Kyushu University Academic Staff Educational and Research Activities Database
List of Papers
Yamamoto Masaru Last modified date:2024.06.03

Associate Professor / Atmospheric dynamics / Division of Earth Environment Dynamics / Research Institute for Applied Mechanics

1. Masaru Yamamoto, Explosive and binary cyclogenesis over a mid‑latitude hotspot and its Rossby number dependence in an idealized general circulation model, Climate Dynamics, in press, 2024.03.
2. Masaru Yamamoto, Kohei Ikeda, Masaaki Takahashi, Masaki Satoh, Rotational/divergent flow and energy conversion of thermal tides in a Venus general circulation model, Icarus,, 411, Article ID 115921, 2024.03, Venusian thermal tides are discussed as a three-dimensional response to solar heating, which is strongly modified by both barotropic and baroclinic energy conversions in a fully developed super-rotation. Thermal tides such as gravity waves propagate upward and downward from the cloud top (∼65 km) at low latitudes, while tidal gyres such as Rossby waves appear at high latitudes according to the general circulation model (GCM) developed at Atmosphere and Ocean Research Institute (AORI), The University of Tokyo. Around the cloud-top heating maximum, strong poleward/equatorward tidal flows are formed by both divergent and rotational flows that are in phase, and equatorial super-rotation is accelerated by the equatorward and vertical momentum fluxes of the diurnal tides and the vertical flux of the semidiurnal tides. These thermal tides are a result of solar heating as well as energy conversions from the zonal-mean jet and its related temperature gradient. The gravity wave is thermally forced in the cloud-top heating maximum where diabatic heating produces eddy available potential energy. The Rossby waves are formed in mid- and high-latitudinal regions where diurnal barotropic energy conversion occurs around the zonal-mean jet core and semidiurnal baroclinic energy conversion occurs below the cloud layer far from the solar heating region..
3. Masaru Yamamoto, Takumi Hirose, Kohei Ikeda, Masaaki Takahashi, Masaki Satoh, Short-period planetary-scale waves in a Venus general circulation model: Rotational and divergent component structures and energy conversions, Icarus,, 392, Article ID 115392, 2023.03, To elucidate the generation and coupling of the short-period waves in the Venus atmosphere, we investigated the three-dimensional wave structure in an AORI (Atmosphere and Ocean Research Institute, University of Tokyo, Japan) Venus general circulation model. The most predominant waves are 7.5-day waves with zonal wavenumber 1 and are slower than observed planetary-scale 5.5-day waves around the cloud bottom (∼50 km), associated with a slower zonal flow in the model. The 7.5-day waves comprise three types: Type I, a Rossby wave in the upper cloud layer; Type II, a Rossby wave around the polar tropopause (∼50 km); and Type III, an equatorial Kelvin-like wave around and below the cloud bottom.

Around the cloud top (65–70 km), the Rossby wave (Type I) has a rotational eddy structure and is produced by potential-energy conversion from zonal mean to eddy, suggesting baroclinic instability in the cloud layer. The geopotential of the Rossby wave in the upper cloud layer vertically connects to that of the equatorial Kelvin-like wave (Type III) across the critical line at ∼55 km and 30° latitudes. At the cloud bottom (∼50 km), the Kelvin-like wave and Rossby wave (Type II) are separated at a critical latitude around the cloud bottom, but are horizontally jointed with the stream function and velocity potential at the critical latitude. These two waves are major equatorward momentum transporters and are generated by horizontal shear (or barotropic) and baroclinic instabilities associated with energy conversion at the critical line. For high-latitude Rossby waves around the polar tropopause (Type II), the positive kinetic-energy conversion by vertical momentum transport is predominant, tending to relax the vertical shear of the zonal flow, leading in turn to relaxation of the horizontal temperature gradient under the cyclostrophic thermal wind. In contrast, the negative potential-energy conversion tends to produce the horizontal temperature gradient in the lower atmosphere where the solar insolation is very weak.

The equatorial jet core rotating with a 7.5-day period is composed of both divergent and rotational wind components of the equatorial Kelvin-like wave at the cloud bottom. Above the critical level of the Kelvin-like wave, the equatorial Rossby wave (downward and equatorward flank of the Type I wave) appears at around 54 km and is produced by the barotropic energy conversion..
4. Hiroki Karyu, Takeshi Kuroda, Kazunari Itoh, Akira Nitta, Kohei Ikeda, Masaru Yamamoto, Norihiko Sugimoto, Naoki Terada, Yasumasa Kasaba, Masaaki Takahashi, Paul Hartogh, Vertical-Wind-Induced Cloud Opacity Variation in Low Latitudes Simulated by a Venus GCM, Journal of Geophysical Research - Planets,, 128, article ID e2022JE007595, 2023.02.
