Ocean general circulation models for parallel architectures
- Los Alamos National Laboratory, NM (United States)
The authors report continuing work in developing ocean general circulation models for parallel architectures. In earlier work, they began with the widely-used Bryan-Cox ocean model, but reformulated the barotropic equations (which describe the vertically integrated flow) to solve for the surface-pressure field rather than the volume-transport streamfunction as in the original model. This had the advantage of being more easily parallelized and allowed for a more realistic representation of coastal and bottom topography. Both streamfunction and surface-pressure formulations use a rigid-lid approximation to eliminate fast surface waves. They have now replaced the rigid-lid with a free surface, and solve the barotropic equations implicitly to overcome the timestep restriction associated with the fast waves. This method has several advantages, including: (1) a better physical representation of the barotropic mode, and (2) a better-conditioned operator matrix, which leads to much faster convergence in the conjugate-gradient solver. They have also extended the model to allow use of arbitrary orthogonal curvilinear coordinates for the horizontal grid. The original model uses a standard polar grid that has a singularity at each pole, making it difficult to include the Arctic basin, which plays an important role in global ocean circulation. They can now include the Arctic (while still using an explicit time-integration scheme without high-latitude filtering) by using a distorted grid with a displaced pole for the North Atlantic - Arctic region of the ocean. The computer code, written in Fortran 90 and developed on the Connection Machine, has been substantially restructured so that all communication occurs in low-level stencil routines. The idea is that the stencil routines may be rewritten to optimize communication costs on a particular architecture, while the remainder of the code is for the most part machine-independent, involving only the simplest Fortran 90 constructs.
- OSTI ID:
- 272809
- Report Number(s):
- CONF-930557--
- Journal Information:
- Bulletin of the American Physical Society, Journal Name: Bulletin of the American Physical Society Journal Issue: 5 Vol. 38; ISSN BAPSA6; ISSN 0003-0503
- Country of Publication:
- United States
- Language:
- English
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