TY - JOUR
T1 - Planetary-size dependence of zonal jets
T2 - Effects of horizontal diffusion in an idealized Earth-like general circulation model
AU - Lu, Liyuan
AU - Yamamoto, Masaru
N1 - Funding Information:
This research was supported by the Ministry of Education, Culture, Sports, Science, and Technology, Japan, via a Grant-in-Aid for Scientific Research from the Japan Society for the Promotion of Science (MEXT/JSPS KAKENHI Grant Number JP17H02960), and via the Ocean and Atmosphere Research Project of the Research Institute for Applied Mechanics, Kyushu University, Japan. The data from the simulations are available upon request from the corresponding author. The source code of the WRF model and the post-processing utility were obtained from the WRF users? page (http://www2.mmm.ucar.edu/wrf/users/).
Funding Information:
This research was supported by the Ministry of Education, Culture, Sports, Science, and Technology, Japan, via a Grant-in-Aid for Scientific Research from the Japan Society for the Promotion of Science ( MEXT/JSPS KAKENHI Grant Number JP17H02960), and via the Ocean and Atmosphere Research Project of the Research Institute for Applied Mechanics, Kyushu University, Japan . The data from the simulations are available upon request from the corresponding author. The source code of the WRF model and the post-processing utility were obtained from the WRF users’ page ( http://www2.mmm.ucar.edu/wrf/users/ ).
Publisher Copyright:
© 2020 The Authors
Copyright:
Copyright 2020 Elsevier B.V., All rights reserved.
PY - 2020/10/1
Y1 - 2020/10/1
N2 - The planetary-size dependence of atmospheric circulation and the effects of subgrid-scale horizontal diffusion are elucidated in this study using an idealized general circulation model. An equatorial super-rotation is formed when a planetary radius is equal to or smaller than 1/3 that of the Earth (r∗ ≤ 1/3, where the planetary-size parameter r∗ is normalized by the Earth's radius). The mid-latitude jet becomes stronger and shifts poleward as r∗ decreases to 1/8. The empirical Smagorinsky horizontal diffusion does not significantly affect mid-latitude jets in large-planet experiments of r∗ ≥ 1/8. In contrast, in small-planet experiments with r∗ = 1/20, equatorial super-rotation is predominant when applying the Smagorinsky diffusion, whereas high-latitude jets are predominant in the absence of such a diffusion. Therefore, the possibility of two different circulation patterns must be considered: an equatorial jet pattern and a high-latitude jet pattern. In the small-planet experiment with the Smagorinsky diffusion, zonal jets are developed around poles where the Reynolds number is low for zonal circulation. In such a case, subgrid-scale dissipations significantly affect the high-latitude jet during spin-up. After this process, the developed high-latitude jets collapse, and the equatorial super-rotation becomes predominant. Because the wind deviating from the rigid-body rotation is sensitive to the subgrid-scale diffusion parameter at high latitudes, the validity of the parameterized horizontal diffusion must be carefully assessed when investigating the planetary-size dependence of the general circulation.
AB - The planetary-size dependence of atmospheric circulation and the effects of subgrid-scale horizontal diffusion are elucidated in this study using an idealized general circulation model. An equatorial super-rotation is formed when a planetary radius is equal to or smaller than 1/3 that of the Earth (r∗ ≤ 1/3, where the planetary-size parameter r∗ is normalized by the Earth's radius). The mid-latitude jet becomes stronger and shifts poleward as r∗ decreases to 1/8. The empirical Smagorinsky horizontal diffusion does not significantly affect mid-latitude jets in large-planet experiments of r∗ ≥ 1/8. In contrast, in small-planet experiments with r∗ = 1/20, equatorial super-rotation is predominant when applying the Smagorinsky diffusion, whereas high-latitude jets are predominant in the absence of such a diffusion. Therefore, the possibility of two different circulation patterns must be considered: an equatorial jet pattern and a high-latitude jet pattern. In the small-planet experiment with the Smagorinsky diffusion, zonal jets are developed around poles where the Reynolds number is low for zonal circulation. In such a case, subgrid-scale dissipations significantly affect the high-latitude jet during spin-up. After this process, the developed high-latitude jets collapse, and the equatorial super-rotation becomes predominant. Because the wind deviating from the rigid-body rotation is sensitive to the subgrid-scale diffusion parameter at high latitudes, the validity of the parameterized horizontal diffusion must be carefully assessed when investigating the planetary-size dependence of the general circulation.
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U2 - 10.1016/j.pss.2020.104976
DO - 10.1016/j.pss.2020.104976
M3 - Article
AN - SCOPUS:85086630670
VL - 190
JO - Planetary and Space Science
JF - Planetary and Space Science
SN - 0032-0633
M1 - 104976
ER -