PortUrb: a performance portable, high-order, moist atmospheric large eddy simulation model with variable-friction immersed boundaries

Abstract. This paper introduces “portUrb”: a moist, compressible, non-hydrostatic atmospheric Large Eddy Simulation model that aims for portability, performance, accuracy, simplicity, readability, robustness, extensibility, and ensemble capabilities. Additionally, there is an emphasis on free-slip immersed boundaries with surface friction to account for urban building geometries. Coded in portable C++ with high-order Weighted Essentially Non-Oscillatory (WENO) numerics, this study investigates the behavior of portUrb under atmospheric boundary layer, supercell, and urban scenarios. PortUrb matches experimental observations and model comparisons closely under several test cases in mean and turbulent statistics. It also provides physically realizable flow through complex building geometries from a portion of Manhattan without needing to pre-process or smooth the building geometry.