FINAM is not a model (v1.0): a new Python-based model coupling framework

Abstract. In this study, we present a new coupling framework named FINAM (short for “FINAM is not a model”). FINAM is designed to facilitate the coupling of models that were developed as standalone tools in the first place and to enable seamless model extensions by wrapping existing models into components with well-specified interfaces. Although established coupling solutions such as Earth System Modeling Framework (ESMF), Ocean Atmosphere Sea Ice Soil (OASIS), or Yet Another Coupler (YAC) focus on highly parallel workflows, complex data processing, and regridding, FINAM prioritizes usability and flexibility, allowing users to focus on scientific exploration of coupling scenarios rather than technical complexities. FINAM emphasizes ease of use for end users to create, run, and modify model couplings, as well as for model developers to create and maintain components for their models. The framework is particularly suited for applications where rapid prototyping and flexible model extensions are desired. It is primarily targeting environmental models, including ecological models for animal populations, individual-based forest models, field-scale crop models, economical models, and hydrological models. Python's robust interoperability features further enhance FINAM's capabilities, allowing us to wrap and use models written in various programming languages like Fortran, C, C++, Rust, and others. This paper describes the main principles and modules of FINAM and presents example workflows to demonstrate its features. These examples range from simple toy models to well-established models like OpenGeoSys and Bodium covering features like bidirectional dependencies, complex model coupling, and spatiotemporal regridding.