| 11 |
\subsubsection{Introduction |
\subsubsection{Introduction |
| 12 |
\label{sec:pkg:obcs:intro}} |
\label{sec:pkg:obcs:intro}} |
| 13 |
|
|
| 14 |
|
The OBCS-package is fundamental to regional ocean modelling with the |
| 15 |
|
MITgcm, but because there are so many details to be considered in |
| 16 |
|
regional ocean modelling that this package cannot accomodate all |
| 17 |
|
imaginable and possible options. Therefore, for a regional simulation |
| 18 |
|
with very particular details, it is recommended to familiarize oneself |
| 19 |
|
not only with the compile- and runtime-options of this package, but |
| 20 |
|
also with the code itself. In many cases it will be necessary to adapt |
| 21 |
|
the obcs-code (in particular \code{S/R OBCS\_CALC}) to the application |
| 22 |
|
in question; in these cases the obcs-package (together with the |
| 23 |
|
rbcs-package, section \ref{sec:pkg:rbcs}) is a very |
| 24 |
|
useful infrastructure for implementing special regional models. |
| 25 |
|
|
| 26 |
%---------------------------------------------------------------------- |
%---------------------------------------------------------------------- |
| 27 |
|
|
| 28 |
\subsubsection{OBCS configuration and compiling |
\subsubsection{OBCS configuration and compiling |
| 29 |
\label{sec:pkg:kpp:comp}} |
\label{sec:pkg:obcs:comp}} |
| 30 |
|
|
| 31 |
As with all MITgcm packages, OBCS can be turned on or off |
As with all MITgcm packages, OBCS can be turned on or off |
| 32 |
at compile time |
at compile time |
| 34 |
\begin{itemize} |
\begin{itemize} |
| 35 |
% |
% |
| 36 |
\item |
\item |
| 37 |
using the \texttt{packages.conf} file by adding \texttt{obcs} to it, |
using the \code{packages.conf} file by adding \code{obcs} to it, |
| 38 |
% |
% |
| 39 |
\item |
\item |
| 40 |
or using \texttt{genmake2} adding |
or using \code{genmake2} adding |
| 41 |
\texttt{-enable=obcs} or \texttt{-disable=obcs} switches |
\code{-enable=obcs} or \code{-disable=obcs} switches |
| 42 |
% |
% |
| 43 |
\item |
\item |
| 44 |
\textit{Required packages and CPP options:} \\ |
\textit{Required packages and CPP options:} \\ |
| 47 |
which differ in the way how OB's are treated in time: |
which differ in the way how OB's are treated in time: |
| 48 |
A simple time-management (e.g. constant in time, or cyclic with |
A simple time-management (e.g. constant in time, or cyclic with |
| 49 |
fixed fequency) is provided through |
fixed fequency) is provided through |
| 50 |
S/R \texttt{obcs\_external\_fields\_load}. |
S/R \code{obcs\_external\_fields\_load}. |
| 51 |
More sophisticated ``real-time'' (i.e. calendar time) management is |
More sophisticated ``real-time'' (i.e. calendar time) management is |
| 52 |
available through \texttt{obcs\_prescribe\_read}. |
available through \code{obcs\_prescribe\_read}. |
| 53 |
The latter case requires |
The latter case requires |
| 54 |
packages \texttt{cal} and \texttt{exf} to be enabled. |
packages \code{cal} and \code{exf} to be enabled. |
| 55 |
% |
% |
| 56 |
\end{itemize} |
\end{itemize} |
| 57 |
(see also Section \ref{sect:buildingCode}). |
(see also Section \ref{sec:buildingCode}). |
| 58 |
|
|
| 59 |
Parts of the OBCS code can be enabled or disabled at compile time |
Parts of the OBCS code can be enabled or disabled at compile time |
| 60 |
via CPP preprocessor flags. These options are set in |
via CPP preprocessor flags. These options are set in |