5. Masaru Yamamoto, Effects of sea surface temperature anomalies on heavy rainfall in Tsushima Strait in late July 2020, Atmospheric Research,, 278, article ID 106336, 2022.11.
6. Masaru Yamamoto, Masaaki Takahashi, Sensitivities of general circulation and waves to horizontal subgrid-scale diffusion in long-term time integrations of a
dynamical core for Venus, Journal of Geophysical Research - Planets,, 127, article ID e2022JE007209, 2022.09.
7. Norihiko Sugimoto, Yukiko Fujisawa, Mimo Shirasaka, Mirai Abe, Shin-ya Murakami, Toru Kouyama, Hiroki Ando, Masahiro Takagi, and Masaru Yamamoto, Kelvin wave and its impact on the Venus atmosphere tested by observing system simulation experiment, Atmosphere,, 13, article ID 182, 2022.02.
8. Masaru Yamamoto, Atmospheric response to the North Pacific hotspot in idealized simulations: Application to explosive and binary cyclogenesis, Atmospheric Science Letters, 10.1002/asl.1060, 22, article ID e1060, 2021.10, Marginal seas of the western North Pacific Ocean act as a hotspot in winter, warming the marine atmosphere. The atmospheric response to lower-level (below 700 hPa altitude) heating localized around this hotspot was studied using an idealized general circulation model with an assumed triangular hotspot. As simulated in previous studies, localized atmospheric heating over the mid-latitude hotspot enhances the westerly jet core, forming a stationary Rossby wave north of the core. This study found that the hotspot remotely influences the Rossby wave source (the sum of vortex stretching and vorticity advection caused by the divergent flow) and temperature deviations at upper levels (200–300 hPa). These results are qualitatively consistent with the winter climatology. The idealized experiment was applied to explosive and binary extratropical cyclones (pairs of surface cyclones located north and south of the main Japanese islands). The active area of transient eddies at lower levels splits into two in the hotspot, leading to regional explosive development and the formation of binary cyclones through an enhanced meridionally elongated trough. The hotspot is an essential factor driving the bifurcation of cyclone tracks into the southern and northern areas of Japan, leading to binary cyclones..
9. Yuma Tsunoda, Masaru Yamamoto, Masaaki Takahashi, Rossby Number Dependence of Venus/Titan‐Type Superrotation and Its Related Intermittency, Journal of Geophysical Research - Planets,, 126, article ID e2020JE006637, 2021.02.
10. Masaru Yamamoto, Kohei Ikeda, Masaaki Takahashi, Atmospheric response to high-resolution topographical and radiative forcings in a general circulation model of Venus: Time-mean structures of waves and variances, Icarus, 10.1016/j.icarus.2020.114154, 355, Article ID 114154, 2021.02, 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 on the nightside..
11. Norihiko Sugimoto, Yukiko Fujisawa, Mimo Shirasaka, Asako Hosono, Mirai Abe, Hiroki Ando, Masahiro Takagi, Masaru Yamamoto., Observing system simulation experiment to reproduce kelvin wave in the venus atmosphere, Atmosphere,, 12, article ID 14, 2021.01.
12. Liyuan Lu and Masaru Yamamoto, Planetary-size dependence of zonal jets: Effects of horizontal diffusion in an idealized Earth-like general circulation model, Planetary and Space Science,, 190, Article ID 104976, 2020.10.
13. Masaru Yamamoto, Ensemble simulations of the influence of regionally warm sea surface on moisture and rainfall in Tsushima Strait during August 2013, Atmospheric Research, 238, article ID 104876, 2020.07.
14. Masaru Yamamoto, Equatorial Kelvin-like waves on slowly rotating and/or small-sized spheres
Application to Venus and Titan, Icarus, 10.1016/j.icarus.2019.01.008, 322, 103-113, 2019.04.
15. Yutaro Yokoyama, Masaru Yamamoto, Influences of surface heat flux on twin cyclone structure during their explosive development over the East Asian marginal seas on 23 January 2008, Weather and Climate Extremes, 10.1016/j.wace.2019.100198, 23, 2019.03.
16. Masaru Yamamoto, Kohei Ikeda, Masaaki Takahashi, Takeshi Horinouchi, Solar-locked and geographical atmospheric structures inferred from a Venus general circulation model with radiative transfer, Icarus, 10.1016/j.icarus.2018.11.015, 321, 232-250, 2019.03.
