Representation of topography by partial steps using the immersed boundary method in a vector vorticity equation model (VVM)

Abstract

In this study, representation of surface topography in the vector vorticity equation model (VVM) is updated with a partial step approach using the immersed boundary method. Compared with the full step approach, the partial step approach provides additional topography forcing to represent micro mountains while preserving the same grid structure through interpolating from adjacent grid points. It maintains the characteristics of dynamics and physics of VVM and improves the representation of gentle slope topography without increasing vertical resolution. This approach produces reasonable results on the simulation of classical mountain waves with coarse vertical resolution. Additional experiments are performed to verify our approach including density driven flow using a cold bubble and 3-D orographic precipitation over a ridge. The results show that vorticity fields in the partial step approach have a smoother response to the gentle slopes due to the improvement in the topography representation.