Design of a dynamical core based on the nonhydrostatic unified system of equations
Seminar Room 1, Newton Institute
In this talk, we present the design of a dry dynamical core based on the nonhydrostatic “unified system” of equations. The unified system filters vertically propagating acoustic waves. The dynamical core predicts the potential temperature and horizontal momentum. It uses the predicted potential temperature to determine the quasi-hydrostatic components of the Exner pressure and density. The continuity equation is diagnostic (and used to determine vertical mass flux) because the time derivative of the quasi-hydrostatic density is obtained from the predicted potential temperature. The nonhydrostatic component of the Exner pressure is obtained from an elliptic equation. The main focus of this paper is on the integration procedure of this unique dynamical core. Height is used as the vertical coordinate, and the equations are vertically discretized on a Lorenz-type grid. Cartesian horizontal coordinates are used along with an Arakawa C-grid in the planar version of the dynamical core. The global version of the dynamical core is based on the vorticity and divergence predicting Z-grid formulation. The performance of the model in simulating a wide range of dynamical scales in the planar and global domains is demonstrated through idealized extratropical cyclogenesis simulations, and warm and cold bubble test cases.