Adding or Changing Default Filenames

To add or change the default filenames you edit the models/lnd/clm/bld/namelist_files/namelist_defaults_clm4_5.xml and either change an existing filename or add a new one. Most entries in the default namelist files, include different attributes that describe the different properties that describe the differences in the datasets. Attributes include the: resolution, year to simulation, range of years to simulate for transient datafiles, the land-mask, the representative concentration pathway (rcp) for future scenarios, and the type of biogeochemistry (bgc) model used. For example the fatmgrid for the 1.9x2.5 resolution is as follows:

<fsurdat hgrid="0.9x1.25" sim_year="1850" crop="off" >
Other fsurdat files are distinguished from this one by their resolution (hgrid), simulation year (sim_year) and prognostic crop (crop) attributes.

To add or change the default filenames for CLM tools edit the models/lnd/clm/bld/namelist_files/namelist_defaults_clm4_5_tools.xml and either change an existing filename or add a new one. Editing this file is similar to the namelist_defaults_clm4_5.xml talked about above.

What are the required files?

Different types of simulations and different types of configurations for CLM require different lists of files. The CLM4.5-BGC or Carbon Nitrogen (cn) Biogeochemistry model for example requires stream_fldfilename_ndep files, which are NOT required by CLMSP. Transient simulations also require transient datasets, and the names of these datasets are sometimes different from the static versions (sometimes both are required as in the dynamic PFT cases).

In the following table we list the different files used by CLM, they are listed in order of importance, dependencies, and customizing. So the required files are all near the top, and the files used only under different conditions are listed later, and files with the fewest dependencies are near the top, as are the files that are least likely to be customized.

Table 3-1. Required Files for Different Configurations and Simulation Types


Config. type

Simulation type

Resol. Dependent?

Other Dependencies?


Not usually customized, as describes plant function type properties. PTCLM copies the file for you so that you can customize it if you like, see step 3.d.


Not usually customized as describes global snow optical properties.


Not usually customized as describes global snow aging properties.


Creating, using mkgriddata usually gives you the amount of customization you need, as it just describes the grid and grid extents.


Describes the land-mask for points with active land, as well as the fraction of each grid-cell covered by land. You might customize it to make sure the land-fraction of your grid-cell matches the expected values for your site. But, usually you will just use what gen_domain gives you (this can be in the CLM only format, or the CESM domain file format the CLM only format is deprecated).


Describes percentages of different land-units, columns and vegetation types within each grid-cell. To customize for a specific point or region you may want to use custom input datasets to mksurfdata_map when creating the file. mksurfdata_map also allows you to customize the PFT, and soil types to it see the Section called Single Point options to mksurfdata_map in Chapter 2. PTCLM takes advantage of this to create customized datasets as well, see the chapter on PTCLM at Chapter 6.


transient land-use land-cover change


Simulation year range, and representative concentration pathway (rcp)

See notes on fsurdat files.



mask, maxpft, bgc, simulation-year, start-date

Used for starting the model from a spun-up state. Create these files by running the model for multiple years and saving the restart file from the end of a spin-up simulation. Or use the CLM tool interpinic to interpolate initial conditions.

fglcmaskglc_nec > 0

Used for simulations with the active glacier ice sheet model "cism"



Needs to match the file used by "cism" and be for the same glacier grid. Only customized as coupled with the glacier model.

stream_fldfilename_ndepCLM4.5-BGC or CLMCNYesNo (interpolates on the fly)


You may customize this file to get the Nitrogen deposition characteristics of your site if available. This file will be interpolated while the model is running from it's resolution to the resolution that CLM is running at.

stream_fldfilename_popdensCLM4.5-BGC or CLM4.5-CN


No (interpolates on the fly)


You may customize this file to run with a different human population density. For example, you might want to do that for past or future scenarios (outside of 1850 to 2010), or for scenarios for a specific region, or to see the impact of humans on an area for fire.

stream_fldfilename_lightngCLM4.5-BGC or CLM4.5-CN


No (interpolates on the fly)

calendar day

You may customize this file to run with a different lightning frequency. The standard dataset is a climatology. You could use a different dataset over a different time-period or data based on convective frequency of an atmosphere model for example.