00-intro.md

Intro

MPAS stands for Model for Prediction Across Scales. It is a "collaborative project" for building earth system model components that can be run at multiple scales. MPAS-A is the atmospheric component of MPAS. Often, at least in our circles, "MPAS" means the standalone version of MPAS-A. But it's important to remember that there are other MPAS component models¹, and MPAS-A has also been used in larger modeling systems, e.g. as the atmosphere component² or as the dynamical core only³.

History

https://doi.org/10.1175/MWR-D-10-05056.1 https://doi.org/10.1175/MWR-D-11-00215.1

Meshes

:alt: Global variable-resolution mesh
:width: 300px

What makes MPAS special is its use of unstructured Voronoi meshes on the sphere (SCVT), including C-grid staggering.

Horizontal velocity components are defined normal to the cell edges, and vertical velocity is defined at cell vertices.

There is a primal mesh (usually mostly hexagons, as above) that most variables are defined on, and a dual mesh made up of triangles formed by connecting the primal mesh cell centers. In the model outputs, vorticity is an example of a dual mesh variable.

Links

• MPAS project website: https://mpas-dev.github.io/
• MPAS-A landing page: https://www2.mmm.ucar.edu/projects/mpas/site/index.html
• MPAS mesh spec document: https://mpas-dev.github.io/files/documents/MPAS-MeshSpec.pdf
• MPAS-A tech note (in development): https://www2.mmm.ucar.edu/projects/mpas/mpas_website_linked_files/MPAS-A_tech_note.pdf
• HTML user guide quick start: https://www2.mmm.ucar.edu/projects/mpas/site/documentation/users_guide/quick_start.html
• PDF user guide: https://www2.mmm.ucar.edu/projects/mpas/mpas_atmosphere_users_guide_8.3.0.pdf
• MPAS official virtual tutorial material: https://www2.mmm.ucar.edu/projects/mpas/tutorial/Virtual2025/
• WRF/MPAS workshop talks: https://www.mmm.ucar.edu/events/133265/agenda (2025)

Footnotes

1. including ocean and sea-ice, used in E3SM ↩

2. e.g. MPAS-CMAQ, MPAS-Hydro (in development), NOAA GSL MPAS for smoke and dust, MPAS-GOCART ↩

3. e.g. in CESM, part of the StormSPEED CSEM/CAM dynamical cores comparison project, and planned for UFS as an alternative to FV3 ↩