| 61 |
\texttt{OBCS\_OPTIONS.h}. Table \ref{tab:pkg:obcs:cpp} summarizes them. |
\code{OBCS\_OPTIONS.h}. Table \ref{tab:pkg:obcs:cpp} summarizes them. |
| 62 |
|
|
| 63 |
\begin{table}[h!] |
\begin{table}[!ht] |
| 64 |
\centering |
\centering |
| 65 |
\label{tab:pkg:obcs:cpp} |
\label{tab:pkg:obcs:cpp} |
| 66 |
{\footnotesize |
{\footnotesize |
| 68 |
\hline |
\hline |
| 69 |
\textbf{CPP option} & \textbf{Description} \\ |
\textbf{CPP option} & \textbf{Description} \\ |
| 70 |
\hline \hline |
\hline \hline |
| 71 |
\texttt{ALLOW\_OBCS\_NORTH} & |
\code{ALLOW\_OBCS\_NORTH} & |
| 72 |
enable Northern OB \\ |
enable Northern OB \\ |
| 73 |
\texttt{ALLOW\_OBCS\_SOUTH} & |
\code{ALLOW\_OBCS\_SOUTH} & |
| 74 |
enable Southern OB \\ |
enable Southern OB \\ |
| 75 |
\texttt{ALLOW\_OBCS\_EAST} & |
\code{ALLOW\_OBCS\_EAST} & |
| 76 |
enable Eastern OB \\ |
enable Eastern OB \\ |
| 77 |
\texttt{ALLOW\_OBCS\_WEST} & |
\code{ALLOW\_OBCS\_WEST} & |
| 78 |
enable Western OB \\ |
enable Western OB \\ |
| 79 |
\hline |
\hline |
| 80 |
\texttt{ALLOW\_OBCS\_PRESCRIBE} & |
\code{ALLOW\_OBCS\_PRESCRIBE} & |
| 81 |
enable code for prescribing OB's \\ |
enable code for prescribing OB's \\ |
| 82 |
\texttt{ALLOW\_OBCS\_SPONGE} & |
\code{ALLOW\_OBCS\_SPONGE} & |
| 83 |
enable sponge layer code \\ |
enable sponge layer code \\ |
| 84 |
\texttt{ALLOW\_OBCS\_BALANCE} & |
\code{ALLOW\_OBCS\_BALANCE} & |
| 85 |
enable code for balancing transports through OB's \\ |
enable code for balancing transports through OB's \\ |
| 86 |
\texttt{ALLOW\_ORLANSKI} & |
\code{ALLOW\_ORLANSKI} & |
| 87 |
enable Orlanski radiation conditions at OB's \\ |
enable Orlanski radiation conditions at OB's \\ |
| 88 |
|
\code{ALLOW\_OBCS\_STEVENS} & |
| 89 |
|
enable Stevens (1990) boundary conditions at OB's \\ |
| 90 |
|
& (currently only implemented for eastern and western \\ |
| 91 |
|
& boundaries and NOT for ptracers) \\ |
| 92 |
\hline |
\hline |
| 93 |
\end{tabular} |
\end{tabular} |
| 94 |
} |
} |
| 102 |
\label{sec:pkg:obcs:runtime}} |
\label{sec:pkg:obcs:runtime}} |
| 103 |
|
|
| 104 |
Run-time parameters are set in files |
Run-time parameters are set in files |
| 105 |
\texttt{data.pkg}, \texttt{data.obcs}, and \texttt{data.exf} |
\code{data.pkg}, \code{data.obcs}, and \code{data.exf} |
| 106 |
if ``real-time'' prescription is requested |
if ``real-time'' prescription is requested |
| 107 |
(i.e. package \texttt{exf} enabled). |
(i.e. package \code{exf} enabled). |
| 108 |
These parameter files are read in S/R |
These parameter files are read in S/R |
| 109 |
\texttt{packages\_readparms.F}, \texttt{obcs\_readparms.F}, and |
\code{packages\_readparms.F}, \code{obcs\_readparms.F}, and |
| 110 |
\texttt{exf\_readparms.F}, respectively. |
\code{exf\_readparms.F}, respectively. |
| 111 |
Run-time parameters may be broken into 3 categories: |
Run-time parameters may be broken into 3 categories: |
| 112 |
(i) switching on/off the package at runtime, |
(i) switching on/off the package at runtime, |
| 113 |
(ii) OBCS package flags and parameters, |
(ii) OBCS package flags and parameters, |
| 114 |
(iii) additional timing flags in \texttt{data.exf}, if selected. |
(iii) additional timing flags in \code{data.exf}, if selected. |
| 115 |
|
|
| 116 |
\paragraph{Enabling the package} |
\paragraph{Enabling the package} |
| 117 |
~ \\ |
~ \\ |
| 118 |
% |
% |
| 119 |
