Title: Improving Global Atmosphere Simulation in Earth System Models with Multiphysics Time Integration Methods

Speaker: Chris Vogl, Lawrence Livermore National Laboratory

Abstract: To reliably predict the frequency and severity of hurricanes, floods, droughts, and other weather-driven disasters, the efficient simulation of Earth system models is crucial. Such an endeavor poses a complex, multiphysics problem involving modeling, temporal and spatial discretization, and software implementation considerations. This work focuses on the time integration of the global atmosphere component, with an emphasis on the bulk atmosphere flow and cloud microphysics models. The nonhydrostatic bulk atmosphere flow models include acoustic waves that make the overall system numerically stiff. Our work has developed a model formulation that is amenable to an IMEX approach, where the acoustic waves are treated implicitly. The performance of both existing and customized additive Runge-Kutta methods is evaluated, with certain methods remaining stable at the hydrostatic timestep. Cloud microphysics models currently use first-order operator splitting to address the multiple timescales in the modeled physics, with at-best-first-order limiters required to keep quantities physical. Our work has shown that higher-order explicit, implicit, and IMEX Runge-Kutta methods with error-based adaptive timestep control are more efficient for the subset of cloud microphysics considered thus far.

Zoom: https://northwestern.zoom.us/j/99632064287

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