The dissertation first investigates gravity wave generation and propagation from
jets within idealized vortex dipoles using a nonhydrostatic mesoscale model. Several
initially balanced and localized jets induced by vortex dipoles are examined here. Within
these dipoles, inertia-gravity waves with intrinsic frequencies 1-2 times the Coriolis
parameter are simulated in the jet exit region. The ray tracing analysis reveals strong
variation of wave characteristics along ray paths. The dependence of wave amplitude on
the Rossby number is examined through experiments in which the two vortices are
initially separated by a large distance but subsequently approach each other and form a
vortex dipole with an associated amplifying localized jet. The amplitude of stationary
gravity waves in the simulations with a 90-km grid spacing increases nearly linearly with
the square of the Rossby number but significantly more rapidly when smaller grid
spacing is used.
To further address the source mechanism of the gravity waves within the vortex
dipole, a linear numerical framework is developed based on the framework proposed by
Plougonven and Zhang (2007). Using the nonlinearly balanced fields as the basic state and driven by three types of large scale forcing, the vorticity, divergence and
thermodynamic forcing, this linear model is utilized to obtain linear wave responses. The
wave packets in the linear responses compare reasonably well with the MM5 simulated
gravity waves. It is suggested that the vorticity forcing is the leading contribution to both
gravity waves in the jet exit region and the ascent/descent feature in the jet core.
This linear model is also adopted to study inertia-gravity waves in the vicinity of
a baroclinic jet during the life cycle of an idealized baroclinic wave. It is found that the
thermodynamic forcing and the vorticity forcing are equally important to the gravity
waves in the low stratosphere, but the divergence forcing is again playing a lesser role.
Two groups of wave packets are present in the linear responses; their sources appear to
locate either near the surface front or near the middle/upper tropospheric jet.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-2875 |
| Date | 15 May 2009 |
| Creators | Wang, Shuguang |
| Contributors | Zhang, Fuqing |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation, text |
| Format | electronic, application/pdf, born digital |
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