The OBCS package is switched on at runtime by setting |
The OBCS package is switched on at runtime by setting |
| 120 |
\texttt{useOBCS = .TRUE.} in \texttt{data.pkg}. |
\code{useOBCS = .TRUE.} in \code{data.pkg}. |
| 121 |
|
|
| 122 |
\paragraph{Package flags and parameters} |
\paragraph{Package flags and parameters} |
| 123 |
~ \\ |
~ \\ |
| 124 |
% |
% |
| 125 |
Table \ref{tab:pkg:obcs:runtime_flags} summarizes the |
Table \ref{tab:pkg:obcs:runtime_flags} summarizes the |
| 126 |
runtime flags that are set in \texttt{data.obcs}, and |
runtime flags that are set in \code{data.obcs}, and |
| 127 |
their default values. |
their default values. |
| 128 |
|
|
| 129 |
\begin{table}[h!] |
\begin{table}[!ht] |
| 130 |
\centering |
\centering |
|
\label{tab:pkg:obcs:runtime_flags} |
|
| 131 |
{\footnotesize |
{\footnotesize |
| 132 |
\begin{tabular}{|l|c|l|} |
\begin{tabular}{|l|c|l|} |
| 133 |
\hline |
\hline |
| 134 |
\textbf{Flag/parameter} & \textbf{default} & \textbf{Description} \\ |
\textbf{Flag/parameter} & \textbf{default} & \textbf{Description} \\ |
| 135 |
\hline \hline |
\hline \hline |
| 136 |
\multicolumn{3}{|c|}{\textit{basic flags \& parameters} } \\ |
\multicolumn{3}{|c|}{\textit{basic flags \& parameters} (OBCS\_PARM01) } \\ |
| 137 |
\hline |
\hline |
| 138 |
OB\_Jnorth & 0 & |
OB\_Jnorth & 0 & |
| 139 |
Nx-vector of J-indices (w.r.t. Ny) of Northern OB |
Nx-vector of J-indices (w.r.t. Ny) of Northern OB |
| 147 |
OB\_Iwest & 0 & |
OB\_Iwest & 0 & |
| 148 |
Ny-vector of I-indices (w.r.t. Nx) of Western OB |
Ny-vector of I-indices (w.r.t. Nx) of Western OB |
| 149 |
at each J-position (w.r.t. Ny) \\ |
at each J-position (w.r.t. Ny) \\ |
| 150 |
useOBCSprescribe & \texttt{.FALSE.} & |
useOBCSprescribe & \code{.FALSE.} & |
| 151 |
~ \\ |
~ \\ |
| 152 |
useOBCSsponge & \texttt{.FALSE.} & |
useOBCSsponge & \code{.FALSE.} & |
| 153 |
~ \\ |
~ \\ |
| 154 |
useOBCSbalance & \texttt{.FALSE.} & |
useOBCSbalance & \code{.FALSE.} & |
| 155 |
~ \\ |
~ \\ |
| 156 |
|
useOrlanskiNorth/South/EastWest & \code{.FALSE.} & |
| 157 |
|
turn on Orlanski boundary conditions for individual boundary\\ |
| 158 |
|
useStevensNorth/South/EastWest & \code{.FALSE.} & |
| 159 |
|
turn on Stevens boundary conditions for individual boundary\\ |
| 160 |
OB\textbf{X}\textbf{y}File & ~ & |
OB\textbf{X}\textbf{y}File & ~ & |
| 161 |
file name of OB field \\ |
file name of OB field \\ |
| 162 |
~ & ~ & |
~ & ~ & |
| 164 |
\textbf{E}(ast), \textbf{W}(est) \\ |
\textbf{E}(ast), \textbf{W}(est) \\ |
| 165 |
~ & ~ & |
~ & ~ & |
| 166 |
\textbf{y}: \textbf{t}(emperature), \textbf{s}(salinity), |
\textbf{y}: \textbf{t}(emperature), \textbf{s}(salinity), |
| 167 |
\textbf{u}(-velocity), \textbf{v}(-velocity) \\ |
\textbf{u}(-velocity), \textbf{v}(-velocity), \\ |
| 168 |
|
~ & ~ & |
| 169 |
|
\textbf{w}(-velocity), \textbf{eta}(sea surface height)\\ |
| 170 |
|
~ & ~ & |
| 171 |
|
\textbf{a}(sea ice area), \textbf{h}(sea ice thickness), |
| 172 |
|
\textbf{sn}(snow thickness), \textbf{sl}(sea ice salinity)\\ |
| 173 |
\hline |
\hline |
| 174 |
\multicolumn{3}{|c|}{\textit{Orlanski parameters} } \\ |
\multicolumn{3}{|c|}{\textit{Orlanski parameters} (OBCS\_PARM02) } \\ |
| 175 |
\hline |
\hline |
| 176 |
cvelTimeScale & 2000 sec & |
cvelTimeScale & 2000 sec & |
| 177 |
averaging period for phase speed \\ |
averaging period for phase speed \\ |
| 179 |
