1
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The first assimilation of Akatsuki single-layer winds and its validation with Venusian atmospheric waves excited by solar heating. Sci Rep 2022; 12:14577. [PMID: 36028537 PMCID: PMC9418169 DOI: 10.1038/s41598-022-18634-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2022] [Accepted: 08/16/2022] [Indexed: 11/08/2022] Open
Abstract
The planetary missions including the Venus Climate Orbiter 'Akatsuki' provide new information on various atmospheric phenomena. Nevertheless, it is difficult to elucidate their three-dimensional structures globally and continuously only from observations because satellite observations are considerably limited in time and space. We constructed the first 'objective analysis' of Venus' atmosphere by assimilating cloud-top horizontal winds on the dayside from the equator to mid-latitudes, which is frequently obtained from Akatsuki's Ultraviolet Imager (UVI). The three-dimensional structures of thermal tides, found recently to play a crucial role in maintaining the super rotation, are greatly improved by the data assimilation. This result is confirmed by comparison with Akatsuki's temperature observations. The momentum transport caused by the thermal tides and other disturbances are also modified by the wind assimilation and agrees well with those estimated from the UVI observations. The assimilated dataset is reliable and will be open to the public along with the Akatsuki observations for further investigation of Venus' atmospheric phenomena.
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2
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Venus Atmospheric Dynamics at Two Altitudes: Akatsuki and Venus Express Cloud Tracking, Ground-Based Doppler Observations and Comparison with Modelling. ATMOSPHERE 2021. [DOI: 10.3390/atmos12040506] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
We present new results of our studies of zonal and meridional winds in both hemispheres of Venus, using ground- and space-based coordinated observations. The results obtained from telescope observations were retrieved with a Doppler velocimetry method. The wind velocities retrieved from space used an improved cloud-tracked technique based on the phase correlation between images. We present evidence that the altitude level sensed by our Doppler velocimetry method is approximately four kilometres higher (~4 km) than that using ground-tracked winds (using 380 or 365 nm). Since we often take advantage of coordinated space and ground observations simultaneously, this altitude difference will be very relevant in order to estimate the vertical wind shear at the related heights in future observation campaigns. We also explored a previous coordinated campaign using Akatsuki observations and its Ultraviolet Imager (UVI) at 283 and 365 nm filters, which showed that cloud-tracked winds showed a difference of about 10–15 ms−1, as in the case of the comparison between the Doppler velocimetry winds and the 365 nm cloudtracked winds. The results’ comparison also strongly suggested that the cloud-tracked winds based on the 283 nm filter’s images were sensing at about the same atmospheric altitude level as the Doppler winds. The observational results were compared with the ground-to-thermosphere 3D model developed at the Laboratoire de Meteorologie Dynamique (IPSL-Venus General Circulation Model (VGCM)) and AFES-Venus General Circulation Model (GCM), at several pressure levels (and related heights). The analysis and results showed the following: (1) additional confirmation of the coherence and complementarity in the results provided by these techniques on both the spatial and temporal time scales of the two methods; (2) we noticed in the following that the results from the two different Akatsuki/UVI filters (283 and 365 nm) showed an average difference of about 10–15 ± 5 ms−1, and we suggest this may be related to SO2 atmospheric fluctuations and the particular conditions in the coordinated observing time window; (3) we present evidence indicating that, in the context of our observations, visible Doppler methods (highly self-consistent) seem to sense wind speeds at a vertical level closer to or within the range sensed by the UVI 283 nm filter images (again, in the context of our observations); (4) modelling predicted wind profiles suggests that the layers of the atmosphere of Venus sensed by the methods referred to in Point 3 differ by approximately four km in altitude (~4 ± 2 km) regarding the cloud-tracked winds retrieved using 365 or 380 nm images.
