- Working Groups
CLM4 does not require an initial condition file and can be initialized with arbitrary initializations. Typically, for deep time, the researcher does not know the land model initial state with enough accuracy to improve upon the arbitrary initialization option. CLM4 will spin up its own variables at runtime. An separate initial condition procedure for deep time is not supported.
To run the land model with CN, you will need to spin up the carbon and nitrogen pools. The land model spinup is typically done using an accelerated land-atm simulation. Alternatively, you could use interpinic to interpolate the carbon pools from a spun up simulation into your land model initialization file.
To turn on CNDV, modify the env_build.xml:
<entry id="CLM_CONFIG_OPTS" value="-phys clm4_0 -bgc cndv" />
e.g., ./xmlchange -file env_run.xml -id CLM_CONFIG_OPTS -val '-phys clm4_0 -bgc cndv'
The script paleo_mkraw_cesm1.csh reads a user-provided lat/lon map of LSM vegetation types in netCDF format (e.g., vegetation.nc) and current day soil texture profiles (mksrf_soitex.10level.nc) to create the ‘raw’ land surface datafiles required by CLM4. These datasets are named ‘mksrf_.nc’ and include surface data information for PFTs (plant functional types), soil color, soil texture, leaf/stem areas and heights (LAI), land water (lakes and wetlands), glaciers, and urban areas (Table 9). From these ‘raw’ datasets, a single land surface data file, tailored to your land and ocean grids, will be created by mksurfdata_map.
HINT: To create the mksrf files required for the surface dataset, specify the resolution of your incoming LSM vegetation dataset by setting longitude/latitude in paleo_mkraw_cesm1_sed.F90. For example, if your LSM vegetation map is at 2x2 degree resolution, then nlon=180 and nlat=90, and your mksrf_<>.nc files will also be 2x2 degree. If your vegetation file has 0.5 degree resolution, nlon=720 and nlat=360 and your mksrf_.nc files will also be at 0.5 degree resolution.
The paleo_mkraw_cesm1.csh script assumes that glaciers=urban=lakes=wetlands=0, soil texture =loam and soil color=4. If this does not suit your needs, you will need to alter paleo_mkraw_cesm1_sed.F90 to make any desired changes.
For example, if you would like to specify glaciers, you will need to edit the subroutine create_mksrf_glacier and add code to test for LSM type 1 (land ice). For each point equal to 1, assign pct_glacier values from 0 to 100%. See the Near-modern section for a discussion on adding glaciers to near-modern simulations.
CLM4 model defines the physiology of each plant functional type (PFT) in an ASCII text files, called pft-physiology. The default (i.e., modern) pft-physiology definitions are generally used for paleo experiments. However, if you wish to change the characteristic of a specific CLM PFT, and you cannot accomplish your goal by modifying paleo_mkraw_cesm1__sed.F90, you may need to edit this dataset. Please read the CLM documentation before altering this file and/or contact a CESM Paleo or Land liaison for a consultation