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Changeset 14644 for NEMO/branches/2020/dev_r14116_HPC-04_mcastril_Mixed_Precision_implementation_final/doc/latex/NEMO/subfiles/chap_time_domain.tex – NEMO

Ignore:
Timestamp:
2021-03-26T15:33:49+01:00 (3 years ago)
Author:
sparonuz
Message:

Merge trunk -r14642:HEAD

Location:
NEMO/branches/2020/dev_r14116_HPC-04_mcastril_Mixed_Precision_implementation_final
Files:
3 edited

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  • NEMO/branches/2020/dev_r14116_HPC-04_mcastril_Mixed_Precision_implementation_final

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  • NEMO/branches/2020/dev_r14116_HPC-04_mcastril_Mixed_Precision_implementation_final/doc/latex/NEMO/subfiles/chap_time_domain.tex

    r11693 r14644  
    66\label{chap:TD} 
    77 
    8 \thispagestyle{plain} 
    9  
    108\chaptertoc 
    119 
     
    1412{\footnotesize 
    1513  \begin{tabularx}{0.5\textwidth}{l||X|X} 
    16     Release          & Author(s)                                       & 
     14    Release          & Author(s)                                       &  
    1715    Modifications                                                      \\ 
    1816    \hline 
    19     {\em        4.0} & {\em J\'{e}r\^{o}me Chanut \newline Tim Graham} & 
     17    {\em        4.0} & {\em J\'{e}r\^{o}me Chanut \newline Tim Graham} &  
    2018    {\em Review \newline Update                                      } \\ 
    21     {\em        3.6} & {\em Christian \'{E}th\'{e}                   } & 
     19    {\em        3.6} & {\em Christian \'{E}th\'{e}                   } &  
    2220    {\em Update                                                      } \\ 
    23     {\em $\leq$ 3.4} & {\em Gurvan Madec                             } & 
     21    {\em $\leq$ 3.4} & {\em Gurvan Madec                             } &  
    2422    {\em First version                                               } \\ 
    2523  \end{tabularx} 
     
    4644 
    4745The time stepping used in \NEMO\ is a three level scheme that can be represented as follows: 
     46 
    4847\begin{equation} 
    4948  \label{eq:TD} 
    5049  x^{t + \rdt} = x^{t - \rdt} + 2 \, \rdt \ \text{RHS}_x^{t - \rdt, \, t, \, t + \rdt} 
    5150\end{equation} 
     51 
    5252where $x$ stands for $u$, $v$, $T$ or $S$; 
    5353RHS is the \textbf{R}ight-\textbf{H}and-\textbf{S}ide of the corresponding time evolution equation; 
     
    9999first designed by \citet{robert_JMSJ66} and more comprehensively studied by \citet{asselin_MWR72}, 
    100100is a kind of laplacian diffusion in time that mixes odd and even time steps: 
     101 
    101102\begin{equation} 
    102103  \label{eq:TD_asselin} 
    103104  x_F^t = x^t + \gamma \, \lt[ x_F^{t - \rdt} - 2 x^t + x^{t + \rdt} \rt] 
    104105\end{equation} 
     106 
    105107where the subscript $F$ denotes filtered values and $\gamma$ is the Asselin coefficient. 
    106108$\gamma$ is initialized as \np{rn_atfp}{rn\_atfp} (namelist parameter). 
     
    134136The conditions for stability of second and fourth order horizontal diffusion schemes are 
    135137\citep{griffies_bk04}: 
     138 
    136139\begin{equation} 
    137140  \label{eq:TD_euler_stability} 
     
    142145  \end{cases} 
    143146\end{equation} 
     147 
    144148where $e$ is the smallest grid size in the two horizontal directions and 
    145149$A^h$ is the mixing coefficient. 
     
    153157To overcome the stability constraint, a backward (or implicit) time differencing scheme is used. 
    154158This scheme is unconditionally stable but diffusive and can be written as follows: 
     159 
    155160\begin{equation} 
    156161  \label{eq:TD_imp} 
     
    170175where RHS is the right hand side of the equation except for the vertical diffusion term. 
    171176We rewrite \autoref{eq:TD_imp} as: 
     177 
    172178\begin{equation} 
    173179  \label{eq:TD_imp_mat} 
    174180  -c(k + 1) \; T^{t + 1}(k + 1) + d(k) \; T^{t + 1}(k) - \; c(k) \; T^{t + 1}(k - 1) \equiv b(k) 
    175181\end{equation} 
     182 
    176183where 
     184 
    177185\[ 
    178186  c(k) = A_w^{vT} (k) \, / \, e_{3w} (k) \text{,} \quad 
     
    241249$Q$ is redistributed over several time step. 
    242250In the modified LF-RA environment, these two formulations have been replaced by: 
     251 
    243252\begin{gather} 
    244253  \label{eq:TD_forcing} 
     
    248257                    - \gamma \, \rdt \, \lt( Q^{t + \rdt / 2} - Q^{t - \rdt / 2} \rt) 
    249258\end{gather} 
     259 
    250260The change in the forcing formulation given by \autoref{eq:TD_forcing} 
    251261(see \autoref{fig:TD_MLF_forcing}) has a significant effect: 
     
    377387  % 
    378388\end{flalign*} 
     389 
    379390\begin{flalign*} 
    380391  \allowdisplaybreaks 
     
    389400  % 
    390401\end{flalign*} 
     402 
    391403\begin{flalign*} 
    392404  \allowdisplaybreaks 
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