Part 12: Modifying the FATES Parameter File

One of the strengths of FATES is the ability to experiment with different plant functional types (PFTs) and trait combinations.

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Create a Two-PFT Parameter File

Move to the parameter directory:

cd $VSC_SCRATCH/cesm/params

Create a new parameter file containing two identical copies of the same PFT:

./FatesPFTIndexSwapper.py \
    --fin=fates_params_default.nc \
    --fout=fates_params-2pfts.nc \
    --pft-indices=1,1

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Convert to CDL

Convert to a human-readable format:

ncdump fates_params-2pfts.nc > fates_params-2pfts.cdl

Open the file:

vi fates_params-2pfts.cdl

You can now modify parameters for each PFT independently.

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Rebuild the NetCDF File

After editing:

ncgen -o fates_params-2pfts.nc fates_params-2pfts.cdl

This step is mandatory.

FATES can only read the NetCDF version.

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Using modify_fates_paramfile.py

Copy the helper script:

cp $VSC_SCRATCH/cesm/sources/ctsm-5.2.0/src/fates/tools/modify_fates_paramfile.py .

The script supports:

--var   parameter name
--pft   PFT index
--fin   input file
--fout  output file
--val   new value
--O     overwrite

Example:

./modify_fates_paramfile.py \
    --var <parameter> \
    --pft 2 \
    --fin input.nc \
    --fout output.nc \
    --val <value> \
    --O

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Comparing Different Trait Strategies

A useful exercise is to create:

Early successional PFT
Late successional PFT

by modifying parameters related to:

• Growth
• Mortality
• Wood density
• Recruitment
• Leaf economics

and comparing their coexistence through time.

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