Research for understanding atmospheric momentum cycle for variation of the super-rotation in the stratosphere of Venus

• Project/Area Number: 19K14789
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 17010:Space and planetary sciences-related
• Research Institution: National Institute of Advanced Industrial Science and Technology
• Principal Investigator: Kouyama Toru 国立研究開発法人産業技術総合研究所, 情報・人間工学領域, 研究チーム長 (40645876)
• Project Period (FY): 2019-04-01 – 2023-03-31
• Project Status: Completed (Fiscal Year 2022)
• Budget Amount: ¥2,990,000 (Direct Cost: ¥2,300,000、Indirect Cost: ¥690,000); Fiscal Year 2021: ¥780,000 (Direct Cost: ¥600,000、Indirect Cost: ¥180,000); Fiscal Year 2020: ¥780,000 (Direct Cost: ¥600,000、Indirect Cost: ¥180,000); Fiscal Year 2019: ¥1,430,000 (Direct Cost: ¥1,100,000、Indirect Cost: ¥330,000)
• Keywords: 金星 / スーパーローテーション / あかつき / LIR / UVI / 雲追跡 / 惑星気象学 / 熱潮汐波 / 惑星波 / 惑星大気

Outline of Research at the Start

近年の金星周回衛星による長期探査から、金星ではわずか数年で太陽光吸収量が全球規模で50％も増減し、それに相関する形で東西風速も顕著に変化するなど、金星版気候変動ともいうべき状態にあることが明らかになった。風速の変化には余った運動量を大気の中で分配、あるいは収集する何らかのメカニズムが必要になるが、このような運動量サイクルは全く明らかでない。そこで本研究では他の惑星で風速を調整する「大気波動」に着目し、背景風速の変化へ大気波動がどのように応答し、それに伴う運動量輸送が逆に背景の風速をどのように変化させるかを観測・数値計算両面から明らかにすることで、金星版気候変動の理解を目指す。

Outline of Final Research Achievements

In this research, to understand what kinds of phenomena cause Venusian global climate change, the main purpose is to investigate three dimensional structures of planetary-scale atmospheric waves, which should cause atmospheric momentum transportation, and their temporal evolutions based on observations, and to contribute progress of data assimilation for Venusian atmosphere.
By using the long-term temperature observation dataset obtained from Longwave Infrared Imager (LIR) onboard Akatsuki, a Venusian orbiter, a global and three-dimensional structure of thermal tides was revealed for the first time, and its temporal evolution (repeating enhancing and reducing) was also confirmed. Through collaboration with studies of a global circulation model, reproductivity of the model was improved with a data assimilation technique by introducing the observational result to the model.

Academic Significance and Societal Importance of the Research Achievements

本研究成果は、あかつき搭載機器の中でもこれまでの金星探査の中でもっとも継続的にデータを収集しているLIRを活用し、重要性が指摘されながらも得られていなかった熱潮汐波と呼ばれる現象の3次元構造を世界で初めて明らかにするなど、金星大気理解を推し進める結果となっている。実際にこの観測結果により数値計算モデルの不完全性が明確になり、その修正が一つの研究テーマにもなるなど学術的な広がりを見せている。
またあかつきミッションとの連携によりコミュニティの他の研究者と連携ができたことで、多数の論文成果が得られたこと、海外コミュニティとのコミュニケーションが継続できるなど科学成果の普及・発展に貢献した。

