================ NEMO 4.0 Release ================ .. contents:: ---------- What's new ---------- Original sea-ice component SI\ :sup:`3`\ ======================================== | Meeting in 2017, the `sea ice working group`_ decided to gather sea ice developers and scientific expertise within the NEMO community in order to build a unified model. The replacement of LIM (Louvain-la-Neuve Ice Model) has required the backport of the desired functionalities from each of CICE, GELATO and LIM into a common code in the NEMO framework. | This new model has been named SI\ :sup:`3`\ ("sea ice cubed") and means "**Sea Ice modelling Integrated Initiative**". - Physics * Landfast ice: simple grounding with a "release" stress (not fully operational) * Lateral melting * Melt ponds: constant or `Holland 2012`_ formulation (and soon topographic melt ponds) * Ice-atm. drags from `Lupkes 2012`_ (depending on ice concentration) or `Lupkes 2014`_ (Depending on sea ice concentration and atm. stability) - Numerics * Advection: Ultimate-Macho scheme * Rheology: adaptive EVP (`Kimmritz 2016`_) * Coupling interface: conductivity as surface forcing instead of heat fluxes (Met Office requirement) - Performance * All thermodynamics in 1D * Reduced mpp communications - Users & developers friendly * Comprehensive set of outputs (universal units and understandable names + includes limp) * New architecture and namelist * All processes can be decoupled from each other (switch on/off) * Ice categories bounds can be defined by the user or set automatically * For open boundaries, the number of ice categories from the forcing model can be different from the number of categories in the regional simulation * Fully compatible with AGRIF First Test Cases ================ Define and install a separate repository for test cases to all easy contributions from the NEMO Users Community +-------------------+--------------------------------------------------------+------------------------------------+ | Name | Purpose | References | +===================+=================+======================================+====================================+ | ``CANAL`` | East-west periodic canal of variable size with several | | | | initial states and associated geostrophic currents | | | | (zonal jets or vortex). | | +-------------------+--------------------------------------------------------+------------------------------------+ | ``ICEDYN`` | East-west + north-south periodic channel. | | | | The common configuration includes an AGRIF zoom (1:3) | | | | in the middle of the basin to test how an ice patch is | | | | advected through it but one can also test the | | | | advection schemes (Prather and Ultimate-Macho) by | | | | removing the ``key_agrif`` in the CPP keys. | | +-------------------+--------------------------------------------------------+------------------------------------+ | ``ISOMIP`` | Simple box configuration with an iceshelf with simple | `Hunter 2006`_ | | | geometry on top. | | | | The purpose of this test case is to evaluate the | | | | impact of various schemes and new development with | | | | iceshelf cavities. | | +-------------------+--------------------------------------------------------+------------------------------------+ | ``LOCK_EXCHANGE`` | Classical fluid dynamics experiment that has been | - `Haidvogel and Beckmann 1999`_ | | | adapted for testing advection schemes in ocean | - `Burchard and Bolding 2002`_ | | | circulation models. | - `Ilıcak 2012`_ | | | This experiment can in particular illustrate the | | | | impact of different choices of numerical schemes | | | | and/or subgrid closures on spurious interior mixing. | | +-------------------+--------------------------------------------------------+------------------------------------+ | ``OVERFLOW`` | Adapted from the non-rotating overflow configuration | - `Haidvogel and Beckmann 1999`_ | | | Illustrates the impact of different choices of | - `Ilıcak 2012`_ | | | numerical schemes and/or subgrid closures on spurious | | | | interior mixing close to bottom topography. | | +-------------------+--------------------------------------------------------+------------------------------------+ | ``VORTEX`` | Illustrates the propagation of an anticyclonic eddy | - `Debreu 2012`_ | | | over a Beta plan and flat bottom. | - `Penven 2006`_ | | | It is implemented here with an online refined | - `Spall and Holland 1991`_ | | | subdomain (thanks to AGRIF library) out of which the | | | | vortex propagates and serves as a benchmark to | | | | diagnose nesting errors. | | +-------------------+--------------------------------------------------------+------------------------------------+ | ``WAD`` | Set of simple closed basin geometries for testing the | | | | wetting and drying capabilities. | | | | Examples range from a closed channel with EW linear | | | | bottom slope to a parabolic EW channel with a Gaussian | | | | ridge. | | +-------------------+--------------------------------------------------------+------------------------------------+ ----------- Improvments ----------- Core components =============== Passive tracer TOP and biogeochemical PISCES components ------------------------------------------------------- - The passive tracers transport component was redesigned toward a modular structure and users can enable each module directly through