Martin van Gijzen : September 11, 2003

Two-level parallelism in a stream-function model for global ocean circulation.

Abstract

In ocean modelling, it is customary to split the ocean flow into a 2D depth-averaged part, and the 3D deviations from it. The 2D part can be formulated in terms of a stream-function, which simplifies the governing partial differential equations.

However, in this formulation additional contour integral conditions around continents are needed. These conditions destroy the structure in the matrix that results after discretisation and pose difficulties to parallelisation.

We will discuss how the continent boundary conditions can be treated in a parallel setting by taking into account the land points in the calculations. Our iterative solution technique combines loop-level parallelism with a domain decomposition method. We will illustrate our approach with a simple but realistic model using field data, and we will analyse the parallel performance on basis of tests on the IBM SP3 and on a cluster of PC's.