Research Products

• [Journal Article] In-orbit recalibration of Longwave Infrared Camera onboard Akatsuki (2023)
  • Author(s): Taguchi Makoto、Kouyama Toru、Sugawa Temma、Murakami Shin-ya、Futaguchi Masahiko
  • Journal Title: Earth, Planets and Space Volume: 75 Issue: 1 Pages: 53-53
  • DOI: 10.1186/s40623-023-01803-w
  • Peer Reviewed / Open Access
• [Journal Article] Inflight calibration of the optical navigation camera for the extended mission phase of Hayabusa2 (2023)
  • Author(s): Yamada Manabu、Kouyama Toru、Yumoto Koki、Tatsumi Eri、et al.
  • Journal Title: Earth, Planets and Space Volume: 75 Issue: 1 Pages: 1-19
  • DOI: 10.1186/s40623-023-01789-5
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Horizontal structures of bow-shaped mountain wave trains seen in thermal infrared images of Venusian clouds taken by Akatsuki LIR (2022)
  • Author(s): Kiichi Fukuya, Takeshi Imamura, Makoto Taguchi, Toru Kouyama
  • Journal Title: Icarus Volume: 378 Pages: 114936-114936
  • DOI: 10.1016/j.icarus.2022.114936
  • Peer Reviewed / Open Access
• [Journal Article] Akatsuki LIR observing system simulation experiments evaluated by thermal tides in the Venus atmosphere (2022)
  • Author(s): Sugimoto Norihiko、Fujisawa Yukiko、Komori Nobumasa、Ando Hiroki、Kouyama Toru、Takagi Masahiro
  • Journal Title: Geoscience Letters Volume: 9 Issue: 1 Pages: 44-44
  • DOI: 10.1186/s40562-022-00253-8
  • Peer Reviewed / Open Access
• [Journal Article] The Mars system revealed by the Martian Moons eXploration mission (2022)
  • Author(s): Ogohara Kazunori、Nakagawa Hiromu、Aoki Shohei et al.
  • Journal Title: Earth, Planets and Space Volume: 74 Issue: 1 Pages: 1-1
  • DOI: 10.1186/s40623-021-01417-0
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Kelvin Wave and Its Impact on the Venus Atmosphere Tested by Observing System Simulation Experiment (2022)
  • Author(s): Sugimoto Norihiko、Fujisawa Yukiko、Shirasaka Mimo、Abe Mirai、Murakami Shin-ya、Kouyama Toru、Ando Hiroki、Takagi Masahiro、Yamamoto Masaru
  • Journal Title: Atmosphere Volume: 13 Issue: 2 Pages: 182-182
  • DOI: 10.3390/atmos13020182
  • Peer Reviewed / Open Access
• [Journal Article] Planetary-Scale Waves Seen in Thermal Infrared Images of Venusian Cloud Top (2021)
  • Author(s): Naoya Kajiwara, Takeshi Imamura, Makoto Taguchi, Toru Kouyama
  • Journal Title: J.Geophys.Res.:Planets Volume: 126 Issue: 12
  • DOI: 10.1029/2021je007047
  • Peer Reviewed / Open Access
• [Journal Article] Thermal tides in the upper cloud layer of Venus as deduced from the emission angle dependence of the brightness temperature by Akatsuki/LIR (2021)
  • Author(s): Masahiro Akiba, Makoto Taguchi, Tetsuya Fukuhara, Takeshi Imamura, Toru Kouyama, Takao M. Sato
  • Journal Title: J. Geophys. Res.: Planets Volume: 126 Issue: 10
  • DOI: 10.1029/2020je006808
  • Peer Reviewed / Open Access
• [Journal Article] Post-arrival calibration of Hayabusa2's optical navigation cameras (ONCs): Severe effects from touchdown events (2021)
  • Author(s): Kouyama Toru、Tatsumi Eri、Yokota Yasuhiro、Yumoto Koki、Yamada Manabu、Honda Rie、Kameda Shingo、Suzuki Hidehiko、Sakatani Naoya、Hayakawa Masahiko、Morota Tomokatsu、Matsuoka Moe、Cho Yuichiro、Honda Chikatoshi、Sawada Hirotaka、Yoshioka Kazuo、Sugita Seiji
  • Journal Title: Icarus Volume: 360 Pages: 114353-114353
  • DOI: 10.1016/j.icarus.2021.114353
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Improved method of hydrous mineral detection by latitudinal distribution of 0.7-μm surface reflectance absorption on the asteroid Ryugu (2021)
  • Author(s): Kameda Shingo、Yokota Yasuhiro、Kouyama Toru、Tatsumi Eri、Ishida Marika、Morota Tomokatsu、Honda Rie、Sakatani Naoya、Yamada Manabu、Matsuoka Moe、Suzuki Hidehiko、Cho Yuichiro、Hayakawa Masahiko、Honda Chikatoshi、Sawada Hirotaka、Yoshioka Kazuo、Ogawa Kazunori、Sugita Seiji
  • Journal Title: Icarus Volume: 360 Pages: 114348-114348
  • DOI: 10.1016/j.icarus.2021.114348