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3
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Yamamoto M, Ikeda K, Takahashi M. Atmospheric response to high-resolution topographical and radiative forcings in a general circulation model of Venus: Time-mean structures of waves and variances. ICARUS 2021; 355:114154. [PMID: 33052146 PMCID: PMC7545273 DOI: 10.1016/j.icarus.2020.114154] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/23/2020] [Revised: 09/28/2020] [Accepted: 10/05/2020] [Indexed: 06/11/2023]
Abstract
Thermal tides, stationary waves, and general circulation are investigated using a T63 Venus general circulation model (GCM) with solar and thermal radiative transfer in the presence of high-resolution surface topography, based on time average analysis. The simulated wind and static stability are very similar to the observed ones (e.g., Horinouchi et al., 2018; Ando et al., 2020). The simulated thermal tides accelerate an equatorial superrotational flow with a speed of ~90 m s-1 around the cloud-heating maximum (~65 km). The zonal-flow acceleration rates of 0.2-0.5 m s-1 Earth day-1 are produced by both horizontal and vertical momentum fluxes at low latitudes. In the GCM simulation, strong solar heating above the cloud top (>69 km) and infrared heating around the cloud bottom (~50 km) modify the vertical structures of thermal tides and their vertical momentum fluxes, which accelerate zonal flow at 103 Pa (~75 km) and 104 Pa (~65 km) at the equator and around 103 Pa at high latitudes. Below and in the cloud layer, surface topography weakens the zonal-mean zonal flow over the Aphrodite Terra and Maxwell Montes, whereas it enhances the zonal flow in the southern polar region. The high-resolution topography produces stationary fine-scale bow structures at the cloud top and locally modifies the variances in the geographical coordinates (i.e., the activity of unsteady wave components). Over the high mountains, vertical spikes of the vertical wind variance are found, indicating penetrative plumes and gravity waves. Negative momentum flux is also locally enhanced at the cloud top over the equatorial high mountains. In the solar-fixed coordinate system, the variances (i.e., the activity of waves other than thermal tides) of flow are relatively higher on the nightside than on the dayside at the cloud top. Strong dependences of the eddy heat and momentum fluxes on local time are predominant. The local-time variation of the vertical eddy momentum flux is produced by both thermal tides and solar-related, small-scale gravity waves.
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Affiliation(s)
- Masaru Yamamoto
- Research Institute for Applied Mechanics, Kyushu University, Kasuga, Fukuoka 816-8580, Japan
| | - Kohei Ikeda
- National Institute for Environmental Studies, Tsukuba, Ibaraki 305-8506, Japan
| | - Masaaki Takahashi
- National Institute for Environmental Studies, Tsukuba, Ibaraki 305-8506, Japan
- Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, Chiba 277-8564, Japan
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4
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Horinouchi T, Hayashi YY, Watanabe S, Yamada M, Yamazaki A, Kouyama T, Taguchi M, Fukuhara T, Takagi M, Ogohara K, Murakami SY, Peralta J, Limaye SS, Imamura T, Nakamura M, Sato TM, Satoh T. How waves and turbulence maintain the super-rotation of Venus' atmosphere. Science 2020; 368:405-409. [PMID: 32327594 DOI: 10.1126/science.aaz4439] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2019] [Accepted: 03/27/2020] [Indexed: 11/02/2022]
Abstract
Venus has a thick atmosphere that rotates 60 times as fast as the surface, a phenomenon known as super-rotation. We use data obtained from the orbiting Akatsuki spacecraft to investigate how the super-rotation is maintained in the cloud layer, where the rotation speed is highest. A thermally induced latitudinal-vertical circulation acts to homogenize the distribution of the angular momentum around the rotational axis. Maintaining the super-rotation requires this to be counteracted by atmospheric waves and turbulence. Among those effects, thermal tides transport the angular momentum, which maintains the rotation peak, near the cloud top at low latitudes. Other planetary-scale waves and large-scale turbulence act in the opposite direction. We suggest that hydrodynamic instabilities adjust the angular-momentum distribution at mid-latitudes.
