https://doi.org/10.5194/gmd-2019-329 Preprint. Discussion started: 28 November 2019 c Author(s) 2019. CC BY 4.0 License. CLASSIC v1.0: the open-source community successor to the Canadian Land Surface Scheme (CLASS) and the Canadian Terrestrial Ecosystem Model (CTEM) - Part 1: Model framework and site-level performance Joe R. Melton1, Vivek K. Arora2, Eduard Wisernig-Cojoc1, Christian Seiler1, Matthew Fortier1, Ed Chan3, and Lina Teckentrup4 1Climate Research Division, Environment and Climate Change Canada, Victoria, B.C., Canada 2Canadian Centre for Climate Modelling and Analysis, Environment and Climate Change Canada, Victoria, B.C., Canada 3Climate Research Division, Environment and Climate Change Canada, Toronto, Ont., Canada 4Max Planck Institute for Meteorology, 20146 Hamburg, Germany Correspondence: Joe Melton (
[email protected]) Abstract. Recent reports by the Global Carbon Project highlight large uncertainties around land surface processes such as land use change, strength of CO2 fertilization, nutrient limitation and supply, and response to variability in climate. Process-based land surface models are well-suited to address these complex and emerging global change problems, but will require extensive de- 5 velopment and evaluation. The coupled Canadian Land Surface Scheme and Canadian Terrestrial Ecosystem Model (CLASS- CTEM) framework has been under continuous development by Environment and Climate Change Canada since 1987. As the open-source model of code development has revolutionized the software industry, scientific software is experiencing a simi- lar evolution. Given the scale of the challenge facing land surface modellers, and the benefits of open-source, or community model, development, we have transitioned CLASS-CTEM from an internally developed model to an open-source community 10 model, which we call the Canadian Land Surface Scheme including Biogeochemical Cycles (CLASSIC) v.