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Abstract
A uniformly valid balanced model that represents the quasigeostrophic model's counterpart in the equatorial region is derived. The quasigeostrophic model itself fails in the equatorial region because it is only valid where the dominant balance is geostrophic, i.e. where the Rossby number is small. The smallness of the Rossby number is assumed in the quasigeostrophic model's standard derivation and therefore this derivation cannot be repeated for the equatorial region. An alternative derivation of the quasigeostrophic model that is independent of the Rossby number was presented by Leith in 1980, using the geometric framework of nonlinear normal mode initialization. Its independence of the Rossby number allows it to be repeated for the equatorial region, leading to an equatorial balanced model that thus represents the equatorial counterpart of the quasigeostrophic model. As such it also coincides with the quasigeostrophic model sufficiently far away from the equator. Its dispersion relation can be expressed in an explicit analytic form and, compared to that of other balanced models of similar simplicity, approximates that of the shallow water equations strikingly well.
Original language  English 

Pages (fromto)  327356 
Number of pages  30 
Journal  Journal of Fluid Mechanics 
Volume  637 
DOIs  
Publication status  Published  25 Oct 2009 
Keywords
 LOCAL MASS CONSERVATION
 BALANCED MODELS
 SERIES EXPANSION
 LIMITED AREA
 INITIALIZATION
 EQUATIONS
 RECONSTRUCTION
 PLANE
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 1 Finished

RESEARCH FELLOWSHIP: CASL algorithms for the dynamical core of global circulation
Mohebalhojeh, A. R.
1/09/04 → 31/08/07
Project: Fellowship