source: NEMO/trunk/RELEASE_NOTES.rst @ 10592

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1**********************
2What's new in NEMO 4.0
3**********************
4
5.. contents::
6   :local:
7     
8Original sea-ice component SI\ :sup:`3`\
9========================================
10
11| Meeting in 2017, the `sea ice working group`_ decided to gather sea ice developers and
12  scientific expertise within the NEMO community in order to build a unified model.
13  The replacement of LIM (Louvain-la-Neuve Ice Model) has required the backport of
14  the desired functionalities from each of CICE, GELATO and LIM into a common code in the NEMO framework.
15| This new model has been named |SI3| ("sea ice cubed") and means "**Sea Ice modelling Integrated Initiative**".
16
17- Physics
18
19  * Landfast ice: simple grounding with a "release" stress (not fully operational)
20  * Lateral melting
21  * Melt ponds: constant or `Holland 2012`_ formulation (and soon topographic melt ponds)
22  * Ice-atm. drags from `Lupkes 2012`_ (depending on ice concentration) or `Lupkes 2014`_
23    (Depending on sea ice concentration and atm. stability)
24- Numerics
25
26  * Advection: Ultimate-Macho scheme
27  * Rheology: adaptive EVP (`Kimmritz 2016`_)
28  * Coupling interface: conductivity as surface forcing instead of heat fluxes (Met Office requirement)
29- Performance
30
31  * All thermodynamics in 1D
32  * Reduced mpp communications
33- Users & developers friendly
34
35  * Comprehensive set of outputs (universal units and understandable names + includes limp)
36  * New architecture and namelist
37  * All processes can be decoupled from each other (switch on/off)
38  * Ice categories bounds can be defined by the user or set automatically
39  * For open boundaries, the number of ice categories from the forcing model can be different
40    from the number of categories in the regional simulation
41  * Fully compatible with AGRIF
42
43First Test Cases
44================
45
46Define and install a separate repository for test cases to all easy contributions from the NEMO Users Community
47
48Core components
49===============
50
51Passive tracer TOP and biogeochemical PISCES components
52-------------------------------------------------------
53
54- The passive tracers transport component was redesigned toward a modular structure and
55  users can enable each module directly through logical flags in namelist_top (no more Fortran macros!).
56- TOP on-line user documentation is available on NEMO Trac platform (`TOP User Quick Guide`_)
57- TOP currently accounts for the following 5 modules:
58
59  * ``CFC`` contains inorganic carbon tracers (CFC11/CFC12/SF6)
60  * ``MY_TRC`` is a template for new modules (or external couplings)
61  * ``AGE`` deals with water age tracking
62  * ``C14`` as a radiocarbon passive tracer
63  * ``PISCES`` the companion ecosystem model
64- A generalized infrastructure was developed to handle the prescription of either surface, coastal, or
65  open boundaries conditions for each passive tracer.
66- PISCES model contains new developments and modifications:
67
68  * Particulate Organic Carbon (POC) component comes with a new liability scheme,
69    while the former Kriest parameterisation was superseded;
70  * A complex iron chemistry scheme is now available, with an improved description of ligands for
71    the marine iron cycle
72  * Carbonate chemistry is based on MOCSY 2.0 routines (see `Orr and Epitalon 2015`_),
73    by complying also with CMIP6 standards.
74  * Ecosystem components can be optionally modelled by means of explicit nutrient quotas (PISCES-QUOTA)
75
76AGRIF (embedded zooms)
77----------------------
78
79The NEMO 4.0 includes new capabilities, configurations and test cases with AGRIF:
80
81:underline:`New capabilities from NEMO 3.6 to NEMO 4.0`
82
83AGRIF is continuously maintained so that it could be activated with all NEMO components (OPA, sea-ice, TOP).
84Depending on NEMO version, it is nevertheless not the case so that some options may not be compatible with
85the use of online grid refinement.
86Check out the table below to know the status according to the NEMO release you may use.
87
88:underline:`Status of available options with AGRIF (if not listed, option is compatible with AGRIF)`:
89
90+--------------------------------------------------------+----------------+---------------------+
91|                                                        | NEMO 3.6       | NEMO 4.0            |
92+========================================================+================+=====================+
93| LIM2                                                   | yes            | ``-``               |
94+--------------------------------------------------------+----------------+---------------------+
95| LIM3/SI3                                               | no             | yes                 |
96+--------------------------------------------------------+----------------+---------------------+
97| TOP                                                    | yes            | yes                 |
98+--------------------------------------------------------+----------------+---------------------+
99| GLS vertical mixing                                    | no             | yes                 |
100+--------------------------------------------------------+----------------+---------------------+
101| z*                                                     | no             | yes                 |
102+--------------------------------------------------------+----------------+---------------------+
103| z~                                                     | no             | no                  |
104+--------------------------------------------------------+----------------+---------------------+
105| Lagrangian icebergs                                    | no             | no                  |
106+--------------------------------------------------------+----------------+---------------------+
107| East-west periodic and/or north fold bcs in zooms      | no             | no                  |
108+--------------------------------------------------------+----------------+---------------------+
109| Online timing                                          | no             | no                  |
110+--------------------------------------------------------+----------------+---------------------+
111| Stochastic parameterization                            | no             | no                  |
112+--------------------------------------------------------+----------------+---------------------+
113| Vertical coordinate change in zooms (``key_vertical``) | no             | yes, but not tested |
114+--------------------------------------------------------+----------------+---------------------+
115| Number of ghost cells                                  | 1 (hard coded) | 3 (parameter)       |
116+--------------------------------------------------------+----------------+---------------------+
117
118[Important notice concerning the change of ghost cells number]
119
120The default number of ghost cells (i.e. the number of cells that serve as open boundary data provision) has been
121increased from 1 to 3 in NEMO 4.0.
122This allows to properly handle boundary conditions for numerical schemes that
123have a discretization order greater than 2.
124On the user point of view this does not change anything++ except in the definition of level 1 grids in
125the ``AGRIF_FixedGrids.in`` file.
126In order to retrieve exactly the position of a nested grid in NEMO 4.0 one has to shift indices by
1272 points to the south-west.
128Taking the ``ICEDYN`` example above for NEMO 4.0, the "old" NEMO 3.6 corresponding file would contain::
129
130   1
131   36 65 36 65 3 3 3
132   0
133
134++ Child grid output files are now greater by 4 points in each direction.
135
136- Now compatible with new sea ice component and z* coordinate
137- Extended ghost cells area to properly handle scheme with spatial order >2
138- Added vertical refinement (beta)
139- Nesting tools for setup now up to date and working
140
141Adding of 3 Reference Configurations
142------------------------------------
143
144- ``AGRIF_DEMO``: 2 interlocked zooms (1:4 & 1:3) in the Nordic Seas + 1 zoom (1:1) at the equator
145- ``ORCA2_OFF_TRC``: a benchmark simulation environment to deal with inert carbon tracers dynamics by
146  exploiting the offline coupling with NEMO.
147- ``SPITZ12``: regional configuration around the Svalbard archipelago.
148
149Misc. improvments
150=================
151
152Physics
153-------
154
155- Bulk formulae : move to aerobulk package (`Brodeau 2017`_), i.e. NCAR, COARE and ECMWF bulk
156  (remove Clio and MFS bulk)
157- Fix for tracer conservation with split explicit free surface
158- Wetting and drying
159- iso-neutral mixing (iso and triad operators): add the Method of Stabilizing Correction (MSC)
160  (more accurate calculation) + add a bilaplacian case
161- Lateral physics (LDF): scale aware setting of eddy viscosity and diffusivity
162- Wave coupling: large scale wave interaction process added in momentum and tracer equations
163- Remove the acceleration of convergence
164
165Numerics
166--------
167
168- Added tidal self attraction and loading either read from a file or from usual "scalar" approximation
169- Vertical physics (ZDF) (modularity, share shear production calculation between TKE and GKS,
170  removal of all ZDF CPP keys, removal of avmu & avmv, minimization of MPP comm.: ~15 removed)
171- Remove the split-explicit ZDF scheme for both TRA and DYN
172- Lateral physics (LDF): simplification of user interface and removal of CPP keys
173- Add a 4th order centered (CEN) and Flux Corrected Transport (FCT) tracer advection
174  (using a 4th compact in the vertical)
175- Generalised lbc_lnk and lbc_nfd
176- Configuration interface completely rewritten (DOM module mainly suppressed,
177  and in place: domain_cfg.nc file, or usr_def module)
178- Vorticity: 2 new energy conserving scheme:  ENT with Coriolis defined at T-point
179  (better for Flux form) and EET a variant of EEN where e3t is used instead of e3f
180  (solved the issue with e3f specification but is not enstrophy conserving)
181- Wave coupling: coupled interface to external wave model
182
183Performances
184------------
185
186- MPI Message passing recoded to reduce number of MPI communications (suppression of redundant communications,
187  gather multiple communications into one)
188- Back to standard dynamical allocation (remove of wrk_alloc/dealloc statements)
189- XIOS software for IOs version 2 as default, and optionally available for restarts
190- Unify mppini
191- Use non uniform jpi/jpj with dynamic allocation to avoid ghost rows/columns
192
193Environment
194-----------
195
196- Revised structure of namelist_ref/_cfg and default reference values.
197- Reorganisation of SVN repository to be compliant with usual directory tree and facilitate building of
198  NEMO executable
199- Improvements of reliability through automatic and regular testing of the changes made in repository
200
201.. _sea ice working group:       http://forge.ipsl.jussieu.fr/nemo/wiki/WorkingGroups/SI3
202.. _TOP User Quick Guide:        http://forge.ipsl.jussieu.fr/nemo/wiki/WorkingGroups/top-dg/TOP-UserQuickGuide
203
204.. The following references should be in the manual bibliographies and referenced via 'bibliography' directive
205.. _Brodeau 2017:                http://doi.org/10.1175/JPO-D-16-0169.1
206.. _Holland 2012:                http://doi.org/10.1175/JCLI-D-11-00078.1
207.. _Lupkes 2012:                 http://doi.org/10.1029/2012JD017630
208.. _Lupkes 2014:                 http://doi.org/10.1002/2014JD022418
209.. _Kimmritz 2016:               http://doi.org/10.1016/j.ocemod.2016.03.004
210.. _Orr and Epitalon 2015:       http://doi.org/10.5194/gmd-8-485-2015
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