Details of a Researcher - Sugimoto, Norihiko

Papers - Sugimoto, Norihiko

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Local Time Dependence of the Thermal Structure in the Venusian Equatorial Upper Atmosphere: Comparison of Akatsuki Radio Occultation Measurements and GCM Results

ANDO Hiroki, TAKAGI Masahiro, FUKUHARA Tetsuya, IMAMURA Takeshi, SUGIMOTO Norihiko, SAGAWA Hideo, NOGUCHI Katsuyuki, TELLMANN Silvia, PATZOLD Martin, HAUSLER Bernd, MURATA Yasuhiro, TAKEUCHI Hiroshi, YAMAZAKI Atsushi, TODA Tomoaki, TOMIKI Atsushi, CHOUDHARY Rajkumar, KUMAR Kishore, RAMKUMAR Geetha, ANTONITA Maria

Journal of Geophysical Research: Planets (American Geophysical Union) 123 ( JE005640 ) 11pp - 2280 2018.07

Research paper (scientific journal), Joint Work, Accepted, ISSN 21699097

©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.

Three dimensional structures of thermal tides simulated by a Venus GCM

TAKAGI Masahiro, SUGIMOTO Norihiko, ANDO Hiroki, MATSUDA Yoshihisa

Journal of Geophysical Research: Planets (American Geophysical Union) 123 ( JE005449 ) 18pp - 352 2018.01

Research paper (scientific journal), Joint Work, Accepted, ISSN 21699097

©2018. American Geophysical Union. All Rights Reserved. Thermal tides in the Venus atmosphere are investigated by using a GCM named as AFES-Venus. The three-dimensional structures of wind and temperature associated with the thermal tides obtained in our model are fully examined and compared with observations. The result shows that the wind and temperature distributions of the thermal tides depend complexly on latitude and altitude in the cloud layer, mainly because they consist of vertically propagating and trapped modes with zonal wave numbers of 1–4, each of which predominates in different latitudes and altitudes under the influence of mid- and high-latitude jets. A strong circulation between the subsolar and antisolar (SS-AS) points, which is equivalent to a diurnal component of the thermal tides, is superposed on the superrotation. The vertical velocity of SS-AS circulation is about 10 times larger than that of the zonal-mean meridional circulation (ZMMC) in 60–70 km altitudes. It is suggested that the SS-AS circulation could contribute to the material transport, and its upward motion might be related to the UV dark region observed in the subsolar and early afternoon regions in low latitudes. The terdiurnal and quaterdiurnal tides, which may be excited by the nonlinear interactions among the diurnal and semidiurnal tides in middle and high latitudes, are detected in the solar-fixed Y-shape structure formed in the vertical wind field in the upper cloud layer. The ZMMC is weak and has a complex structure in the cloud layer; the Hadley circulation is confined to latitudes equatorward of 30°, and the Ferrel-like one appears in middle and high latitudes.

A dynamical mechanism for Secondary Eyewall Formation in Tropical Cyclones

MIYAMOTO Yoshiaki, NOLAN David, SUGIMOTO Norihiko

Journal of the Atmospheric Sciences (American Meteorological Society) 75 ( 11 ) 3965 - 3986 2018

Research paper (scientific journal), Joint Work, Accepted, ISSN 00224928

© 2018 American Meteorological Society. This study proposes that secondary eyewall formation (SEF) of tropical cyclones (TCs) can be attributed to an instability of flow in the free atmosphere coupled with Ekman pumping. Unstable solutions of a 1.5-layer shallow-water system are obtained under fast-wind speed conditions in the free atmosphere. The instability condition derived in the linear model indicates the importance of the ratio of angular velocity to vorticity, and the condition is more likely to be satisfied when the ratio is large and its radial gradient is positive. Thus, fast angular velocity, low absolute vertical vorticity, small negative radial gradient of angular velocity, and large negative gradient of vertical vorticity are favorable. Eigenvalue analyses are performed over a wide range of parameters using a vorticity profile with an infinitesimal secondary maximum. The growth rate increases with vorticity outside the radius of maximum wind (RMW), the radius of the secondary vorticity maximum, its magnitude, and the Rossby number defined by maximum tangential velocity, the RMW, and the Coriolis parameter. Furthermore, the growth rate is positive only between 2 and 7 times the RMW, and it is negative close to or far outside the RMW. These features are consistent with previous studies on SEF. A dimensionless quantity γ obtained from the unstable condition in the linear theory is applied to SEF events simulated by two different full-physics numerical models;γ increases several hours before a secondary peak of tangential velocity forms, suggesting that the initial process of SEF can be attributed to the proposed mechanism.

Inertia-gravity wave radiation from the elliptical vortex in the f-plane shallow water system

SUGIMOTO Norihiko

Fluid Dynamics Research (The Japan Society of Fluid Mechanics) 49 ( 025508 ) 17pp 2017

Research paper (scientific journal), Single Work, Accepted

Vertical structure of the axi-asymmetric temperature disturbance in the Venusian polar atmosphere: Comparison between radio occultation measurements and GCM results

ANDO Hiroki, IMAMURA Takeshi, SUGIMOTO Norihiko, TAKAGI Masahiro, TELLMANN Silvia, PATZOLD Martin, HAUSLER Bernd, KASHIMURA Hiroki, and MATSUDA Yoshihisa

Journal of Geophysical Research: Planets (American Geophysical Union) 122 ( JE005213 ) 17pp 2017

Research paper (scientific journal), Joint Work, Accepted

Development of an ensemble Kalman filter data assimilation system for the Venusian atmosphere

