ERF boundary file (erfbdy)

[wiersema1]

BLUF

This PR introduces the ERF boundary data (erfbdy) file format, AMReX-native storage of boundary data FABs for real data cases using the wrfinput and metgrid pathways.

Summary

• Preprocessing Mode: ERF can be run as a preprocessor (set max_steps = 0) to generate erfbdy and a checkpoint file.
• Reduces Memory Consumption: Keeps only the minimum required boundary data times in memory.
• Improves I/O Performance: Eliminates the periodic need to open, read, and close wrfbdy NetCDF files during time integration.
• Enables Restart Capability: Resolves restart issues with the metgrid pathway.
• Maintains Compatibility: Works with the metgrid and wrfinput pathways. The capability for as-needed reading and processing of wrfbdy is retained as an option.

Directory Structure

The erfbdy file uses a hierarchical directory structure:

erfbdy/
├── Header                          # Metadata: ntimes, nvars, real_width, time stamps, domain box
└── Time_XXXXXX/                    # One directory per boundary time
    ├── BdyData_xlo_varN            # X-lo boundary data (binary FArrayBox format)
    ├── BdyData_xhi_varN            # X-hi boundary data (binary FArrayBox format)
    ├── BdyData_ylo_varN            # Y-lo boundary data (binary FArrayBox format)
    └── BdyData_yhi_varN            # Y-hi boundary data (binary FArrayBox format)

New Input Parameters

Parameter	Type	Default	Mandatory	Description
erf.erfbdy_file	String	"erfbdy"	No	Name of the erfbdy directory
erf.write_erfbdy	Boolean	true (for clean starts) false (for restarts)	No	Write erfbdy file during initialization
erf.real_width	Integer	0	Yes (for metgrid/wrfinput)	Total width of lateral boundary nudging region

Notes:

• erf.real_width must be specified when using erf.init_type = "metgrid" or erf.init_type = "wrfinput".
• erf.write_erfbdy automatically defaults to true for clean starts with erf.init_type of "metgrid" or "wrfinput" and false for restarts or other erf.init_type.
• erf.write_erfbdy can be set to false for init_type = wrfinput to process boundary data on-the-fly, but must remain true for erf.init_type = metgrid if using model restarts.

Technical Details

New source files added in Source/IO/:

• ERF_ReadFromERFBdy.H/cpp: Functions to read erfbdy header metadata and time slices.
• ERF_WriteERFBdy.H/cpp: Functions to initialize and write erfbdy files.

Resolves

This PR resolves restart failures with init_type = metgrid by ensuring boundary data is properly managed across checkpoint/restart cycles. Previously, metgrid initialization could not be restarted because boundary data state was not preserved.

Testing

• init_type = "metgrid"
  • clean start (with erfbdy)
    • real_width = 1
    • real_width = 10
  • restart at chk_00000 (with erfbdy)
  • restart at chk_27000 (with erfbdy)
  • clean start (without erfbdy)
  • restart (after deleting erfbdy) throws expected error
• init_type = "wrfinput"
  • clean start (with erfbdy)
  • restart at chk_00000 (with erfbdy)
  • restart at chk_27000 (with erfbdy)
  • clean start (without erfbdy)
  • restart at chk_27000 (without erfbdy)