability of Euler equation determines C∞stability of some models when viscosity (molecule viscosity,turbulent viscosity) is neglected during atmospheric motion.3. For the equations setâ… ,â…¡,â…¢, their structures of local solution space are discussed and analyzed respectively.4. On the hypersurface {t = 0}?R4, the initial value problem established by the equations setâ… is well posed, and then the analytical solution of its analytic well-posed problem is also gained.5. For the equations setâ…¡,â…¢, their initial value problems on the hypersurface {t = 0}?R4are ill-posed. |