CONSEQUENCES OF USING THE SPLITTING METHOD FOR IMPLEMENTING PHYSICAL FORCINGS IN A SEMIIMPLICIT SEMI-LAGRANGIAN MODEL

Any comprehensive numerical model is composed of two parts: a dynamica l kernel solving for the fluid mechanical field equations and a physic al package to parameterize the ensemble effect of subgrid-scale proces ses upon the resolved scales of the model. There are a number of techn iques that can be used for combining the dynamics and physics contribu tions. One such method called ''splitting'' is used in some models bec ause of its simplicity and stability property. In this article the aut hors demonstrate that the splitting method may introduce serious trunc ation errors when used in conjunction with long time steps that are pe rmitted by semi-implicit and semi-Lagrangian marching algorithms.