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| Titel |
Testing the limits of quasi-geostrophic theory: application to observed laboratory flows outside the quasi-geostrophic regime |
| VerfasserIn |
Paul Williams, Peter Read, Thomas Haine |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250031943
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| Zusammenfassung |
| We compare laboratory observations of equilibrated baroclinic waves in the rotating
two-layer annulus, with numerical simulations from a quasi-geostrophic model. The
laboratory experiments lie well outside the quasi-geostrophic regime: the Rossby number
reaches unity; the depth-to-width aspect ratio is large; and the fluid contains ageostrophic
inertia-gravity waves.
Despite being formally inapplicable, the quasi-geostrophic model captures the laboratory
flows reasonably well. The model displays several systematic biases, which are
consequences of its treatment of boundary layers and neglect of interfacial surface
tension, and which may be explained without invoking the dynamical effects of the
moderate Rossby number, large aspect ratio or inertia-gravity waves. We conclude
that quasi-geostrophic theory appears to continue to apply well outside its formal
bounds.
This is an unexpected and intriguing result that could not have been predicted from the
existing literature. It is also potentially useful, for example by permitting the use of a
low-order quasi-geostrophic model to easily map out the bifurcation structure —
which would be very difficult with a primitive equations model — followed by
the use of a primitive equations model for more quantitative agreement in specific
cases.
Reference
Williams, PD, PL Read and TWN Haine (2010) Testing the limits of quasi-geostrophic
theory: application to observed laboratory flows outside the quasi-geostrophic regime.
Journal of Fluid Mechanics, in press. |
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