--- manual/s_phys_pkgs/text/obcs.tex 2005/08/11 23:58:07 1.1 +++ manual/s_phys_pkgs/text/obcs.tex 2011/02/25 17:26:17 1.6 @@ -5,7 +5,8 @@ \end{rawhtml} -Authors: Martin Losch and Patrick Heimbach +Authors: +Alistair Adcroft, Patrick Heimbach, Samar Katiwala, Martin Losch \subsubsection{Introduction \label{sec:pkg:obcs:intro}} @@ -15,7 +16,7 @@ %---------------------------------------------------------------------- \subsubsection{OBCS configuration and compiling -\label{sec:pkg:kpp:comp}} +\label{sec:pkg:obcs:comp}} As with all MITgcm packages, OBCS can be turned on or off at compile time @@ -23,11 +24,11 @@ \begin{itemize} % \item -using the \texttt{packages.conf} file by adding \texttt{obcs} to it, +using the \code{packages.conf} file by adding \code{obcs} to it, % \item -or using \texttt{genmake2} adding -\texttt{-enable=obcs} or \texttt{-disable=obcs} switches +or using \code{genmake2} adding +\code{-enable=obcs} or \code{-disable=obcs} switches % \item \textit{Required packages and CPP options:} \\ @@ -36,20 +37,20 @@ which differ in the way how OB's are treated in time: A simple time-management (e.g. constant in time, or cyclic with fixed fequency) is provided through -S/R \texttt{obcs\_external\_fields\_load}. +S/R \code{obcs\_external\_fields\_load}. More sophisticated ``real-time'' (i.e. calendar time) management is -available through \texttt{obcs\_prescribe\_read}. +available through \code{obcs\_prescribe\_read}. The latter case requires -packages \texttt{cal} and \texttt{exf} to be enabled. +packages \code{cal} and \code{exf} to be enabled. % \end{itemize} -(see also Section \ref{sect:buildingCode}). +(see also Section \ref{sec:buildingCode}). Parts of the OBCS code can be enabled or disabled at compile time via CPP preprocessor flags. These options are set in -\texttt{OBCS\_OPTIONS.h}. Table \ref{tab:pkg:obcs:cpp} summarizes them. +\code{OBCS\_OPTIONS.h}. Table \ref{tab:pkg:obcs:cpp} summarizes them. -\begin{table}[h!] +\begin{table}[!ht] \centering \label{tab:pkg:obcs:cpp} {\footnotesize @@ -57,23 +58,27 @@ \hline \textbf{CPP option} & \textbf{Description} \\ \hline \hline - \texttt{ALLOW\_OBCS\_NORTH} & + \code{ALLOW\_OBCS\_NORTH} & enable Northern OB \\ - \texttt{ALLOW\_OBCS\_SOUTH} & + \code{ALLOW\_OBCS\_SOUTH} & enable Southern OB \\ - \texttt{ALLOW\_OBCS\_EAST} & + \code{ALLOW\_OBCS\_EAST} & enable Eastern OB \\ - \texttt{ALLOW\_OBCS\_WEST} & + \code{ALLOW\_OBCS\_WEST} & enable Western OB \\ \hline - \texttt{ALLOW\_OBCS\_PRESCRIBE} & + \code{ALLOW\_OBCS\_PRESCRIBE} & enable code for prescribing OB's \\ - \texttt{ALLOW\_OBCS\_SPONGE} & + \code{ALLOW\_OBCS\_SPONGE} & enable sponge layer code \\ - \texttt{ALLOW\_OBCS\_BALANCE} & + \code{ALLOW\_OBCS\_BALANCE} & enable code for balancing transports through OB's \\ - \texttt{ALLOW\_ORLANSKI} & + \code{ALLOW\_ORLANSKI} & enable Orlanski radiation conditions at OB's \\ + \code{ALLOW\_OBCS\_STEVENS} & + enable Stevens (1990) boundary conditions at OB's \\ + & (currently only implemented for eastern and western \\ + & boundaries and NOT for ptracers) \\ \hline \end{tabular} } @@ -87,39 +92,38 @@ \label{sec:pkg:obcs:runtime}} Run-time parameters are set in files -\texttt{data.pkg}, \texttt{data.obcs}, and \texttt{data.exf} +\code{data.pkg}, \code{data.obcs}, and \code{data.exf} if ``real-time'' prescription is requested -(i.e. package \texttt{exf} enabled). +(i.e. package \code{exf} enabled). These parameter files are read in S/R -\texttt{packages\_readparms.F}, \texttt{obcs\_readparms.F}, and -\texttt{exf\_readparms.F}, respectively. +\code{packages\_readparms.F}, \code{obcs\_readparms.F}, and +\code{exf\_readparms.F}, respectively. Run-time parameters may be broken into 3 categories: (i) switching on/off the package at runtime, (ii) OBCS package flags and parameters, -(iii) additional timing flags in \texttt{data.exf}, if selected. +(iii) additional timing flags in \code{data.exf}, if selected. \paragraph{Enabling the package} ~ \\ % The OBCS package is switched on at runtime by setting -\texttt{useOBCS = .TRUE.