# IFS¶

Provided by European Centre for Medium-Range Weather Forecasts (ECMWF), UK

## Model description¶

IFS-H is a hydrostatic spectral transform atmosphere model with a semi-Lagrangian semi-implicit solution procedure, discretised on a cubic octahedral grid (Wedi 2014; Malardel et al. 2016). We have used the single precision version of IFS (cycle 47r1) that is using IEEE single precision for almost all model components except for the ocean model.

Information about IFS CY47r1 can be found at the IFS documentation.

## Experiment runs¶

### IFS-NEMO 4.0km coupled¶

Location:

/work/bk1040/DYAMOND/data/winter_data/DYAMOND_WINTER/ECMWF/IFS-4km/DW-CPL/

containing grid files in /atmos/fx/

Setup:

The model was coupled to the HTESSEL land model, the WAM wave model and the NEMO3.4 ocean model.

Resolution:
• The spectral IFS model for the atmosphere has been run with 4 km grid-spacing (TCo2559) and 137 vertical levels.

• The NEMO3.4 ocean model run with 1/4 degree resolution.

• The standard set of IFS parametrisation schemes was used but the parametrisation for deep convection was switched off and the parametrisation of orographic gravity waves was inactive. Information about IFS (version CY47r1) can be found at the IFS documentation.

• The vertical discretisation of the IFS atmosphere uses hybrid vertical levels defined as $$A(eta) + B(eta)*p_s$$, with $$A$$, $$B$$ fixed defined parameters and where $$p_s$$ is the provided surface pressure. Pressure on model levels needs to be calculated by the given formula.

Data description:

IFS 4km

Contact person:

Peter Dueben (ECMWF)

### IFS-NEMO 9.0km coupled¶

Location:

/work/bk1040/DYAMOND/data/winter_data/DYAMOND_WINTER/ECMWF/IFS-9km/DW-CPL/

containing grid files in /atmos/fx/ and in /work/bk1040/DYAMOND/data/winter_data/grid_files/

Setup:

The model was coupled to the HTESSEL land model, the WAM wave model and the NEMO3.4 ocean model.

Resolution:
• The spectral IFS model for the atmosphere has been run with 9 km grid-spacing (TCo1279).

• The NEMO3.4 ocean model run with 1/4 degree resolution.

• The vertical discretisation of the IFS atmosphere uses hybrid vertical levels defined as $$A(eta) + B(eta)*p_s$$, with $$A$$, $$B$$ fixed defined parameters and where $$p_s$$ is the provided surface pressure. Pressure on model levels needs to be calculated by the given formula.