Near-global climate simulation at 1 km resolution: establishing a performance baseline on 4888 GPUs with COSMO 5.0.

The best hope for reducing long-standing global climate model biases, is through increasing the resolution to the kilometer scale. Here we present results from an ultra-high resolution non-hydrostatic climate model for a near-global setup running on the full Piz Daint supercomputer on 4888 GPUs. The dynamical core of the model has been completely rewritten using a domain-specific language (DSL) for performance portability across different hardware architectures. Physical parameterizations and diagnostics have been ported using compiler directives. To our knowledge this represents the first complete atmospheric model being run entirely on accelerators at this scale. At a grid spacing of 930 m (1.9 km), we achieve a simulation throughput of 0.043 (0.23) simulated years per day and an energy consumption of 596 MWh per simulated year. Furthermore, we propose the new memory usage efficiency metric that considers how efficiently the memory bandwidth - the dominant bottleneck of climate codes - is being used. [ABSTRACT FROM AUTHOR]