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Joseph Mouallem

Computational Scientist / Research Software Engineer

Focus area:

                    • Dynamical Core development and algorithm implementation
                    • Multiple same level and telescoping grid nesting
                    • Duo-Grid and grid imprinting
                    • FV3 & SHiELD reproducibility and regression testing

Education and training:

                    • B.Sc. Mechanical Engineering, ULFG2, Lebanon
                    • M.Sc. Fluid mechanics, INSA Lyon, France
                    • Ph.D. Thermal and Fluids, University of Sao Paulo, Brazil
                    • Postdoctoral fellow and sessional lecturer, University of Waterloo, Canada

FV3 team

Contact Information:

Multiple same level and telescoping grid nesting:

Two-way multiple same-level and telescoping grid nesting capabilities are implemented in FV3 using GFDL’s Flexible Modeling System (FMS). A nest is an additional grid that zooms in over a region of interest to resolve small-scale structures necessary to get a better forecast of localized weather events such as severe storms and hurricanes. A telescoping nest is a nest within a nest. The nested grids run concurrently on different sets of processors and interact with their parent grids, thus providing more accurate results on both grids and reducing load imbalances between different processors. Nests could be used in global and regional domains. Starting from the latest FV3 public release of 2021, multiple same level and telescoping nests are now fully functional and available for use by the broader scientific community. This will drastically improve the overall forecast performance, bringing unprecedented accuracy, and open the door to numerous research possibilities for scientists and meteorologists alike. Article





A Duo-Grid in FV3:

The gnomonic cubed-sphere grid has excellent accuracy and uniformity, but the ‘kink’ in the coordinates at the cube edges in the halo region can leave an imprint of the cube in the solution, and requires special edge handling. To reduce grid imprinting, we implement the novel ‘Duo-Grid’ within FV3. The Duo-Grid remaps a cube face’s data from neighboring face from kinked to natural locations along great circle lines using 1D piecewise linear interpolation. A 2D interpolation algorithm is used to fill correct data at the eight corners of the cubed-sphere needed for FV3’s 2D advection scheme. The Duo-Grid was tested in idealized tests using the 2D shallow water solver and the 3D hydrostatic and non-hydrostatic solvers: Rossby-Haurwitz wave lasts longer and the southern hemisphere of the baroclinic wave test is noise free. We found that error norms are greatly reduced and grid imprinting is practically eliminated when employing the Duo-Grid. These results indicate that FV3’s robustness has improved. (Article under review)