A Semi-Lagrangian and Semi-Implicit Numerical Integration Scheme for Multilevel Atmospheric Models

A complete multilevel atmospheric model of the primitive meteorological equations is integrated at high spatial resolution with a large time step of 90 min. Numerical stability is achieved by associating a semi-Lagrangian technique with the commonly used semi-implicit algorithm. A detailed description of the method is given and some results are presented. From these runs, it seems possible to infer that the time truncation errors remain relatively small. Because of the 1arger time step, the semi-Lagrangian technique contributes to a significant enhancement of the efficiency of the semi-implicit integration scheme.