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Timestamp:
2008-01-03T12:10:08+01:00 (13 years ago)
Author:
smasson
Message:

doc update, see ticket:1

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1 edited

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  • trunk/DOC/BETA/Chapters/Chap_DOM.tex

    r707 r781  
    316316the ocean. This is unnecessary when the ocean is forced by fixed atmospheric  
    317317conditions. A possibility is offered to the user to set to zero the  
    318 bathymetry in rectangular regions covering those closed seas (see \S\ref{MISC_closea}) 
     318bathymetry in rectangular regions covering those closed seas (see \S\ref{MISC_closea}), but the code has to be adapted to the user's configuration.  
    319319 
    320320% ------------------------------------------------------------------------------------------------------------- 
     
    515515 
    516516In case of rigid-lid approximation and islands in the computational domain (\np{ln\_dynspg\_rl}=true and \key{island} defined), the \textit{mbathy} array must be provided and takes values from $-N$ to \jp{jpk}-1. It provides the  
    517 following information: $mbathy(i,j) = -n, \ n \in \left] 0,N \right]$, $T-$points are land points of the $n^{th}$ island ; $mbathy(i,j) =0$, $T-$points are land points of the main land (continent) ; $mbathy(i,j) =k$, the first $k$ $T$- and $w$-points are ocean points, the others land points. This is used to compute the island barotropic stream function used in rigid lid computation (see \S\ref{LBC_isl}). 
     517following information: $mbathy(i,j) = -n, \ n \in \left] 0,N \right]$, $T-$points are land points of the $n^{th}$ island ; $mbathy(i,j) =0$, $T-$points are land points of the main land (continent) ; $mbathy(i,j) =k$, the first $k$ $T$- and $w$-points are ocean points, the others land points. This is used to compute the island barotropic stream function used in rigid lid computation (see \S\ref{MISC_solisl}). 
    518518 
    519519From the \textit{mbathy} array, the mask fields are defined as follows: 
     
    553553well as the implication in term of starting or restarting a model  
    554554simulation. Note that the time stepping is generally performed in a one step  
    555 operation: it would be dangerous to let a prognostic variable evolve in time for each term successively. 
     555operation. With such a complex and nonlinear system of equations it would be dangerous to let a prognostic variable evolve in time for each term successively. 
    556556 
    557557The three level scheme requires three arrays for the prognostic variables. For each variable $x$ there is $x_b$ (before) and $x_n$ (now). The third array, although referred to as $x_a$ (after) in the code, is usually not the variable $x_a$ at the next time step; rather, it is used to store the time derivative (RHS in \eqref{Eq_DOM_nxt}) prior to time-stepping the equation. Generally, the time stepping is performed once at each time step in \mdl{tranxt} and \mdl{dynnxt} modules, excepted for implicit vertical diffusion or sea surface height when time-splitting options are used. 
     
    621621\end{equation}  
    622622 
    623 Equations  \ref{Eq_DOM_nxt2} and \ref{Eq_DOM_nxt3} suggest several remarks. First the Asselin filter is definitively a second order time diffusive operator which is evaluated at centered time step. The magnitude of this diffusion is proportional to the time step (with $\gamma$ usually taken between $10^{-1}$ to $10^{-3}$). Second, this term have to be taken into account in all budget of the equations (mass, heat content, salt content, kinetic energy...). Nevertheless, we stress here that it is small and does not systematic biases. Indeed let evaluates how it contributes to time evolution of $x$ between $t_o$ and $t_1$: 
     623Equations  \ref{Eq_DOM_nxt2} and \ref{Eq_DOM_nxt3} suggest several remarks. First the Asselin filter is definitively a second order time diffusive operator which is evaluated at centered time step. The magnitude of this diffusion is proportional to the time step (with $\gamma$ usually taken between $10^{-1}$ to $10^{-3}$) . Second, this term has to be taken into account in all budgets of the equations (mass, heat content, salt content, kinetic energy...). Nevertheless,we stress here that it is small and does not create systematic biases. Indeed let us evaluate how it contributes to the time evolution of $x$ between $t_o$ and $t_1$: 
    624624\begin{equation} \label{Eq_DOM_nxt4} 
    625625\begin{split} 
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