RIKEN Center for Computational Science

OVERVIEW 計算科学研究機構とは

Computational Climate Science Research Team

Fundamental Study of Global-LES Simulations, with a Development of a Basic Library for Climate Science

Advanced supercomputers, including the K computer, make possible simulation of the global atmosphere by using a high-resolution global cloud-resolving model with a grid size of less than 1km. Since the global cloud-resolving model still cannot explicitly express sub-grid scale phenomena related to atmospheric small eddies and cloud generation, these phenomena are parameterized even in high-resolution models. The use of the parameterization scheme leads to uncertainty and/or bias in the simulated results. In the future, such uncertainty is expected to be reduced by using a global-LES (large eddy simulation) model relying on basic climate principles.

However, to realize global-LES simulations a number of challenges have to be overcome: understanding the spatial-resolution dependency of LES schemes, the development of a new theoretical basis of LES for real-atmosphere simulation, raising the sophistication level of physical process schemes, improving their computational performance, and preparation of a post-process library for analyzing a huge number of model outputs. To advance global-LES simulations, we will address several climate science targets: hierarchical structure of clouds, and exploration of multiple equilibrium solutions under ideal conditions, as well as regional climate studies under real atmospheric conditions.

Recent Achievements

Realistic expression of cumulonimbus clouds with a super-high-resolution simulation of the global atmosphere
The world’s first simulation of the global atmosphere with a horizontal resolution less than 1 km was performed using a global cloud-resolving model. This exceedingly high-resolution experiment enabled clouds such as cumulonimbus to be resolved using several grid cells in the model. When the grid size was reduced to less than 2 km, expression of the simulated cumulonimbi were improved and resembled the observed clouds. In other words, the clouds were explicitly resolved in the model. To examine the convergence of results from simulations with different horizontal grid-sizes and to evaluate uncertainty in the conclusions, further studies using a LES model with finer spatial resolution will be required.

Global atmospheric simulation with a grid spacing of 870 meters


Team Leader Hirofumi TOMITA

Team Leader
Hirofumi Tomita

Biography: Detail
Annual Report
FY2017 (PDF 1MB)
FY2016 (PDF 3MB)
FY2015 (PDF 1.21MB)
FY2014 (PDF 1.55MB)
FY2013 (PDF 3.43MB)
FY2012 (PDF 3.08MB)
FY2011 (PDF 2.54MB)