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\end{description} |
\end{description} |
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\subsection{Using MNC} |
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\subsubsection{``Grid--Types'' and ``Variable--Types''} |
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As a convenience for users, the MNC package includes numerous routines |
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to aid in the writing of data to NetCDF format. Probably the biggest |
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convenience is the use of pre-defined ``grid types'' and ``variable |
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types''. These ``types'' are simply look-up tables that store |
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dimensions, indicies, attributes, and other information that can all |
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be retrieved using a single character string. |
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The ``grid types'' are a way of mapping variables within MITgcm to |
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NetCDF arrays. Within MITgcm, most spatial variables are defined |
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using two-- or three--dimensional arrays with ``overlap'' regions (see |
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Figures \ref{fig:communication_primitives}, a possible vertical index, |
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and \ref{fig:tiling-strategy}) and tile indicies such as the following |
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``U'' velocity: |
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\begin{verbatim} |
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_RL uVel (1-OLx:sNx+OLx,1-OLy:sNy+OLy,Nr,nSx,nSy) |
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\end{verbatim} |
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as defined in \filelink{model/inc/DYNVARS.h}{model-inc-DYNVARS.h} |
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The grid type is a character string that encodes the presence and |
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types associated with the four possible dimensions. The character |
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string follows the format |
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\begin{center} |
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\texttt{H0\_H1\_H2\_\_V\_\_T} |
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\end{center} |
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where the terms \textit{H0,H1,H2,V,T} can be almost any combination of |
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the following: |
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\begin{center} |
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\begin{tabular}[h]{|ccc|c|c|}\hline |
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\multicolumn{3}{|c|}{Horizontal} & Vertical & \\ |
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Location & Direction & Halo & Location & Time \\\hline |
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H0 & H1 & H2 & V & T \\\hline |
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\texttt{-} & xy & Hn & \texttt{-} & \texttt{-} \\ |
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U & x & Hy & i & t \\ |
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V & y & & c & \\ |
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Cen & & & & \\ |
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Cor & & & & \\\hline |
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\end{tabular} |
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\end{center} |
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A example list of all pre-defined combinations is contained in the |
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file |
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\begin{center} |
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\texttt{pkg/mnc/pre-defined\_grids.txt}. |
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\end{center} |
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\subsubsection{An Example} |
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Writing variables to NetCDF files can be accomplished in as few as two |
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function calls. The first function call defines a variable type, |
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associates it with a name (character string), and provides additional |
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information about the indicies for \texttt{bi,bj} dimensions. The |
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second function call will write variable at, if necessary, the |
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current time level within the model. |
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Examples of the initialization calls can be found in the file |
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\begin{center} |
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\filelink{model/src/initialise\_fixed.F}{model-src-initialise_fixed.F} |
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\end{center} |
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where these four function calls: {\footnotesize |
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\begin{verbatim} |
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C Create MNC definitions for DYNVARS.h variables |
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CALL MNC_CW_ADD_VNAME(myThid, 'iter', '-_-_--__-__t', 0,0) |
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CALL MNC_CW_ADD_VATTR_TEXT(myThid,'iter',1, |
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& 'long_name','iteration_count') |
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CALL MNC_CW_ADD_VNAME(myThid, 'U', 'U_xy_Hn__C__t', 4,5) |
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CALL MNC_CW_ADD_VATTR_TEXT(myThid,'U',1,'units','m/s') |
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\end{verbatim} } |
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{\noindent initialize two \texttt{VNAME}s and add one attribute to each.} |
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The two variables are subsequently written at specific time steps |
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within |
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\begin{center} |
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\filelink{model/src/write\_state.F}{model-src-write_state.F} |
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\end{center} |
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using the function calls: {\footnotesize |
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\begin{verbatim} |
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C Write the DYNVARS.h variables using the MNC package |
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mnc_iter = myIter |
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CALL MNC_CW_RL_W_R(myThid,'state',0,0,'iter',-1,mnc_iter) |
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CALL MNC_CW_RL_W_D(myThid,'state',0,0,'U', 0, uVel) |
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\end{verbatim} } |
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\subsection{Key subroutines, parameters and files} |
\subsection{Key subroutines, parameters and files} |
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All of the variables used to implement the lookup tables are described |
All of the variables used to implement the lookup tables are described |
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in \filelink{pkg/mnc/mnc\_common.h}{pkg/mnc/mnc_common}. |
in \filelink{model/src/write\_state.F}{model-src-write_state.F} |
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\subsection{Package Reference} |
\subsection{Package Reference} |
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