Speaker
Description
We introduce numerical techniques and physical implementation for the development of a global large-eddy simulation model by the Nonhydrostatic Icosahedral Atmospheric Model (NICAM). NICAM has been studied for global kilometer-scale simulations since the first global 3.5-km mesh aqua-planet simulation by Tomita et al. (2005). Miyamoto et al. (2013) conducted a global 870-m mesh simulation using the K computer in Japan. Using the supercomputer Fugaku, we conducted a global 220-m mesh simulation. The model with this horizontal mesh scale is in the range of large eddy simulation (LES) for specific types of flow fields, including deep convection (Brian et al. 2003), although a higher resolution of O(10m) is ideal for more general purposes of LES.
To enable NICAM to function as a global large-eddy simulation model, we introduced the Smagorinsky-type LES scheme for turbulence. We also applied a smoother grid modification method by a transfer function based on Iga and Tomita (2014) instead of the spring dynamics and introduced several numerical stabilizations and less computationally demanding methods, such as using single precision arithmetic. We conducted the NICAM simulations for the horizontal mesh ranging from 220 m to 3. 5 km to analyze the resolution dependency and the turbulence scheme dependency between the eddy-diffusivity (Mellor-Yamada) type scheme and the Smagorinsky scheme. Additionally, we applied the satellite simulator, the Joint Simulator for Satellite Sensors, to the simulation results to compare with the recently launched satellite EarthCARE (Roh et al. 2024).
References:
Bryan, G. H., J. C. Wyngaard, and J. M. Fritsch, 2003: Resolution Requirements for the Simulation of Deep Moist Convection. Mon. Wea. Rev., 131, 2394–2416.
Iga, S., and H. Tomita, 2014: Improved smoothness and homogeneity of icosahedral grids using the spring dynamics method. J. Comp. Phys., 258, 208-226.
Miyamoto, Y., Y. Kajikawa, R. Yoshida, T. Yamaura, H. Yashiro, and H. Tomita, 2013: Deep moist atmospheric convection in a subkilometer global simulation, Geophys. Res. Lett., 40, 4922-4926.
Roh, W., Satoh, M., Hashino, T., Matsugishi, S., Nasuno, T., Kubota, T., 2023: Introduction to EarthCARE synthetic data using a global storm-resolving simulation. Atmos. Meas. Tech., 16, 3331–334.
Tomita, H, Miura, H., Iga, S., Nasuno, T., and Satoh, M., 2005: A global cloud-resolving simulation: preliminary results from an aqua planet experiment. Geophys. Res. Lett., vol.32, L08805.
