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Interpolation Semi-Lagrangian Element-Based Transport (Islet) with p-refinement for extremely high-resolution tracer transport

Presentation Date
Tuesday, December 14, 2021 at 8:10am - Tuesday, December 14, 2021 at 8:14am



Two new methods together increase the computational efficiency of the E3SM Atmosphere Model (EAM) version 2 (E3SMv2) over version 1 by a factor of approximately two in multiple configurations and on multiple platforms: first, high-order, property-preserving, remap-form, Interpolation Semi-Lagrangian (ISL) tracer transport; second, high-order, property-preserving physics-dynamics-grid remap. We describe extensions to these algorithms that together produce an extremely high-resolution tracer transport method coupled to a standard dynamics grid. In this method, the atmosphere has three point grids that share one element grid: the finite-volume physics grid with parameter nf, the dynamics grid with Gauss-Lobatto-Legendre (GLL) basis parameter npv, and the tracer transport grid with parameter npt. We set npv=4, as in all E3SM configurations, then increase nf and npt from their E3SMv2 values of, respectively, 2 and 4. Importantly for performance, the model time steps and number of communication rounds per unit of simulated time do not change. The GLL natural interpolant does not provide a stable Interpolation Semi-Lagrangian method for npt ≥ 4. Thus, we describe new element-based, stabilized, high-order basis sets for the ISL method that are constructed to satisfy a stability criterion. We derive basis sets up to order of accuracy 9. Then we describe the property-preserving remap methods we use to transfer fields among the three point grids. Finally, we show results for a number of solution quality diagnostics on standard validation problems.

Funding Program Area(s)