A New Model Using a Cut-Cell Immersed Boundary Method in Complex 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 is accommodated through a cut-cell immersed boundary method (IBM) capable of incorporating steep terrain. We show comparisons between the IBM implementation and a terrain-following coordinate for smooth analytic terrain elements, and compare with idealized cases exhibiting steep slope.