maximum allowable phase speed-CFL for AB-II \\ |
maximum allowable phase speed-CFL for AB-II \\ |
| 180 |
CFIX & 0.8 m/s & |
CFIX & 0.8 m/s & |
| 181 |
fixed boundary phase speed \\ |
fixed boundary phase speed \\ |
| 182 |
useFixedCEast & .FALSE. & |
useFixedCEast & \code{.FALSE.} & |
| 183 |
~ \\ |
~ \\ |
| 184 |
useFixedCWest & .FALSE. & |
useFixedCWest & \code{.FALSE.} & |
| 185 |
~ \\ |
~ \\ |
| 186 |
\hline |
\hline |
| 187 |
\multicolumn{3}{|c|}{\textit{Sponge-layer parameters} } \\ |
\multicolumn{3}{|c|}{\textit{Sponge-layer parameters} (OBCS\_PARM03)} \\ |
| 188 |
\hline |
\hline |
| 189 |
spongeThickness & 0 & |
spongeThickness & 0 & |
| 190 |
sponge layer thickness (in \# grid points) \\ |
sponge layer thickness (in \# grid points) \\ |
| 200 |
Vrelaxobcsbound & 0 sec & |
Vrelaxobcsbound & 0 sec & |
| 201 |
relaxation time scale at the |
relaxation time scale at the |
| 202 |
outermost sponge layer point of a zonal OB \\ |
outermost sponge layer point of a zonal OB \\ |
| 203 |
|
\hline |
| 204 |
|
\multicolumn{3}{|c|}{\textit{Stevens parameters} (OBCS\_PARM04) } \\ |
| 205 |
|
\hline |
| 206 |
|
T/SrelaxStevens & 0~sec & relaxation time scale for |
| 207 |
|
temperature/salinity \\ |
| 208 |
|
useStevensPhaseVel & \code{.TRUE.} & \\ |
| 209 |
|
useStevensAdvection & \code{.TRUE.} & \\ |
| 210 |
\hline |
\hline |
| 211 |
\hline |
\hline |
| 212 |
\end{tabular} |
\end{tabular} |
| 213 |
} |
} |
| 214 |
\caption{~} |
\caption{pkg OBCS run-time parameters} |
| 215 |
|
\label{tab:pkg:obcs:runtime_flags} |
| 216 |
\end{table} |
\end{table} |
| 217 |
|
|
| 218 |
|
|
| 226 |
Northern, Southern, Eastern, and Western. |
Northern, Southern, Eastern, and Western. |
| 227 |
All OB locations are specified by their absolute |
All OB locations are specified by their absolute |
| 228 |
meridional (Northern/Southern) or zonal (Eastern/Western) indices. |
meridional (Northern/Southern) or zonal (Eastern/Western) indices. |
| 229 |
Thus, for each zonal position $i=1,\ldots,Nx$ a meridional index |
Thus, for each zonal position $i=1,\ldots,N_x$ a meridional index |
| 230 |
$j$ specifies the Northern/Southern OB position, |
$j$ specifies the Northern/Southern OB position, |
| 231 |
and for each meridional position $j=1,\ldots,Ny$, a zonal index |
and for each meridional position $j=1,\ldots,N_y$, a zonal index |
| 232 |
$i$ specifies the Eastern/Western OB position. |
$i$ specifies the Eastern/Western OB position. |
| 233 |
For Northern/Southern OB this defines an $Nx$-dimensional |
For Northern/Southern OB this defines an $N_x$-dimensional |
| 234 |
``row'' array $\tt OB\_Jnorth(Ny)$ / $\tt OB\_Jsouth(Ny)$, |
``row'' array $\tt OB\_Jnorth(Ny)$ / $\tt OB\_Jsouth(Ny)$, |
| 235 |
and an $Ny$-dimenisonal |
and an $N_y$-dimenisonal |
| 236 |
``column'' array $\tt OB\_Ieast(Nx)$ / $\tt OB\_Iwest(Nx)$ |
``column'' array $\tt OB\_Ieast(Nx)$ / $\tt OB\_Iwest(Nx)$. |
| 237 |
Positions determined in this way allows Northern/Southern |
Positions determined in this way allows Northern/Southern |
| 238 |
OBs to be at variable $j$ (or $y$) positions, and Eastern/Western |
OBs to be at variable $j$ (or $y$) positions, and Eastern/Western |
| 239 |
OBs at variable $i$ (or $x$) positions. |
OBs at variable $i$ (or $x$) positions. |
| 273 |
\paragraph{OBCS\_READPARMS:} ~ \\ |
\paragraph{OBCS\_READPARMS:} ~ \\ |
| 274 |
Set OB positions through arrays |
Set OB positions through arrays |
