Discontinuous Galerkin transport on the spherical Yin-Yang overset mesh

A discontinuous Galerkin (DG) transport scheme is presented that employs the Yin-Yang grid on the sphere. The Yin-Yang grid is a quasi-uniform overset mesh comprising two notched latitude-longitude meshes placed at right angles to each other. Surface fluxes of conserved scalars are obtained at the overset boundaries by interpolation from the interior of the elements on the complimentary grid, using high-order polynomial interpolation intrinsic to the DG technique. A series of standard tests are applied to evaluate its performance, revealing it to be robust and its accuracy to be competitive with other global advection schemes at equivalent resolutions. Under p-type grid refinement, the DG Yin-Yang method exhibits spectral error convergence for smooth initial conditions and third-order geometric convergence for C1 continuous functions. In comparison with finite-volume implementations of the Yin-Yang mesh, the DG implementation is less complex, as it does not require a wide halo region of elements for accurate boundary value interpolation. With respect to DG cubed-sphere implementations, the Yin-Yang grid exhibits similar accuracy and appears to be a viable alternative suitable for global advective transport. A variant called the Yin-Yang polar (YY-P) mesh is also examined and is shown to have properties similar to the original Yin-Yang mesh while performing better on tests with strictly zonal flow.