MPAS

"The Model for Prediction Across Scales (MPAS) is a collaborative project for developing atmosphere, ocean and other earth-system simulation components for use in climate, regional climate and weather studies. The primary development partners are the climate modeling group at Los Alamos National Laboratory (COSIM) and  the National Center for Atmospheric Research.  Both primary partners are responsible for the MPAS framework, operators and tools common to the applications; LANL has primary responsibility for the ocean and land ice models, and NCAR has primary responsibility for the atmospheric model.

The defining features of MPAS are the unstructured Voronoi meshes and C-grid discretization used as the basis for many of the model components.  The unstructured Voronoi meshes, formally Spherical Centriodal Voronoi Tesselations (SCVTs), allow for both quasi-uniform discretization of the sphere and local refinement.  The C-grid discretization, where the normal component of velocity on cell edges is prognosed, is especially well-suited for higher-resolution, mesoscale atmosphere and ocean simulations. The land ice model takes advantage of the SCVT-dual mesh, which is a triangular Delaunay tessellation appropriate for use with Finite-Element-based discretizations.

The current MPAS release is version 5.0. Please refer to each core for changes, and the github repository for source.

Atmosphere

The atmospheric component of MPAS, as with all MPAS components, uses an unstructured centroidal Voronoi mesh (grid, or tessellation) and C-grid staggering of the state variables as the basis for the horizontal discretization in the fluid-flow solver.  The unstructured variable resolution meshes can be generated having smoothly-varying mesh transitions (see the figure to the right); we believe that this capability will ameliorate many issues associated with the traditional mesh refinement strategy of one-way and two-way grid nesting where the transitions are abrupt.

The MPAS atmosphere consists of an atmospheric fluid-flow solver (the dynamical core) and a subset of the Advanced Research WRF (ARW) model atmospheric physics.  The MPAS atmospheric dynamical core solves the fully compressible nonhydrostatic equations of motion.  

The MPAS-Atmosphere solver can use a traditional terrain-following height coordinate, where the horizontal coordinate surfaces are terrain following at the lowest level and relax to a constant height surface at the rigid-lid upper boundary.  MPAS-A can also use a generalized hybrid coordinate that can be configured to relax to a constant height at an intermediate height below the lid and, additionally, preferentially filter the small wavelength topography features in the terrain-following component at higher levels.

The MPAS-Atmosphere solver uses a physics suite taken from the Advanced Research WRF model focusing on the physics configurations used in the ARW Nested Regional Climate Model application (WRF-NRCM) and the tropical cyclone prediction experiments.

Ocean

MPAS-O is designed for the simulation of the ocean system from time scales of months to millenia and spatial scales from sub 1 km to global circulations.

MPAS-O has demonstrated the ability to accurately reproduce mesoscale ocean activity with a local mesh refinement strategy.

In addition to faciliating the study of multiscale phenomena within the ocean system, MPAS-O is intended for the study of anthropogenic climate change as the ocean component of climate system models.

MPAS-O is presently developed and maintained by the ocean model development team within the COSIM project at Los Alamos National Laboratory.

Land Ice

MPAS-Land-Ice is being designed for large-scale, hi-resolution simulations of ice sheet dynamics, using Finite Element Methods on variable resolution meshes.

Two dynamical cores are currently under development for implementation within MPAS-Land-Ice. These include a 1st-order accurate approximation to the momentum balance equations, a prototype of which has been described by Perego et al. (2012) , and a "full" Stokes momentum balance, described in Leng et al. (2012).

Sea Ice

MPAS-Seaice is a new sea ice model that uses a Voronoi tesselation grid to allow variable resolution. It uses the same EVP rheology, horizontal variational operators and incremental remppaing for transport as CICE but adapted for arbitrarily shaped polygonal cells. It uses the same column package library as CICE for column physics (vertical thermodynamics, shortwave radiation, mechanical redistribution) and biogeochemistry."

http://mpas-dev.github.io/

https://github.com/MPAS-Dev/MPAS-Release

A multi-resolution approach to global ocean modeling - http://www.sciencedirect.com/science/article/pii/S1463500313000760