| 275 |
{\tt OB\_Jnorth(Ny), OB\_Jsouth(Ny), OB\_Ieast(Nx), OB\_Iwest(Nx)}, |
{\tt OB\_Jnorth(Ny), OB\_Jsouth(Ny), OB\_Ieast(Nx), OB\_Iwest(Nx)}, |
| 276 |
and runtime flags see Table \ref{tab:???}. |
and runtime flags (see Table \ref{tab:pkg:obcs:runtime_flags}). |
| 277 |
|
|
| 278 |
\paragraph{OBCS\_CALC:} ~ \\ |
\paragraph{OBCS\_CALC:} ~ \\ |
| 279 |
% |
% |
| 297 |
\item |
\item |
| 298 |
prescribed time-constant or time-varying fields (see below). |
prescribed time-constant or time-varying fields (see below). |
| 299 |
% |
% |
| 300 |
|
\item |
| 301 |
|
use prescribed boundary fields to compute Stevens boundary conditions. |
| 302 |
\end{itemize} |
\end{itemize} |
| 303 |
|
|
| 304 |
|
\paragraph{ORLANSKI:} ~ \\ |
|
\paragraph{ORLANSKI} ~ \\ |
|
|
% |
|
|
Orlanski radiation conditions |
|
|
|
|
|
\paragraph{OBCS\_PRESCRIBE\_READ} Setting OB fields and updates \\ |
|
| 305 |
% |
% |
| 306 |
~ |
Orlanski radiation conditions \citep{orl:76}, examples can be found in |
| 307 |
|
\code{verification/dome} and |
| 308 |
\paragraph{OBCS\_BALANCE} ~ \\ |
\code{verification/tutorial\_plume\_on\_slope} |
| 309 |
% |
(\ref{sec:eg-gravityplume}). |
| 310 |
~ |
|
| 311 |
|
\paragraph{OBCS\_PRESCRIBE\_READ:} ~ \\ |
| 312 |
|
% |
| 313 |
|
When \code{useOBCSprescribe = .TRUE.} the model tries to read |
| 314 |
|
temperature, salinity, u- and v-velocities from files specified in the |
| 315 |
|
runtime parameters \code{OB[N/S/E/W][t/s/u/v]File}. These files are |
| 316 |
|
the usual IEEE, big-endian files with dimensions of a section along an |
| 317 |
|
open boundary: |
| 318 |
|
\begin{itemize} |
| 319 |
|
\item For North/South boundary files the dimensions are |
| 320 |
|
$(N_x\times N_r\times\mbox{time levels})$, for East/West boundary |
| 321 |
|
files the dimensions are $(N_y\times N_r\times\mbox{time levels})$. |
| 322 |
|
\item If a non-linear free surface is used |
| 323 |
|
(\ref{sec:nonlinear-freesurface}), additional files |
| 324 |
|
\code{OB[N/S/E/W]etaFile} for the sea surface height $\eta$ with |
| 325 |
|
dimension $(N_{x/y}\times\mbox{time levels})$ may be specified. |
| 326 |
|
\item If non-hydrostatic dynamics are used |
| 327 |
|
(\ref{sec:non-hydrostatic}), additional files |
| 328 |
|
\code{OB[N/S/E/W]wFile} for the vertical velocity $w$ with |
| 329 |
|
dimensions $(N_{x/y}\times N_r\times\mbox{time levels})$ can be |
| 330 |
|
specified. |
| 331 |
|
\item If \code{useSEAICE=.TRUE.} then additional files |
| 332 |
|
\code{OB[N/S/E/W][a,h,sl,sn,uice,vice]} for sea ice area, thickness |
| 333 |
|
(\code{HEFF}), seaice salinity, snow and ice velocities |
| 334 |
|
$(N_{x/y}\times\mbox{time levels})$ can be specified. |
| 335 |
|
\end{itemize} |
| 336 |
|
As in \code{S/R external\_fields\_load} or the \code{exf}-package, the |
| 337 |
|
code reads two time levels for each variable, e.g.\ \code{OBNu0} and |
| 338 |
|
\code{OBNu1}, and interpolates linearly between these time levels to |
| 339 |
|
obtain the value \code{OBNu} at the current model time (step). When the |
| 340 |
|
\code{exf}-package is used, the time levels are controlled for each |
| 341 |
|
boundary separately in the same way as the \code{exf}-fields in |
| 342 |
|
\code{data.exf}, namelist \code{EXF\_NML\_OBCS}. The runtime flags |
| 343 |
|
follow the above naming conventions, e.g. for the western boundary the |
| 344 |
|
corresponding flags are \code{OBCWstartdate1/2} and |
