Using a Sponge Layer as a Boundary Treatment for Open-ocean Boundaries in a Barotropic Coastal Ocean Model

In numerical computations of coastal circulation, a computational domain is truncated at locations aways from areas of interest and appropriate boundary conditions are prescribed at these locations. On the open ocean boundaries, it is important that a boundary treatment accurately introduce the desired information and minimize reflections of any outgoing waves. One of the most widely-used open-ocean boundary conditions simply forces a surface water level and is to a certain degree adequate for the former purpose. Unfortunately, this boundary condition is not a non-reflecting boundaries and could introduce detrimental effects. In this talk, we investigate the use of a sponge layer as a treatment for open-ocean boundaries in the context of (massively-parallel) continuous finite-element-based shallow water flow model. The sponge layer treatment yields a satisfactory results in a set of numerical tests and improve the robustness of the numerical model.