Nonlinear evolution of a gravity wave propagating from the tropopause

By using a Full-Implicite-Continuous-Eulerian (FICE) scheme, a two-dimensional numerical model for describing nonlinear propagation of a gravity wave in the compressible and nonisothermal atmosphere is established. The result shows that gravity wave excited by the tropopause forcing can propagate stably to the mesosphere through the stratosphere so that the energy and momentum can be transferred from a region to another. In the propagation, gravity wave undergoes growth, overturning, convection and breaking. The breaking of gravity wave is the important source of convection and smallscale waves, and convective instability and overturn are the character of nonlinear phenomenon. It can be inferred that the size of the perturbing source affects directly the propagation of nonlinear gravity. wave. When the source is sufficiently small gravity wave can propagate stably, and large amplitude forcing can accelerate the breaking of gravity wave.