| 345 |
|
\code{OBCWperiod}. Sea-ice boundary values are controlled separately |
| 346 |
|
with \code{siobWstartdate1/2} and \code{siobWperiod}. When the |
| 347 |
|
\code{exf}-package is not used, the time levels are controlled by the |
| 348 |
|
runtime flags \code{externForcingPeriod} and \code{externForcingCycle} |
| 349 |
|
in \code{data}, see \code{verification/exp4} for an example. |
| 350 |
|
|
| 351 |
|
\paragraph{OBCS\_CALC\_STEVENS:} ~ \\ |
| 352 |
|
(THE IMPLEMENTATION OF THESE BOUNDARY CONDITIONS IS NOT COMPLETE. SO |
| 353 |
|
FAR ONLY EASTERN AND WESTERN BOUNDARIES ARE SUPPORTED.) \\ |
| 354 |
|
The boundary conditions following \citet{stevens:90} require the |
| 355 |
|
vertically averaged normal velocity (originally specified as a stream |
| 356 |
|
function along the open boundary) $\bar{u}_{ob}$ and the tracer fields |
| 357 |
|
$\chi_{ob}$ (note: passive tracers are currently not implemented and |
| 358 |
|
the code stops when package \code{ptracers} is used together with this |
| 359 |
|
option). Currently, the code vertically averages the normal velocity |
| 360 |
|
as specified. From these prescribed values the code computes the |
| 361 |
|
boundary values for the next timestep $n+1$ as follows (as an |
| 362 |
|
example, we use the notation for an eastern or western boundary): |
| 363 |
|
\begin{itemize} |
| 364 |
|
\item $u^{n+1}(y,z) = \bar{u}_{ob}(y) + u'(y,z)$, where $u_{n}'$ is the |
| 365 |
|
deviation from the vertically averaged velocity one grid point |
| 366 |
|
inward from the boundary. |
| 367 |
|
\item If $u^{n+1}$ is directed into the model domain, the boudary |
| 368 |
|
value for tracer $\chi$ is restored to the prescribed values: |
| 369 |
|
\[\chi^{n+1} = \chi^{n} + \frac{\Delta{t}}{\tau_\chi} (\chi_{ob} - |
| 370 |
|
\chi^{n}),\] where $\tau_\chi$ is the relaxation time |
| 371 |
|
scale \texttt{T/SrelaxStevens}. |
| 372 |
|
\item If $u^{n+1}$ is directed out of the model domain, the tracer is |
| 373 |
|
advected out of the domain with $u^{n+1}+c$, where $c$ is a phase |
| 374 |
|
velocity estimated as |
| 375 |
|
$\frac{1}{2}\frac{\partial\chi}{\partial{t}}/\frac{\partial\chi}{\partial{x}}$. |
| 376 |
|
For test purposes, the phase velocity contribution or the entire |
| 377 |
|
advection can |
| 378 |
|
be turned off by setting the corresponding parameters |
| 379 |
|
\texttt{useStevensPhaseVel} and \texttt{useStevensAdvection} to |
| 380 |
|
\texttt{.FALSE.}.\end{itemize} See \citet{stevens:90} for details. |
| 381 |
|
|
| 382 |
|
\paragraph{OBCS\_BALANCE:} ~ \\ |
| 383 |
|
% |
| 384 |
|
This is not (yet) a separate routine in the code, but it may become |
| 385 |
|
one to make this code more transparent. The code is part of |
| 386 |
|
\code{S/R~OBCS\_CALC}. When turned on (\code{ALLOW\_OBCS\_BALANCE} |
| 387 |
|
defined in \code{OBCS\_OPTIONS.h} and \code{useOBCSbalance=.true.} in |
| 388 |
|
\code{data.obcs/OBCS\_PARM01}), the normal velocities across each of |
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|
the four boundaries are modified separately, so that the net volume |
| 390 |
|
transport across \emph{each} boundary is zero. For example, for the |
| 391 |
|
western boundary at $i=i_{b}$, the modified velocity is: |
| 392 |
|
\[ |
| 393 |
|
u(y,z) - \int_{\mbox{western boundary}}u\,dy\,dz \approx OBNu(j,k) - \sum_{j,k} |
| 394 |
|
