The OASIS Coupler Un site utilisant Réseau Cerfacs

Welcome to the OASIS homepage

The OASIS coupler is a software allowing synchronized exchanges of coupling information between numerical codes representing different components of the climate system. Current OASIS developers are CERFACS (Toulouse, France) and Centre National de la Recherche Scientifique (Paris, France)

Our last user survey, conducted in 2019, confirmed that OASIS3-MCT is used by at least 67 modelling groups around the world (see the Map) to assemble more than 80 different coupled systems.OASIS3-MCT

OASIS3-MCT, the version of the OASIS coupler interfaced with the Model Coupling Toolkit (MCT) from the Argonne National Laboratory, offers today a fully parallel implementation of coupling field regridding and exchange. Low-intrusiveness, portability and flexibility are OASIS3-MCT key design concepts as for all previous OASIS versions. OASIS3-MCT is a coupling library that needs to be linked to the component models, with the main function of interpolating and exchanging the coupling fields between these components.

OASIS3-MCT supports coupling of general two-dimensional fields. Unstructured grids and 3D grids are also supported using a one-dimension representation of the two- or three-dimensional structures. Thanks to MCT, all transformations, including regridding, are executed in parallel on the set of source or target component processes and all coupling exchanges are now executed in parallel directly between the components via Message Passing Interface (MPI). OASIS3-MCT also includes a mixed OpenMP/MPI version of the SCRIP library, allowing fully parallel calculation of the remapping weights in the initialisation phase. OASIS3-MCT also supports file I/O using NetCDF, allowing an easy switch between the coupled and forced modes; the implementation of this functionality is however non-parallel with the reading/writing of the fields performed by the master process only.

In spite of the significant changes in underlying implementation, usage of OASIS3-MCT in the component code has largely remained unchanged with respect to OASIS3.3. To communicate with another model, or to perform I/O actions, a component model needs to include a few specific calls to the OASIS3-MCT coupling library, using the same API as in OASIS3.3. The namcouple configuration file is also largely unchanged relative to OASIS3, although few options are either not used or not supported.

The scalability tests done with OASIS3-MCT at high number of cores and the fact that it supports unstructured grids allow us to conclude that this coupler offers today a fully parallel and efficient coupling solution answering the short- and mid-term needs of the European climate modelling community.

The current developments of OASIS3-MCT are funded in the framework of the EU IS-ENES3 - Infrastructure for the European Network for Earth System modelling - Phase 3 project (GA # 824084), the ESiWACE Center of Excellence (grant agreement no. 823988).

News

OASIS3-MCT_5.0 official release December 2021

15 December 2021

The last version of the coupler, OASIS3-MCT_5.0, is now available ! To get it, please follow instructions at OASIS3- MCT_5.0 comes with the following novelties: Python, C and C++ bindings A new load balancing analysis tool An environment to use either SCRIP, ESMF or XIOS to generate regridding weights and to analyse the quality of the regridding A new locally conservative remapping, to be used in particular for runoffs Extension of BLASNEW operation to support combination of coupling fields Improved and additional diagnostics in CHECKIN and CHECKOUT SCRIPR/CONSERV option for normalisation by the true area of the grid cells New options for global CONSERV Extension of oasis_get_intracomm to support multiple components Communication/exchange of simple scalars Update examples in oasis3-mct/examples directory Update to MCT 2.11 Update of compiling environment Migration from SVN to GIT for source management Migration of the OASIS3-MCT web site to Cerfacs, see the new site at Inclusion of the number of neighbours used in the remapping file name For SCRIPR/CONSERV, specification through the namcouple of North thresh and South thresh values, above which a Lambert projection is activated New NetCDF file format setting through the namcouple Overload oasis_def_var interface to support excluding the argument id_var_shape from the argument list Systematic tests of NetCDF returned error code Update oasis_abort to also write to unit 0 (stderr)- Different bugfixes Have fun with this new version of OASIS3-MCT and let us know about your difficulties (if any) and successes ! The OASIS3-MCT development teamRead more


SPOC on line on OASIS3-MCT, April 29 – May 12 2021

3 April 2021

A new Small Private Online Course (SPOC) on OASIS3-MCT is planned from April 29 - May 12 2021. Information about next SPOC session is available here. To register please fill the following form.  Read more


OASIS3-MCT now has new python, C and C++ interfaces.

3 March 2021

This development was funded through IS-ENES3. We are looking for beta testers!Read more

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