A Nonlinear Vertical Mode Initialization Scheme for a Limited Area Prediction Model

Abstract

A vertical mode initialization scheme for a limited area baroclinic primitive equations prediction model is proposed. The scheme is based on the approach employed in nonlinear normal mode initialization but incorporates a substantial simplification: the linearized equations with respect to which the model modes are defined admit only gravity modes. A variational constraint on induced increments is possible within the scheme. In the framework of the Australian Region Primitive Equations model the approach has been found to effectively control spurious model oscillations. A number of filtering conditions are considered and tested within the overall approach of this vertical mode scheme.