A Comparison Between Cut-Cell Immersed Boundary Method and Hybrid Terrain-Following Coordinate in Steep Terrain

Application of numerical models to microscale environments requires treating complex terrain. Excessive terrain smoothing and strong numerical diffusion may allow stable integration but can significantly reduce the generation of flow structures present in observations. We detail a new microscale model employing a low-numerical-diffusion, semi-implicit, finite-volume scheme. Terrain can be accommodated through a cut-cell immersed boundary method (IBM) or a hybrid terrain-following (sigma) coordinate. Both methods are capable of incorporating steep terrain, and we show comparisons between the two for smooth analytic terrain elements and idealized cases exhibiting steep slope.