THE NONLINEAR PROPAGATION OF GRAVITY WAVE PACKETS IN A NONISOTHERMAL AND COMPRESSIBLE ATMOSPHERE

By using two-dimentional Full-Implicit-Continuous-Eulerian(FICE)scheme,a numerical simulation of nonlinear propagation of a Gaussian gravity-wave-packet in the compressible and nonisothermal atmosphere is carried out,and a quantitative comparison with the propagation in an isothermal atmosphere and the linear gravity wave theory under the WKB approximation is also presented.The numerical analysis shows that for an initially given upgoing gravity-wave-packet although affected by the nonlinear interaction and the inhomogeneity of background temperature, during the propagation, the whole wave packet and the wave-associated energy keep moving upward,while the wave front moving downward. Affected by the inhomogeneity of the background temperature, the shape of the wave packet alters more significantly than in isothermal case, and there occurs wave breaking at the downstream region of the wave packet. The nonlinear energy propagation path of the gravity-wave-packet shows evident difference from the ray path derived from the linear ray theory under the WKB approximation,this indicates that it is not feasible to describe quantitatively the nonlinear propagation of gravity-wave-packet in a nonisothermal atmosphere by using the linear gravity wave theory under the WKB approximation.