Advanced Use of the GCM

Running in parallel

For large simulation (long run, high resolution etc...), the waiting time can becomes very long. To overcome this issue, the model can works in parallel. It first needs to be compiled in parallel mode and then be run with a specific command. For all the details see the page Parallelism

Distinctions beween ifort, mpi, etc.

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Distinction between using IOIPSL or XIOS

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How to Change Vertical and Horizontal Resolutions

To run at a different grid resolution than available initial conditions files, one needs to use the tools newstart.e and start2archive.e

For example, to create initial states at grid resolution 32×24×25 from NetCDF files start and startfi at grid resolution 64×48×32 :

• Create file start_archive.nc with start2archive.e compiled at grid resolution 64×48×32 using old file z2sig.def used previously
• Create files restart.nc and restartfi.nc with newstart.e compiled at grid resolution 32×24×25, using a new file z2sig.def (more details below on the choice of the z2sig.def)

What you need to know about the z2sig.def file (change of vertical resolution only)

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How to Change the Topography (or remove it)

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How to Change the Opacity Tables

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How to Manage Tracers

The model can include different types of tracers:

• condensed species (e.g., CO₂, H₂O, dust)
• chemically active species
• radiatively active gases (e.g., water vapor)

In the code, all tracers are stored in one three-dimensional array q, the third index of which corresponds to each individual tracer.

In input and output files (“start.nc”, “startfi.nc”), tracers are stored separately using their individual names.

Loading specific tracers requires that the approriate tracer names are set in the traceur.def file, and specific computations for given tracers (e.g. computing the water or CO2 cycles) is controlled by setting the corresponding options in the callphys.def file.

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