神戸大学　理学研究科　惑星学専攻・惑星学科　Home　Page

Fluid Geophysics (Earth and Planetary Atmospheric Science)

• URL: http://epa.scitec.kobe-u.ac.jp/index.htm.en

• Members:
  Associate Prof. Yoshiyuki O. Takahashi (URL), Associate Prof. Hiroki Kashimura (URL)
  4 Master course students, 7 Undergraduate students
• Location:
  Science and Technology Bldg 3, 503 (Takahashi), 502 (Kashimura), 506 (students)

Research Interests:

Atmosphere and ocean play important roles in determining the surface environments of the Earth and many of the other planets. The mean surface temperature of the present Earth, for example, is about 15 degrees C and is maintained by the greenhouse effect of the atmosphere and the meridional heat transport due to circulations of the atmosphere and the oceans. Consequently, the surface environment is expected to change when the atmospheric composition and/or the circulations of the atmosphere and the oceans are varied. However, at present, mechanisms that rule the actual changes in the surface environment have not been fully clarified, and therefore an evaluation of possible change is still quite difficult. A surprising fact is that, although there were events like the global ice-covered age, the Earth's surface environment has been relatively stable for about 4.5 billion years to be a planet of nourishing life. It is one of the issues to be considered that the stability of the environment has been kept for such a long duration. In our laboratory, collaborating with Center for Planetary Science (CPS), we are trying to understand principles that control meteorology and climate systems of the planetary atmospheres and the oceans including the Earth through investigating the following three main themes:

1. Planetary meteorology and climatology - studies on evolution and diversity of planetary atmospheres and surface environments -
It is well known that the characteristics of the atmospheric motions of Mars and Venus are quite different from those of the Earth. For example, in the Venusian atmosphere, high-speed wind, so-called superrotation, which circulates around the planet in a direction of the planetary rotation in 4 to 5 Earth days, exists almost uniformly over the planet. In the Martian atmosphere, dust storms of many sizes, ranging from small to global scales, frequently occur. Furthermore, exoplanets have parameters that are very different from those of planets in our solar system, and the surface environment and circulation structure of those exoplanets may be significantly different from those of planets in our solar system. In our laboratory, we are performing theoretical and numerical studies to understand mechanisms controlling the diversity of such atmospheric motions, and to predict possible atmospheric circulations on the extra-solar planets. We are also contributing to both planning exploration missions and analyzing data obtained from spacecrafts such as the Venus Climate Orbiter/Akatsuki.

2. Geophysical fluid dynamics - studies on elementary processes of fluid dynamics controlling atmospheric and ocean phenomena -
There are some curious characteristics in the flows of the atmospheres and the oceans that we may feel difficult to understand from our daily intuition. Those characteristics are actually caused by the effects of the rotation of planets and the density stratification due to gravity. There are also unexpected similarities between the circulations in the terrestrial oceans and in the Jovian and the Saturnian atmospheres. In order to understand these circulations in the various planetary atmospheres, it is necessary to investigate the features of flows, vortices, and waves appearing there and the interactions between them. In our laboratory, we are studying theoretically and numerically a variety of fluid motions influenced by rotation and stratification as a basis for the understanding of the circulations in the planetary atmospheres.

3. Computation and information meteorology - development research on numerical simulation models and numerical data analysis tools -
Numerical calculation is a very powerful method to study behaviors of geophysical fluids, and meteorology and climate of the planetary atmospheres. In our laboratory, by collaboration with research groups all over the country (GFD Dennou Club; http://www.gfd-dennou.org/), we are working on the development of numerical models and utility software that are useful to handle huge datasets produced by numerical models. By use of these tools, we are performing a number of simulations and experiments on the supercomputer Fugaku, the Earth Simulator, and supercomputers in NAOJ (National Astronomical Observatory of Japan), ISAS/JAXA (Institute of Space and Astronautical Science/Japan Aerospace Exploration Agency), and NIES (National Institute for Environmental Studies).

Current Projects:

• Structure of atmospheric general circulation (Mars, the Earth, Venus, giant planets, and exoplanets)
• Data analyses of the Venus Climate Orbiter/Akatsuki's observational data
• Moist convection (Earth) vs. dry convection (Mars)
• Organization of convection (Earth's equatorial region), Multi-component cloud convection (giant planets), Convection with major component condensation (Mars)
• Structure of the geophysical fluid trubulence
• Wave-mean flow interaction and formation of atmospheric zonal structure
• Numerical simulations of a three-dimensional convection in a rotating spherical shell (planetary cores, giant planets)
• Development of input/output library that is useful for the numerical models and data analysis
• Development of a general circulation model for the terrestrial planetary atmospheres

UPDATE　05/Apr./2024