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Affiliation(s)
- Takeshi Horinouchi
- Faculty of Environmental Earth Science, Hokkaido University, Sapporo, Japan. .,Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Sagamihara, Japan
| | - Yoshi-Yuki Hayashi
- Department of Planetology and Center for Planetary Science, Kobe University, Kobe, Japan
| | - Shigeto Watanabe
- Space Information Center, Hokkaido Information University, Ebetsu, Japan
| | - Manabu Yamada
- Planetary Exploration Research Center, Chiba Institute of Technology, Narashino, Japan
| | - Atsushi Yamazaki
- Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Sagamihara, Japan
| | - Toru Kouyama
- Artificial Intelligence Research Center, National Institute of Advanced Industrial Science and Technology, Tokyo, Japan
| | | | | | | | - Kazunori Ogohara
- School of Engineering, University of Shiga Prefecture, Hikone, Japan
| | - Shin-Ya Murakami
- Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Sagamihara, Japan
| | - Javier Peralta
- Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Sagamihara, Japan
| | - Sanjay S Limaye
- Space Science and Engineering Center, University of Wisconsin-Madison, Madison, WI, USA
| | - Takeshi Imamura
- Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Japan
| | - Masato Nakamura
- Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Sagamihara, Japan.,Department of Space and Astronautical Science, School of Physical Sciences, The Graduate University for Advanced Studies (SOKENDAI), Tokyo, Japan
| | - Takao M Sato
- Space Information Center, Hokkaido Information University, Ebetsu, Japan
| | - Takehiko Satoh
- Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Sagamihara, Japan.,Department of Space and Astronautical Science, School of Physical Sciences, The Graduate University for Advanced Studies (SOKENDAI), Tokyo, Japan
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5
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Abstract
General circulation models (GCMs) are valuable instruments to understand the most peculiar features in the atmospheres of planets and the mechanisms behind their dynamics. Venus makes no exception and it has been extensively studied thanks to GCMs. Here we validate the current version of the Institut Pierre Simon Laplace (IPSL) Venus GCM, by means of a comparison between the modelled temperature field and that obtained from data by the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) and the Venus Express Radio Science Experiment (VeRa) onboard Venus Express. The modelled thermal structure displays an overall good agreement with data, and the cold collar is successfully reproduced at latitudes higher than +/−55°, with an extent and a behavior close to the observed ones. Thermal tides developing in the model appear to be consistent in phase and amplitude with data: diurnal tide dominates at altitudes above 102 Pa pressure level and at high-latitudes, while semidiurnal tide dominates between 102 and 104 Pa, from low to mid-latitudes. The main difference revealed by our analysis is located poleward of 50°, where the model is affected by a second temperature inversion arising at 103 Pa. This second inversion, possibly related to the adopted aerosols distribution, is not observed in data.
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6
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Yamazaki A, Yamada M, Lee YJ, Watanabe S, Horinouchi T, Murakami SY, Kouyama T, Ogohara K, Imamura T, Sato TM, Yamamoto Y, Fukuhara T, Ando H, Sugiyama KI, Takagi S, Kashimura H, Ohtsuki S, Hirata N, Hashimoto GL, Suzuki M, Hirose C, Ueno M, Satoh T, Abe T, Ishii N, Nakamura M. Ultraviolet imager on Venus orbiter Akatsuki and its initial results. EARTH, PLANETS, AND SPACE : EPS 2018; 70:23. [PMID: 31983883 PMCID: PMC6954016 DOI: 10.1186/s40623-017-0772-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Accepted: 12/25/2017] [Indexed: 05/28/2023]
Abstract
The ultraviolet imager (UVI) has been developed for the Akatsuki spacecraft (Venus Climate Orbiter mission). The UVI takes ultraviolet (UV) images of the solar radiation reflected by the Venusian clouds with narrow bandpass filters centered at the 283 and 365 nm wavelengths. There are absorption bands of SO2 and unknown absorbers in these wavelength regions. The UV images provide the spatial distribution of SO2 and the unknown absorber around cloud top altitudes. The images also allow us to understand the cloud top morphologies and haze properties. Nominal sequential images with 2-h intervals are used to understand the dynamics of the Venusian atmosphere by estimating the wind vectors at the cloud top altitude, as well as the mass transportation of UV absorbers. The UVI is equipped with off-axial catadioptric optics, two bandpass filters, a diffuser installed in a filter wheel moving with a step motor, and a high sensitivity charge-coupled device with UV coating. The UVI images have spatial resolutions ranging from 200 m to 86 km at sub-spacecraft points. The UVI has been kept in good condition during the extended interplanetary cruise by carefully designed operations that have maintained its temperature maintenance and avoided solar radiation damage. The images have signal-to-noise ratios of over 100 after onboard desmear processing.
