Using the 1D version of the Titan PCM (rcm1d)

One can run a 1D version of the Titan LMDz PCM. It uses the same physics as the 3D PCM but without dynamics, and for a single column. Very useful for some studies and when debugging or developing parametrizations.

Compilation

The model is initialized the same way gcm.F does on 3D, but only on a single column. In practice, the simulation is controlled from a main program called rcm1d.F, located in the phytitan/dyn1d directory, which, after initialization, calls the master subroutine of the physics physiq mod.F90. The rcm1d tool can be compiled sequentially, or in parallel if you want to obtain outputs via XIOS. However, it must always be run sequentially. In case of parallel compilation, make sure to run it on a single core.

• Compilation for 1D configuration for 55 pressure layers, with sequential execution :

./makelmdz_fcm -cpp CPP_1D -d 55 -b 23x23 -s 1 -p titan -j 8 rcm1d

• Compilation for 1D configuration for 55 pressure layers with XIOS enabled :

./makelmdz_fcm -cpp CPP_1D -parallel mpi -io xios -d 55 -b 23x23 -s 1 -p titan -j 8 rcm1d

You can find the executable rcm1d.e (the compiled model) in the directory from which you ran the makelmdz command.

Input files

To run the 1D model, you need to retrieve the following files from the deftank and copy them into your working directory:

• rcm1d.def : controls the 1D run parameters and initializations. See the dedicated section of this page for more details.
• callphys.def : controls the options in the physics, just like for the 3D PCM.
• z2sig.def : controls the vertical discretization (no change needed, in general), functions as with the 3D PCM.
• traceur.def : controls the tracer names. This file may not be present, as long as you run without tracers (option tracer=.false. in callphys.def). In case you decide to run with tracers, initial profiles must be provided (else, it will be set to zero.)
• run.def : this is actually the file run.def.1d in the deftank directory, which must be renamed run.def to be read by the program. It is different from the 3D PCM’s run.def input file, as it is only used to access rcm1d.def.
• profile.def
• gases.def

Using these files and an initial temperature vertical profile defined in the profile.F routine (with options available through rcm1d.def), the model is initialized and a first startfi.nc file is written, to be read again at the first call of physiq.

Tracer profiles

In case you decide to run with tracers, profiles must be provided to the model. In your working directory, each tracer defined in traceur.def must have a corresponding profile_<tracer_name> file, containing nlevels + 1 values : the first one for the tracer value at the surface and then one per pressure layer. For all chemical tracers, a profile for the extended photochemistry (up to 1300km) must also be provided : profile_<species>_up. BEWARE : mixing ratios must be in kg/kg

Specific rcm1d.def file

This file is read by rcm1d during initialization. It can be found in the deftank directory. Each line has a comment explaining what the parameter is. The number of timestep per day (third parameter) is the number of calls to the physics per day, since no dynamics is involved here. It also includes parameters for the temperature profile definition.

Outputs

All aspects of the outputs (name, units, file, post-processing operations, etc.) are controlled by XIOS. In order to be able to access the outputs, the model must be computed in parallel. The sequential compilation and run (without XIOS) only provides the temperature profile at the last timestep. To run the model with XIOS, the working directory must contain two dedicated XML files which are read at run-time, and provided in the deftank directory : iodef.xml and context_lmdz_physics.xml.