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Gigantic Vortices From Barotropic Instability Observed in the Atmosphere of Venus

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Title: Gigantic Vortices From Barotropic Instability Observed in the Atmosphere of Venus
Authors: Horinouchi, Takeshi Browse this author →KAKEN DB
Satoh, Takehiko Browse this author →KAKEN DB
Peralta, Javier Browse this author
Keywords: Venus
barotropic instability
vortex street
geophysical fluid dynamics
planetary atmospheres
Issue Date: 28-Jan-2023
Publisher: American Geophysical Union
Journal Title: Geophysical Research Letters
Volume: 50
Issue: 2
Start Page: e2022GL101633
Publisher DOI: 10.1029/2022GL101633
Abstract: Until recently, the lower to middle cloud region of Venus had been supposed to be dynamically quiet, accommodating nearly steady superrotating westward flow. However, observations of the regions by Akatsuki, the latest Venus orbiter operating since 2015, have revealed a variety of cloud features indicative of vortices and waves. Here we report another, and arguably the most conspicuous, example. Akatsuki's near-infrared imager IR2 captured gigantic vortices rotating cyclonically on 25 August 2016. By using winds estimated by cloud tracking, the feature is shown to be quantitatively consistent with barotropic instability. The size of the vortices (similar to 1,000 km) and their spacing (similar to 2,500 km) are more than several times greater than the vortex-like features reported previously from the observations of Venus, and they are also greater than the largest barotropic instability observed in the Earth's troposphere. Hydrodynamical instabilities play important roles in the general circulation of the Earth and planetary atmospheres. Barotropic instability is a kind of instability that arises from horizontal differences in predominantly parallel horizontal flows. We report herewith the first concrete evidence of its occurrence in the atmosphere of Venus. Before this study, reports are limited to vortex-like cloud features whose appearance is consistent with this instability, but no analyses of flows have been conducted before. The cloud feature like a vortex street reported in this study has a spatial scale far greater than any of previously reported ones, and our study shows that it is dynamically consistent with barotropic instability.
Type: article
Appears in Collections:環境科学院・地球環境科学研究院 (Graduate School of Environmental Science / Faculty of Environmental Earth Science) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

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