SUGIMOTO Norihiko, YAMAZAKI Akira, KOUYAMA Toru, KASHIMURA Hiroki, ENOMOTO Takeshi, TAKAGI Masahiro,

Scientific Reports (Nature Publishing Group) 7 ( 9321 ) 9pp 2017

Research paper (scientific journal), Joint Work, Lead author, Corresponding author, Accepted

Wave analysis in the atmosphere of Venus below 100-km altitude, simulated by LMD Venus GCM

LEBONNOIS Sébastien, SUGIMOTO Norihiko, GILLI Gabriella

Icarus 278 38 - 51 2016.06

Research paper (scientific journal), Joint Work, Accepted

Generation and backreaction of spontaneously emitted inertia-gravity waves

SUGIMOTO Norihiko, Riwal Plougonven

Geophysical Research Letters (American Geophysical Union) 43 3519 - 3525 2016.04

Research paper (scientific journal), Joint Work, Lead author, Corresponding author, Accepted

The puzzling Venusian polar atmospheric structure reproduced by a general circulation model

ANDO Hiroki, SUGIMOTO Norihiko, TAKAGI Masahiro, KASHIMURA Hiroki, IMAMURA Takeshi, MATSUDA Yoshihisa

Nature Communications (Nature Publishing Group) 7 ( 10398 ) 8pp 2016.02

Research paper (scientific journal), Joint Work, Accepted

A theoretical study on the spontaneous radiation of inertia-gravity waves using the renormalization group method. Part I: Derivation of the renormalization group equations

YASUDA Yuki, SATO Kaoru, SUGIMOTO Norihiko

Journal of the Atmospheric Sciences (American Meteorological Society) 72 ( 3 ) 957 - 983 2015

Research paper (scientific journal), Joint Work, Accepted

A theoretical study on the spontaneous radiation of inertia-gravity waves using the renormalization group method. Part II: Verification of the theoretical equations by numerical simulation

YASUDA Yuki, SATO Kaoru, SUGIMOTO Norihiko

Journal of the Atmospheric Sciences (American Meteorological Society) 72 ( 3 ) 984 - 1009 2015

Research paper (scientific journal), Joint Work, Accepted

Cyclone-anticyclone asymmetry in gravity wave radiation from a co-rotating vortex pair in rotating shallow water

SUGIMOTO Norihiko, ISHIOKA Keiichi, KOBAYASHI Hiromichi, SHIMOMURA Yutaka

Journal of Fluid Mechanics 772 80 - 106 2015

Research paper (scientific journal), Joint Work, Lead author, Corresponding author, Accepted

Inertia-gravity wave radiation from the merging of two co-rotating vortices in the f-plane shallow water system

SUGIMOTO Norihiko

Physics of Fluids 27 121701 2015

Research paper (scientific journal), Single Work, Lead author, Last author, Corresponding author, Accepted

Inverse insolation dependence of Venus' cloud-level convection

IMAMURA Takeshi, HIGUCHI Takehito, MAEJIMA Yasumitsu, TAKAGI Masahiro, SUGIMOTO Norihiko, IKEDA Kohei, ANDO Hiroki

Icarus 228 181 - 188 2014.01

Research paper (scientific journal), Joint Work, Accepted

Waves in a Venus general circulation model

SUGIMOTO Norihiko, TAKAGI Masahiro, MATSUDA Yoshihisa,

Geophysical Research Letters (American Geophysical Union) 41 7461 - 7467 2014

Research paper (scientific journal), Joint Work, Accepted

Baroclinic modes in the Venus atmosphere simulated by GCM

SUGIMOTO Norihiko, TAKAGI Masahiro, MATSUDA Yoshihisa,

Journal of Geophysical Research: Planets (American Geophysical Union) 119 1950 - 1968 2014

Research paper (scientific journal), Joint Work, Accepted

A Reynolds-averaged turbulence modeling approach to the maintenance of the Venus superrotation

YOSHIZAWA Akira, KOBAYASHI Hiromichi, SUGIMOTO Norihiko, YOKOI Nobumitsu, SHIMOMURA Yutaka

Geophysical and Astrophysical Fluid Dynamics 107 ( 6 ) 614-639 2013

Research paper (scientific journal), Joint Work, Accepted

Baroclinic modes in the atmosphere on Venus simulated by AFES

SUGIMOTO Norihiko, TAKAGI Masahiro, MATSUDA Yoshihisa, TAKAHASHI O. Yoshiyuki, ISHIWATARI Masaki, HAYASHI Yoshi-Yuki,

Theoretical and Applied Mechanics Japan (National Committee for IUTAM) 61 11-21 2013

Research paper (scientific journal), Joint Work, Accepted

Toward high resolution simulation for the atmosphere on Venus by AFES (Atmospheric GCM For the Earth Simulator)

SUGIMOTO Norihiko, TAKAGI Masahiro, MATSUDA Yoshihisa, TAKAHASHI O. Yoshiyuki, ISHIWATARI Masaki, HAYASHI Yoshi-Yuki,

Proceedings of International Conference on Simulation Technology (JSST 2012) 315-322 2012

Research paper (international conference proceedings), Joint Work, Accepted

Spontaneous Gravity Wave Radiation in a Shallow Water System on a Rotating Sphere

SUGIMOTO Norihiko, ISHII Katsuya

Journal of the Meteorological Society of Japan (Meteorological Society of Japan) 90 ( 1 ) 101-125 2012

Research paper (scientific journal), Joint Work, Accepted

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