17. Young Hyang Park, Baek Min Kim, Gyundo Pak, Masaru Yamamoto, Frédéric Vivier, Isabelle Durand, A key process of the nonstationary relationship between ENSO and the Western Pacific teleconnection pattern, Scientific reports, 10.1038/s41598-018-27906-z, 8, 1, 2018.12.
18. Masaru Yamamoto, Migration of contact binary cyclones and atmospheric river
Case of explosive extratropical cyclones in East Asia on December 16, 2014, Dynamics of Atmospheres and Oceans, 10.1016/j.dynatmoce.2018.05.003, 83, 17-40, 2018.09.
19. Ning Zhao, Shinsuke Iwasaki, Masaru Yamamoto, Atsuhiko Isobe, Modulation of Extratropical Cyclones by Previous Cyclones via the Sea Surface Temperature Anomaly Over the Sea of Japan in Winter, Journal of Geophysical Research: Atmospheres, 10.1029/2017JD027503, 123, 12, 6312-6330, 2018.06.
20. Masaru Yamamoto, Masaaki Takahashi, Effects of polar indirect circulation on superrotation and multiple equilibrium in long-term AGCM experiments with an idealized Venus-like forcing: sensitivity to horizontal resolution and initial condition, Journal of Geophysical Research - Planets, 123, 708-728, 2018.03.
21. Masaru Yamamoto and Masaaki Takahashi, Dynamical relationship between wind speed magnitude and meridional temperature contrast: Application to an interannual oscillation in Venusian middle atmosphere GCM, Icarus, 303, 131-148, 2018.03.
22. Masaru Yamamoto, Probability distribution of surface wind speed induced by convective adjustment on Venus, Icarus, 284, 314-324, 2017.03.
23. M. Nakamura et al., (31st author) Masaru Yamamoto, AKATSUKI returns to Venus, Earth, Planets and Space, 10.1186/s40623-016-0457-6, 68, article ID 75, 2016.05.
24. Masaru Yamamoto, Masaaki Takahashi, General circulation driven by baroclinic forcing due to cloud-layer heating: significance of planetary rotation and polar eddy heat transport, Journal of Geophysical Research - Planets, 121, 558-573, 2016.04.
25. Masaru Yamamoto, Masaaki Takahashi, Dynamics of polar vortices at cloud top and base on Venus inferred from a general circulation model: case of a strong diurnal thermal tide, Planetary and Space Science, 113-114, 109-119, 2015.08.
26. Masaru Yamamoto, Vertical momentum and heat transport induced by wave breaking and cloud feedback heating in the Venusian atmosphere, Theoretical and Applied Mechanics Japan, 63, 165-174, 2015.06.
27. Masaru Yamamoto, Meteorological impacts of sea-surface temperature associated with the humid airflow from Tropical Cyclone Talas (2011), Annales Geophysicae, 32, pp.841-857, 2014.07.
28. Masaru Yamamoto, A Moment Method of the Log-Normal Size Distribution with the Critical Size Limit in the Free-Molecular Regime, Aerosol Science and Technology, 47, pp.725-737, 2014.05.
29. Masaru Yamamoto, Idealized numerical experiments on microscale eddies in the Venusian cloud layer, Earth Planets Space, 66:27 (15 pages), 2014.04.
30. Masaru Yamamoto, Effects of a semi-enclosed ocean on extratropical cyclogenesis: the dynamical processes around the Japan Sea on 23-25 January 2008, Journal of Geophysical Research, DOI:10.1002/jgrd.50802, 118, pp.10391-10404, 2013.08.
31. Yamamoto Masaru, Numerical error analysis of solvers using cumulative number distribution with volume-ratio grid spacing in initially particle-free nucleation-condensation systems, Aerosol and Air Quality Research, doi:10.4209/aaqr.2012.02.0042, 12, pp.1125-1134, 2012.12.
32. Masaru Yamamoto, Rapid merger and recyclogenesis of twin extratropical cyclones leading to heavy precipitation around Japan on 9-10 October 2001, Meteorological Applications, doi:10.1002/met.255, 19, 36-53, 2012.03.
33. Yamamoto, M., Mesoscale structures of two types of cold-air outbreaks over the East China Sea and the effect of coastal sea surface temperature, Meteorology and Atmospheric Physics, doi:10.1007/s00703-011-0176-2, 115, 89-112, 2012.02.
