fsurdat_modifier is a tool that modifies fsurdat files. It reads a surface
dataset (fsurdat file) and outputs a modified copy of the same file.

Current applications are limited to the simplest CTSM(SP) mode, so bgc, fire,
urban, vic, lake, transient, and crop-related variables in the fsurdat file
remain unchanged.

It differs from modify_singlept_site_neon.py in that the latter specifically
modifies soil properties of single-point surface datasets.

It also differs from the subset_data tool in that the latter subsets fsurdat
files to regional or single-point domains; subset_data does include some
"modify" functionality when subsetting, but such functionality is more
prescriptive in subset_data. In particular:

fsurdat_modifier options               subset_data options
-----------------------------------    -------------------
std_elev (user sets STD_ELEV value)    uniform-snowpack (sets STD_ELEV to 20)
max_sat_area (user sets FMAX value)    cap-saturation (sets FMAX to zero)

Files involved
--------------
python/ctsm/modify_input_files/fsurdat_modifier.py
python/ctsm/modify_input_files/modify_fsurdat.py
tools/modify_input_files/fsurdat_modifier
tools/modify_input_files/modify_fsurdat_template.cfg

Instructions
------------
To run on various machines:
1) (Un)load, execute, and activate the following:
1a) First step to activate conda on your system
1a) Casper:
module unload python
module load conda
1a) Izumi:
module load python
1a) Derecho (nothing needs to be done for this step)
1a) Elsewhere (do what's needed to activate conda)
1b) On all systems
./py_env_create
conda activate ctsm_pylib
(Use "deactivate" to reverse the latter.)
2) Copy, then modify the configure file named modify_fsurdat_template.cfg, which
contains all the arguments needed by the script.
3) Run the script ./fsurdat_modifier pointing to the copied/modified .cfg file,
e.g. modify_users_copy.cfg
./fsurdat_modifier modify_users_copy.cfg
See modify_fsurdat_template.cfg for required and optional settings.
4) Use the --verbose option to see progress output on your screen