Climate modeling is a grand challenge problem where scientific progress is measured not in terms of the largest problem that can be solved but by the highest achievable integration rate. These models have been notably absent in previous Gordon Bell competitions due to their inability to scale to large processor counts. A scalable and efficient spectral element atmospheric model is presented. A new semi-implicit time stepping scheme accelerates the integration rate relative to an explicit model by a factor of two, achieving 130 years per day at T63L30 equivalent resolution. Execution rates are reported for the standard shallow water and Held-Suarez climate benchmarks on IBM SP clusters. The explicit T170 equivalent multi-layer shallow water model sustains 343 Gflops at NERSC, 206 Gflops at NPACI (SDSC) and 127 Gflops at NCAR. An explicit Held-Suarez integration sustains 369 Gflops on 128 16-way IBM nodes at NERSC.

In November 1994, the NEC Corporation announced the SX-4 supercomputer. It is the third in the SX series of supercomputers and is upward compatible from the SX-3R vector processor with enhancements for scalar processing, short vector processing, and parallel processing. In this paper we describe the architecture of the SX-4 which has an 8.0 ns clock cycle and a peak performance of 2 Gflops per processor. We also describe the composition of the NCAR Benchmark Suite, designed to evaluate the computers for use on climate modeling applications. Additionally, we contrast this benchmark suite with other benchmarks. Finally, we detail the scalability and performance of the SX-4/32 relative to the NCAR Benchmark Suite.