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Changeset 10419 for NEMO/branches/2018/dev_r10164_HPC09_ESIWACE_PREP_MERGE/doc/latex/NEMO/subfiles/chap_model_basics_zstar.tex – NEMO

Ignore:
Timestamp:
2018-12-19T20:46:30+01:00 (5 years ago)
Author:
smasson
Message:

dev_r10164_HPC09_ESIWACE_PREP_MERGE: merge with trunk@10418, see #2133

Location:
NEMO/branches/2018/dev_r10164_HPC09_ESIWACE_PREP_MERGE/doc/latex
Files:
4 edited

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  • NEMO/branches/2018/dev_r10164_HPC09_ESIWACE_PREP_MERGE/doc/latex/NEMO/subfiles/chap_model_basics_zstar.tex

    r10368 r10419  
    1 \documentclass[../tex_main/NEMO_manual]{subfiles} 
     1\documentclass[../main/NEMO_manual]{subfiles} 
     2 
    23\begin{document} 
    34% ================================================================ 
    4 % Chapter 1 ——— Model Basics 
     5% Chapter 1 Model Basics 
    56% ================================================================ 
    67% ================================================================ 
     
    2021 
    2122\colorbox{yellow}{  end of to be updated} 
    22 \newline 
    2323 
    2424% from MOM4p1 documentation 
    2525 
    2626To overcome problems with vanishing surface and/or bottom cells, we consider the zstar coordinate  
    27 \begin{equation} \label{eq:PE_} 
    28    z^\star = H \left( \frac{z-\eta}{H+\eta} \right) 
    29 \end{equation} 
     27\[ 
     28  % \label{eq:PE_} 
     29  z^\star = H \left( \frac{z-\eta}{H+\eta} \right) 
     30\] 
    3031 
    3132This coordinate is closely related to the "eta" coordinate used in many atmospheric models 
     
    6566the surface height, again so long as $\eta > -H$.  
    6667 
    67  
    68  
    6968%%% 
    7069%  essai update time splitting... 
    7170%%% 
    7271 
    73  
    7472% ================================================================ 
    7573% Surface Pressure Gradient and Sea Surface Height 
     
    7977%-----------------------------------------nam_dynspg---------------------------------------------------- 
    8078 
    81 \nlst{nam_dynspg}  
     79%\nlst{nam_dynspg}  
    8280%------------------------------------------------------------------------------------------------------------ 
    8381Options are defined through the \ngn{nam\_dynspg} namelist variables. 
     
    105103describe the external gravity waves (typically a few ten seconds). 
    106104The sea surface height is given by: 
    107 \begin{equation} \label{eq:dynspg_ssh} 
    108 \frac{\partial \eta }{\partial t}\equiv \frac{\text{EMP}}{\rho _w }+\frac{1}{e_{1T}  
    109 e_{2T} }\sum\limits_k {\left( {\delta _i \left[ {e_{2u} e_{3u} u}  
    110 \right]+\delta _j \left[ {e_{1v} e_{3v} v} \right]} \right)}  
     105\begin{equation} 
     106  \label{eq:dynspg_ssh} 
     107  \frac{\partial \eta }{\partial t}\equiv \frac{\text{EMP}}{\rho_w }+\frac{1}{e_{1T} 
     108    e_{2T} }\sum\limits_k {\left( {\delta_i \left[ {e_{2u} e_{3u} u} 
     109        \right]+\delta_j \left[ {e_{1v} e_{3v} v} \right]} \right)} 
    111110\end{equation} 
    112111 
    113112where EMP is the surface freshwater budget (evaporation minus precipitation, and minus river runoffs 
    114113(if the later are introduced as a surface freshwater flux, see \autoref{chap:SBC}) expressed in $Kg.m^{-2}.s^{-1}$, 
    115 and $\rho _w =1,000\,Kg.m^{-3}$ is the volumic mass of pure water. 
     114and $\rho_w =1,000\,Kg.m^{-3}$ is the volumic mass of pure water. 
    116115The sea-surface height is evaluated using a leapfrog scheme in combination with an Asselin time filter, 
    117116i.e. the velocity appearing in (\autoref{eq:dynspg_ssh}) is centred in time (\textit{now} velocity).  
    118117 
    119118The surface pressure gradient, also evaluated using a leap-frog scheme, is then simply given by: 
    120 \begin{equation} \label{eq:dynspg_exp} 
    121 \left\{ \begin{aligned} 
    122  - \frac{1}                      {e_{1u}} \; \delta _{i+1/2} \left[  \,\eta\,  \right]    \\ 
    123  \\ 
    124  - \frac{1}                      {e_{2v}} \; \delta _{j+1/2} \left[  \,\eta\,  \right]   
    125 \end{aligned} \right. 
     119\begin{equation} 
     120  \label{eq:dynspg_exp} 
     121  \left\{ 
     122    \begin{aligned} 
     123      - \frac{1}                    {e_{1u}} \; \delta_{i+1/2} \left[  \,\eta\,  \right] \\ \\ 
     124      - \frac{1}                    {e_{2v}} \; \delta_{j+1/2} \left[  \,\eta\,  \right] 
     125    \end{aligned} 
     126  \right. 
    126127\end{equation}  
    127128 
    128 Consistent with the linearization, a $\left. \rho \right|_{k=1} / \rho _o$ factor is omitted in 
     129Consistent with the linearization, a $\left. \rho \right|_{k=1} / \rho_o$ factor is omitted in 
    129130(\autoref{eq:dynspg_exp}).  
    130131 
     
