Abstract
Abstract. The model error in climate models depends on mesh resolution, among other factors. While global refinement of the computational mesh is often not feasible computationally, adaptive mesh refinement (AMR) can be an option for spatially localized features. Creating a climate model with AMR has been prohibitive so far. We use AMR in one single-model component, namely the tracer transport scheme. Particularly, we integrate AMR into the tracer transport module of the atmospheric model ECHAM6 and test our implementation in several idealized scenarios and in a realistic application scenario (dust transport). To achieve this goal, we modify the flux-form semi-Lagrangian (FFSL) transport scheme in ECHAM6 such that we can use it on adaptive meshes while retaining all important properties (such as mass conservation) of the original FFSL implementation. Our proposed AMR scheme is dimensionally split and ensures that high-resolution information is always propagated on (locally) highly resolved meshes. We utilize a data structure that can accommodate an adaptive Gaussian grid. We demonstrate that our AMR scheme improves both accuracy and efficiency compared to the original FFSL scheme. More importantly, our approach improves the representation of transport processes in ECHAM6 for coarse-resolution simulations. Hence, this paper suggests that we can overcome the overhead of developing a fully adaptive Earth system model by integrating AMR into single components while leaving data structures of the dynamical core untouched. This enables studies to retain well-tested and complex legacy code of existing models while still improving the accuracy of specific components without sacrificing efficiency.
Highlights
We propose a new approach toward adaptivity in climate models
Our method is different from the traditional adaptive mesh refinement (AMR) approach, which constructs a completely new climate model using AMR
Our approach overcomes the difficulty of integrating AMR into operational climate models
Summary
Adaptive mesh refinement (AMR) is an attractive alternative for global high-resolution climate models. We propose an alternative pathway towards adaptivity in climate models to address difficulties applying AMR in operational climate models ranging from properties of numerical schemes to the coupling between dynamical core and physics packages (Weller et al, 2010). St-Cyr et al (2008) adopted the FFSL scheme for shallow water equations on a block-structured AMR scheme that did not retain the large Courant number Another approach to deal with the interface between high- and low-resolution areas is to substitute the existing transport scheme by a mass conservative semi-Lagrangian scheme, which can handle irregular meshes. 3. We further demonstrate the idea of integrating AMR into more realistic single-component tracer transport of the existing ECHAM6 model in Sect.
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