Abstract
A non-normal-mode initialization scheme, that is, an initialization scheme that does not require an explicit computation of the normal modes of the linearized equations, is considered. Such a scheme is applied to a shallow-water limited-area model on a stereographic projection, for which the computation of the normal modes is too expensive due to nonseparability. The numerical tests for the initialization concern the problem of relaxation toward constant or time-variable boundary conditions, the consistency of the initialization scheme with the semi-implicit scheme of the model, and the effect of orography. The scheme is then applied to a similar limited-area model but with a stretched grid, whose domain is greatly extended in latitude with the regular grid domain being located at its center. Numerical tests are performed for the initialization of this model to assess the impact of using a more comprehensive linearization including most of the β terms. Certain diagnostic quantities, used to test the convergence of the initialization scheme, are computed during the simulations.
