CESM Models

CCSM2.0.1 FAQs


Grids and Model Resolutions

CCSM Model Restarts


Computer Resources


Grids and Model Resolutions

What grids and model resolutions are scientifically validated in CCSM2?

The CCSM2.0 release officially supported only one resolution, referred to as "T42_gx1v3", and one configuration, fully active (B) with respect to scientific results. This combination was used in the CCSM2.0 Control Run and is the default configuration in the test.a1 case. The CCSM2.0.1 release supports a second, coarser resolution, "T31_gx3v4" version of the fully active coupled model. "T31" and "T42" are short-hand references to the resolution of the atmosphere and land models; "gx1v3" and "gx3v4" are short-hand references to the resolution of the ocean and ice models. In addition to these two scientifically validated configurations, a number of other configurations are available for scientific testing and research.

What are the "gx1v3" and "gx3v4" resolutions?

The CCSM2 ocean and ice models share the identical horizontal grid, two of which are presently officially supported in CCSM: gx1v3 and gx3v4. In both of these grids, the north pole has been displaced into Greenland. The former is the finer of the two, with longitudinal resolution approximately one degree. The latitudinal resolution is variable, with finer resolution near the equator (approximately 0.3 degrees). The latter is the coarser grid, with longitudinal resolution of 3.6 degrees. The latitudinal resolution is variable, with finer resolution near the equator (approximately 0.9 degrees).

In the ocean model, there are 40 levels in the vertical associated with the gx1v3 resolution, with level thickness monotonically increasing from approximately 10 to 250 meters. In the ocean model, it is the combination of the horizontal grid, horizontal land mask, vertical grid, and bottom topography that collectively define the "gx1v3" resolution.

There are 25 ocean-model levels in the vertical associated with the gx3v4 resolution, with level thickness monotonically increasing from approximately 12 to 450 meters. The combination of the horizontal grid, horizontal land mask, vertical grid, and bottom topography is referred to collectively as the "gx3v4" resolution in the ocean model.

What are the "T31" and "T42" resolutions?

The CCSM2 atmosphere and land models share the identical horizontal grid. T42 is a 128 by 64 regular longitude/latitude global horizontal grid (approximately 2.8 degree resolution). T42 indicates the truncation level in spectral space. The T31 is a similar grid by has 96 by 48 horizontal grids cells (approximately 3.75 degree resolution).

How many vertical levels does the atmosphere model have?

First off, the term "vertical levels" is a paradox and makes no sense, you're probably asking about the number of levels in the vertical. To answer your question, the atmosphere model in CCSM2 has 26 levels in the vertical for both T42 and T31 horizontal resolutions.

What are the different CCSM model components? How can they be configured?

CCSM is run as a coupled model that always includes 5 components; atmosphere, land, ocean, ice, and coupler. There are several different versions of each component. These are

In general, individual versions of each component can be combined in any combination to produce a model configuration. However, there are several standard configurations for the coupled model. These are named using a single capital letter.

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Which resolutions and configurations are generally supported?

The following table provides a suite of configurations that are supported and should run "out of the box" with the gui. NOTE: Only the B configurations have been scientifically validated.

  A B C D F G H I K M
T42_gx1v3 * * * * *   * * *  
T31_gx3v4 * * * * *   * * *  
T62_gx1v3   v       *       *
T62_gx3v4   v       *       *

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How do I get the various component models to all write monthly time-averaged history files?

By default, all the components write monthly time-averaged history files. The history files can be modified for each component individually, although the data model components do not have history file writing capability. History files are not coordinated between each component (unlike restart files which are coordinated through the coupler). Please see the individual component model documentation for more information about how to change the components' history output.

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I don't have "gmake" on my system. Where can I get a copy?

The CCSM build process assumes that gmake is currently installed on your system. If it isn't already available, there are a number of steps that you can take to resolve this.

First, ask your system administrator if you already have gmake (the GNU make utility). If so, you may need to change your unix PATH definition to include the path to your copy of gmake.

Second, the gmake program is often called "make" or "gnumake". Issue the command "make -v" the "make" you are using is actually gnu make. You should see something like:

	make -v
	GNU Make version 3.76.1, by Richard Stallman and Roland McGrath	

If your version of make doesn't recognize the "-v" open, then it is not the required gnumake utility, and you will see the following error message:

	make -v
	make: Not a recognized flag: v

Finally, if you do not have the gnumake utility anywhere on your system, you can build and install gmake yourself. The gmake utility can be obtained off the web from:


The gmake utility can also be obtained via anonymous ftp using the following commands:

	ftp ftp.gnu.org
	cd gnu/make
	get make-3.79.tar.gz

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What about model performance? How do I estimate how long my job will take to run one model year?

The fully coupled model will run about 4 years per wall clock day in the default configuration on 104 processors on the NCAR IBM-SP blackforest machine. There are a number of considerations to take into account when setting up other configurations or running on other machines. The model performance and efficiency are dependent on the processor layout, resolution, configuration (active or data models), hardware performance, and physics options. In addition, both the active atmosphere and land components can run either MPI, OpenMP or hybrid mode. A number of timers are printed in the log files to help determine optimal configurations. If you need help determining optimal processor configurations for productions runs, please contact cesm.ucar.edu for help on your specific problem.

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How can I get more help?

Please contact cesm.ucar.edu if you have questions.

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