SORS/WomenInBSC: OASIS, a community coupler for climate modelling

The development of the OASIS coupler started in 1991 in CERFACS. At that time, it was used by two climate modelling groups in France to couple two different atmosphere models to one ocean model. 30 years later, i. e. in 2021, the latest version of the coupler, OASIS3-MCT₅. 0, was released. OASIS3-MCT is used today by about 60 modelling groups over the 5 continents to assemble more than 80 different coupled applications including ocean and atmosphere components but also sea ice, sea level, wave, ocean biogeochemistry, land, river routing and atmospheric chemistry models. The success of OASIS3-MCT is due to its key features in terms of performance, flexibility and low intrusiveness. And the developers’ constant care to provide detailed documentation, active user support and training also favoured its use by a large community. Its wide adoption is certainly also linked to its community governance. Since 2017 a formal Advisory Board, composed of 6 persons chosen among the main user groups, periodically reviews a development plan proposed by the developers based on the users’ feedbacks. In this presentation, we will first describe the different technical solutions and coupling frameworks that exist for code coupling in climate modelling and then briefly review the historical evolution of OASIS3-MCT. We will also present in more detail the recent developments and the plan of evolution foreseen in the framework of the COMPACT project funded by the French Agence Nationale de la Recherche under the TRACCS umbrella.