Dynamical core model intercomparison project: Tracer transport test cases

Three-dimensional advection tests are required to assess the ability of transport schemes of dynamical cores to model tracer transport on the sphere accurately. A set of three tracer-transport test cases for three-dimensional flow is presented. The tests focus on the physical and numerical issues that are relevant to three-dimensional tracer transport: positivity preservation, inter-tracer correlations, horizontal-vertical coupling, order of accuracy and choice of vertical coordinate. The first test is a three-dimensional deformational flow. The second test is a Hadley-like global circulation. The final test is a solid-body rotation test in the presence of rapidly varying orography. A variety of assessment metrics, such as error norms, convergence rates and mixing diagnostics, are used. The tests are designed for easy implementation within existing and developing dynamical cores and have been a cornerstone of the 2012 Dynamical Core Model Intercomparison Project (DCMIP). Example results are shown using the transport schemes in two dynamical cores: the Community Atmosphere Model finite-volume dynamical core (CAM-FV) and the cubed-sphere finite-volume MCore dynamical core.