coupling esmf atm.yaml

ROMS ESMF/NUOPC Metadata File: coupling_esmf_atm.yaml

The coupling_esmf_<atm>.yaml (where <atm> is the model name) file specifies the native ROMS Coupling ESMF/NUOPC System Import/Export Metadata Dictionary. Starting svn revision -r 1902 released on March 1, 2022, the ROMS coupling metadata is managed with a YAML file, and the regular text file coupling_esmf_<atm>.dat is deprecated. The YAML files are simple, easy to follow, elegant, portable, and expandable. ROMS can now process YAML files with its parser module, yaml_parser.F. Therefore, there is no need to use third-party YAML parsers. Basically, coupling_esmf_<atm>.yaml has the following structure:

ATM_component: &ATM WRF

DATA_component: data.nc # NetCDF data model

ROMS_component: &OCN ROMS

metadata: # Export and Import fields

- standard_name: sea_surface_temperature
long_name: sea surface temperature
short_name: SST
data_variables: [temperature, time]
source_units: C
destination_units: K
source_grid: cell_center
destination_grid: cell_center
add_offset: 273.15d0
scale: 1.0d0
debug_write: false
connected_to: *OCN
regrid_method: bilinear
extrapolate_method: nearest

- standard_name: sea_surface_temperature_data
long_name: sea surface temperature data
short_name: dSST
data_variables: [temperature, time]
source_units: C
destination_units: K
source_grid: cell_center
destination_grid: cell_center
add_offset: 273.15d0
scale: 1.0d0
debug_write: false
connected_to: *ATM
regrid_method: bilinear
extrapolate_method: nearest

# And so on. It is an expandable blocking list ...

The description key for each pair member of the YAML blocking list is as follows:

Key	Description
standard_name	The field's standard name. A list of all exchanged standard_name field are shown below.
long_name	The field's long descriptive name.
short_name	The field's short name private to the ESMF/NUOPC cap module
data_variables	The DATA component NetCDF field and associated time variable names.
source_units	The field's source units.
destination_units	The field's destination units.
source_grid	The field's source grid-cell location.
destination_grid	The field's destination grid-cell location.
add_offset	The value to add to the exchanged field.
scale	The scale to use to convert data from source to destination units.
debug_write	A switch indicating whether or not to write out exchanged field, if DebugLevel>2.
connected_to	The source component to which the field is connected.
regrid_method	The field regridding method from source to destination: Value Description bilinear bilinear interpolation patch high-order patch recovery conservative1 first-order conservative conservative2 second-order conservative nearest nearest neighbor interpolation
extrapolate_method	The field extrapolation method for unmapped points: Value Description none no extrapolation nearest nearest source to destination idavg nearest inverse distance average creep creep fill at specified level 2steps Turuncoglu's 2 steps extrapolation

The ESM imported fields are processed as:

field (destination_units) = field (source_units) * scale + add_offset

YAML allows Anchors and Aliases to avoid repetition. In YAML, single or multiple line comments start with a hash #. Also, comment after a key/value pair is allowed. All comments are skipped during processing.

Exchanged Fields Metadata: short_name and standard_name

The following table shows the coupling metadata short_name and standard_name for the ESMF/NUOPC Export and Import states. They follow CF conventions closely. However, we needed to create lots of them because are not available in the CF tables but followed their established syntax. The list of exchanged fields is application dependent and YAML files are expandable and easy to modify.

short_name	standard_name
dLWrad	surface_net_downward_longwave_flux
dSWrad	net_downward_shortwave_flux_at_sea_water_surface
dSST	sea_surface_temperature_data
Hair	surface_specific_humidity
LHfx	surface_latent_heat_flux
LWrad	surface_net_downward_longwave_flux
Pair	surface_air_pressure
Pmsl	mean_sea_level_pressure
Qair	surface_relative_humidity
rain	precipitation_flux
shflux	surface_downward_heat_flux_in_sea_water
SHfx	surface_sensible_heat_flux
SST	sea_surface_temperature
sustr	surface_downward_x_stress
svstr	surface_downward_y_stress
swflux	surface_upward_water_flux
SWrad	net_shortwave_flux_at_sea_water_surface
Tair	surface_air_temperature
Uwind	surface_eastward_wind
Vwind	surface_northward_wind