Generation of Inertia-Gravity Waves from Jets within vortex dipoles

Gravity waves are ubiquitous in the atmosphere and play a fundamental role in a wide variety of atmospheric processes. This study investigates gravity wave generation and propagation from idealized jets within vortex dipoles by using numerical models. Inertial gravity waves with the intrinsic frequencies 1-2 times the Coriolis parameter are simulated in the jet exit region using a mesoscale model (MM5). To further address the source mechanism of the gravity waves within the vortex dipole, a numerical model linearized upon nonlinear state is developed based on the framework proposed by Plougonven and Zhang (2007). By imposing three types of large scale forcing, i.e., the vorticity, divergence and thermodynamic forcing, linear wave responses are obtained from this linear model. The linear wave packets compare reasonably well with the MM5 simulated gravity waves. On the other hand, the residual of the nonlinear balance equation is also used to as the forcing; the response from our linear model shows clean gravity waves, similar to the MM5-simulated gravity waves, despite of some phase difference. This linear model is further adopted to study inertia-gravity waves in the vicinity of a baroclinic jet during the life cycle of an idealized baroclinic wave. Results will also be discussed.