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| Titel |
Statistical mechanics of Fofonoff flows in an oceanic basin |
| VerfasserIn |
Bérengère Dubrulle, Aurore Naso, Pierre-Henri Chavanis |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250050499
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| Zusammenfassung |
| We study the minimization of potential enstrophy at fixed circulation and energy in an
oceanic basin with arbitrary topography. For illustration, we consider a rectangular basin and
a linear topography h = by which represents either a real bottom topography or the β-effect
appropriate to oceanic situations. Our minimum enstrophy principle is motivated by different
arguments of statistical mechanics reviewed in the article. It leads to steady states of the
quasigeostrophic (QG) equations characterized by a linear relationship between potential
vorticity q and stream function Ï. For low values of the energy, we recover Fofonoff flows [J.
Mar. Res. 13, 254 (1954)] that display a strong westward jet. For large values of the energy,
we obtain geometry induced phase transitions between monopoles and dipoles similar
to those found by Chavanis & Sommeria [J. Fluid Mech. 314, 267 (1996)] in the
absence of topography. In the presence of topography, we recover and confirm
the results obtained by Venaille & Bouchet [Phys. Rev. Lett. 102, 104501 (2009)]
using a different formalism. In addition, we introduce relaxation equations towards
minimum potential enstrophy states and perform numerical simulations to illustrate the
phase transitions in a rectangular oceanic basin with linear topography (or β-effect). |
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