Enlarge

The challenge is to achieve the required scalability while retaining the accuracy of the current dynamical core. Designing such a core, therefore, requires a mix of numerical analysis, geophysical fluid dynamics and computational science. To bring this expertise together, the Met Office, NERC and STFC are proposing a five-year program, starting in 2010, to research, design and develop the new dynamical core.

Some of the key aspects that require research:

• The grid that the model is discretized on: removal of the singularity in the current latitude-longitude grid is considered essential to achieving good scalability, yet there is currently no alternative that does not have a significant disadvantage of one kind or another.
• Highly scalable implicit solvers: there are significant advantages to retaining a two-time-level implicit temporal discretization, but this is only viable if the resulting implicit system, with its global connectivity, can be efficiently solved on hundreds of thousands of processors.
• Inherently conservative advection schemes: only dry mass is inherently conserved by the current dynamical core, yet there is a growing need to exactly conserve a number of tracer fields, as well as possibly such quantities as energy and angular momentum. This will require replacement of the current pointwise semi-Lagrangian scheme with a flux-form conserving advection scheme, be that a semi-Lagrangian one (e.g. SLICE) or an Eulerian one, while preserving the good phase properties of the current scheme.
• The spatial discretization: spatial discretization, alternative to the current finite-difference/finite-volume approach, may permit the use of alternative grid structures without some of the disadvantages that those grids incur with a finite-difference discretization.

A further important element is how each of the above interacts with, and depends upon, each other.

Key aims

• To design and develop a dynamical core that scales well on hundreds of thousands of processors while maintaining at least the accuracy and robustness of its contemporary dynamical core.
• To improve the conservation properties of the dynamical core.