Computational Climate Science Research Team

Research summary

Main research results

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

Representative papers

• Kawai Y., and Tomita, H.:
  “Numerical Accuracy Necessary for Large-Eddy Simulation of Planetary Boundary Layer Turbulence using Discontinuous Galerkin Method”
  Mon. Weather. Rev., 151(6), 1479-1508 (2023).
• Yanase, T., S. Nishizawa, H. Miura, and H. Tomita:
  “Characteristic form and distance in high-level hierarchical structure of self-aggregated clouds in radiative-convective equilibrium”
  Geophysical Research Letters, Vol. 49, Issue 18, e2022GL100000 (2022).
• Kawai, Y., and Tomita, H.:
  "Numerical Accuracy of Advection Scheme Necessary for Large-Eddy Simulation of Planetary Boundary Layer Turbulence"
  Mon. Weather. Rev., 149(9), 2993-3012 (2021).
• Yanase, T., Nishizawa, S., Miura, H., Takemi, T., and Tomita, H.:
  "New critical length for the onset of self-aggregation of moist convection"
  Geophys. Res. Lett., 47, e2020GL088763 (2020).
• Adachi, S. A. and Tomita, H.:
  "Methodology of the constraint condition in dynamical downscaling for regional climate evaluation: A review"
  J. Geophys. Res., 125 (11), e2019JD032166 (2020).
• Sueki, K., Yamaura, T., Yashiro, H., Nishizawa, S., Yoshida, R., Kajikawa, Y., and Tomita, H.:
  "Convergence of convective updraft ensembles with respect to the grid spacing of atmospheric models"
  Geophys. Res. Lett., 46, 14817-14825 (2019).
• Adachi, S. A., Nishizawa, S., Yoshida, R., Yamaura, T., Ando, K., Yashiro, H., Kajikawa, Y., and Tomita, H.:
  "Contributions of changes in climatology and perturbation and the resulting nonlinearity to regional climate change"
  Nature Communications, 8, 2224 (2017).
• Sato, Y., Miura, H., Yashiro, H., Goto, D., Takemura, T., Tomita, H., and Nakajima, T.:
  "Unrealistically pristine air in the Arctic produced by current global scale models"
  Scientific Reports, 6, Article number: 26561 (2016).
• Nishizawa, S., Yashiro, H., Sato, Y., Miyamoto, Y., and Tomita, H.:
  "Influence of grid aspect ratio on planetary boundary layer turbulence in large-eddy simulations"
  Geosci. Model Dev., 8, 3393-3419 (2015).
• Miyamoto, Y., Kajikawa, Y., Yoshida, R., Yamaura, T., Yashiro, H., and Tomita, H.:
  "Deep moist atmospheric convection in a sub-kilometer global simulation"
  Geophys. Res. Lett., pp.4922–4926 (2013).

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