34. Yamamoto, M. and M. Takahashi, Venusian middle-atmospheric dynamics in the presence of a strong planetary-scale 5.5-day wave, Icarus , doi:10.1016/j.icarus.2011.06.017, 217, 702-713, 2012.01.
35. Yamamoto, M. T. Ohigashi, K. Tsuboki and N. Hirose, Cloud-resolving simulation of heavy snowfalls in Japan for late December 2005: application of ocean data assimilation to a snow disaster case, Natural Hazards and Earth System Sciences, 11, 2555-2565, 2011.09.
36. Maeda, Y., M.Yamamoto, N.Hirose, Meteorological influences of eddy-resolving ocean assimilation around the cold tongue to the north of the Japanese Islands during winter 2004/2005, Asia-Pacific Journal of Atmospheric Sciences, 47, 4, 319-327, 2011.08.
37. M. Nakamura et al. (JAXA 他), (30th author) Masaru Yamamoto, Overview of Venus orbiter, Akatsuki, Earth Planets Space, 63, 5, 443-457, 2011.05.
38. Ueda, A., M. Yamamoto, and N. Hirose, Meteorological influences of SST anomaly over the East Asian marginal sea on the subpolar and polar regions: A case of an extratropical cyclone on 5-8 November 2006, Polar Science, 5, 1-10, 2011.04.
39. Kae Kuriyama, Masaru Yamamoto, Interannual and synoptic-scale features of two types of cold-air outbreaks over the East China Sea during 1988–2006, Theoretical and Applied Climatology, 103, 291-304, 2011.02.
40. Yamamoto, M. and N. Hirose, Possible modification of atmospheric circulation over the northwestern Pacific induced by a small semi-enclosed ocean, Geophysical Research Letters, doi:10.1029/2010GL046214, 38, L03804, 2011.02.
41. Yamamoto, M., Microscale simulations of Venus’ convective adjustment and mixing near the surface: thermal and material transport , Icarus , 211, 993-1006, 2011.01.
42. Yamamoto, M. and N. Hirose, Atmospheric simulations using OGCM-assimilation SST: Influence of the wintertime Japan Sea on monthly precipitation, Terrestrial, Atmospheric and Oceanic Sciences, 21, 1, 113-122, 2010.02.
43. Yamamoto, M. and M. Takahashi, Dynamical effects of solar heating below the cloud layer in a Venus-like atmosphere, Journal of Geophysical Research -Planets, doi:10.1029/2009JE003381, 114, E12004, 2009.12.
44. Yamamoto, M. and N. Hirose, Regional atmospheric simulation of monthly precipitation using high-resolution SST obtained from an ocean assimilation model: Application to the wintertime Japan Sea, Monthly Weather Review, 137, 7, 2164–2174, 2009.07.
45. Hirose. N., K. Nishimura, and M. Yamamoto, Observational evidence of a warm ocean current preceding a winter teleconnection pattern in the northwestern , Geophysical Research Letters, doi:10.1029/2009GL037448, 36, L09705, 2009.05.
46. Yamamoto, M and M. Takahashi, Prograde and retrograde atmospheric rotation of cloud-covered terrestrial planets: Significance of astronomical parameters in the middle atmosphere, Astronomy and Astrophysics, Vol.490, L11-L14, 2008.11.
47. Yamamoto. M and N. Hirose, Influence of assimilated SST on regional atmospheric simulation: A case of a cold-air outbreak over the Japan Sea, Atmospheric Science Letters, Vol 9, pp 13-17, 2008.01.
48. Yamamoto, M. and M. Takahashi, A parametric study of superrotation of Venus-like planets: Effects of obliquity and period of planetary rotation, Theoretical and Applied Mechanics Japan, Vol 56, pp.335-341, 2007.11.
49. Yamamoto, M. and M. Takahashi, A parametric study of atmospheric superrotation on Venus-like planets: effects of oblique angle of planetary rotation axis, Geophysical Research Letters, Vol. 34, L16202, doi:10.1029/2007GL030220, 2007.08.
50. Yamamoto, M. and M. Takahashi, Simulations of superrotation using a GCM for Venus’ middle atmosphere, Earth Planets Space, Vol.59, pp. 971–979, 2007.08.
51. Yamamoto, M, A Moment Method for Evaporation in the Free Molecular Regime: Sensitivity to Time-Integration Scheme, Journal of Aerosol Research Japan (Earozoru Kenkyu), Vol. 22, No. 1, pp.41-47, 2007.03.