OBNu(j,k) h_{w}(i_{b},j,k)\Delta{y_G(i_{b},j)}\Delta{z(k)}. |
| 395 |
|
\] |
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|
This also ensures a net total inflow of zero through all boundaries to |
| 397 |
|
make it a useful flag to prevent infinite sea-level change within the |
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|
domain, but the flag is \emph{not} useful if you want to simulate, |
| 399 |
|
say, a sector of the Southern Ocean with a strong ACC entering through |
| 400 |
|
the western and leaving through the eastern boundary, because this |
| 401 |
|
flag will make sure that the strong inflow is removed. It is |
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|
recommended that this part of the code is adapted to the particular |
| 403 |
|
needs of the simulation in question. |
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|
|
| 405 |
\paragraph{OBCS\_APPLY\_*:} ~ \\ |
\paragraph{OBCS\_APPLY\_*:} ~ \\ |
| 406 |
~ |
~ |
| 439 |
Available output fields are summarized in |
Available output fields are summarized in |
| 440 |
Table \ref{tab:pkg:obcs:diagnostics}. |
Table \ref{tab:pkg:obcs:diagnostics}. |
| 441 |
|
|
| 442 |
\begin{table}[h!] |
\begin{table}[!ht] |
| 443 |
\centering |
\centering |
| 444 |
\label{tab:pkg:obcs:diagnostics} |
\label{tab:pkg:obcs:diagnostics} |
| 445 |
{\footnotesize |
{\footnotesize |
| 456 |
%---------------------------------------------------------------------- |
%---------------------------------------------------------------------- |
| 457 |
|
|
| 458 |
\subsubsection{Reference experiments} |
\subsubsection{Reference experiments} |
| 459 |
|
In the directory \code{verifcation}, the following experiments use |
| 460 |
|
\code{obcs}: |
| 461 |
|
\begin{itemize} |
| 462 |
|
\item \code{exp4}: box with 4 open boundaries, simulating flow over a |
| 463 |
|
Gaussian bump based on \citet{adcroft:97}, also tests |
| 464 |
|
Stevens-boundary conditions; |
| 465 |
|
\item \code{dome}: based on ``Denmark Strait Overflow Model |
| 466 |
|
Experiment'', use Orlanski-BCs; |
| 467 |
|
\item \code{internal\_wave}: uses a heavily modified \code{S/R~OBCS\_CALC} |
| 468 |
|
\item \code{seaice\_obcs}: simple example who to use the sea-ice |
| 469 |
|
related code, based on \code{lab\_sea}; |
| 470 |
|
\item \code{tutorial\_plume\_on\_slope}: uses Orlanski-BCs, see also |
| 471 |
|
section~\ref{sec:eg-gravityplume}. |
| 472 |
|
\end{itemize} |
| 473 |
|
|
| 474 |
|
|
| 475 |
|
|
| 477 |
|
|
| 478 |
\subsubsection{References} |
\subsubsection{References} |
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|
|
| 480 |
|
\subsubsection{Experiments and tutorials that use obcs} |
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|
\label{sec:pkg:obcs:experiments} |
| 482 |
|
|
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|
\begin{itemize} |
| 484 |
|
\item \code{tutorial\_plume\_on\_slope} (section~\ref{sec:eg-gravityplume}) |
| 485 |
|
\end{itemize} |
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|
|
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|
|
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%%% Local Variables: |
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%%% mode: latex |
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%%% TeX-master: "../../manual" |
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%%% End: |
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