logical flags in namelist_top (no more Fortran macros!). - TOP on-line user documentation is available on NEMO Trac platform (TOP-UserQuickGuide_) - TOP currently accounts for the following 5 modules: * ``CFC`` contains inorganic carbon tracers (CFC11/CFC12/SF6) * ``MY_TRC`` is a template for new modules (or external couplings) * ``AGE`` deals with water age tracking * ``C14`` as a radiocarbon passive tracer * ``PISCES`` the companion ecosystem model - A generalized infrastructure was developed to handle the prescription of either surface, coastal, or open boundaries conditions for each passive tracer. - PISCES model contains new developments and modifications: * Particulate Organic Carbon (POC) component comes with a new liability scheme, while the former Kriest parameterisation was superseded; * A complex iron chemistry scheme is now available, with an improved description of ligands for the marine iron cycle * Carbonate chemistry is based on MOCSY 2.0 routines (see `Orr and Epitalon 2015`_), by complying also with CMIP6 standards. * Ecosystem components can be optionally modelled by means of explicit nutrient quotas (PISCES-QUOTA) AGRIF (embedded zooms) ---------------------- - Now compatible with new sea ice component and z* coordinate - Extended ghost cells area to properly handle scheme with spatial order >2 - Added vertical refinement (beta) - Nesting tools for setup now up to date and working Adding of 3 Reference Configurations ------------------------------------ - ``AGRIF_DEMO``: 2 interlocked zooms (1:4 & 1:3) in the Nordic Seas + 1 zoom (1:1) at the equator - ``ORCA2_OFF_TRC``: a benchmark simulation environment to deal with inert carbon tracers dynamics by exploiting the offline coupling with NEMO. - ``SPITZ12``: regional configuration around the Svalbard archipelago. Misc. improvments ================= Physics ------- - Bulk formulae : move to aerobulk package (`Brodeau 2017`_), i.e. NCAR, COARE and ECMWF bulk (remove Clio and MFS bulk) - Fix for tracer conservation with split explicit free surface - Wetting and drying - iso-neutral mixing (iso and triad operators): add the Method of Stabilizing Correction (MSC) (more accurate calculation) + add a bilaplacian case - Lateral physics (LDF): scale aware setting of eddy viscosity and diffusivity - Wave coupling: large scale wave interaction process added in momentum and tracer equations - Remove the acceleration of convergence Numerics -------- - Added tidal self attraction and loading either read from a file or from usual "scalar" approximation - Vertical physics (ZDF) (modularity, share shear production calculation between TKE and GKS, removal of all ZDF CPP keys, removal of avmu & avmv, minimization of MPP comm.: ~15 removed) - Remove the split-explicit ZDF scheme for both TRA and DYN - Lateral physics (LDF): simplification of user interface and removal of CPP keys - Add a 4th order centered (CEN) and Flux Corrected Transport (FCT) tracer advection (using a 4th compact in the vertical) - Generalised lbc_lnk and lbc_nfd - Configuration interface completely rewritten (DOM module mainly suppressed, and in place: domain_cfg.nc file, or usr_def module) - Vorticity: 2 new energy conserving scheme: ENT with Coriolis defined at T-point (better for Flux form) and EET a variant of EEN where e3t is used instead of e3f (solved the issue with e3f specification but is not enstrophy conserving) - Wave coupling: coupled interface to external wave model Performances ------------ - MPI Message passing recoded to reduce number of MPI communications (suppression of redundant communications, gather multiple communications into one) - Back to standard dynamical allocation (remove of wrk_alloc/dealloc statements) - XIOS software for IOs version 2 as default, and optionally available for restarts - Unify mppini - Use non uniform jpi/jpj with dynamic allocation to avoid ghost rows/columns Environment ----------- - Revised structure of namelist_ref/_cfg and default reference values. - Reorganisation of SVN repository to be compliant with usual directory tree and facilitate building of NEMO executable - Improvements of reliability through automatic and regular testing of the changes made in repository .. _sea ice working group: http://forge.ipsl.jussieu.fr/nemo/wiki/WorkingGroups/SI3 .. _TOP-UserQuickGuide: http://forge.ipsl.jussieu.fr/nemo/wiki/WorkingGroups/top-dg/TOP-UserQuickGuide .. _Hunter 2006: http://staff.acecrc.org.au/~bkgalton/ISOMIP/test_cavities.pdf .. _Brodeau 2017: http://doi.org/10.1175/JPO-D-16-0169.1 .. _Haidvogel and Beckmann 1999: http://hdl.handle.net/10013/epic.11761 .. _Burchard and Bolding 2002: http://www.researchgate.net/publication/258128069_GETM_A_General_Estuarine_Transport_Model_Scientific_Documentation .. _Ilıcak 2012: http://doi.org/10.1016/j.ocemod.2011.10.003 .. _Debreu 2012: http://doi.org/10.1016/j.ocemod.2012.03.003 .. _Penven 2006: http://doi.org/10.1016/j.ocemod.2005.05.002 .. _Spall and Holland 1991: http://www.researchgate.net/publication/232101325_A_Nested_Primitive_Equation_Model_for_Oceanic_Applications .. _Holland 2012: http://doi.org/10.1175/JCLI-D-11-00078.1 .. _Lupkes 2012: http://doi.org/10.1029/2012JD017630 .. _Lupkes 2014: http://doi.org/10.1002/2014JD022418 .. _Kimmritz 2016: http://doi.org/10.1016/j.ocemod.2016.03.004 .. _Orr and Epitalon 2015: http://doi.org/10.5194/gmd-8-485-2015