} in \texttt{data.pkg}. +\code{useOBCS = .TRUE.} in \code{data.pkg}. \paragraph{Package flags and parameters} ~ \\ % Table \ref{tab:pkg:obcs:runtime_flags} summarizes the -runtime flags that are set in \texttt{data.obcs}, and +runtime flags that are set in \code{data.obcs}, and their default values. -\begin{table}[h!] +\begin{table}[!ht] \centering - \label{tab:pkg:obcs:runtime_flags} {\footnotesize \begin{tabular}{|l|c|l|} \hline \textbf{Flag/parameter} & \textbf{default} & \textbf{Description} \\ \hline \hline - \multicolumn{3}{|c|}{\textit{basic flags \& parameters} } \\ + \multicolumn{3}{|c|}{\textit{basic flags \& parameters} (OBCS\_PARM01) } \\ \hline OB\_Jnorth & 0 & Nx-vector of J-indices (w.r.t. Ny) of Northern OB @@ -133,12 +137,16 @@ OB\_Iwest & 0 & Ny-vector of I-indices (w.r.t. Nx) of Western OB at each J-position (w.r.t. Ny) \\ - useOBCSprescribe & \texttt{.FALSE.} & + useOBCSprescribe & \code{.FALSE.} & ~ \\ - useOBCSsponge & \texttt{.FALSE.} & + useOBCSsponge & \code{.FALSE.} & ~ \\ - useOBCSbalance & \texttt{.FALSE.} & + useOBCSbalance & \code{.FALSE.} & ~ \\ + useOrlanskiNorth/South/EastWest & \code{.FALSE.} & + turn on Orlanski boundary conditions for individual boundary\\ + useStevensNorth/South/EastWest & \code{.FALSE.} & + turn on Stevens boundary conditions for individual boundary\\ OB\textbf{X}\textbf{y}File & ~ & file name of OB field \\ ~ & ~ & @@ -146,9 +154,14 @@ \textbf{E}(ast), \textbf{W}(est) \\ ~ & ~ & \textbf{y}: \textbf{t}(emperature), \textbf{s}(salinity), - \textbf{u}(-velocity), \textbf{v}(-velocity) \\ + \textbf{u}(-velocity), \textbf{v}(-velocity), \\ + ~ & ~ & + \textbf{w}(-velocity), \textbf{eta}(sea surface height)\\ + ~ & ~ & + \textbf{a}(sea ice area), \textbf{h}(sea ice thickness), + \textbf{sn}(snow thickness), \textbf{sl}(sea ice salinity)\\ \hline - \multicolumn{3}{|c|}{\textit{Orlanski parameters} } \\ + \multicolumn{3}{|c|}{\textit{Orlanski parameters} (OBCS\_PARM02) } \\ \hline cvelTimeScale & 2000 sec & averaging period for phase speed \\ @@ -156,12 +169,12 @@ maximum allowable phase speed-CFL for AB-II \\ CFIX & 0.8 m/s & fixed boundary phase speed \\ - useFixedCEast & .FALSE. & + useFixedCEast & \code{.FALSE.} & ~ \\ - useFixedCWest & .FALSE. & + useFixedCWest & \code{.FALSE.} & ~ \\ \hline - \multicolumn{3}{|c|}{\textit{Sponge-layer parameters} } \\ + \multicolumn{3}{|c|}{\textit{Sponge-layer parameters} (OBCS\_PARM03)} \\ \hline spongeThickness & 0 & sponge layer thickness (in \# grid points) \\ @@ -177,42 +190,191 @@ Vrelaxobcsbound & 0 sec & relaxation time scale at the outermost sponge layer point of a zonal OB \\ + \hline + \multicolumn{3}{|c|}{\textit{Stevens parameters} (OBCS\_PARM04) } \\ + \hline + T/SrelaxStevens & 0~sec & relaxation time scale for + temperature/salinity \\ + useStevensPhaseVel & \code{.TRUE.} & \\ + useStevensAdvection & \code{.TRUE.