Changeset 2286 for branches/nemo_v3_3_beta/DOC/TexFiles/Chapters/Chap_TRA.tex

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Timestamp:
2010-10-17T17:42:40+02:00 (11 years ago)
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ticket:#658 minor corrections in TRA chapter

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• branches/nemo_v3_3_beta/DOC/TexFiles/Chapters/Chap_TRA.tex

 r2285 by using the following equality : $\nabla \cdot \left( \vect{U}\,T \right)=\vect{U} \cdot \nabla T$ which results from the use of the continuity equation, $\nabla \cdot \vect{U}=0$ or $\partial _t e_3 + e_3\;\nabla \cdot \vect{U}=0$ in constant or variable volume case, respectively. $\partial _t e_3 + e_3\;\nabla \cdot \vect{U}=0$ in constant volume or variable volume case, respectively. Therefore it is of paramount importance to design the discrete analogue of the advection tendency so that it is consistent with the continuity equation in order to which is advected} , implying that false extrema are permitted. Their use is not recommended on passive tracers ; (3) It is highly recommended that the same advection-diffusion scheme is (3) It is recommended that the same advection-diffusion scheme is used on both active and passive tracers. Indeed, if a source or sink of a passive tracer depends on an active one, the difference of treatment of active and passive tracers can create very nice-looking frontal structures that are pure numerical artefacts. \sgacomment{not sure whether 3 is still relevant after TRA-TRC branch is merged in?} that are pure numerical artefacts. Nevertheless, most of our users set a different treatment on passive and active tracers, that's the reason why this possibility is offered. We strongly suggest them to perform a sensitivity experiment using a same treatment to assess the robustness of their results. % ------------------------------------------------------------------------------------------------------------- %        2nd order centred scheme with coarse resolution, and the vicinity of ice cover area ($i.e.$ when the ocean temperature is close to the freezing point). This combined scheme has been included for specific grid points in the ORCA2 and ORCA4 configurations only. This combined scheme has been included for specific grid points in the ORCA2 and ORCA4 configurations only. This is an obsolescent feature as the recommended advection scheme for the ORCA configuration is TVD (see  \S\ref{TRA_adv_tvd}). Note that using the cen2 scheme, the overall tracer advection is of second In the current version, the situation is a little bit more complicated. } The surface module (\mdl{sbcmod}, see \S\ref{SBC}) provides the following forcing fields (used on tracers): non-zero heat flux across the seafloor that is associated with solid earth cooling. This flux is weak compared to surface fluxes (a mean global value of $\sim0.1\;W/m^2$ \citep{Stein_Stein_Nat92}), but it is systematically positive \sgacomment{positive definite?} and acts on the densest water masses. global value of $\sim0.1\;W/m^2$ \citep{Stein_Stein_Nat92}), but it warms systematically the ocean and acts on the densest water masses. Taking this flux into account in a global ocean model increases the deepest overturning cell ($i.e.$ the one associated with the Antarctic implementation of the BBL, only the tracers are modified, not the velocities. Furthermore, it only connects ocean bottom cells, and therefore does not include the improvements introduced by \citet{Campin_Goosse_Tel99}. all the improvements introduced by \citet{Campin_Goosse_Tel99}. % -------------------------------------------------------------------------------------------------------------
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