JIGSAW-GEO (1.0): Locally Orthogonal Staggered Unstructured Grid Generation for General Circulation Modelling on the Sphere

• Published in: Geoscientific Model Development 2017-06, Vol.10 (6), p.2117-2140
• Main Author: Engwirda, Darren
• Format: Article
• Language: English
• Subjects: Adaptation; Algorithms; Atmospheric circulation; Atmospheric models; Climatology; Computer applications; Computer simulation; Constraint modelling; Construction methods; Decomposition; Evaluation; Finite element method; General circulation; General circulation models; Geometric constraints; Grading; Grid generation (mathematics); High resolution; Investigations; Marine parks; Mathematical analysis; Mathematical models; Mesh generation; Meteorology And Climatology; Methods; Modelling; Numerical Analysis; Numerical weather forecasting; Numerical weather prediction; Ocean models; Optimization; Quality; Resolution; Scale (ratio); Simulation; Unstructured grids (mathematics); Voronoi graphs; Weather forecasting
• ISSN: 1991-959X; 1991-9603; 1991-962X; 1991-9603; 1991-962X
• DOI: 10.5194/gmd-10-2117-2017

An algorithm for the generation of non-uniform, locally orthogonal staggered unstructured spheroidal grids is described. This technique is designed to generate very high-quality staggered VoronoiDelaunay meshes appropriate for general circulation modelling on the sphere, including applications to atmospheric simulation, ocean-modelling and numerical weather prediction. Using a recently developed Frontal-Delaunay refinement technique, a method for the construction of high-quality unstructured spheroidal Delaunay triangulations is introduced. A locally orthogonal polygonal grid, derived from the associated Voronoi diagram, is computed as the staggered dual. It is shown that use of the Frontal-Delaunay refinement technique allows for the generation of very high-quality unstructured triangulations, satisfying a priori bounds on element size and shape. Grid quality is further improved through the application of hill-climbing-type optimisation techniques. Overall, the algorithm is shown to produce grids with very high element quality and smooth grading characteristics, while imposing relatively low computational expense. A selection of uniform and non-uniform spheroidal grids appropriate for high-resolution, multi-scale general circulation modelling are presented. These grids are shown to satisfy the geometric constraints associated with contemporary unstructured C-grid-type finite-volume models, including the Model for Prediction Across Scales (MPAS-O). The use of user-defined mesh-spacing functions to generate smoothly graded, non-uniform grids for multi-resolution-type studies is discussed in detail.