generate square grid SCRIP files for coupling FastIsostasy to MALI

[hollyhan]

Add Python script to create square grid SCRIP files for
FastIsostasy MALI coupling

Summary

• Add create_square_grid_scripfile.py tool to generate
  SCRIP-format files for FastIsostasy coupling
• FastIsostasy requires a perfect square grid (nx × nx)
  for bedrock deformation coupling
• Script reads MALI mesh SCRIP file, extracts domain
  bounds, and creates a square regular lat-lon grid
• Enables users to generate mapping weight files with
  ESMF_RegridWeightGen

Motivation

FastIsostasy coupling in MALI requires two mapping weight
files:

• mpas_to_fastisostasy.nc (MALI mesh → square grid)
• fastisostasy_to_mpas.nc (square grid → MALI mesh)

The target grid must be a perfect square (code checks `nX

• nX = nGridinmpas_li_bedtopo.F:1021-1027`). This
  script automates the creation of the required square grid
  SCRIP file.

Changes

• New file: create_square_grid_scripfile.py
  • Reads MALI SCRIP file to determine domain extent
  • Creates nx × nx square grid with proper SCRIP format
  • Supports optional padding around domain
  • Includes usage documentation and example workflow

Usage Example

# Create 512×512 square grid for FastIsostasy
python create_square_grid_scripfile.py \
    --mali_scripfile mali_mesh.scripfile.nc \
    --nx 512 \
    --output fastisostasy_512x512.scripfile.nc

# Generate mapping weights with ESMF
ESMF_RegridWeightGen -s mali_mesh.scripfile.nc -d
fastisostasy_512x512.scripfile.nc \
    -w mpas_to_fastisostasy.nc -i --64bit_offset
--src_regional


Grid comparison:

┌─────┬──────────────┬──────────┬─────────────────────┐
│ nx  │     Lat      │  Memory  │      Use case       │
│     │  resolution  │          │                     │
├─────┼──────────────┼──────────┼─────────────────────┤
│ 128 │ ~24 km       │ Small    │ Quick testing       │
├─────┼──────────────┼──────────┼─────────────────────┤
│ 150 │ ~20 km       │ Small    │ Testing             │
├─────┼──────────────┼──────────┼─────────────────────┤
│ 256 │ ~12 km       │ Medium   │ Moderate runs       │
├─────┼──────────────┼──────────┼─────────────────────┤
│ 384 │ ~8 km        │ Large    │ Production          │
│     │              │          │ (stability limit)   │
├─────┼──────────────┼──────────┼─────────────────────┤
│ 512 │ ~6 km        │ Very     │ Too fine (unstable) │
│     │              │ large    │                     │
└─────┴──────────────┴──────────┴─────────────────────┘

Test Plan

- [ ] Run script on example MALI mesh SCRIP file
- [ ] Verify output SCRIP file has correct dimensions (nx
= ny)
- [ ] Generate weight files with ESMF_RegridWeightGen
- [ ] Test weight files in MALI run with
config_uplift_method='fastisostasy'

🤖 Generated with Claude Code

[hollyhan]

Hi @matthewhoffman,

This PR ready to be reviewed.

A sample test run result is shown below:

(e3sm-unified) hollyhan@login40:/pscratch/sd/h/hollyhan> python ~/scripfile_for_fastisostasy/create_square_grid_scripfile.py --mali_scripfile ~/scripfile_for_fastisostasy/relaxed_10yrs_4km.nc.scripfile --nx 384 --output fastisostasy_384x384.scripfile.nc
Reading MALI scripfile: /global/homes/h/hollyhan/scripfile_for_fastisostasy/relaxed_10yrs_4km.nc.scripfile
  Domain: lat [-89.93, -62.82]°
          lon [0.00, 360.00]°
  Longitude convention: [0, 360]
Creating 384x384 square grid:
  Resolution: dlat=0.0708°, dlon=0.9399°
  Total cells: 147456
Writing SCRIP file: fastisostasy_384x384.scripfile.nc
SUCCESS: Created fastisostasy_384x384.scripfile.nc

Next steps:
1. Generate weight files with ESMF_RegridWeightGen:
   # MALI to FastIsostasy
   ESMF_RegridWeightGen -s /global/homes/h/hollyhan/scripfile_for_fastisostasy/relaxed_10yrs_4km.nc.scripfile -d fastisostasy_384x384.scripfile.nc \
       -w mpas_to_fastisostasy.nc -i --64bit_offset --src_regional --dst_regional
   # FastIsostasy to MALI
   ESMF_RegridWeightGen -s fastisostasy_384x384.scripfile.nc -d /global/homes/h/hollyhan/scripfile_for_fastisostasy/relaxed_10yrs_4km.nc.scripfile \
       -w fastisostasy_to_mpas.nc -i --64bit_offset --src_regional --dst_regional