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Commit be5a7b53 authored by Nicolas Martin's avatar Nicolas Martin :speech_balloon:
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../../../../src/OCE/CRS/README.rst
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**********************************
On line biogeochemistry coarsening
**********************************
.. todo::
.. contents::
:local:
Presentation
============
A capacity of coarsening physics to force a BGC model coupled to NEMO has been developed.
This capacity allow to run 'online' a BGC model coupled to OCE-SI3 with a lower resolution,
to reduce the CPU cost of the BGC model, while preserving the effective resolution of the dynamics.
A presentation is available [attachment:crs_wiki_1.1.pdf​ here], where the methodology is presented.
What is available and working for now in this version
=====================================================
[To be completed]
Description of the successful validation tests
==============================================
[To be completed]
What is not working yet with on line coarsening of biogeochemistry
==================================================================
[To be completed]
''should include precise explanation on MPI decomposition problems too''
How to set up and use on line biogeochemistry
=============================================
Extract the on line biogeochemistry branch
------------------------------------------
To get the appropriate source code with the on line coarsening of biogeochemistry feature:
.. code-block:: console
$ svn co https://forge.ipsl.jussieu.fr/nemo/browser/NEMO/branches/2018/dev_r5003_MERCATOR6_CRS
How to activate coarsening?
---------------------------
To activate the coarsening, ``key_crs`` should be added to list of CPP keys.
This key will only activate the coarsening of dynamics.
Some parameters are available in the namelist_cfg:
.. code-block:: fortran
! passive tracer coarsened online simulations
!-----------------------------------------------------------------------
nn_factx = 3 ! Reduction factor of x-direction
nn_facty = 3 ! Reduction factor of y-direction
nn_msh_crs = 0 ! create (=1) a mesh file or not (=0)
nn_crs_kz = 3 ! 0, volume-weighted MEAN of KZ
! 1, MAX of KZ
! 2, MIN of KZ
! 3, 10^(MEAN(LOG(KZ))
! 4, MEDIANE of KZ
ln_crs_wn = .false. ! wn coarsened (T) or computed using horizontal divergence ( F )
! !
ln_crs_top = .true. !coarsening online for the bio
/
- Only ``nn_factx = 3`` is available and the coarsening only works for grids with a T-pivot point for
the north-fold lateral boundary condition (ORCA025, ORCA12, ORCA36, ...).
- ``nn_msh_crs = 1`` will activate the generation of the coarsened grid meshmask.
- ``nn_crs_kz`` is the operator to coarsen the vertical mixing coefficient.
- ``ln_crs_wn``
- when ``key_vvl`` is activated, this logical has no effect;
the coarsened vertical velocities are computed using horizontal divergence.
- when ``key_vvl`` is not activated,
- coarsened vertical velocities are computed using horizontal divergence (``ln_crs_wn = .false.``)
- or coarsened vertical velocities are computed with an average operator (``ln_crs_wn = .true.``)
- ``ln_crs_top = .true.``: should be activated to run BCG model in coarsened space;
so only works when ``key_top`` is in the cpp list and eventually ``key_pisces`` or ``key_my_trc``.
Choice of operator to coarsene KZ
---------------------------------
A sensiblity test has been done with an Age tracer to compare the different operators.
The 3 and 4 options seems to provide the best results.
Some results can be found [xxx here]
Example of xml files to output coarsened variables with XIOS
------------------------------------------------------------
In the [attachment:iodef.xml iodef.xml] file, a "nemo" context is defined and
some variable defined in [attachment:file_def.xml file_def.xml] are writted on the ocean-dynamic grid.
To write variables on the coarsened grid, and in particular the passive tracers,
a "nemo_crs" context should be defined in [attachment:iodef.xml iodef.xml] and
the associated variable are listed in [attachment:file_crs_def.xml file_crs_def.xml ].
Passive tracers tracers initial conditions
------------------------------------------
When initial conditions are provided in NetCDF files, the field might be:
- on the coarsened grid
- or they can be on another grid and
interpolated `on-the-fly <http://forge.ipsl.jussieu.fr/nemo/wiki/Users/SetupNewConfiguration/Weight-creator>`_.
Example of namelist for PISCES :
.. code-block:: fortran
!-----------------------------------------------------------------------
&namtrc_dta ! Initialisation from data input file
!-----------------------------------------------------------------------
!
sn_trcdta(1) = 'DIC_REG1' , -12 , 'DIC' , .false. , .true. , 'yearly' , 'reshape_REG1toeORCA075_bilin.nc' , '' , ''
sn_trcdta(2) = 'ALK_REG1' , -12 , 'ALK' , .false. , .true. , 'yearly' , 'reshape_REG1toeORCA075_bilin.nc' , '' , ''
sn_trcdta(3) = 'O2_REG1' , -1 , 'O2' , .true. , .true. , 'yearly' , 'reshape_REG1toeORCA075_bilin.nc' , '' , ''
sn_trcdta(5) = 'PO4_REG1' , -1 , 'PO4' , .true. , .true. , 'yearly' , 'reshape_REG1toeORCA075_bilin.nc' , '' , ''
sn_trcdta(7) = 'Si_REG1' , -1 , 'Si' , .true. , .true. , 'yearly' , 'reshape_REG1toeORCA075_bilin.nc' , '' , ''
sn_trcdta(10) = 'DOC_REG1' , -12 , 'DOC' , .false. , .true. , 'yearly' , 'reshape_REG1toeORCA075_bilin.nc' , '' , ''
sn_trcdta(14) = 'Fe_REG1' , -12 , 'Fe' , .false. , .true. , 'yearly' , 'reshape_REG1toeORCA075_bilin.nc' , '' , ''
sn_trcdta(23) = 'NO3_REG1' , -1 , 'NO3' , .true. , .true. , 'yearly' , 'reshape_REG1toeORCA075_bilin.nc' , '' , ''
rn_trfac(1) = 1.0e-06 ! multiplicative factor
rn_trfac(2) = 1.0e-06 ! - - - -
rn_trfac(3) = 44.6e-06 ! - - - -
rn_trfac(5) = 122.0e-06 ! - - - -
rn_trfac(7) = 1.0e-06 ! - - - -
rn_trfac(10) = 1.0e-06 ! - - - -
rn_trfac(14) = 1.0e-06 ! - - - -
rn_trfac(23) = 7.6e-06 ! - - - -
cn_dir = './' ! root directory for the location of the data files
PISCES forcing files
--------------------
They might be on the coarsened grid.
Perspectives
============
For the future, a few options are on the table to implement coarsening for biogeochemistry in 4.0 and
future releases.
Those will be discussed in Autumn 2018
../../../../src/README.rst
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*******
Sources
*******
.. todo::
:file:`ICE`: |NEMO-ICE|
:file:`NST`: AGRIF for embedded zooms
:file:`OCE`: |NEMO-OCE|
:file:`TOP`: |NEMO-MBG|
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