1. Study of different techniques for physics-dynamics interface (hydrostatic dynamics)
Any modern numerical model is composed of two parts : a dynamical part solving mechanical field equations and a physical parameterisation package to account for the ensemble effect of subgrid-scale processes upon the resolved scales of the model. There are several techniques that can be used for combining the dynamics and physics contributions in a semi-implicit model. One such method, called time-splitting, is used in some models because of its simplicity and stability property. In this context time-splitting consists in solving the dynamical part of the model equations with semi-implicit scheme, without the physical contribution to tendencies, and then adding contributions from physics as a second, correction step. The more traditional alternative, used also in ALADIN, is to add physical tendencies together with nonlinear tendencies as part of the explicit component of the semi-implicit scheme. Within this research topic different techniques for the application of the contributions from the physical parameterisations are being tested for the hydrostatic version of ALADIN.
2. Study of the treatment of diabatic terms (non-hydrostatic dynamics)
A number of empirically derived approximations to the treatment of the diabatic heating are being tested. There are labelled quasi-anelastic and quasi-hydrostatic approximations to the diabatic heating because they produce results analogous to those obtained with the correspondingly approximated dynamical models, when using short timesteps.