A regional capability for MPAS-Atmosphere

The atmospheric component of the Model for Prediction Across Scales (MPAS-Atmosphere) was originally designed as a global model employing an unstructured Voronoi (nominally hexagonal) horizontal mesh. It was developed, as part of a joint project with the Department of Energy’s Los Alamos National Laboratory, to circumvent the pole problems inherent in the global configuration of the Weather Research and Forecasting (WRF) model which used a latitude longitude mesh, and to provide for smoothly varying refinement in contrast to the step refinement inherent in WRF’s grid-nesting strategy. We have recently developed and released to the community a regional capability in MPAS-A. With this new capability we provide a consistent regional solver to complement global MPAS-A. Given that the global and regional configurations are contained within a single implementation, both capabilities of MPAS-A are positioned to take advantage of next-generation computer architectures, e.g. GPUs and other accelerators. MPAS-A is being implemented as a dynamical core in NCAR’s Community Earth System Model (CESM), and this will provide a regional capability within CESM that will be available to the community. Finally, we expect that the regional capability within MPAS-A will perform better than nesting in WRF because its smoothly varying mesh can be configured to reduce lateral boundary condition errors relative to those inherent in any WRF configurations.

Left: A variable-resolution MPAS-A regional mesh centered over North America; the mesh is coarse so that the cells are visible, and much finer meshes are used in applications. Right: Radar reflectivity (dBZ) from 24h squall-line forecasts valid on 00 UTC 27 April 2017 with global and regional MPAS-A along with the observed reflectivity.
Figure: Left: A variable-resolution MPAS-A regional mesh centered over North America; the mesh is coarse so that the cells are visible, and much finer meshes are used in applications. Right: Radar reflectivity (dBZ) from 24h squall-line forecasts valid on 00 UTC 27 April 2017 with global and regional MPAS-A along with the observed reflectivity.