Variable-Resolution Global Atmospheric Simulations Bridging the Hydrostatic and Nonhydrostatic Regimes

Abstract:

The atmospheric component of the Model for Prediction Across Scales (MPAS-A) uses a fully compressible global nonhydrostatic solver that employs an unstructured variable-resolution Voronoi mesh to tile the sphere along with C-grid staggering. Preliminary tests with a full complement of atmospheric physics, using both variable-resolution and uniform meshes, indicate that the dynamical solver is robust. MPAS-A tests using variable-resolution meshes in the hydrostatic regime, where convection is parameterized, show no obvious problems appearing in or around the mesh transition zones for regional climate (years) and weather prediction (days to weeks) timescales. We are now testing meshes spanning hydrostatic (dx > 10 km) to nonhydrostatic (dx ~ few km) scales. These applications require a more sophisticated treatment of the atmospheric physics, particularly for the parameterization of deep convection. Several extensions of existing deep-convection physics schemes are being developed for MPAS-A applications bridging the hydrostatic and nonhydrostatic regimes. We will present results illustrating the current capabilities of MPAS-A for multi-scale atmospheric simulation in these regimes with the new deep convection schemes, focusing on explicitly simulated severe convective events over the US.