} & \\ \hline \hline \end{tabular} } - \caption{~} + \caption{pkg OBCS run-time parameters} + \label{tab:pkg:obcs:runtime_flags} \end{table} %---------------------------------------------------------------------- +\subsubsection{Defining open boundary positions +\label{sec:pkg:obcs:defining}} + +There are four open boundaries (OBs), a +Northern, Southern, Eastern, and Western. +All OB locations are specified by their absolute +meridional (Northern/Southern) or zonal (Eastern/Western) indices. +Thus, for each zonal position $i=1,\ldots,N_x$ a meridional index +$j$ specifies the Northern/Southern OB position, +and for each meridional position $j=1,\ldots,N_y$, a zonal index +$i$ specifies the Eastern/Western OB position. +For Northern/Southern OB this defines an $N_x$-dimensional +``row'' array $\tt OB\_Jnorth(Ny)$ / $\tt OB\_Jsouth(Ny)$, +and an $N_y$-dimenisonal +``column'' array $\tt OB\_Ieast(Nx)$ / $\tt OB\_Iwest(Nx)$. +Positions determined in this way allows Northern/Southern +OBs to be at variable $j$ (or $y$) positions, and Eastern/Western +OBs at variable $i$ (or $x$) positions. +Here, indices refer to tracer points on the C-grid. +A zero (0) element in $\tt OB\_I\ldots$, $\tt OB\_J\ldots$ +means there is no corresponding OB in that column/row. +For a Northern/Southern OB, the OB V point is to the South/North. +For an Eastern/Western OB, the OB U point is to the West/East. + +\begin{verbatim} + For example + OB_Jnorth(3)=34 means that: + T( 3 ,34) is a an OB point + U(3:4,34) is a an OB point + V( 4 ,34) is a an OB point + while + OB_Jsouth(3)=1 means that: + T( 3 ,1) is a an OB point + U(3:4,1) is a an OB point + V( 4 ,2) is a an OB point +\end{verbatim} + +For convenience, negative values for Jnorth/Ieast refer to +points relative to the Northern/Eastern edges of the model +eg. $\tt OB\_Jnorth(3)=-1$ means that the point $\tt (3,Ny)$ +is a northern OB. + +\noindent +\textsf{Add special comments for case \#define NONLIN\_FRSURF, +see obcs\_ini\_fixed.F} + +%---------------------------------------------------------------------- + \subsubsection{Equations and key routines \label{sec:pkg:obcs:equations}} -\paragraph{OBCS\_READPARMS:} Setting OB positions \\ -~ +\paragraph{OBCS\_READPARMS:} ~ \\ +Set OB positions through arrays +{\tt OB\_Jnorth(Ny), OB\_Jsouth(Ny), OB\_Ieast(Nx), OB\_Iwest(Nx)}, +and runtime flags (see Table \ref{tab:pkg:obcs:runtime_flags}). \paragraph{OBCS\_CALC:} ~ \\ -~ +% +Top-level routine for filling values to be applied at OB for +$T,S,U,V,\eta$ into corresponding +``slice'' arrays $(x,z)$, $(y,z)$ for each OB: +$\tt OB[N/S/E/W][t/s/u/v]$; e.g. for salinity array at +Southern OB, array name is $\tt OBSt$. +Values filled are either +% +\begin{itemize} +% +\item +constant vertical $T,S$ profiles as specified in file +{\tt data} ({\tt tRef(Nr), sRef(Nr)}) with zero velocities $U,V$, +% +\item +$T,S,U,V$ values determined via Orlanski radiation conditions +(see below), +% +\item +prescribed time-constant or time-varying fields (see below). +% +\item +use prescribed boundary fields to compute Stevens boundary conditions. +\end{itemize} -\paragraph{OBCS\_APPLY\_*:} ~ \\ -~ -\paragraph{OBCS\_PRESCRIBE\_READ} Setting OB fields and updates \\ +\paragraph{ORLANSKI:} ~ \\ % -~ +Orlanski radiation conditions \citep{orl:76}, examples can be found in +\code{verification/dome} and +\code{verification/tutorial\_plume\_on\_slope} +(\ref{sec:eg-gravityplume}). + +\paragraph{OBCS\_PRESCRIBE\_READ:} ~ \\ +% +When \code{useOBCSprescribe = .TRUE.} the model tries to read +temperature, salinity, u- and v-velocities from files specified in the +runtime parameters \code{OB[N/S/E/W][t/s/u/v]File}. These files are +the usual IEEE, big-endian files with dimensions of a section along an +open boundary: +\begin{itemize} +\item For North/South boundary files the dimensions are + $(N_x\times N_r\times\mbox{time levels})$, for East/West boundary + files the dimensions are $(N_y\times N_r\times\mbox{time levels})$. +\item If a non-linear free surface is used + (\ref{sec:nonlinear-freesurface}), additional files + \code{OB[N/S/E/W]etaFile} for the sea surface height $\eta$ with + dimension $(N_{x/y}\times\mbox{time levels})$ may be specified. +\item If non-hydrostatic dynamics are used + (\ref{sec:non-hydrostatic}), additional files + \code{OB[N/S/E/W]wFile} for the vertical velocity $w$ with + dimensions $(N_{x/y}\times N_r\times\mbox{time levels})$ may be + specified. +\item If \code{useSEAICE=.TRUE.