The new TSMP2 coupled Earth system model

Abstract. The Terrestrial Systems Modeling Platform (TSMP, github.com/HPSCTerrSys/TSMP2) is a scale-consistent, highly modular, physics-based, massively parallel, and fully integrated coupled groundwater-vegetation-atmosphere modeling system for regional Earth system modeling. TSMP is composed of the atmospheric models ICON or COSMO, the land surface model Community Land Model (CLM), and the ParFlow subsurface-surface hydrological model, linked to each other through the OASIS3-MCT coupler. TSMP is used across a wide range of spatio-temporal scales, ranging from individual field plots, large eddy simulations to continental scale climate mode runs in a variety of applied research topics, such as water resources, land-atmosphere coupling, or climate change projections. In version 2, or short TSMP2, we have comprehensively modernized the coupled model system. One of the main changes from version 1 is the replacement of component models with their current state-of-the-art successors for the atmosphere and the land surface, and a modified coupling design to improve the mass and energy balances between the compartments. TSMP2 now relies entirely on a CMake build-system, which enhances the system’s portability across different computer infrastructures. Through a Git-based framework TSMP2 includes auxiliary tools for model setup, a workflow engine and case study simulation experiments to meet reproducibility, research software engineering, and FAIR data best practices. The TSMP2 coupled model system and all its components are free open-source software. Aside from a description of the TSMP2 infrastructure, we present the impact of coupling approaches between the compartments on model states in TSMP2, and outline our development strategy along with technical and performance aspects arising from the coupling.