\chapter{Utilities}

\label{sc:utilities}

A few post-processing tools, which handle GCM outputs (files
{\tt diagfi.nc} and {\tt stats.nc}) are available in the
{\tt LMDZ.MARS/util} subdirectory.
This directory contains the sources codes along with a {\tt README.exec}
file which explains what the various programs are for and
how to compile them.

\section{concatnc}
This program concatenates consecutive
output files ({\tt diagfi.nc} or even {\tt stats.nc} files) for a selection of 
variable, in order to obtain one single big file.
The time dimension of the output can
be "sols" or "Ls" (note that in that latter case, Ls values won't be
evenly distributed, and
software like Grads may not be able to use and plot the data).\\
To obtain an evenly sampled "Ls"
timescale, you can use the {\tt lslin.e} program (described below).\\
The output file created by {\tt conctanc.e} is {\tt concat.nc}

\section{lslin}

This program is designed to interpolate data given
in  irregular Solar Longitude (Ls) into an evenly sampled
linear time coordinate (usable with Grads).
Input Netcdf files may be {\tt diagfi.nc} or {\tt concat.nc}  
files and the resulting
output file is {\tt lslin.nc}
lslin also create a {\tt lslin.ctl} file that can be read
directly by grads (\verb+>xdfopen lslin.ctl+) to plot in Ls coordinate to
avoid some problem with grads when Grads think that "the time interval
is too small"...

\section{localtime}

The {\tt localtime.e} program is designed to re-interpolate data in order
to yield values at the same given local time (useful to mimic satellite
observations, or analyse day to day variations at given local time).\\
Input files may be of {\tt diagfi.nc}, {\tt stats.nc} or {\tt concat.nc}
type and the output file name is build from the input one, to which 
{\tt \_LT.nc} is appened (e.g. if the input file is {\tt myfile.nc} then
output file will be {\tt myfile\_LT.nc}).

\section{zrecast}
With this program you can recast atmospheric (i.e.: 4D-dimentional
longitude-latitude-altitude-time) data from GCM outputs (e.g. as given in
{\tt diagfi.nc}, {\tt concat.nc} and {\tt stats.nc} files) onto
either {\it pressure} or {\it altitude above areoid} vertical coordinates.\\
Since integrating the hydrostatic equation is required to recast the data,
the input file must contain surface pressure and atmospheric temperature,
as well as the ground geopotential.\\
If recasting data onto {\it pressure} coordinates, then the output file name
is given by the input file name to which {\tt\_P.nc} will be appened.
If recasting data onto {\it altitude above areoid} coordinates, then a
{\tt\_A.nc} will be appened.

\section{hrecast}
This program can interpolate GCM output on any horizontal grid
(regular lat - lon) as long as it cover all the
planet. Useful to compare runs obtained at different horizontal resolutions.

\section{expandstartfi}
This program takes a physics start file ({\tt startfi.nc}) and recasts it
on the corresponding  lonxlat grid (so its contents may easily be displayed
using Grads, Ferret, etc.)

\section{extract}
This program extracts (ie: interpolates) pointwise values of an atmospheric 
variable from a 'zrecast'ed diagfi file (works if altitude is geometrical 
height or a pressure vertical coordinates).