THE NONLINEAR PROPAGATION OF GRAVITYWAVE PACKETS IN THE SHEARED AMBIENT

By using a two-dimentional Full-Implicit-Continucus-Eulerian (FICE) scheme,a numerical simulation of nonlinear propagation of a Gaussian gravity-wave-packetin sheared ambient is carried out. The numerical analysis shows that for an initiallygiven upgoing gravity-wave-packet, in absence of a critical layer, although there exists nonlinear interaction during the propagation, the whole wave packet and thewave-associated energy keep moving upward, while the wave front moving downward. Wave-associated perturbation velocity increases with the increasing height,and the vertical wavelength decreases with the increasing height. The propagationpath of wave energy flux coincides well with the ray path predicted by the lineargravity wave theory, but the magnitude of wave energy propagation velocity is evidently smaller than the group velocity derived from the linear gravity wave theory.This indicates that the nonlinear propagation characteristics of gravity wave packetsin sheared ambient are essentially linear.