サガワ ヒデオ   SAGAWA HIDEO
  佐川 英夫
   所属   京都産業大学  理学部 宇宙物理・気象学科
   職種   教授
言語種別 英語
発行・発表の年月 2018/07
形態種別 研究論文
査読 査読あり
標題 Local Time Dependence of the Thermal Structure in the Venusian Equatorial Upper Atmosphere: Comparison of Akatsuki Radio Occultation Measurements and GCM Results
執筆形態 その他
掲載誌名 Journal of Geophysical Research: Planets
巻・号・頁 123(9),pp.2270-2280
著者・共著者 Ando, H,Takagi, M,Fukuhara, T,Imamura, T,Sugimoto, N,Sagawa, H,Noguchi, K.,Tellmann, S.,Pätzold, M.,Häusler, B.,Murata, Y.,Takeuchi, H.,Yamazaki, A.,Toda, T.,Tomiki, A.,Choudhary, R.,Kumar, K.,Ramkumar, G.,Antonita M.
概要 ©2018. American Geophysical Union. All Rights Reserved. Temperature profiles of the Venus atmosphere obtained by the Akatsuki radio occultation measurements showed a prominent local time dependence above 65-km altitude at low latitudes equatorward of 35°. A zonal wavenumber 2 component is predominant in the temperature field, and its phase (i.e., isothermal) surfaces descend with local time, suggesting its downward phase propagation. A general circulation model (GCM) for the Venus atmosphere, AFES-Venus, reproduced the local time-dependent thermal structure qualitatively consistent with the radio occultation measurements. Based on a comparison between the radio occultation measurements and the GCM results, the observed zonal wavenumber 2 structure is attributed to the semidiurnal tide. Applying the dispersion relationship for internal gravity waves to the observed wave structure, the zonally averaged zonal wind speed at 75- to 85-km altitudes was found to be significantly smaller than that at the cloud top. The decrease of the zonal wind speed with altitude is attributed to the momentum deposition by the upwardly propagating semidiurnal tide excited in the cloud layer.
DOI 10.1029/2018JE005640
ISSN 2169-9097/2169-9100