This paper describes LFRic: the new weather and climate modelling
system being developed by the UK Met Office to replace the existing
Unified Model in preparation for exascale computing in the 2020s.
LFRic uses the GungHo dynamical core and runs on a semi-structured
cubed-sphere mesh. The design of the supporting infrastructure follows
object-oriented principles to facilitate modularity and the use of
external libraries where possible. In particular, a `separation of concerns'
between the science code and parallel code is imposed to promote
performance portability. An application called PSyclone, developed at the
STFC Hartree centre, can generate the parallel code enabling deployment of
a single source science code onto different machine architectures.
This paper provides an overview of the scientific requirement, the design
of the software infrastructure, and examples of PSyclone usage. Preliminary
performance results show strong scaling and an indication that hybrid
MPI/OpenMP performs better than pure MPI