52. Yamamoto, M. and N. Hirose, Impact of SST reanalyzed using OGCM on weather simulation: A case of a developing cyclone in the Japan-Sea area, Geophys. Res. Lett., Vol. 34, L05808, doi:10.1029/2006GL028386, 2007.03.
53. Yamamoto, M. and M. Takahashi, Superrotation Maintained by Meridional Circulation and Waves in a Venus-Like AGCM, J. Atmos. Sci., Vol.63, No.12, pp.3296-3314, 2006.12.
54. Yamamoto, M. and M. Takahashi, Stationary and slowly propagating waves in a Venus-like AGCM: Roles of topography in Venus' atmospheric dynamics, Theor. Appl. Mech. Japan, Vol 55, pp.201-207, 2006.11.
55. Yamamoto, M. and M. Takahashi, An aerosol transport model based on a two-moment microphysical parameterization in the Venus middle atmosphere: Model description and preliminary experiments, J. Geophy. Res., Vol.111, E08002, doi:10.1029/2006JE002688, 2006.08.
56. Yamamoto, M. and H. Tanaka, Are geostrophic and quasigeostrophic approximations valid in Venus' differential superrotation?, Geophy. Astrophys. Fluid Dyn., Vol. 100, No. 3, pp.185-195, 2006.06.
57. Yamamoto, M., Application of a Multipurpose Finite Element Solver to Condensation Simulation: Use of Adaptive Mesh Refinement and Automatic Time Step Control, J. Aeros. Res. Japan (Earozoru Kenkyu), Vol. 21, pp.51-58, 2006.03.
58. Yamamoto, M., A Moment Method for Evaporation Using a Logarithmic Size Distribution with the Smallest Size, Aerosol Science and Technology, Vol.39, pp.790-798, 2005.08.
59. Yamamoto, M. and H. Tanaka, Geostrophic Approximation in Horizontally Differential Atmospheric Rotation, Theor. Appl. Mech. Japan, Vol.53, pp.273-279, 2004.10.
60. Yamamoto, M., A Solver for Aerosol Condensation Equation by Semi-Lagrangian Scheme with Correction Exactly Conserving Total Particle Number, Aerosol Science and Technology, Vol. 38, pp.1033-1043, 2004.10.
61. Yamamoto, M. and M. Takahashi, Dynamics of Venus' superrotation: the eddy momentum transport processes newly found in a GCM, Geophys. Res. Lett., Vol.31, doi:10.1029/2004GL019518, 2004.05.
62. Yamamoto, M., A Moment Method of an Extended Log-Normal Size Distribution (ELND): Application to Brownian Aerosol Coagulation, J. Aeros. Res. Japan (Earozoru Kenkyu), Vol.19, pp.41-49, 2004.03.
63. Yamamoto, M., 2003: Atmospheric general circulation model of Venus' atmosphere (in Japanese), Planetary People, 12, 242-247..
64. Yamamoto, M., Gravity waves and convection cells resulting from feedback heating of Venus' lower clouds, J. Meteor. Soc. Japan, Vol.81, pp.885-892, 2003.08.
65. Yamamoto, M. and M. Takahashi, Superrotation and equatorial waves in a T21 Venus-like AGCM, Geophys. Res. Lett., Vol.30, doi:10.1029/2003GL016924, 2003.05.
66. Yamamoto, M. and M. Takahashi, The Fully Developed Superrotation Simulated by a General Circulation Model of a Venus-like Atmosphere, J. Atmos. Sci., Vol.60, pp.561-574, 2003.02.
67. Yamamoto, M. and M. Takahashi, Roles of Atmospheric Waves in Venus' Superrotation : Results of a Venus-Like GCM for a 3D Thermal Forcing, Theor, Appl. Mech. Japan, Vol.51, pp.225-230, 2002.10.
68. Yamamoto, M., A parametric study of SO2 scale height as a probe of the sulfur cycle at the Venusian cloud top, J. Geophys. Res., Vol.106 pp.7611-7627, 2001.04.
69. Yamamoto, M., Blocky Markings and Planetary-Scale Waves in the Equatorial Cloud Layer of Venus, J. Atmos. Sci., Vol.58, pp.365-375, 2001.02.
70. Yamamoto, M. and H. Tanaka, The Venusian Y-shaped Cloud Pattern Based on an Aerosol-Transport Model, J. Atmos. Sci., Vol.55, pp.1400-1416, 1998.04.
71. Yamamoto, M. and H. Tanaka, Formation and Maintenance of the 4-Day Circulation in the Venus Middle Atmosphere, J. Atmos. Sci., Vol. 54, pp.1472-1489, 1997.06.