A prototype model for coupled simulations of regional climate suitable for massively parallel architectures
The formulation of regional climate models has been undergoing major changes, including advances in variable-resolution models and attempts to simulate regionally the coupled atmosphere-ocean system. This talk outlines the design of a prototype global variable-resolution, coupled atmosphere-ocean model. Although the grid can be smoothly deformed into a global simulation, the climate model has been optimised for regional simulations where the grid can be focused over a specified location using a Schmidt transformation. Both atmosphere and ocean dynamical cores employ a reversible staggerring between Arakawa A and C grids. Theoretically this approach can produce very good dispersion characteristics for both atmosphere and ocean models. The performance of the model scales well for 300+ processors and is expected to be suitable for massively parallel architectures, as the approach avoids latency problems associated with mismatched atmosphere and ocean grids. Furthermore, th e approach could be appropriate for global climate models if computing resources are increased by a factor of 10 with the next generation of supercomputers. We can suppress error growth on the coarser regions of the variable-resolution grid by downscaling with a system of scale-selective filters, where the filters use an efficient convolution-based approach that can operate with non-periodic boundary conditions and irregular coastlines, in the case of the ocean model. Some preliminary results are presented for practical applications of the model simulating regional climate, as well as a discussion of the algorithms used for the reversible staggering and the scale-selective filters.