    144145 
    145146%>   >   >   >   >   >   >   >   >   >   >   >   >   >   >   >   >   >   >   >   >   >   >   >   >   >   >   > 
    146 \begin{figure}[!t]   \begin{center} 
    147 \includegraphics[width=0.90\textwidth]{Fig_DYN_dynspg_ts} 
    148 \caption{    \protect\label{fig:DYN_dynspg_ts} 
    149   Schematic of the split-explicit time stepping scheme for the barotropic and baroclinic modes, 
    150   after \citet{Griffies2004}. 
    151   Time increases to the right. 
    152   Baroclinic time steps are denoted by $t-\Delta t$, $t, t+\Delta t$, and $t+2\Delta t$. 
    153   The curved line represents a leap-frog time step, 
    154   and the smaller barotropic time steps $N \Delta t=2\Delta t$ are denoted by the zig-zag line. 
    155   The vertically integrated forcing \textbf{M}(t) computed at 
    156   baroclinic time step t represents the interaction between the barotropic and baroclinic motions. 
    157   While keeping the total depth, tracer, and freshwater forcing fields fixed, 
    158   a leap-frog integration carries the surface height and vertically integrated velocity from 
    159   t to $t+2 \Delta t$ using N barotropic time steps of length $\Delta t$. 
    160   Time averaging the barotropic fields over the N+1 time steps (endpoints included) 
    161   centers the vertically integrated velocity at the baroclinic timestep $t+\Delta t$. 
    162   A baroclinic leap-frog time step carries the surface height to $t+\Delta t$ using the convergence of 
    163   the time averaged vertically integrated velocity taken from baroclinic time step t. } 
    164 \end{center} 
     147\begin{figure}[!t] 
     148  \begin{center} 
     149    \includegraphics[width=0.90\textwidth]{Fig_DYN_dynspg_ts} 
     150    \caption{ 
     151      \protect\label{fig:DYN_dynspg_ts} 
     152      Schematic of the split-explicit time stepping scheme for the barotropic and baroclinic modes, 
     153      after \citet{Griffies2004}. 
     154      Time increases to the right. 
     155      Baroclinic time steps are denoted by $t-\Delta t$, $t, t+\Delta t$, and $t+2\Delta t$. 
     156      The curved line represents a leap-frog time step, 
     157      and the smaller barotropic time steps $N \Delta t=2\Delta t$ are denoted by the zig-zag line. 
     158      The vertically integrated forcing \textbf{M}(t) computed at 
     159      baroclinic time step t represents the interaction between the barotropic and baroclinic motions. 
     160      While keeping the total depth, tracer, and freshwater forcing fields fixed, 
     161      a leap-frog integration carries the surface height and vertically integrated velocity from 
     162      t to $t+2 \Delta t$ using N barotropic time steps of length $\Delta t$. 
     163      Time averaging the barotropic fields over the N+1 time steps (endpoints included) 
     164      centers the vertically integrated velocity at the baroclinic timestep $t+\Delta t$. 
     165      A baroclinic leap-frog time step carries the surface height to $t+\Delta t$ using the convergence of 
     166      the time averaged vertically integrated velocity taken from baroclinic time step t. 
     167    } 
     168  \end{center} 
    165169\end{figure} 
    166170%>   >   >   >   >   >   >   >   >   >   >   >   >   >   >   >   >   >   >   >   >   >   >   >   >   >   >   > 
     
