\section{Conversion of FM synchronous file to diachronic format}
Short description is given here, readers must refer to the original documentation on the Meso-NH web site:
``{\sc traitement graphique des fichiers synchrones produits par le mod\`ele
mesonh}, J. Duron''. 

\subsection{Synchronous and diachronic formats} \label{diachro_file}
The Meso-NH graphic utility ({\tt diaprog}) works on FM files which are on
diachronic format. A diachronic FM file is either
\begin{itemize}
\item
a file produced during the simulation 
which contain time series of self-documented informations
(e.g. file with name CEXP.1.CSEG.000).
An information is one of the following: 
\subitem - a
3-dimensional, 2-dimensional, 1-dimensional or 0-dimensional field (eventually
time-averaged, or compressed in one direction): type {\sc cart}, 
\subitem - a set of vertical profiles at points checking some criteria:
type {\sc mask}, 
\subitem - spectral coefficients obtained by FFT along the X or Y direction:
type {\sc spxy},
\subitem - pseudo-observations (ground station: type {\sc ssol};
dropsonde: type {\sc drst}; radiosonde: type {\sc rspl};
airborne radar: type {\sc rapl}).
 \\
A diachronic file can contains informations of one or several previous types
stored at different time frequency.
For a whole description about the diachronic file type, reader must refer
to the original documentation on the Meso-NH web site:
``{\sc cr\'eation et exploitation de fichiers diachroniques}, J. Duron''. 
\end{itemize}
or
\begin{itemize}
\item a `pseudo'-diachronic file resulting of the conversion of a synchronous
file (e.g. with name CEXP.1.CSEG.00n where n$>$0).
Recall that such a file contains all the pronostic fields of the model at one 
instant (initial or during the simulation).
When converted it is a 'pseudo'-diachronic file, because it contains only one 
instant and one type of diachronic information ({\sc cart}).
The next subsection presents the conversion tool (named \texttt{conv2dia})
to apply to synchronous files, necessary step to use \texttt{diaprog} graphic
tool.
\end{itemize}

\subsection{{\tt conv2dia} tool}
The conversion tool works on files produced by
the initialisation programs ({\sc prep\_pgd, prep\_ideal\_case,
prep\_real\_case}), the model simulation, or the post-processing program
({\tt\sc diag}). It allows to convert one synchronous file onto one diachronic 
file, as well as merge several synchronous files with chronological times
(outputs of one run, or files initialised from large-scale model)
onto one diachronic file.

With {\tt conv2dia.elim} tool, you can choose not to convert all the fields of
the input file(s). The pronostic fields at $t-dt$ instant, or at $t$ instant,
or any other fields can be eliminated.
With {\tt conv2dia.select} tool, you have to indicate the fields to select
for conversion.
This is done to reduce the size of the output file.

The output file contains informations whose type is {\sc cart} stored in arrays
with size of {\tt (IIU*IJU*IKU), (IIU*IJU), (IIU*IKU),} or 1.


\subsection{Example}

Only the binary (\textsc{LFI}) part of the input FM files is required
in the current directory (split the FM file with the {\tt fm2deslfi} 
script if not).

All characters typed on keyboard are saved in {\tt dirconv.elim} or 
{\tt dirconv.select} file, it can be appended and used as input (after being 
renamed) for the next call of the tool
\newline (e.g.  {\tt conv2dia.elim < dirconv.elim.ex}).

Below is the example of questions when {\tt conv2dia.elim} is invoked.

\small
\begin{tabular}{l}
\\
\\
{\tt ENTER NUMBER OF INPUT FM FILES}  \\
{\tt\it 2 }  \\
{\tt ENTER FM FILE NAME}  \\
{\tt\it CEXP.1.CSEG.001}  \\
{\tt ENTER FM FILE NAME}  \\
{\tt\it CEXP.1.CSEG.002}  \\
{\tt ENTER DIACHRONIC FILE NAME}  \\
{\tt\it CEXP.1.CSEG.1-2.dia}  \\
{\tt DELETION OF PARAMETERS AT TIME t-dt ? (enter 1) } \\
{\tt DELETION OF PARAMETERS AT TIME t    ? (enter 2) } \\
{\tt NO DELETION                         ? (enter 0) } \\
{\tt\it 2 }  \\
{\tt Do you want to suppress others parameters ? (y/n) }\\
{\tt\it y }  \\
{\tt Enter their names in UPPERCASE  (1/1 line) }\\
{\tt End by END}\\
{\tt\it DTHCONV }  \\
{\tt\it DRVCONV }  \\
{\tt\it END }  \\
\end{tabular}
\normalsize