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Category:Titan-LMDZ

2026-04-03T09:20:39Z

Lrosset: Created blank page

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

2026-04-03T09:19:23Z

Lrosset: Created page with "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 deb..."

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 <code>gcm.F</code> does on 3D, but only on a single column. In practice, the simulation is controlled from a main program called <code>rcm1d.F</code>, located in the phytitan/dyn1d directory, which, after initialization, calls the master subroutine of the physics <code>physiq mod.F90</code>.
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 :
<syntaxhighlight lang="bash">
./makelmdz_fcm -cpp CPP_1D -d 55 -b 23x23 -s 1 -p titan -j 8 rcm1d
</syntaxhighlight>
* Compilation for 1D configuration for 55 pressure layers with XIOS enabled :
<syntaxhighlight lang="bash">
./makelmdz_fcm -cpp CPP_1D -parallel mpi -io xios -d 55 -b 23x23 -s 1 -p titan -j 8 rcm1d
</syntaxhighlight>
You can find the executable <code>rcm1d.e</code> (the compiled model) in the directory from which you ran the <code>makelmdz</code> 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 <code>tracer=.false.</code> in <code>callphys.def</code>). 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 <code>run.def.1d</code> in the deftank directory, which must be renamed <code>run.def</code> to be read by the program. It is different from the 3D PCM’s <code>run.def</code> input file, as it is only used to access <code>rcm1d.def</code>.
* '''profile.def'''
* '''gases.def'''
Using these files and an initial temperature vertical profile defined in the <code>profile.F</code> routine (with options available through <code>rcm1d.def</code>), the model is initialized and a first <code>startfi.nc</code> file is written, to be read again at the first call of <code>physiq</code>.

== 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 <code>traceur.def</code> must have a corresponding <code>profile_<tracer_name> </code> 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 : <code>profile_<species>_up</code>.
'''BEWARE : mixing ratios must be in kg/kg'''

== Specific rcm1d.def file ==
This file is read by <code>rcm1d</code> during initialization. It can be found in the <code>deftank</code> 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 : <code>iodef.xml</code> and <code>context_lmdz_physics.xml</code>.

[[Category:Titan-Model]]
[[Category:Titan-LMDZ]]

Overview of the Titan PCM

2026-04-03T08:40:22Z

Lrosset:

== The Titan PCM (Planetary Climate Model) ==
In a nutshell, the Titan Planetary Climate Model is a General Circulation Model (GCM) of the titanian atmosphere. It is in fact a suite of models which may be run in various configurations: with the historical lon-lat (LMDz) dynamics, or as a regional model using [[WRF dynamical core for LES/mesoscale simulations|'''WRF''']] (a limited area dynamical core), or even as a [[Using the 1D version of the Titan PCM (rcm1d)|'''1D (single column) model''']].

== Getting started ==
The traditional Titan LMDz PCM (formerly know as the IPSL Titan GCM) is the most commonly used version. For a first try at installing and running the Titan PCM we recommend you start from the [[Quick Install and Run Titan PCM]] page. You will also most likely be interested in all the pages tagged as "Titan-Model" or "Venus-LMDZ" in the [[Special:Categories|Categories]] section.

== Bibliography ==

==== 2025 ====
* Bruno De Batz De Trenquelléon, Lucie Rosset, Jan Vatant d’Ollone, Sébastien Lebonnois, Pascal Rannou, Jérémie Burgalat, et Sandrine Vinatier. « The New Titan Planetary Climate Model. I. Seasonal Variations of the Thermal Structure and Circulation in the Stratosphere ». The Planetary Science Journal 6, no 4 (1 avril 2025): 78. https://doi.org/10.3847/PSJ/adbbe7.
* Bruno De Batz De Trenquelléon, Pascal Rannou, Jérémie Burgalat, Sébastien Lebonnois, et Jan Vatant d’Ollone. « The New Titan Planetary Climate Model. II. Titan’s Haze and Cloud Cycles ». The Planetary Science Journal 6, no 4 (1 avril 2025): 79. https://doi.org/10.3847/PSJ/adbb6c.
==== 2020 ====
* Vatant d’Ollone, Jan. « Numerical modelling of the seasonal variations in Titan’s atmosphere ». These de doctorat, Sorbonne université, 2020. https://theses.fr/2020SORUS401.
==== 2019 ====
* Lora, J. M., T. Tokano, J. Vatant d'Ollone, S. Lebonnois, and R. D. Lorenz A model intercomparison of Titan's climate and low-latitude environment. Icarus, 333, 113. (2019) https://www.sciencedirect.com/science/article/pii/S0019103518307838?via%3Dihub
==== 2015 ====
* Charnay, Benjamin, Erika Barth, Scot Rafkin, Clément Narteau, Sébastien Lebonnois, Sébastien Rodriguez, Sylvain Courrech du Pont, et Antoine Lucas. « Methane Storms as a Driver of Titan’s Dune Orientation ». Nature Geoscience 8, no 5 (mai 2015): 362‑66. https://doi.org/10.1038/ngeo2406.
==== 2012 ====
* Lebonnois, Sébastien, Jérémie Burgalat, Pascal Rannou, et Benjamin Charnay. « Titan Global Climate Model: A New 3-Dimensional Version of the IPSL Titan GCM ». Icarus 218, no 1 (mars 2012): 707‑22. https://doi.org/10.1016/j.icarus.2011.11.032.
* Charnay, B. and S. Lebonnois Two boundary layers in Titan's lower troposphere inferred from a climate model. Nature Geoscience, 5, 106. (2012) https://www.nature.com/articles/ngeo1374

[[Category:Titan-Model]]