2018 Fiscal Year Final Research Report

Study of gravity waves in planetary atmospheres using radio occultation experiments and numerical modeling

Research Project

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Project/Area Number	16H04060
Research Category	Grant-in-Aid for Scientific Research (B)
Allocation Type	Single-year Grants
Section	一般
Research Field	Space and upper atmospheric physics
Research Institution	The University of Tokyo
Principal Investigator	Imamura Takeshi 東京大学, 大学院新領域創成科学研究科, 教授 (40311170)
Co-Investigator(Kenkyū-buntansha)	安藤紘基京都産業大学, 理学部, 助教 (00706335) 中島健介九州大学, 理学研究院, 助教 (10192668) 林祥介神戸大学, 理学研究科, 教授 (20180979) 野口克行奈良女子大学, 自然科学系, 助教 (20397839) 杉山耕一朗松江工業高等専門学校, 情報工学科, 准教授 (60463733) 小高正嗣北海道大学, 理学研究院, 助教 (60344462)
Project Period (FY)	2016-04-01 – 2019-03-31
Keywords	大気重力波 / 電波掩蔽 / 金星
Outline of Final Research Achievements	Radio occultation observation data of Venus was analyzed by radio holography method to improve the vertical resolution, and universal existence of waves and neutral layers with vertical scales of several hundred meters were revealed. Sharp inversion layers were also found to exist at the top of high latitude convection layers. We also carried out numerical simulations of the convective layer with high vertical resolution and a wide computational domain, and reproduced the convective motion and the gravity waves excited by convection. Breaking of gravity waves is suggested to be caused by shear instability and convective instability. Furthermore, we could understand the height of breaking of gravity waves and the amplitude of gravity waves in comparison with the observational results of radio wave occultation observation.
Free Research Field	惑星大気科学
Academic Significance and Societal Importance of the Research Achievements	地球をはじめ惑星大気に普遍的に存在して大気構造や気候形成に影響を与える内部重力波について、金星と地球の比較により研究を進めた。電波掩蔽観測の新たな手法により従来とらえられなかった微細構造を明らかにすることにより、金星においても地球と同様な詳細な解析が可能となった。また数値シミュレーションにより観測結果を再現して背後のメカニズムの理解を深めることができた。