NICAM 870m mesh simulations on the K computer and a road toward global LES
Abstract:We opened a door of extreme-scale computing by using the first ten peta-FLOPS supercomputer, the K computer, and the Non-hydrostatic Icosahedral Atmospheric Model (NICAM). NICAM achieved up to 10% of peak performance, and showed good scalability from 5 nodes to 81920 nodes on the K computer. The maximum computational performance reached to 0.9 PFLOPS. We carried out the 48 hour simulation of the global sub-km atmosphere simulation and found out the change of represented structures in deep convective core (Miyamoto et al., 2013). The reproduction skill of Madden-Jullian Oscillation (MJO) was evaluated using statistical approach (Miyakawa et al, 2014). The AMIP-like climate simulation with 14km-mesh was also conducted (Kodama et al., in prep.).
Towards to the exa-scale supercomputer, several activities of co-design between the machine and application have been started. NICAM is used for the evaluation of single-node performance, network communication, and file systems. We implemented GPU-based calculations of the dynamical core using OpenACC. In scientific aspects, we are increasing the complexity of the model by adding new components such as new cloud microphysics, chemistry, coupling system with ocean model, ensemble assimilation system, and so on. As the spatial resolution becomes higher, we should be careful about the range of the applicable horizontal scale of the physics schemes. Especially for the “gray zone” issue, approaches by Large Eddy Simulation (LES) will be necessary.