Transparent Boundary Conditions for the Shallow-Water Equations: Testing in a Nested Environment

Most operational numerical weather prediction models update their lateral boundaries via the Davies–Kållberg relaxation scheme. In this paper some potential alternatives that take transparency and well-posedness into consideration are derived and tested for the shallow-water equations. The accuracy of the new boundary strategies is displayed by integrating the shallow-water equations in a nested environment using real meteorological data. In these tests they are seen to be superior to the traditional relaxation boundary strategy.