} then additional files + \code{OB[N/S/E/W][a,h,sl,sn,uice,vice]} for sea ice area, thickness + (\code{HEFF}), seaice salinity, snow and ice velocities + $(N_{x/y}\times\mbox{time levels})$ may be specified. +\end{itemize} +When the \code{exf}-package is used, the time levels are controlled +for each boundary separately in the same way as the \code{exf}-fields +in \code{data.exf}, namelist \code{EXF\_NML\_OBCS}. The runtime flags +follow the above naming conventions, e.g. for the western boundary the +corresponding flags are \code{OBCWstartdate1/2} and +\code{OBCWperiod}. Sea-ice boundary values are controlled separately +with \code{siobWstartdate1/2} and \code{siobWperiod}. +When the \code{exf}-package is not used, the time levels are +controlled by the runtime flags \code{externForcingPeriod} and +\code{externForcingCycle} in \code{data}, see \code{verification/exp4} +for an example. + +\paragraph{OBCS\_CALC\_STEVENS:} ~ \\ +(THE IMPLEMENTATION OF THESE BOUNDARY CONDITIONS IS NOT COMPLETE. SO +FAR ONLY EASTERN AND WESTERN BOUNDARIES ARE SUPPORTED.) \\ +The boundary conditions following \citet{stevens:90} require the +vertically averaged normal velocity (originally specified as a stream +function along the open boundary) $\bar{u}_{ob}$ and the tracer fields +$\chi_{ob}$ (note: passive tracers are currently not implemented and +the code stops when package \code{ptracers} is used together with this +option). Currently, the code vertically averages the normal velocity +as specified. From these prescribed values the code computes the +boundary values for the next timestep $n+1$ as follows (as an +example, we use the notation for an eastern or western boundary): +\begin{itemize} +\item $u^{n+1}(y,z) = \bar{u}_{ob}(y) + u'(y,z)$, where $u_{n}'$ is the + deviation from the vertically averaged velocity one grid point + inward from the boundary. +\item If $u^{n+1}$ is directed into the model domain, the boudary + value for tracer $\chi$ is restored to the prescribed values: + \[\chi^{n+1} = \chi^{n} + \frac{\Delta{t}}{\tau_\chi} (\chi_{ob} - + \chi^{n}),\] where $\tau_\chi$ is the relaxation time + scale \texttt{T/SrelaxStevens}. +\item If $u^{n+1}$ is directed out of the model domain, the tracer is + advected out of the domain with $u^{n+1}+c$, where $c$ is a phase + velocity estimated as + $\frac{1}{2}\frac{\partial\chi}{\partial{t}}/\frac{\partial\chi}{\partial{x}}$. + For test purposes, the phase velocity contribution or the entire + advection can + be turned off by setting the corresponding parameters + \texttt{useStevensPhaseVel} and \texttt{useStevensAdvection} to + \texttt{.FALSE.}.\end{itemize} See \citet{stevens:90} for details. -\paragraph{OBCS\_SPONGE} Setting sponge layer characteristics \\ +\paragraph{OBCS\_BALANCE} ~ \\ % ~ -\paragraph{OBCS\_BALANCE} ~ \\ -% +\paragraph{OBCS\_APPLY\_*:} ~ \\ ~ -\paragraph{ORLANSKI} Orlanski radiation conditions \\ +\paragraph{OBCS\_SPONGE} Setting sponge layer characteristics \\ % ~ @@ -246,7 +408,7 @@ Available output fields are summarized in Table \ref{tab:pkg:obcs:diagnostics}. -\begin{table}[h!] +\begin{table}[!ht] \centering \label{tab:pkg:obcs:diagnostics} {\footnotesize @@ -270,3 +432,15 @@ \subsubsection{References} +\subsubsection{Experiments and tutorials that use obcs} +\label{sec:pkg:obcs:experiments} + +\begin{itemize} +\item{Ocean experiment in exp4 verification directory. } +\end{itemize} + + +%%% Local Variables: +%%% mode: latex +%%% TeX-master: "../../manual" +%%% End: