[10187] | 1 | ====================== |
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| 2 | What's new in NEMO 4.0 |
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| 3 | ====================== |
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[10150] | 4 | |
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[10201] | 5 | .. include:: .global.rst |
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| 6 | |
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[10150] | 7 | .. contents:: |
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[10187] | 8 | :local: |
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| 9 | |
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[10150] | 10 | Original sea-ice component SI\ :sup:`3`\ |
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| 11 | ======================================== |
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| 12 | |
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| 13 | | Meeting in 2017, the `sea ice working group`_ decided to gather sea ice developers and |
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| 14 | scientific expertise within the NEMO community in order to build a unified model. |
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| 15 | The replacement of LIM (Louvain-la-Neuve Ice Model) has required the backport of |
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| 16 | the desired functionalities from each of CICE, GELATO and LIM into a common code in the NEMO framework. |
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| 17 | | This new model has been named SI\ :sup:`3`\ ("sea ice cubed") and |
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| 18 | means "**Sea Ice modelling Integrated Initiative**". |
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| 19 | |
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| 20 | - Physics |
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| 21 | |
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| 22 | * Landfast ice: simple grounding with a "release" stress (not fully operational) |
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| 23 | * Lateral melting |
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| 24 | * Melt ponds: constant or `Holland 2012`_ formulation (and soon topographic melt ponds) |
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| 25 | * Ice-atm. drags from `Lupkes 2012`_ (depending on ice concentration) or `Lupkes 2014`_ |
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| 26 | (Depending on sea ice concentration and atm. stability) |
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| 27 | - Numerics |
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| 28 | |
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| 29 | * Advection: Ultimate-Macho scheme |
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| 30 | * Rheology: adaptive EVP (`Kimmritz 2016`_) |
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| 31 | * Coupling interface: conductivity as surface forcing instead of heat fluxes (Met Office requirement) |
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| 32 | - Performance |
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| 33 | |
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| 34 | * All thermodynamics in 1D |
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| 35 | * Reduced mpp communications |
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| 36 | - Users & developers friendly |
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| 37 | |
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| 38 | * Comprehensive set of outputs (universal units and understandable names + includes limp) |
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| 39 | * New architecture and namelist |
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| 40 | * All processes can be decoupled from each other (switch on/off) |
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| 41 | * Ice categories bounds can be defined by the user or set automatically |
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| 42 | * For open boundaries, the number of ice categories from the forcing model can be different |
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| 43 | from the number of categories in the regional simulation |
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| 44 | * Fully compatible with AGRIF |
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| 45 | |
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| 46 | First Test Cases |
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| 47 | ================ |
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| 48 | |
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| 49 | Define and install a separate repository for test cases to all easy contributions from the NEMO Users Community |
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| 50 | |
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| 51 | Core components |
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| 52 | =============== |
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| 53 | |
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| 54 | Passive tracer TOP and biogeochemical PISCES components |
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| 55 | ------------------------------------------------------- |
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| 56 | |
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| 57 | - The passive tracers transport component was redesigned toward a modular structure and |
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| 58 | users can enable each module directly through logical flags in namelist_top (no more Fortran macros!). |
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[10187] | 59 | - TOP on-line user documentation is available on NEMO Trac platform (`TOP User Quick Guide`_) |
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[10150] | 60 | - TOP currently accounts for the following 5 modules: |
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| 61 | |
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| 62 | * ``CFC`` contains inorganic carbon tracers (CFC11/CFC12/SF6) |
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| 63 | * ``MY_TRC`` is a template for new modules (or external couplings) |
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| 64 | * ``AGE`` deals with water age tracking |
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| 65 | * ``C14`` as a radiocarbon passive tracer |
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| 66 | * ``PISCES`` the companion ecosystem model |
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| 67 | - A generalized infrastructure was developed to handle the prescription of either surface, coastal, or |
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| 68 | open boundaries conditions for each passive tracer. |
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| 69 | - PISCES model contains new developments and modifications: |
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| 70 | |
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| 71 | * Particulate Organic Carbon (POC) component comes with a new liability scheme, |
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| 72 | while the former Kriest parameterisation was superseded; |
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| 73 | * A complex iron chemistry scheme is now available, with an improved description of ligands for |
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| 74 | the marine iron cycle |
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| 75 | * Carbonate chemistry is based on MOCSY 2.0 routines (see `Orr and Epitalon 2015`_), |
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| 76 | by complying also with CMIP6 standards. |
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| 77 | * Ecosystem components can be optionally modelled by means of explicit nutrient quotas (PISCES-QUOTA) |
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| 78 | |
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| 79 | AGRIF (embedded zooms) |
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| 80 | ---------------------- |
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| 81 | |
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[10187] | 82 | The NEMO 4.0 includes new capabilities, configurations and test cases with AGRIF: |
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| 83 | |
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| 84 | .. role:: underline |
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| 85 | :class: underline |
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| 86 | |
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| 87 | :underline:`New capabilities from NEMO 3.6 to NEMO 4.0` |
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| 88 | |
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| 89 | AGRIF is continuously maintained so that it could be activated with all NEMO components (OPA, sea-ice, TOP). |
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| 90 | Depending on NEMO version, it is nevertheless not the case so that some options may not be compatible with |
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| 91 | the use of online grid refinement. |
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| 92 | Check out the table below to know the status according to the NEMO release you may use. |
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| 93 | |
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| 94 | :underline:`Status of available options with AGRIF (if not listed, option is compatible with AGRIF)`: |
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| 95 | |
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| 96 | +--------------------------------------------------------+----------------+---------------------+ |
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| 97 | | | NEMO 3.6 | NEMO 4.0 | |
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| 98 | +========================================================+================+=====================+ |
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| 99 | | LIM2 | yes | ``-`` | |
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| 100 | +--------------------------------------------------------+----------------+---------------------+ |
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| 101 | | LIM3/SI3 | no | yes | |
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| 102 | +--------------------------------------------------------+----------------+---------------------+ |
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| 103 | | TOP | yes | yes | |
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| 104 | +--------------------------------------------------------+----------------+---------------------+ |
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| 105 | | GLS vertical mixing | no | yes | |
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| 106 | +--------------------------------------------------------+----------------+---------------------+ |
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| 107 | | z* | no | yes | |
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| 108 | +--------------------------------------------------------+----------------+---------------------+ |
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| 109 | | z~ | no | no | |
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| 110 | +--------------------------------------------------------+----------------+---------------------+ |
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| 111 | | Lagrangian icebergs | no | no | |
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| 112 | +--------------------------------------------------------+----------------+---------------------+ |
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| 113 | | East-west periodic and/or north fold bcs in zooms | no | no | |
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| 114 | +--------------------------------------------------------+----------------+---------------------+ |
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| 115 | | Online timing | no | no | |
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| 116 | +--------------------------------------------------------+----------------+---------------------+ |
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| 117 | | Stochastic parameterization | no | no | |
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| 118 | +--------------------------------------------------------+----------------+---------------------+ |
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| 119 | | Vertical coordinate change in zooms (``key_vertical``) | no | yes, but not tested | |
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| 120 | +--------------------------------------------------------+----------------+---------------------+ |
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| 121 | | Number of ghost cells | 1 (hard coded) | 3 (parameter) | |
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| 122 | +--------------------------------------------------------+----------------+---------------------+ |
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| 123 | |
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| 124 | [Important notice concerning the change of ghost cells number] |
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| 125 | |
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| 126 | The default number of ghost cells (i.e. the number of cells that serve as open boundary data provision) has been |
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| 127 | increased from 1 to 3 in NEMO 4.0. |
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| 128 | This allows to properly handle boundary conditions for numerical schemes that |
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| 129 | have a discretization order greater than 2. |
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| 130 | On the user point of view this does not change anything++ except in the definition of level 1 grids in |
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| 131 | the ``AGRIF_FixedGrids.in`` file. |
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| 132 | In order to retrieve exactly the position of a nested grid in NEMO 4.0 one has to shift indices by |
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| 133 | 2 points to the south-west. |
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| 134 | Taking the ``ICEDYN`` example above for NEMO 4.0, the "old" NEMO 3.6 corresponding file would contain:: |
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| 135 | |
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| 136 | 1 |
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| 137 | 36 65 36 65 3 3 3 |
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| 138 | 0 |
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| 139 | |
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| 140 | ++ Child grid output files are now greater by 4 points in each direction. |
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| 141 | |
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[10150] | 142 | - Now compatible with new sea ice component and z* coordinate |
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| 143 | - Extended ghost cells area to properly handle scheme with spatial order >2 |
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| 144 | - Added vertical refinement (beta) |
