Implementation Of The Novel Duo-Grid Within The GFDL FV3 Dynamical Core

The current edge handling of the cubed sphere grid introduces numerical errors in simulations and creates grid imprinting due to the discontinuity of the great­-circle grid lines between two adjacent tiles. In this work, we implement a new edge/corner handling method to greatly reduce the grid imprinting in GFDL's dynamical core FV3. First, we extend on the duo-grid method (Chen 2021) to support halo updates of staggered variables. Second, we implement a corner handling algorithm to fill the corner regions using a lagrangian polynomial interpolation. Results of idealized shallow water test cases show that the new halo update methods are able to reduce the numerical noise at the edges/corners and thus reduce the grid imprinting in the numerical solution. This improvement is especially useful for coarse-grid models such as climate models in which the cube edges are most noticeable.