OASIS4 - a coupling software for next generation earth system modelling

In this article we present a new version of the Ocean Atmosphere Sea Ice Soil coupling software (OASIS4). With this new fully parallel OASIS4 coupler we target the needs of Earth system modelling in its full com- plexity. The primary focus of this article is to describe the design of the OASIS4 software and how the coupling soft- ware drives the whole coupled model system ensuring the synchronization of the different component models. The ap- plication programmer interface (API) manages the coupling exchanges between arbitrary climate component models, as well as the input and output from and to files of each indivi- dual component. The OASIS4 Transformer instance per- forms the parallel interpolation and transfer of the coupling data between source and target model components. As a new core technology for the software, the fully parallel search algorithm of OASIS4 is described in detail. First bench- mark results are discussed with simple test configurations to demonstrate the efficiency and scalability of the software when applied to Earth system model components. Typically the compute time needed to perform the search is in the order of a few seconds and is only weakly dependant on the grid size. observe a rapid and continuous increase of activity in global coupled modelling as additional computer resources have be- come available. Climate models can be considered as multi- disciplinary or multi-physics software tools to simulate the interactions of the atmosphere, oceans, land surface, sea ice and other components of the climate system. They are used for a variety of purposes from studies of the dynamics of the weather and climate system to projections of future climate. These models can range from relatively simple to quite com- plex, that is from zero-dimensional models and Earth-system Models of Intermediate Complexity (EMIC) to complex 3-D Global Climate Models (GCM) and Regional Climate Mo-