About the MODAVE Research Project

The MODAVE project is aimed at providing Mosaic, or composite, grid support to applications such as the Climate Data Analysis Tools to enable them to correctly interpret and visualize data on the cubed-sphere and other grids exhibiting complex folding patterns.

Composite meshes are becoming more prevalent in scientific applications. These grids cannot be simply described as either unstructured or structured, because they in fact share features of both unstructured and structured grids. While structured meshes are such that each cell has the same number of neighbors, composite meshes violate this condition at specific locations. Examples of such composite meshes on the sphere are the Calhoun-Helzel-LeVeque mesh [D. Calhoun, C. Helzel, R. J. LeVeque. “Logically rectangular grids and finite volume methods for PDEs in circular and spherical domains,” SIAM Review Vol. 50, Issue 4, pp. 723-752 (2008)] and the tripolar grid used by some ocean models [R J Murray. "Explicit generation of orthogonal grids in ocean models," J. Comput. Phys. Vol 126, No 2, pp. 251-273], which are shown here.

Note that the cell on the equator of this Calhoun-Helzel-LeVeque grid has only 6 neighbors, whereas two-dimensional structured grids would have 8 neighbors (north, north-west, west, south-west, south, south-east, east, and north-east).

Both the below right tripolar grid and the above right CHL grid have a topological folding either along the equator or across the north pole.

The cubed-sphere grids, above left, are another example of composite grids with complex folding patterns. Exploiting the connectivity between cubed-sphere tiles is essential in order to correctly visualize cell-centered data.