    178182the small barotropic time step $\Delta t$. 
    179183We have 
    180 \begin{equation} \label{eq:DYN_spg_ts_eta} 
    181 \eta^{(b)}(\tau,t_{n+1}) - \eta^{(b)}(\tau,t_{n+1}) (\tau,t_{n-1}) 
    182    = 2 \Delta t \left[-\nabla \cdot \textbf{U}^{(b)}(\tau,t_n) + \text{EMP}_w(\tau) \right]  
    183 \end{equation} 
    184 \begin{multline} \label{eq:DYN_spg_ts_u} 
    185 \textbf{U}^{(b)}(\tau,t_{n+1}) - \textbf{U}^{(b)}(\tau,t_{n-1})  \\ 
    186    = 2\Delta t \left[ - f \textbf{k} \times \textbf{U}^{(b)}(\tau,t_{n})  
    187    - H(\tau) \nabla p_s^{(b)}(\tau,t_{n}) +\textbf{M}(\tau) \right] 
    188 \end{multline} 
     184\[ 
     185  % \label{eq:DYN_spg_ts_eta} 
     186  \eta^{(b)}(\tau,t_{n+1}) - \eta^{(b)}(\tau,t_{n+1}) (\tau,t_{n-1}) 
     187  = 2 \Delta t \left[-\nabla \cdot \textbf{U}^{(b)}(\tau,t_n) + \text{EMP}_w(\tau) \right]  
     188\] 
     189\begin{multline*} 
     190  % \label{eq:DYN_spg_ts_u} 
     191  \textbf{U}^{(b)}(\tau,t_{n+1}) - \textbf{U}^{(b)}(\tau,t_{n-1})  \\ 
     192  = 2\Delta t \left[ - f \textbf{k} \times \textbf{U}^{(b)}(\tau,t_{n}) 
     193    - H(\tau) \nabla p_s^{(b)}(\tau,t_{n}) +\textbf{M}(\tau) \right] 
     194\end{multline*} 
    189195\ 
    190196 
     
    197203the duration of the barotropic time stepping over a single cycle. 
    198204This is also the time that sets the barotropic time steps via  
    199 \begin{equation} \label{eq:DYN_spg_ts_t} 
    200 t_n=\tau+n\Delta t    
    201 \end{equation} 
     205\[ 
     206  % \label{eq:DYN_spg_ts_t} 
     207  t_n=\tau+n\Delta t    
     208\] 
    202209with $n$ an integer. 
    203210The density scaled surface pressure is evaluated via  
    204 \begin{equation} \label{eq:DYN_spg_ts_ps} 
    205 p_s^{(b)}(\tau,t_{n}) = \begin{cases} 
    206    g \;\eta_s^{(b)}(\tau,t_{n}) \;\rho(\tau)_{k=1}) / \rho_o  &      \text{non-linear case} \\ 
    207    g \;\eta_s^{(b)}(\tau,t_{n})  &      \text{linear case}  
    208    \end{cases} 
    209 \end{equation} 
     211\[ 
     212  % \label{eq:DYN_spg_ts_ps} 
     213  p_s^{(b)}(\tau,t_{n}) = 
     214  \begin{cases} 
     215    g \;\eta_s^{(b)}(\tau,t_{n}) \;\rho(\tau)_{k=1}) / \rho_o  &      \text{non-linear case} \\ 
     216    g \;\eta_s^{(b)}(\tau,t_{n})  &      \text{linear case} 
     217  \end{cases} 
     218\] 
    210219To get started, we assume the following initial conditions  
    211 \begin{equation} \label{eq:DYN_spg_ts_eta} 
    212 \begin{split} 
    213 \eta^{(b)}(\tau,t_{n=0}) &= \overline{\eta^{(b)}(\tau)} 
    214 \\ 
    215 \eta^{(b)}(\tau,t_{n=1}) &= \eta^{(b)}(\tau,t_{n=0}) + \Delta t \ \text{RHS}_{n=0}  
    216 \end{split} 
    217 \end{equation} 
     220\[ 
     221  % \label{eq:DYN_spg_ts_eta} 
     222  \begin{split} 
     223    \eta^{(b)}(\tau,t_{n=0}) &= \overline{\eta^{(b)}(\tau)} \\ 
     224    \eta^{(b)}(\tau,t_{n=1}) &= \eta^{(b)}(\tau,t_{n=0}) + \Delta t \ \text{RHS}_{n=0} 
     225  \end{split} 
     226\] 
    218227with  
    219 \begin{equation} \label{eq:DYN_spg_ts_etaF} 
    220  \overline{\eta^{(b)}(\tau)} = \frac{1}{N+1} \sum\limits_{n=0}^N \eta^{(b)}(\tau-\Delta t,t_{n}) 
    221 \end{equation} 
     228\[ 
     229  % \label{eq:DYN_spg_ts_etaF} 
     230  \overline{\eta^{(b)}(\tau)} = \frac{1}{N+1} \sum\limits_{n=0}^N \eta^{(b)}(\tau-\Delta t,t_{n}) 
     231\] 
    222232the time averaged surface height taken from the previous barotropic cycle. 
    223233Likewise, 
    224 \begin{equation} \label{eq:DYN_spg_ts_u} 
    225 \textbf{U}^{(b)}(\tau,t_{n=0}) = \overline{\textbf{U}^{(b)}(\tau)}   \\ 
    226 \\ 
    227 \textbf{U}(\tau,t_{n=1}) = \textbf{U}^{(b)}(\tau,t_{n=0}) + \Delta t \ \text{RHS}_{n=0}    
    228 \end{equation} 
     234\[ 
     235  % \label{eq:DYN_spg_ts_u} 
     236  \textbf{U}^{(b)}(\tau,t_{n=0}) = \overline{\textbf{U}^{(b)}(\tau)} \\ \\ 
     237  \textbf{U}(\tau,t_{n=1}) = \textbf{U}^{(b)}(\tau,t_{n=0}) + \Delta t \ \text{RHS}_{n=0} 
     238\] 
    229239with  
    230 \begin{equation} \label{eq:DYN_spg_ts_u} 
    231  \overline{\textbf{U}^{(b)}(\tau)}  
    232    = \frac{1}{N+1} \sum\limits_{n=0}^N\textbf{U}^{(b)}(\tau-\Delta t,t_{n}) 
    233 \end{equation} 
     240\[ 
     241  % \label{eq:DYN_spg_ts_u} 
     242  \overline{\textbf{U}^{(b)}(\tau)} = \frac{1}{N+1} \sum\limits_{n=0}^N\textbf{U}^{(b)}(\tau-\Delta t,t_{n}) 
     243\] 
    234244the time averaged vertically integrated transport. 
    235245Notably, there is no Robert-Asselin time filter used in the barotropic portion of the integration.  
     
