Towards an advanced atmospheric chemistry-enabled ESM with dynamic land surface processes: Part I - Linking LPJ-GUESS (v4.0) with EMAC modelling system (v2.53)

Earth System Models (ESMs) are invaluable tools that have emerged from decades of research modelling the earth system. Central to this development has been the coupling of previously separate model types, such as ocean, atmospheric and vegetation models, to provide interactive feedbacks between these earth system components. Here we present the initial steps of coupling LPJ-GUESS, a dynamic global vegetation model, to EMAC, an atmospheric chemistry enabled atmosphere-ocean general circulation model. The LPJ-GUESS framework includes a comparatively detailed tree-individual based model of vegetation dynamics, a crop and managed-land scheme, a nitrogen cycle and a choice of fire models; and hence represents many important terrestrial biosphere processes and provides a wide range of prognostic trace gas emissions from vegetation, soil and fire. When development is complete, these trace gas emissions will form key inputs to the state-of-art atmospheric chemistry representations in EMAC allowing for bi-directional chemical interactions of the surface with the atmosphere. % At this point, the full model will be a complete ESM with a fully prognostic land surface and detailed atmospheric chemistry, and will become a powerful tool for investigating land-atmosphere interactions such as: the methane cycle and lifetime and the atmospheric chemistry of reduced carbon; fire effects and feedbacks; future nitrogen deposition rates and fertilisation scenarios; ozone damage to plants; and the contribution of biogenic volatile organic compounds to aerosol load and, via cloud condensation nuclei activation, to cloud formation (e.g., bioprecipitation cycles). Initial results show that the one-way, on-line coupling from EMAC to LPJ-GUESS gives a good description of the global vegetation patterns and reasonable agreement with a suite of remote sensing datasets.