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Radiometric Calibration for a Multispectral Sensor Onboard RISESAT Microsatellite Based on Lunar Observations (2021)
  • Author(s): Imai Masataka、Kurihara Junichi、Kouyama Toru、Kuwahara Toshinori、Fujita Shinya、Sakamoto Yuji、Sato Yuji、Saitoh Sei-Ichi、Hirata Takafumi、Yamamoto Hirokazu、Takahashi Yukihiro
  • Journal Title: Sensors Volume: 21 Issue: 7 Pages: 2429-2429
  • DOI: 10.3390/s21072429
  • Peer Reviewed / Open Access
• [Journal Article] How waves and turbulence maintain the super-rotation of Venus’ atmosphere (2020)
  • Author(s): Horinouchi Takeshi、Hayashi Yoshi-Yuki、Watanabe Shigeto、Yamada Manabu、Yamazaki Atsushi、Kouyama Toru、Taguchi Makoto、Fukuhara Tetsuya、Takagi Masahiro、Ogohara Kazunori、Murakami Shin-ya、Peralta Javier、Limaye Sanjay S.、Imamura Takeshi、Nakamura Masato、Sato Takao M.、Satoh Takehiko
  • Journal Title: Science Volume: 368 Issue: 6489 Pages: 405-409
  • DOI: 10.1126/science.aaz4439
  • NAID: 120006863171
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] 一番星へ行こう！日本の金星探査機の挑戦 その41 ～LIRの新しい可能性～ (2020)
  • Author(s): 神山徹, 福谷貴一, 今村剛
  • Journal Title: 日本惑星科学会誌 遊・星・人 Volume: 29 Pages: 22-27
  • NAID: 130007845649
• [Journal Article] Global Structure of Thermal Tides in the Upper Cloud Layer of Venus Revealed by LIR on Board Akatsuki (2019)
  • Author(s): Kouyama T.、Taguchi M.、Fukuhara T.、Imamura T.、Horinouchi T.、Sato T. M.、Murakami S.、Hashimoto G. L.、Lee Y. J.、Futaguchi M.、Yamada T.、Akiba M.、Satoh T.、Nakamura M.
  • Journal Title: Geophysical Research Letters Volume: 46 Issue: 16 Pages: 9457-9465
  • DOI: 10.1029/2019gl083820
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Lunar Calibration for ASTER VNIR and TIR with Observations of the Moon in 2003 and 2017 (2019)
  • Author(s): Kouyama、Kato、Kikuchi、Sakuma、Miura、Tachikawa、Tsuchida、Obata、Nakamura
  • Journal Title: Remote Sensing Volume: 11 Issue: 22 Pages: 2712-2712
  • DOI: 10.3390/rs11222712
  • Peer Reviewed / Open Access
• [Journal Article] Planetary‐Scale Variations in Winds and UV Brightness at the Venusian Cloud Top: Periodicity and Temporal Evolution (2019)
  • Author(s): Imai Masataka、Kouyama Toru、Takahashi Yukihiro、Yamazaki Atsushi、Watanabe Shigeto、Yamada Manabu、Imamura Takeshi、Satoh Takehiko、Nakamura Masato、Murakami Shin‐ya、Ogohara Kazunori、Horinouchi Takeshi
  • Journal Title: Journal of Geophysical Research: Planets Volume: 124 Issue: 10 Pages: 2635-2659
  • DOI: 10.1029/2019je006065
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Presentation] Long-Term Temperature Variation at the Cloud Top Level of Venus and Its Correlation with Zonal Windspeed Revealed by Akatsuki LIR/UVI Observations (2023)
  • Author(s): Toru Kouyama, Masataka Imai, Takeshi Imamura, Takeshi Horinouchi, Shin'ya Murakami, Yeon Joo Lee, Makoto Taguchi
  • Organizer: Venus Surface and Atmosphere Conference
  • Int'l Joint Research
• [Presentation] 10 Venusian-year scale temperature variation at the cloud level of Venus revealed by long-term observation of Akatsuki/LIR (2022)
  • Author(s): Toru Kouyama, Makoto Taguchi, Takeshi Horinouchi, Takeshi Imamura, Sin'ya Murakami, Masataka Imai
  • Organizer: 44th COSPAR Scientific Assembly
  • Int'l Joint Research
• [Presentation] Detection of large stationary gravity waves over ten Venusian solar days seen in LIR images (2019)
  • Author(s): Toru Kouyama, Makoto Taguchi, Tetsuya Fukuhara, Takeshi Imamura, Takao M. Sato, Masahiko Futaguchi, Takeru Yamada, Shin-ya Murakami, George L. Hashimoto, Hideo Sagawa, Takehiko Satoh, and Masato Nakamura
  • Organizer: International Venus Conference 2019
  • Int'l Joint Research
• [Presentation] Venusian yearly-scale variation of super rotation seen in Akatsuki observations (2019)
  • Author(s): Toru Kouyama, Takeshi Horinouchi, Takeshi Imamura, Yeon Joo Lee, Masahiro Takagi, Kazunori Ogohara, Hiroki Kashimura, Shin-ya Murakami, Naoya Satoh, Masataka Imai
  • Organizer: International Venus Conference 2019
  • Int'l Joint Research