A Proposed Test Suite for Atmospheric Model Dynamical Cores

Tests of atmospheric General Circulation Models (GCMs) and, in particular, tests of their dynamical cores are important steps towards future model improvements. They reveal the influence of an individual model design on climate and weather simulations and indicate whether the circulation is described representatively by the numerical approach. Testing a global 3D atmospheric model is not straightforward. In the absence of non-trivial analytic solutions, the model evaluations most commonly rely on intuition, experience and model intercomparisons. In addition, GCM simulation statistics are typically compared to global reanalysis data while numerical weather forecasts are compared to local observations. Such approaches are not applicable to pure dynamical core assessments that isolate the dynamics package from the physical parameterizations. As modeling groups now move towards the next generation of dynamical cores a standard test suite for hydrostatic and non-hydrostatic dynamics packages on the sphere is highly desirable. In general, three different sets of equations are most commonly used in dynamical cores. These include the hydrostatic primitive equations as well as the non-hydrostatic shallow-atmosphere and non-hydrostatic deep-atmosphere equation sets. A test suite with increasing complexity for these types of dynamical cores is suggested.