WPS Export¶

cfdb-ingest can export cfdb datasets to WPS intermediate format files for use with metgrid.exe. This enables a workflow where WRF output is first ingested into cfdb, then exported to WPS format for driving a new subdomain in a different coordinate system.

The WPS Preset¶

The --preset wps flag for the cfdb-ingest wrf command auto-selects everything needed for WPS export:

All required variables (see list below)
Pressure-level interpolation (--vertical-coord pressure)
26 standard pressure levels (1000, 975, 950, 925, 900, 850, 800, 750, 700, 650, 600, 550, 500, 450, 400, 350, 300, 250, 200, 150, 100, 70, 50, 30, 20, 10 hPa)

The user can override the pressure levels with --target-levels and add extra variables with --variables (they are merged with the preset list).

Variables included in the WPS preset¶

3D pressure-level fields:

Key	Description
`T`	Temperature (from potential temperature)
`U`	U-wind component (unstaggered, earth-relative)
`V`	V-wind component (unstaggered, earth-relative)
`GHT`	Geopotential height
`RH`	Relative humidity
`Q_SH`	Specific humidity

Surface fields:

Key	Description
`PSFC`	Surface pressure
`SLP`	Mean sea level pressure
`TSK`	Skin temperature
`T2`	2m temperature
`U10`	10m U-wind (earth-relative)
`V10`	10m V-wind (earth-relative)
`TD2`	2m dewpoint temperature
`RH2`	2m relative humidity
`XLAND`	Land-sea mask
`HGT`	Terrain height
`SNOWH`	Physical snow depth
`SST_VAR`	Sea surface temperature
`SEAICE_VAR`	Sea ice fraction
`SNOW_VAR`	Snow water equivalent

Soil fields:

Key	Description
`SMOIS`	Soil moisture (per layer)
`TSLB`	Soil temperature (per layer)

Full Pipeline¶

Step 1: Ingest WRF output¶

cfdb-ingest wrf /path/to/wrfout/ output.cfdb \
    --preset wps \
    -s 2023-02-10T00:00 -e 2023-02-10T06:00

Step 2: Export to WPS intermediate format¶

cfdb-to-int output.cfdb -s 2023-02-10 -e 2023-02-10_06 -h 6

This produces files named WRF:2023-02-10_00, WRF:2023-02-10_06, etc.

Step 3: Run metgrid.exe¶

Set fg_name in your namelist.wps to point to the output files:

&metgrid
 fg_name = '/path/to/output/WRF'
 ...
/

Then run metgrid.exe as usual.

cfdb-to-int CLI¶

Available as both a subcommand and a standalone command:

# As subcommand:
cfdb-ingest cfdb-to-int output.cfdb -s 2023-02-10 -e 2023-02-10_06 -h 6

# As standalone command:
cfdb-to-int output.cfdb -s 2023-02-10 -e 2023-02-10_06 -h 6

Options¶

cfdb-to-int [OPTIONS] CFDB_PATH

Option	Short	Description
`--start-date`	`-s`	Starting date-time to convert (required)
`--end-date`	`-e`	Ending date-time to convert (required)
`--hour-interval`	`-h`	Interval in hours between records (default: 6)
`--prefix`	`-p`	Output file prefix (default: `WRF`)

Python API¶

from cfdb_ingest.cfdb_to_int import convert_cfdb_to_int
from datetime import datetime

convert_cfdb_to_int(
    cfdb_path='output.cfdb',
    output_prefix='WRF',
    start_date=datetime(2023, 2, 10),
    end_date=datetime(2023, 2, 10, 6),
    hour_interval=6,
)

Implementation Notes¶

WPS intermediate file writing¶

The WPS intermediate file format is handled by the wrf_to_int package, which provides the shared IntermediateFile, Projections, MapProjection, and write_slab tools used by both cfdb-to-int and era5_to_int. See the wrf_to_int library API for details on building custom converters.

Key conventions for the WPS intermediate file format:

Projection codes: Lat-Lon=0, Mercator=1, Lambert Conformal=3, Gaussian=4, Polar Stereographic=5, Cassini=6
dx/dy: must be in km (metgrid multiplies by 1000)
earth_radius: must be in km (6371.229, not 6371229.0)