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Choice of radiative transfer model

There are three radiative transfer codes available in LMDZ: "old radiative transfer code", RRTM and ECRad. RRTM was used for CMIP6. ECRad will probably become the recommended code in the near future. But, for now, the recommended settings are:

  • Compile with option -rad rrtm.
  • Set iflag_rrtm = 1 in physiq.def. It means we use RRTM.
  • Set nsw = 6 in physiq.def. This is the number of spectral bands for solar radiation.

Note: these are not the default values in the Fortran files (for the sake of backward compatibility) so make sure you specify them in the getin files.