Abstract

The Model for Prediction Across Scales (MPAS) is comprised of geophysical fluid flow solvers using horizontally-unstructured spherical centriodal Voronoi meshes and a C-grid staggering of the prognostic variables. We have constructed a global atmospheric model for these meshes that solves the fully compressible nonhydrostatic equations using a finite-volume formulation coupled with a split-explicit time integration technique to handle acoustic modes. The Voronoi meshes are unstructured grids that permit variable horizontal resolution, and we plan to make use of variable-resolution meshes in our weather and regional climate applications. Towards this end, we have begun testing the robustness of variable-resolution global mesh simulations using both idealized test cases (baroclinic waves) and full NWP forecasts. Preliminary results for hydrostatic-scale tests (dx > 10 km) indicate that flow features are appropriately resolved relative to the local resolution if the mesh t ransition zones provide a smooth transition from coarser to finer resolution regions and if model filters are appropriately scaled by the local mesh spacing. We will present these results and discuss their implications for variable-resolution mesh configurations and for the end applications.