\subsection{Switching physics parameterizations}
\label{sec:switch-phys-param}

\begin{itemize}
\item Prepare for five more days of simulation: rename files
  \verb+restart.nc+ and \verb+restartphy.nc+ (created at the end of
  the first simulation) to \verb+start.nc+ and \verb+startphy.nc+.
\item Create a directory where you will run the model with modified
  \verb+.def+ files. In this new directory, you can create symbolic
  links to the files \verb+start.nc+, \verb+startphy.nc+ and
  \verb+limit.nc+ which are in TUTORIAL, and you need to copy the
  \verb+*.def+ files from TUTORIAL, except those beginning with
  \verb+used_+.
\item In your new directory, in file \verb+physiq.def+, change the
  boundary layer parameterization by deactivating the Mellor and
  Yamada scheme for the boundary layer, based on a prognostic equation
  for the Turbulent Kinetic Energy:
\begin{verbatim}
iflag_pbl = 1
\end{verbatim}
  instead of the nominal value 11 (which corresponds to the variant
  for very stable planetary boundary layer and exact dissipation).
  Thus, you will switch to the "Standard Physics" (SP, LMDZ5A).
\item Run the model in the two directories and compare the results.
\item Another test you can try is to deactivate the thermal plume model:
\begin{verbatim}
iflag_thermals=0
\end{verbatim}
  instead of the nominal value 15.
\end{itemize}

Remember that you can modify the content or time frequency of the
output files if you want to focus on a particular question.

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