    237247Upon reaching $t_{n=N} = \tau + 2\Delta \tau$ , the vertically integrated velocity is time averaged to 
    238248produce the updated vertically integrated velocity at baroclinic time $\tau + \Delta \tau$  
    239 \begin{equation} \label{eq:DYN_spg_ts_u} 
    240 \textbf{U}(\tau+\Delta t) = \overline{\textbf{U}^{(b)}(\tau+\Delta t)}  
    241    = \frac{1}{N+1} \sum\limits_{n=0}^N\textbf{U}^{(b)}(\tau,t_{n}) 
    242 \end{equation} 
     249\[ 
     250  % \label{eq:DYN_spg_ts_u} 
     251  \textbf{U}(\tau+\Delta t) = \overline{\textbf{U}^{(b)}(\tau+\Delta t)} 
     252  = \frac{1}{N+1} \sum\limits_{n=0}^N\textbf{U}^{(b)}(\tau,t_{n}) 
     253\] 
    243254The surface height on the new baroclinic time step is then determined via 
    244255a baroclinic leap-frog using the following form  
    245 \begin{equation} \label{eq:DYN_spg_ts_ssh} 
    246 \eta(\tau+\Delta) - \eta^{F}(\tau-\Delta) = 2\Delta t \ \left[ - \nabla \cdot \textbf{U}(\tau) + \text{EMP}_w \right]   
     256\begin{equation} 
     257  \label{eq:DYN_spg_ts_ssh} 
     258  \eta(\tau+\Delta) - \eta^{F}(\tau-\Delta) = 2\Delta t \ \left[ - \nabla \cdot \textbf{U}(\tau) + \text{EMP}_w \right] 
    247259\end{equation} 
    248260 
     
    257269reasonably good maintenance of tracer conservation properties (see ??)  
    258270 
    259 \begin{equation} \label{eq:DYN_spg_ts_sshf} 
    260 \eta^{F}(\tau-\Delta) =  \overline{\eta^{(b)}(\tau)}  
     271\begin{equation} 
     272  \label{eq:DYN_spg_ts_sshf} 
     273  \eta^{F}(\tau-\Delta) =  \overline{\eta^{(b)}(\tau)} 
    261274\end{equation} 
    262275Another approach tried was  
    263276 
    264 \begin{equation} \label{eq:DYN_spg_ts_sshf2} 
    265 \eta^{F}(\tau-\Delta) = \eta(\tau)  
    266    + (\alpha/2) \left[\overline{\eta^{(b)}}(\tau+\Delta t) 
    267                 + \overline{\eta^{(b)}}(\tau-\Delta t) -2 \;\eta(\tau) \right] 
    268 \end{equation} 
     277\[ 
     278  % \label{eq:DYN_spg_ts_sshf2} 
     279  \eta^{F}(\tau-\Delta) = \eta(\tau) 
     280  + (\alpha/2) \left[\overline{\eta^{(b)}}(\tau+\Delta t) 
     281    + \overline{\eta^{(b)}}(\tau-\Delta t) -2 \;\eta(\tau) \right] 
     282\] 
    269283 
    270284which is useful since it isolates all the time filtering aspects into the term multiplied by $\alpha$. 
     
    274288be more conservative, and so is recommended.  
    275289 
    276  
    277  
    278  
    279  
    280290%------------------------------------------------------------- 
    281291% Filtered formulation  
     
    304314In particular, this means that in filtered case, the matrix to be inverted has to be recomputed at each time-step. 
    305315 
     316\biblio 
    306317 
    307318\end{document} 
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