!=======================================
! Activation of online coarsening
!=======================================
- coarsening of physics for output: compile with key_crs
- coarsening of physics for BCG model:  compile with key_crs and ln_crs_top  = .true.

-Be carefull:
 All the files read in TOP_SRC ( initial conditions for tracers ) and in BCG model ( river, dust, par,... in PISCES )
should be on the coarsened grid or read using interpolation-on-the-fly with a weight files toward coarsened grid.

!=======================================
! namelist parameter
!=======================================

!-----------------------------------------------------------------------
&namcrs        !   Grid coarsening for dynamics output and/or
               !   passive tracer coarsened online simulations
!-----------------------------------------------------------------------
   nn_factx    = 3         !  Reduction factor of x-direction
   nn_facty    = 3         !  Reduction factor of y-direction
   nn_msh_crs  = 1         !  create (=1) a mesh file or not (=0)
   nn_crs_kz   = 0         ! 0, MEAN of volume boxes
                           ! 1, MAX of boxes
                           ! 2, MIN of boxes
                           ! 3, 10**(MEAN(LOG()) of volume boxes
                           ! 4, MEDIANE of boxes
   ln_crs_wn   = .true.    ! wn coarsened (T) or computed using horizontal divergence ( F )
   ln_crs_top  = .true.    ! coarsening online for the BCG model ( T) or only for outpout of physics ( F )
/


- only nn_factx=3 and nn_facty=3 are available ( ORCA025 to ORCA075, ORCA12 to ORCA025,...)
- nn_msh_crs=1 shall be activated to generate coarsened grid meshmask ( rebuild with REBUILD_NEMO )
- ln_crs_wn : T: vertical velocities are coarsened ; F: vertical velocities computed using horizontal divergence
- ln_crs_top: T  coarsening online for the BCG model ; F outpout of physics only

!=======================================
! XML files
!=======================================

use:
 - field_def.xml :  CONFIG/SHARED/field_def.xml
 - domain_def.xml:  CONFIG/SHARED/domain_def.xml for XIOS1 
                    CONFIG/GYRE_XIOS/EXP00/domain_def.xml for XIOS2
 - iodef.xml     :  a new context "nemo_crs" might be created after the existing "nemo" context in iodef.xml ( see iodef.xml in XML_EXAMPLE )
 - file_def.xml  :  the full-resolution files in  "nemo"     context ( see file_def.xml     in in XML_EXAMPLE )
                    the coarsened       files in  "nemo_crs" context ( see file_crs_def.xml in in XML_EXAMPLE )