Understanding multiscale interactions within the complex hierarchy of various phenomena on wide ranges of temporal and spatial scales is an essential part of the study of the atmosphere and ocean circulation systems. Despite significant progress, the complex interactions have not yet been fully understood, due mainly to the lack of continuous, mesoscale resolving observations of the global three-dimensional circulations, whose realization is difficult, especially for the ocean.
However, computer simulations with ultra-high resolution, if possible, would be a powerful tool to tackle this difficult issue. Such simulations are now under way on the Earth Simulator (ES), a Japanese gigantic vectorparallel computer that has been in operation since March 2002 and was the world's fastest general-purpose supercomputer until early fall 2004. Even though the ES is now the third-fastest supercomputer by both peak performance and UNPACK test, which is a benchmark test by liner algebra computations, our 10-km mesh atmospheric general circulation simulation remains the fastest real-world computation on a general-purpose supercomputer even after two and half years.