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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
languagetext
titleDefault settings in the NAMRLX namelist
    &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 coefficients
      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,

      CLPSHRLX='../rlxml/sh/',  ! relative path to spectral forcing files
      CLPGGRLX='../rlxml/gg/',  ! relative path to gridpoint forcing files
    /

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