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== HOW TO set up user’s configuration in NEMO version 4.0 : ==
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This document describes how a configuration is set up in NEMO.

In NEMO 4.0 two types of configurations can be build: global/regional and idealized.

- create NEMOGCM/CONFIG/your_config
- case 1: regional or global 
    => ln_read_cfg = .true. in NEMOGCM/CONFIG/your_config/EXP00/namelist_cfg (i.e. read domain_cfg.nc)
- case 2: idealized 
    =>in NEMOGCM/CONFIG/your_config/EXP00/namelist_cfg :
      ln_read_cfg = .false. (need to define usrdef_hgr.F90 and usrdef_zgr.F90) 
      ln_usr = .true.       (need to define usrdef_sbc.F90)    
    => copy NEMOGCM/NEMO/OPA_SRC/USR in NEMOGC/CONFIG/your_config/MY_SRC routines nedeed to set up domain, forcing fields and initial state
    
  Routines in NEMOGCM/NEMO/OPA_SRC/USR define analytically the domain, the initial state and the surface boundary conditions for the reference configuration GYRE.
     •   usrdef_hgr.F90 and usrdef_zgr.F90 : define horizontal and vertical grid
     •   usrdef_sbc.F90    : provides at each time-step the surface boundary condition, i.e. the momentum, heat and freshwater fluxes
     •   usrdef_istate.F90 : defines initialization of the dynamics and tracers
     •   usrdef_fmask.F90  : used just in ORCA CONFIGURATIONS for alteration of f-point land/ocean mask in some straits 
     •   usrdef_closea.F90 : used just in ORCA CONFIGURATIONS for specific treatments associated with closed seas
     •   usrdef_nam.F90    : set the domain characteristics of a user configuration

  Other analytical examples are given in NEMOGCM/CONFIG/TEST_CASES.

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== The domain_cfg.nc file must contain : ==
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   int ORCA  , ORCA_index            : configuration name, configuration resolution
   int jpiglo, jpjglo , jpkglo       : global domain sizes 
   int jperio                        : lateral global domain b.c. 
   int ln_zco, ln_zps, ln_sco        : flags for z-coordinate, z-coordinate with partial steps and s-coordinate 
   int ln_isfcav                     : flag  for ice shelf cavities 
   double glamt, glamu, glamv, glamf : geographic position 
   double gphit, gphiu, gphiv, gphif : geographic position
   double iff, ff_f, ff_t            : Coriolis parameter (if not on the sphere)
   double e1t, e1u, e1v, e1f         : horizontal scale factors
   double e2t, e2u, e2v, e2f         : horizontal scale factors
   double ie1e2u_v, e1e2u, e1e2v     : U and V surfaces (if grid size reduction in some straits)
   double e3t_1d, e3w_1d             : reference vertical scale factors at T and W points
   double e3t_0, e3u_0, e3v_0, e3f_0, e3w_0 : vertical scale factors 3D coordinate at T,U,V,F and W points
   double e3uw_0,e3vw_0              : vertical scale factors 3D coordinate at UW and VW points
   int bottom_level, top_level       : last wet T-points, 1st wet T-points (for ice shelf cavities)

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= HOW TO CREATE domain_cfg.nc file : ==
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Two options are possible :

 - users can create with his own tool the domain_cfg.nc with all mandatory fields.  

 - tool is available in NEMOGCM/TOOLS/DOMAINcfg based on NEMO 3.6 version. See NEMOGCM/TOOLS/DOMAINcfg/README.