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Affiliation(s)
- Atsushi Yamazaki
- Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA), 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 Japan
- Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033 Japan
| | - Manabu Yamada
- Planetary Exploration Research Center (PERC), Chiba Institute of Technology, 2-17-1 Tsudanuma, Narashino, Chiba 275-0016 Japan
| | - Yeon Joo Lee
- Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA), 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 Japan
- Present Address: Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561 Japan
| | - Shigeto Watanabe
- Hokkaido Information University, 59-2 Nishinopporo, Ebetsu, Hokkaido 069-8585 Japan
| | - Takeshi Horinouchi
- Faculty of Environmental Earth Science, Hokkaido University, N10W5, Sapporo, Hokkaido 060-0810 Japan
| | - Shin-ya Murakami
- Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA), 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 Japan
| | - Toru Kouyama
- Artificial Intelligence Research Center, National Institute of Advanced Industrial Science and Technology, 2-3-26 Aomi, Koto-ku, Tokyo, 135-0064 Japan
| | - Kazunori Ogohara
- School of Engineering, University of Shiga Prefecture, 2500 Hassaka-cho, Hikone, Shiga 522-8533 Japan
| | - Takeshi Imamura
- Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561 Japan
| | - Takao M. Sato
- Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA), 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 Japan
| | - Yukio Yamamoto
- Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA), 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 Japan
| | - Tetsuya Fukuhara
- Department of Physics, Rikkyo University, 3-34-1 Nishi-Ikebukuro, Toshima-ku, Tokyo, 171-8501 Japan
| | - Hiroki Ando
- Faculty of Science, Kyoto Sangyo University, Motoyama, Kamigamo, Kita-ku, Kyoto, Kyoto 603-8555 Japan
| | - Ko-ichiro Sugiyama
- Department of Information Engineering, National Institute of Technology, Matsue College, 14-4 Nishi-Ikuma, Matsue, Shimane 690-8518 Japan
| | - Seiko Takagi
- Research and Information Center, Tokai University, 4-1-1 Kitakaname, Hiratsuka, Kanagawa 259-1292 Japan
- Present Address: Hokkaido University, N10W5, Sapporo, Hokkaido 060-0810 Japan
| | - Hiroki Kashimura
- Department of Planetology/Center for Planetary Science, Kobe University, 7-1-48, Minamimachi, Minatojima Chuo-ku, Kobe, 650-0047 Japan
| | - Shoko Ohtsuki
- School of Commerce, Senshu University, 2-1-1 Higashimita, Tama-ku, Kawasaki, Kabagawa 214-8580 Japan
| | - Naru Hirata
- School of Computer Science and Engineering, The University of Aizu, 90 Kami-Iawase, Tsuruga, Ikki-machi, Aizu-Wakamatsu, Fukushima 965-8580 Japan
| | - George L. Hashimoto
- Department of Earth Science, Okayama University, 3-1-1 Tsushimanaka, Kita, Okayama 700-8530 Japan
| | - Makoto Suzuki
- Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA), 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 Japan
| | - Chikako Hirose
- Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA), 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 Japan
| | - Munetaka Ueno
- Center for Planetary Science (CPS), Graduate School of Science, Kobe University, 7-1-48 Minatojima-minamimachi, Chuo-ku, Kobe, Hyogo 650-0047 Japan
| | - Takehiko Satoh
- Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA), 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 Japan
- Department of Space and Astronautical Science, School of Physical Sciences, SOKENDAI, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 Japan
| | - Takumi Abe
- Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA), 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 Japan
- Department of Space and Astronautical Science, School of Physical Sciences, SOKENDAI, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 Japan
| | - Nobuaki Ishii
- Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA), 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 Japan
| | - Masato Nakamura
- Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA), 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 Japan
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7
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Development of an ensemble Kalman filter data assimilation system for the Venusian atmosphere. Sci Rep 2017; 7:9321. [PMID: 28839201 PMCID: PMC5571110 DOI: 10.1038/s41598-017-09461-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2017] [Accepted: 07/26/2017] [Indexed: 11/28/2022] Open
Abstract
The size and mass of Venus is similar to those of the Earth; however, its atmospheric dynamics are considerably different and they are poorly understood due to limited observations and computational difficulties. Here, we developed a data assimilation system based on the local ensemble transform Kalman filter (LETKF) for a Venusian Atmospheric GCM for the Earth Simulator (VAFES), to make full use of the observational data. To examine the validity of the system, two datasets were assimilated separately into the VAFES forecasts forced with solar heating that excludes the diurnal component Qz; one was created from a VAFES run forced with solar heating that includes the diurnal component Qt, whereas the other was based on observations made by the Venus Monitoring Camera (VMC) onboard the Venus Express. The VAFES-LETKF system rapidly reduced the errors between the analysis and forecasts. In addition, the VAFES-LETKF system successfully reproduced the thermal tide excited by the diurnal component of solar heating, even though the second datasets only included horizontal winds at a single altitude on the dayside with a long interval of approximately one Earth day. This advanced system could be useful in the analysis of future datasets from the Venus Climate Orbiter ‘Akatsuki’.
