The MESSy DWARF (based on MESSy v2.55.2)

Abstract. Adaptation of Earth system model (ESM) codes to modern computing architectures is challenging, as ESMs consist of a multitude of different components. Historically grown and developed by scientists rather than software engineers, the codes of the individual components are often interwoven, making the optimisation of the ESMs on modern computing architectures rather challenging, if not impossible. Thus, in the last years the codes became increasingly modularised and with that, different components are disentangled from each other. This helps porting the code section by section to modern computing architectures, e.g. to GPUs. Since more than 20 years, the modularisation is the fundamental concept of the Modular Earth Submodel System (MESSy). It is an integrated framework providing data structures and methods to build comprehensive ESMs from individual components. Each component is coded as an individual, so-called submodel. Components in that meaning can be individual process implementations, e.g. a cloud microphysical scheme, a convection scheme, dry deposition of tracer gases, or diagnostic tools, e.g. output on a profile station location, on (flight) trajectories, or on satellite orbits. Each submodel is connected via the MESSy infrastructure with all other components, together forming a comprehensive model system. MESSy was mainly developed for research in atmospheric chemistry, and so far it is always connected to a dynamical (climate or weather forecast) model, what we call basemodel. The basemodel is a development outside the MESSy framework. However, running a full dynamical model for technical tests when porting only one submodel is a tedious task and unnecessarily resource consuming. Especially, as for such technical tests a simple grid, parallelisation scheme, and time control are sufficient in many cases. Therefore, we developed the so-called MESSy DWARF, a simplified basemodel based on the MESSy infrastructure. We implemented the definition of a very simple grid, parallelisation scheme, and a time control to replace a fully-fledged base model. The MESSy DWARF can not only be used for technical applications, such as porting individual component implementations to GPUs, but it is also applicable for scientific purposes running simplified models (with only a selection of submodels), e.g., a chemical box model for the analysis of chamber experiments. In this paper we introduce the technical setup of the MESSy DWARF and show four (two technical, two scientific) example applications.