Generation of gravity waves from thermal tides in the Venus atmosphere

Norihiko Sugimoto,Takeshi Kuroda,Yukiko Fujisawa,Masahiro Takagi,Hiroki Kashimura,Katsuyuki Noguchi,Yoshi-Yuki Hayashi

doi:10.1038/s41467-021-24002-1

Norihiko Sugimoto, Takeshi Kuroda + Show 5 more

Open Access

https://doi.org/10.1038/s41467-021-24002-1

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Abstract

Gravity waves play essential roles in the terrestrial atmosphere because they propagate far from source regions and transport momentum and energy globally. Gravity waves are also observed in the Venus atmosphere, but their characteristics have been poorly understood. Here we demonstrate activities of small-scale gravity waves using a high-resolution Venus general circulation model with less than 20 and 0.25 km in the horizontal and vertical grid intervals, respectively. We find spontaneous gravity wave radiation from nearly balanced flows. In the upper cloud layer (~70 km), the thermal tides in the super-rotation are primary sources of small-scale gravity waves in the low-latitudes. Baroclinic/barotropic waves are also essential sources in the mid- and high-latitudes. The small-scale gravity waves affect the three-dimensional structure of the super-rotation and contribute to material mixing through their breaking processes. They propagate vertically and transport momentum globally, which decelerates the super-rotation in the upper cloud layer (~70 km) and accelerates it above ~80 km.

Highlights

Gravity waves play essential roles in the terrestrial atmosphere because they propagate far from source regions and transport momentum and energy globally
In the nominal case (Supplementary Fig. 1a), super-rotation with the equatorial wind speed of more than 100 m s−1 and with weak mid-latitude jets at the cloud-top (~70 km) level reached a quasi-equilibrium state, which was similar to those reported in previous Venus general circulation models (GCMs) studies[24,25]
These results indicated that the gravity waves were spontaneously radiated at the jet-exit regions (i.e., Jet-Exit Region Emitted (JEREmi) waves) produced by the thermal tides in the low-latitudes for the nominal case

Summary

Introduction

Gravity waves play essential roles in the terrestrial atmosphere because they propagate far from source regions and transport momentum and energy globally. We demonstrate activities of small-scale gravity waves using a high-resolution Venus general circulation model with less than 20 and 0.25 km in the horizontal and vertical grid intervals, respectively. The small-scale gravity waves affect the three-dimensional structure of the super-rotation and contribute to material mixing through their breaking processes They propagate vertically and transport momentum globally, which decelerates the super-rotation in the upper cloud layer (~70 km) and accelerates it above ~80 km. Visible and Infra-red Thermal Imaging Spectrometer-Mapper (VIRTIS-M) onboard the Venus Express suggested that small-scale gravity waves with horizontal wavelengths in the range of 90–400 km exist in the upper atmosphere in the range of 110–140 km altitudes[17]. It has been highlighted that the medium-scale gravity waves appear in moderate resolution Venus GCMs24,25

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