Changes between Initial Version and Version 1 of 2014WP/2014_SystemSimplification_v2

Timestamp:

2013-11-20T12:18:51+01:00 (11 years ago)

Author:

gm

Comment:

--

2014WP/2014_SystemSimplification_v2

@@ +1 @@
+'''Note on possible system simplification'''
+
+'''Motivation''':
+
+We need to simplify the code for maintenance, robustness and future evolution (change in time stepping, …etc). This means fewer options, and a consensus on the default (and thus well validated) set of numerics.
+
+The idea is to change the current most used choices from : 
+
+linear filtered free surface zps ocean with TVD, "Madec" isoneutral diffusion, and standard equation of state ;  levitating sea-ice with virtual salt fluxes
+
+possibly to :
+
+Non linear (vvl), split-explicit (ts) free surface, mixte zps/s-coordinate ocean with 3rd order advection (UBS),  "Griffies" isoneutral diffusion ; embedded multi-category sea-ice (exact fluxes).
+
+And this with a removing of obsolescent features and a cleaning of the code.
+
+Timing: ideally, no more than 2 years from now (to be ready for CMIP6, and on time for the foreseen evolution of the time stepping)
+
+'''* core action (supported by all system team)'''
+
+'''- desired, but subject to discussion '''
+
+'''? feasible but all conditions required are not yet met  '''
+
+'''CHANGE in paradigm'''
+
+'''*''' • default : non-linear free surface ('''planned''' '''in 2014''')
+
+'''*''' • remove filtered free surface and all associated solvers (if yes when? 2014?)
+
+                (required AGRIF with time-splitting, '''done''' in 2013) and deeply tested ('''planned''' 2014)
+
+'''*''' • vertical coordinate : default option mixte zps/s-tilde coordinate (thus with variable volume level), with mixte zps*/s*, mixte z/s, zps, z and s coordinate system as sub-option (same code used) (2014-2015 ?)
+
+                - tracer solved as thickness weighted tracer: D,,t,,(e,,3t,, T) ('''planned''' '''2014''')
+
+                - thickness weighted quantities in the outputs ('''planned''' '''2014''')
+
+                - no more substitute (domzgr_substitute.h90): all e3 always defined at before, now and after time steps ('''partly done''' in 2013, '''achieved''' in 2014).  
+
+                - adapte OFF line for tracer to variable volume (2015?) 
+
+'''*''' • linear ssh option set without optimization (i.e. starting from the non-linear case with minimal changes, not optimal changes), or linear case suppressed ?? We should probably keep a linear case for test cases. (2014-2015 ?)
+
+'''*''' • sea-ice : embedded sea-ice as default
+
+                - suppress levitating sea ice with virtual salt fluxes. (2014 ?)
+
+                - Suppress levitating sea ice with mass exchange (?)  CICE issue…
+
+                - need land-fast ice ('''planned''' '''2014''')
+
+                - need BDY compatibility with embedded sea-ice …. (who when?)
+
+'''-''' • tracer advection scheme: diminish their number (?). Typically one module for 2^nd^/4^th^ order and one for a 3^rd^ order scheme, both associated with an optional flux limiter to ensure positivity.
+
+'''-''' • vertical physics:  simplification versus diversity
+
+                - keep only one (GLS) ? or maintain some diversity? 
+
+                - KPP remove unless if-less KPP is implemented (Lemarié et al 2012). Keeping a validated KPP scheme in the system make sense for comparison purposes. 
+
+                - suppress or keep the explicit vertical diffusion
+
+'''OBSOLESCENT features'''
+
+mains:
+
+'''*''' • remove LIM2 : only LIM3 remains in the system (planed 2014)
+
+'''*''' • remove OBC : only BDY remains in the system (planed 2013, early 2014)
+
+'''*''' • remove OASIS 3 and 4 :  OASIS-MCT (planed 2014)
+
+'''-''' • duplicate isoneutral operator: keep only the Griffies' one (tests needed before decision, tests planed in 2014 NOCS+LOCEAN) 
+
+smaller one
+
+'''-''' • Non-penetrative convection : either correct it (using alpha & beta) or remove it (who?)
+
+'''*''' • remove acceleration of convergence (notably rdttra=F(k) ==> unique rdt)
+
+'''*''' • remove Neptune effect : ORCA1 runs shows its inefficiency.
+
+'''-''' • Smagorinsky (?) : use 3rd order operator (UBS) instead and remove it ?
+
+I/O 
+
+'''-''' • remove Dimg format (?) (agreement needed from DRAKKAR group) 
+
+'''?''' • remove IOIPSL : 2 issues, still use in some places, and XIOs portability… (''probably much too early to decide that'')
+
+'''*''' • use of XIOS logical to control the computation of diagnostics (2014-2015, '''who?''')
+
+'''CODE cleaning'''
+
+'''*''' • OBS operator : clean the stand-alone implementation ('''planned 2014''')
+
+'''*''' • suppress most of the CPP keys, if not all of them (2015 ?)
+
+'''*''' • dynamical allocation: return back to standard allocation (?) (no more '''CALL '''wrk_alloc and '''CALL '''wrk_dealloc)  Evaluation to decided what to do ('''planned 2014''')
+
+'''*''' • no more potential density (zdfnpc and MLD computed from alpha & beta) ('''planned''' '''2014''')
+
+'''*''' • remove all hard coded specific alterations associated with configurations (ORCA,…) while introducing associated input files (2015 ?)
+
+'''*'''         • same for the definition of coordinate system (s, mixed z-s): only a simple case hard coded. For more sophisticated cases, the required information should be  read in an input file. (2015 ?)
+
+'''*''' • avm defined at t-point ==> suppress avmu, avmv and ~10 lbc_lnk calls (2015 ?)
+
+'''-''' • LDF: remove 1D and 2D cases, keep only 3D ; laplacian and bilaplacian coefficients defined at the same points (T and F) ;  time varying coefficients (Smagorinsky, function of growth rate of baroclinic instabilities): better integration rather than configuration dependent cases (2015 ?)