Generation of inertia-gravity waves from jets within vortex dipoles

This study investigates gravity waves from the localized jet within an initially balanced vortex dipole. Inertia-gravity waves with the intrinsic frequencies 1-2 times the Coriolis parameter are first simulated in the jet exit region using a nonlinear numerical model. Such wave generation is further studied in a linear framework (Plougonven and Zhang 2007) in which wave response is considered as a forced, linear disturbance about a balanced background state. Following this framework, a nonhydrostatic numerical linear model is developed. Three types of large scale forcing, i.e., the vorticity, divergence and thermodynamic forcing, are diagnosed from the large scale balance flow. Imposing these forcing in the linear model leads to gravity wave generation in the exit region of the localized jet. The spatial structure of these linear wave packets compare reasonably well with that of waves in the nonlinear model. The role of the three types of the forcing is also discussed.