Author: '''Jérôme Chanut, Mercator Océan'''

Page related to ticket: #1620 and associated to the following development branch: [​https://forge.ipsl.jussieu.fr/nemo/browser/branches/2015/dev_r5847_MERCATOR9_solveur_simplification]

This development is part of the shared simplication process, task: SIMPLIF-2: Removal of filtered free surface. Split explicit and explicit free surface only.

'''Step 1: Remove filtered free surface option and associated key_dynspg_flt key'''

  1) Remove parts of the code specific to "key_dynspg_flt" or lk_dynspg_flt=T and the need for solver modules in the code.[[BR]]    2) Suppress SOL directory and dynspg_flt module[[BR]]

3) Clean momentum trend routines related to filtered free surface (trddyn, trdken, trd_oce).[[BR]] 4) Update reference configurations: [[BR]]

 * Replace key_dynspg_flt by key_dynspg_ts if needed in CONFIG/* directories. [[BR]]
 * Remove namsol block in namelist_* and references to flt variables (trends) in field_def.xml[[BR]]
 * SETTE: update sette.sh, to remove modifications of namelist variables related to solver. [[BR]]

NB: one should change "solver.stat" file and numsol names in stp_ctl and in_out_manager... keep it as is for the time being[[BR]]

==> '''Commit changes to revision 5868''' [https://forge.ipsl.jussieu.fr/nemo/changeset?old_path=%2Fbranches%2F2015%2Fdev_r5847_MERCATOR9_solveur_simplification&old=5867&new_path=%2Fbranches%2F2015%2Fdev_r5847_MERCATOR9_solveur_simplification&new=5868]

==> Passes Sette tests:YES

'''Step 2: Suppress implicit pressure gradient option, ln_hpg_imp=T '''

Since this option is not supported with the now default split explicit free surface: remove it ( => simpler step routine). ln_hpg_imp namelist variable suppressed in reference namelist.[[BR]]

==> '''Commit changes to revision 5869'''[ https://forge.ipsl.jussieu.fr/nemo/changeset?old_path=%2Fbranches%2F2015%2Fdev_r5847_MERCATOR9_solveur_simplification&old=5868&new_path=%2Fbranches%2F2015%2Fdev_r5847_MERCATOR9_solveur_simplification&new=5869] [[BR]]

==> Passes Sette tests: YES

'''Step 3: Time Stepping readibility / cleaning '''[[BR]]

1)''' dynzdf'''[[BR]] Make time stepping identical in explicit or split-explicit cases => assume that "after" velocities not tendencies are available after vertical diffusion of momentum (as for tracers) => modify dynzdf/dynnxt routines

2) '''step'''[[BR]]

 * Group all dynamical trends at the same place (at the beginning of the time stepping). Still keep dynnxt after tracer time stepping at the end.[[BR]]
 * Assuming ua/va are not used anymore during tracer computation as working arrays, remove temporary 3d arrays ua_sv, va_sv

3) '''Suppress obsolete''' dynspg_oce module, '''remove key_dynspg_ts / key_dynspg_exp''' (add namelist variables instead)

4) '''Reviewed AGRIF code in the case of explicit free surface''': slight changes in agrif_opa_interp module, but otherwise ok (quickly tested in ORCA2 Agulhas configuration)

==> Commit changes to revision: ???[[BR]] ==> Passes Sette tests:???

'''Step 4: Additional things to do:'''

 * Correct momentum trend computation with time splitting
 * Remove filtered free surface from documentation
 * Others ?

==> Commit changes to revision: ???[[BR]] ==> Pass Sette tests:???