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| 145 | - Nesting tools for setup now up to date and working |
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| 146 | |
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| 147 | Adding of 3 Reference Configurations |
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| 148 | ------------------------------------ |
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| 149 | |
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| 150 | - ``AGRIF_DEMO``: 2 interlocked zooms (1:4 & 1:3) in the Nordic Seas + 1 zoom (1:1) at the equator |
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| 151 | - ``ORCA2_OFF_TRC``: a benchmark simulation environment to deal with inert carbon tracers dynamics by |
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| 152 | exploiting the offline coupling with NEMO. |
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| 153 | - ``SPITZ12``: regional configuration around the Svalbard archipelago. |
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| 154 | |
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| 155 | Misc. improvments |
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| 156 | ================= |
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| 157 | |
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| 158 | Physics |
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| 159 | ------- |
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| 160 | |
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| 161 | - Bulk formulae : move to aerobulk package (`Brodeau 2017`_), i.e. NCAR, COARE and ECMWF bulk |
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| 162 | (remove Clio and MFS bulk) |
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| 163 | - Fix for tracer conservation with split explicit free surface |
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| 164 | - Wetting and drying |
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| 165 | - iso-neutral mixing (iso and triad operators): add the Method of Stabilizing Correction (MSC) |
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| 166 | (more accurate calculation) + add a bilaplacian case |
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| 167 | - Lateral physics (LDF): scale aware setting of eddy viscosity and diffusivity |
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| 168 | - Wave coupling: large scale wave interaction process added in momentum and tracer equations |
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| 169 | - Remove the acceleration of convergence |
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[10187] | 170 | |
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[10150] | 171 | Numerics |
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| 172 | -------- |
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| 173 | |
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| 174 | - Added tidal self attraction and loading either read from a file or from usual "scalar" approximation |
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| 175 | - Vertical physics (ZDF) (modularity, share shear production calculation between TKE and GKS, |
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| 176 | removal of all ZDF CPP keys, removal of avmu & avmv, minimization of MPP comm.: ~15 removed) |
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| 177 | - Remove the split-explicit ZDF scheme for both TRA and DYN |
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| 178 | - Lateral physics (LDF): simplification of user interface and removal of CPP keys |
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| 179 | - Add a 4th order centered (CEN) and Flux Corrected Transport (FCT) tracer advection |
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| 180 | (using a 4th compact in the vertical) |
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| 181 | - Generalised lbc_lnk and lbc_nfd |
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| 182 | - Configuration interface completely rewritten (DOM module mainly suppressed, |
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| 183 | and in place: domain_cfg.nc file, or usr_def module) |
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| 184 | - Vorticity: 2 new energy conserving scheme: ENT with Coriolis defined at T-point |
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| 185 | (better for Flux form) and EET a variant of EEN where e3t is used instead of e3f |
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| 186 | (solved the issue with e3f specification but is not enstrophy conserving) |
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| 187 | - Wave coupling: coupled interface to external wave model |
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| 188 | |
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| 189 | Performances |
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| 190 | ------------ |
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| 191 | |
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| 192 | - MPI Message passing recoded to reduce number of MPI communications (suppression of redundant communications, |
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| 193 | gather multiple communications into one) |
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| 194 | - Back to standard dynamical allocation (remove of wrk_alloc/dealloc statements) |
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| 195 | - XIOS software for IOs version 2 as default, and optionally available for restarts |
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| 196 | - Unify mppini |
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| 197 | - Use non uniform jpi/jpj with dynamic allocation to avoid ghost rows/columns |
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| 198 | |
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| 199 | Environment |
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| 200 | ----------- |
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| 201 | |
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| 202 | - Revised structure of namelist_ref/_cfg and default reference values. |
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| 203 | - Reorganisation of SVN repository to be compliant with usual directory tree and facilitate building of |
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| 204 | NEMO executable |
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| 205 | - Improvements of reliability through automatic and regular testing of the changes made in repository |
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| 206 | |
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| 207 | .. _sea ice working group: http://forge.ipsl.jussieu.fr/nemo/wiki/WorkingGroups/SI3 |
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[10187] | 208 | .. _TOP User Quick Guide: http://forge.ipsl.jussieu.fr/nemo/wiki/WorkingGroups/top-dg/TOP-UserQuickGuide |
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[10150] | 209 | |
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| 210 | .. _Brodeau 2017: http://doi.org/10.1175/JPO-D-16-0169.1 |
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| 211 | .. _Holland 2012: http://doi.org/10.1175/JCLI-D-11-00078.1 |
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| 212 | .. _Lupkes 2012: http://doi.org/10.1029/2012JD017630 |
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| 213 | .. _Lupkes 2014: http://doi.org/10.1002/2014JD022418 |
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| 214 | .. _Kimmritz 2016: http://doi.org/10.1016/j.ocemod.2016.03.004 |
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| 215 | .. _Orr and Epitalon 2015: http://doi.org/10.5194/gmd-8-485-2015 |
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