Implementation of Atmospheric Models on Large Multi-Processor Surfaces

Abstract

In this paper we discuss an implementation of a spherical shallow water model and the U.K. Meteorological Office rainfall benchmark code on the Edinburgh Concurrent Supercomputer consisting of approximately 200 Inmos T800 transputers.

Multi-tasking in atmospheric models can be divided into two distinct problems:

• Dynamics — time evolution using an approximation to the Navier-Stokes and thermodynamics equations. An implementation of a simple two dimensional model, which is representative of the dynamics code used by the Meteorological Office, has been completed successfully. Linear speedup has been demonstrated for the model on a plane but the spherical version suffers scaling problems.

• Subgrid processes — a series of parameterisation schemes for the physical processes happening in the atmosphere. A naive implementation of the subgrid processes may lead to load balancing problems depending on the state of the atmosphere. This paper discusses this issue using the U.K. Meteorological Office‘s rainfall benchmark code as an example.