[A-AS01] Evolution of Global Environmental Research based on Atmospheric Vertical Motions

[AAS01-02] Deep convection and atmospheric energy spectra in an ultra-high-resolution global model

*Shuhei Matsugishi¹, Tomoki Ohno², Junshi Ito³, Masaki Satoh¹, Yoshiyuki Kajikawa⁴, Yuta Kawai⁵, Masuo Nakano⁶, Hiroshi G. Takahashi⁷, Daisuke Takasuka¹, Hirofumi Tomita⁵, Hisashi Yashiro⁸ (1.Atmosphere and Ocean Research Institute, The University of Tokyo, 2.Meteorological Research Institute, Japan Meteorological Agency, 3.Tohoku University, 4.Research Center for Urban Safety and Security, Kobe University, 5.RIKEN Center for Computational Science, 6.JAMSTEC Japan Agency for Marine-Earth Science and Technology, 7.Department of Geography, Tokyo Metropolitan University, 8.National Institute for Environmental Studies)

Keywords:Global sub-km resolution simulation, Convection, Vertical wind, Energy spectra

Atmospheric motion is driven by deep cumulus convection (cumulonimbus clouds), where the upward motion is localized in a narrow region. The core of the upwelling associated with deep cumulus convection is less than a kilometer. An O(100m) mesh is required to represent the upwelling in numerical simulations adequately (Brian et al. 2003). In this study, a 3.5 km to 220 m global atmospheric simulation is performed to investigate the behavior of vertical motion by convection and the energy spectrum of the atmosphere. The model used is NICAM (Satoh et al. 2014). Horizontal resolutions of 3.5 km, 1.7 km, 870 m, 440 m, and 220 m were used. Starting at the initial time (2016/08/01) of DYAMOND1 (Stevens et al. 2019), the integration of the 3.5 km experiment was started, and simulations were run with progressively higher resolutions.
The maximum or 99th percentile value of grid-scale vertical wind speed at each resolution increases. However, the vertical wind speed becomes small as weaker circulation at higher resolutions when averaged over the horizontal with a few-degree scale.
A global energy spectrum was calculated. The vertical wind energy spectrum showed signs of convergence toward 220m. The horizontal kinetic energy spectrum showed a significant change from 870 m, confirming an increase in energy injection into the stratosphere. This may have been injected by gravity waves at resolutions of 1 km or less, but it needs to be investigated carefully.
In addition, following previous studies, deep convection is diagnosed and analyzed using cloud discrimination by the ISCCP simulator and vertical winds. From such analysis, we discuss how deep convection distributed globally varies with resolutions and cloud systems.