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To enable nudging the namelist NAMRLX will need to be included in the namelist file fort.4. The values below show one possible configuration reflecting standard settings. As described previously, the question of which variables should be relaxed to the external analysis, the model grid domain where relaxation is applied, and the tightness of the nudging, controlled by the relaxation coefficient, are very much dependent on the objective of the model experiment.
| Code Block | ||
|---|---|---|
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&NAMRLX
LRLXG=true, ! Master switch to enable nudging
LRLXVO=true, ! vorticity
LRLXDI=true, ! divergence
LRLXTE=true, ! temperature
LRLXQ=true, ! specific humidity
LRLXQL=true, ! liquid water
LRLXQI=true, ! ice water
LRLXQC=true, ! cloud fraction
LRLXLP=true, ! log surf pressure
LRLXO3=true, ! ozone
NFRLXG=2, ! number of analysis time steps in memory
NFRLXU=6, ! interval between two references fields (in hours) - this is equal to NFRHIS in nudging
NRLXLMIN=1, ! top model level for nudging
NRLXLMAX=60, ! bottom model level for nudging
NRLXLMINU=-1, ! uppermost model level for velocity variables (-1 sets to NRLXLMIN)
NRLXLMAXU=-1, ! lowermost model level for velocity variables (-1 sets to NRLXLMAX)
XRLXVO=0.5, ! relaxation coefficientcoefficients
XRLXDI=0.5,
XRLXTE=0.5,
XRLXQ=0.5,
XRLXO3=0.5,
XRLXLP=0.5,
ALATRLX1=90, ! latitude domain for nudging
ALATRLX2=-90,
ALONRLX1=0, ! longitude domain for nudging
ALONRLX2=360,
AXRLX=-0.5, ! smoothing parameter for lon, lat and in the vertical
AYRLX=-0.5,
AZRLX=1.0,
NRLXLMIN=1, ! top model level for nudging
NRLXLMAX=60, ! bottom model level for nudging
CLPSHRLX='../rlxml/sh/', ! relative path to spectral forcing files
CLPGGRLX='../rlxml/gg/', ! relative path to gridpoint forcing files
/ |
Please note that when using OpenIFS versions prior to CY43R3 the available namelist parameters can differ from these shown above. For instance nudging of ozone is not available in CY40R1.
References
- Jeuken, A., et al. (1996) On the potential of assimilating meteorological analyses in a global climate model for the purposes of model validation, J. Geophys. Res., 101, 16,939–16,950. doi:10.1029/96JD01218.