====== a. Shell and CDO ======

[[https://code.mpimet.mpg.de/projects/cdo/|CDO]] is a collection of command line operators to manipulate and analyse Climate and NWP model output. Supported output formats are among others netCDF and GRIB. It is very useful for postprocessing  e.g. ICON output by selecting parts of the model output that are of interest to the user. Beyond that, it can also be used for further analysis of the output. On levante (DKRZ), you can load it via 
<code bash> module load cdo </code> 
You can use 
<code bash> module avail </code> 
to view all available CDO versions. It would make sense to load the most current version. \\
If the output is very large, it can be useful to allocate an exclusive computation environment via the [[https://slurm.schedmd.com/|SLURM]] workload manager.\\ An interactive possibility for this would be the [[https://slurm.schedmd.com/salloc.html|salloc]] method. For example, you can ask for an exclusive node on some partition, say interactive with 1 node, for some duration, say 2 hours, and the computational resources will be charged to the specified project account (PROJECTNAME):
<code bash>
salloc --x11 -p interactive -A PROJECTNAME -n 1 -t 2:00:00 
</code>

This will open up a new shell from which interactively individual CDO commands or shell scripts with multiple CDO commands can be executed. See the [[https://docs.dkrz.de/doc/levante/data-processing-on-levante.html|levante]] documentation for more information on how to submit batch scripts. When you are done using the allocated resources, you can close the shell by simply logging out and then your allocated resources will be closed. \\