An external view of the Met Office building at night.

GungHo - a next generation atmospheric dynamical core for weather and climate modelling

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 implemented a five-year program (2011-2016), to research, design and develop a new dynamical core.

Some of the key aspects

  • 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. Although no alternative grid is without its own issues, the cubed-sphere grid has a number of advantages over other choices and is currently the preferred option.
  • 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 requires replacement of the current pointwise semi-Lagrangian scheme with a flux-form conserving advection scheme, be that a semi-Lagrangian one or an Eulerian one, while preserving the good phase properties of the current scheme.
  • The spatial discretization. A mixed finite-element spatial discretization, as distinct from the current finite-difference/finite-volume approach, permits the use of alternative grid structures without some of the disadvantages that those grids incur with a finite-difference discretization.
  • A new modelling infrastructure has been designed to permit the efficient implementation of these changes. This is called LFRic after Lewis Fry Richardson (see Related pages).

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.