\chapter{1D version of the generic model}

\label{sc:rcm1d}

The physical part of the model can be used to run 1D radiative-convective simulations (one atmospheric column / globally averaged climate). In practice, the simulation is controlled from a main program called \verb+ rcm1d.F+ which, after initialization, then calls the master subroutine of the physics \verb+ physiq.F90+ described in the previous chapters.

\section{Compilation}
{\bf -} For example, to compile the generic model in 1D with 25 layers, type (in compliance with the makegcm function manual described in section \ref{sc:compil1})

\begin{verbatim}
makegcm -d 25 -t 1 -b 32x36 -p std rcm1d
\end{verbatim}

You can find executable {\bf rcm1d.e} (the compiled model)
in the directory from which you ran the makegcm command.

\section{1-D runs and input files}

The 1D model does not use an initial state file (the simulation must be long enough to obtain a balanced state). Thus, to generate a simulation simply type:

\begin{verbatim}
> rcm1d.e
\end{verbatim}

The following example files are available in the {\tt deftank} directory
(copy them into your working directory first):

- {\bf callphys.def}~: controls the options in the physics,
  just like for the 3D GCM.

- {\bf z2sig.def}~:
 controls the vertical discretization
 (no change needed, in general), functions as with the 3D GCM.

- {\bf traceur.def}~:
 controls the tracer names (this file may not be present, as long
 as you run without tracers (option {\tt tracer=.false.} in
 callphys.def)

- {\bf run.def}~: controls the 1D run parameters and initializations
(this is actually file {\tt run.def.1d} the {\tt deftank} directory,
which must be renamed {\tt run.def} to be read by the program).\\

The last file is different from the 3D GCM's {\tt run.def} input file,
as it contains options specific to the 1D model, as shown in the example
below:
\input{input/run.def.1d.tex}
Note that, just as for the 3D GCM {\tt run.def} file, input
parameters may be given in any order, or even not given at all
(in which case default values are used by the program).


\section{Output data}

During the entire 1D simulation, you can obtain output data for any
variable from any physical subroutine by using subroutine \verb+ writeg1d+.
This subroutine creates file \verb+ g1d.nc+ that can be read by GRADS.
This subroutine is typically called at the end of subroutine
\verb+ physiq +. \\

Example of a call to subroutine {\tt writeg1d} requesting
temperature output:
(\verb+ ngrid+ horizontal point, \verb+ nlayer + layers, variable
\verb+ pt + called ``T'' in K units):

\begin{verbatim}
      CALL writeg1d(ngrid,nlayer,pt,'T','K')
\end{verbatim}