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8
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Horinouchi T, Murakami SY, Satoh T, Peralta J, Ogohara K, Kouyama T, Imamura T, Kashimura H, Limaye SS, McGouldrick K, Nakamura M, Sato TM, Sugiyama KI, Takagi M, Watanabe S, Yamada M, Yamazaki A, Young EF. Equatorial jet in the lower to middle cloud layer of Venus revealed by Akatsuki. NATURE GEOSCIENCE 2017; 10:646-651. [PMID: 29887914 PMCID: PMC5990972 DOI: 10.1038/ngeo3016] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
The Venusian atmosphere is in a state of superrotation where prevailing westward winds move much faster than the planet's rotation. Venus is covered with thick clouds that extend from about 45 to 70 km altitude, but thermal radiation emitted from the lower atmosphere and the surface on the planet's night-side escapes to space at narrow spectral windows of near-infrared. The radiation can be used to estimate winds by tracking the silhouettes of clouds in the lower and middle cloud regions below about 57 km in altitude. Estimates of wind speeds have ranged from 50 to 70 m/s at low- to mid-latitudes, either nearly constant across latitudes or with winds peaking at mid-latitudes. Here we report the detection of winds at low latitude exceeding 80 m/s using IR2 camera images from the Akatsuki orbiter taken during July and August 2016. The angular speed around the planetary rotation axis peaks near the equator, which we suggest is consistent with an equatorial jet, a feature that has not been observed previously in the Venusian atmosphere. The mechanism producing the jet remains unclear. Our observations reveal variability in the zonal flow in the lower and middle cloud region that may provide new challenges and clues to the dynamics of Venus's atmospheric superrotation.
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Affiliation(s)
- Takeshi Horinouchi
- Faculty of Environmental Earth Science, Hokkaido University, N10W5, Sapporo, Hokkaido 060-0810, Japan
- Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency
- Corresponding author: Takeshi Horinouchi,
| | - Shin-ya Murakami
- Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency
| | - Takehiko Satoh
- Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency
- Department of Space and Astronautical Science, School of Physical Sciences, SOKENDAI
| | - Javier Peralta
- Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency
| | | | - Toru Kouyama
- Artificial Intelligence Research Center, National Institute of Advanced Industrial Science and Technology
| | - Takeshi Imamura
- Graduate School of Frontier Sciences, the University of Tokyo
| | - Hiroki Kashimura
- Department of Planetology / Center for Planetary Science, Kobe University
| | - Sanjay S. Limaye
- Space Science and Engineering Center, the University of Wisconsin-Madison
| | - Kevin McGouldrick
- Laboratory for Atmospheric and Space Physics, University of Colorado Boulder
| | - Masato Nakamura
- Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency
| | - Takao M. Sato
- Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency
| | | | | | | | - Manabu Yamada
- Planetary Exploration Research Center, Chiba Institute of Technology
| | - Atsushi Yamazaki
- Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency
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9
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The puzzling Venusian polar atmospheric structure reproduced by a general circulation model. Nat Commun 2016; 7:10398. [PMID: 26832195 PMCID: PMC4740379 DOI: 10.1038/ncomms10398] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2015] [Accepted: 12/07/2015] [Indexed: 11/16/2022] Open
Abstract
Unlike the polar vortices observed in the Earth, Mars and Titan atmospheres, the observed Venus polar vortex is warmer than the midlatitudes at cloud-top levels (∼65 km). This warm polar vortex is zonally surrounded by a cold latitude band located at ∼60° latitude, which is a unique feature called ‘cold collar' in the Venus atmosphere. Although these structures have been observed in numerous previous observations, the formation mechanism is still unknown. Here we perform numerical simulations of the Venus atmospheric circulation using a general circulation model, and succeed in reproducing these puzzling features in close agreement with the observations. The cold collar and warm polar region are attributed to the residual mean meridional circulation enhanced by the thermal tide. The present results strongly suggest that the thermal tide is crucial for the structure of the Venus upper polar atmosphere at and above cloud levels. Unlike some planets, the Venusian polar vortex is warmer than the mid-latitudes at cloud-top level, but the mechanism behind this is unknown. Here, the authors use a general circulation model and suggest the cold collar and warm polar regions are due to residual mean meridional circulation intensified by thermal tides.
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10
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Lebonnois S, Hourdin F, Eymet V, Crespin A, Fournier R, Forget F. Superrotation of Venus' atmosphere analyzed with a full general circulation model. ACTA ACUST UNITED AC 2010. [DOI: 10.1029/2009je003458] [Citation(s) in RCA: 153] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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11
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Yamamoto M, Takahashi M. Dynamical effects of solar heating below the cloud layer in a Venus-like atmosphere. ACTA ACUST UNITED AC 2009. [DOI: 10.1029/2009je003381] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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