A numerical model for the hydrostatic equations of atmospheric motion using mimetic finite differences on spherical triangular grids.

Atmospheric general circulation models (AGCMs) are important tools for atmospheric research, climate modelling and numerical weather forecast.
At the base of an AGCM is the numerical solution of the partial differential equations governing the atmospheric motions. In recent years, quasi-uniform triangular grids on the sphere and mimetic finite-difference methods have gained popularity due to their suitability for the massively parallel computing and for achieving important conservation properties in the numerical model.
The ICON project, initiated in 2001 by the Max Planck Institute for Meteorology and the German Weather Service aims at developing new climate and weather forecasting models using spherical triangular grids.
As the first step, the horizontal grids and mimetic differencing operators were defined and a 2D shallow water model was developed by Bonaventura et al.
Since 2006, further development has been carried out to extend the 2D model a 3D hydrostatic atmospheric circulation model.

In this talk the 3D hydrostatic model will be described, and the properties of the numerical schemes used therein will be discussed.
The performance of the new model will be demonstrated by selected idealized experiments. The numerical results show that the new model can successfully simulate important mechanisms of the large-scale atmospheric dynamics.
Good numerical stability is observed in both deterministic tests and an idealized climate simulation. The new model thus forms a good basis for a full AGCM.