World-highest resolution global atmospheric model and its performance on the Earth Simulator

Mechanisms of interactions among different scale phenomena play important roles for forecasting of weather and climate. Multi-scale Simulator for the Geoenvironment (MSSG), which deals with multi-scale multi-physics phenomena, is a coupled non-hydrostatic atmosphere-ocean model designed to be run efficiently on the Earth Simulator. We present its simulation results with the world-highest 1.9km horizontal resolution for the entire globe. To gain high performance by exploiting the system capabilities, we propose novel performance evaluation metrics that incorporate the effects of the data caching mechanism between CPU and memory. A potentially attainable computational performance is also introduced by evaluating both computational and memory intensities. With the useful code optimization guideline based on such metrics, we demonstrate that MSSG can achieve an excellent peak performance ratio of 32.2% on the Earth Simulator with the single-core performance found to be a key to reduced time-to-solution.