Generation of inertia-gravity waves in the rotating thermal annulus by a localised boundary layer instability

Jacoby, T. N. L., Read, P. L., Williams, P. D. ORCID: https://orcid.org/0000-0002-9713-9820 and Young, R. M. B. (2011) Generation of inertia-gravity waves in the rotating thermal annulus by a localised boundary layer instability. Geophysical & Astrophysical Fluid Dynamics, 105 (2-3). pp. 161-181. ISSN 0309-1929 doi: 10.1080/03091929.2011.560151

Abstract/Summary

Waves with periods shorter than the inertial period exist in the atmosphere (as inertia-gravity waves) and in the oceans (as Poincaré and internal gravity waves). Such waves owe their origin to various mechanisms, but of particular interest are those arising either from local secondary instabilities or spontaneous emission due to loss of balance. These phenomena have been studied in the laboratory, both in the mechanically-forced and the thermally-forced rotating annulus. Their generation mechanisms, especially in the latter system, have not yet been fully understood, however. Here we examine short period waves in a numerical model of the rotating thermal annulus, and show how the results are consistent with those from earlier laboratory experiments. We then show how these waves are consistent with being inertia-gravity waves generated by a localised instability within the thermal boundary layer, the location of which is determined by regions of strong shear and downwelling at certain points within a large-scale baroclinic wave flow. The resulting instability launches small-scale inertia-gravity waves into the geostrophic interior of the flow. Their behaviour is captured in fully nonlinear numerical simulations in a finite-difference, 3D Boussinesq Navier-Stokes model. Such a mechanism has many similarities with those responsible for launching small- and meso-scale inertia-gravity waves in the atmosphere from fronts and local convection.

Item Type	Article
URI	https://reading-clone.eprints-hosting.org/id/eprint/19577
Item Type	Article
Refereed	Yes
Divisions	Science > School of Mathematical, Physical and Computational Sciences > Department of Meteorology Science > School of Mathematical, Physical and Computational Sciences > NCAS
Publisher	Taylor & Francis Ltd
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