Adding your own runoff product to the CESM (Advanced)

To add your own runoff product to the CESM, you need three things. A Stream Definition File, an ESMF Mesh file, and the dimensions of your raw data.

ESMF Mesh File¶

An ESMF Mesh File can be created like below, using CrocoDash Grids.

from CrocoDash.grid import Grid
from CrocoDash.topo import Topo
import xarray as xr

grid = Grid(
    lenx=360,
    leny       = 150,         # grid length in y direction
    cyclic_x=True   ,    
    ystart     = -60,       # start/end 10 degrees above/below poles to avoid singularity
    resolution = 0.10,
    name = "GLOFAS",
)
topo = Topo(grid, min_depth = 0)
topo.set_flat(10)
topo.write_esmf_mesh("<path>")

Stream Definition File¶

In your case directory, copy the following file and name it drof.streams.xml:

<?xml version="1.0"?>
<file id="stream" version="2.0">

  <stream_info name="rof.<PRODUCT_NAME>">
    <taxmode>cycle</taxmode>
    <tintalgo>upper</tintalgo>
    <readmode>single</readmode>
    <mapalgo>bilinear</mapalgo>
    <dtlimit>3.0</dtlimit>
    <year_first>"START_YEAR"</year_first>
    <year_last>"END_YEAR"</year_last>
    <year_align>"START_YEAR"</year_align>
    <vectors>null</vectors>
    <meshfile>"PATH_TO_THE_PREVIOUSLY_GENERATED_ESMF_MESH_FILE"</meshfile>
    <lev_dimname>null</lev_dimname>
    <datafiles>
      <file>"PATH_TO_RAW_DATA_FILE_IN_NETCDF3_64BIT_OFFSET"</file>
    </datafiles>
    <datavars>
      <var>"NETCDF_VARIABLE_NAME_IN_FILE" Forr_rofl</var>
    </datavars>
    <offset>0</offset>
  </stream_info>

</file>

Additional Notes¶

Update the CESM components/cdeps/drof directory.
The following entry should already exist in namelist_definition_drof.xml:

<value drof_mode="<PRODUCT_NAME>">rof.<PRODUCT_NAME></value>

Update config_component with the new <PRODUCT_NAME>:

<desc rof="DROF[%NULL][%NYF][%<PRODUCT_NAME>]...">

Make sure to replace placeholders (<PRODUCT_NAME>, START_YEAR, END_YEAR, file paths, and variable names) with your actual values.

Add the dimensions¶

Make the following xml changes in your case directory:

./xmlchange ROF_NY=1500

./xmlchange ROF_NX=3600

./xmlchange ROF_DOMAIN_MESH=<MESH PATH>

There may be a few additional changes in the CESM, but this covers a majority of them.

Then, you can add the mapping files generated through CrocoDash to your case (which requires a passed in ESMF mesh file)