Fluid Dynamics in Earth and Planetary Sciences (FDEPS)
23rd FDEPS workshop, Nov. 28 - Dec. 1, 2023 at Kansai Seminar House

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Twenty-third Workshop "Fluid Dynamics in Earth and Planetary Sciences"

Date:
Nov. 28 - Dec. 1, 2023

Co-organizer:
  • Research Institute for Mathematical Sciences (RIMS), Kyoto University
  • Center for Planetary Science (CPS), Kobe University
Place:
Kansai Seminar House
23 Takenouchi-cho, Ichijojii, Sakyo-ku, Kyoto 606-8134 JAPAN
Phone:+81-75-711-2115 FAX:+81-75-701-5256

Program

Lecturer: Peter L. Read (Professor Emeritus and Senior Researcher, Dept. of Physics, Univ. of Oxford)

  • Intensive Lecture Series and Free Discussion
    Fast and Slow: Super-rotation Phenomena in Planetary Atmospheres
    Super-rotation is a term that describes the tendency for planetary atmospheres to rotate more rapidly than their underlying planet, either locally or in a global average. Such a tendency can be either quite small relative to the rotation of the planet (e.g. in the case of the Earth) or extremely large, as in slowly rotating planetary bodies such as Venus or Titan. In these lectures we will consider how to define super-rotation more precisely, taking into account the conservation of angular momentum, and will explore the range of dynamical processes that can induce and maintain super-rotation. The role of waves and eddies is crucial in this respect and, amongst other things, limits how much an atmosphere can super-rotate, depending on a range of planetary parameters. We will examine a variety of theoretical ideas and models that provide insights to help understand and even predict the strength and form of atmospheric super-rotation. These are then applied to help interpret observations of real atmospheres, including that of the Earth, other Solar System planets (especially Venus and Titan) and even extrasolar planets.
    • Nov. 28 (Tue)
      • 14:00 - 17:00 Lecture 1-a Lecture 1-b Lecture 1-c Lecture 1-d pdf document 1
        Lecture 1. Fundamental concepts
        • How to define “super-rotation” (historical)?
        • Angular momentum and Hide’s “first theorem”
        • Quantifying local and global super-rotation
        • Observations of global and local super-rotation: where do we find it?
        • Role of eddies: Hide’s “second theorem”
        • What is actually mixed by eddies?
      • Evening : Free discussion
    • Nov. 29 (Wed)
      • 9:00 - 12:00 Lecture 2-a Lecture 2-b Lecture 2-c pdf document 2
        Lecture 2. Idealized models of super-rotation
        • Held-Hou (1980) model of Hadley circulations
        • Gierasch (1975) & Rossow-Williams (1979) [GRW model]
        • Generalisations of GRW: tides and equatorial waves
        • Wave-mean flow interactions
      • 14:00 - 17:00 Lecture 3-a Lecture 3-b Lecture 3-c pdf document 3
        Lecture 3. Super-rotation in more complex systems
        • Super-rotation demonstrated in Laboratory experiments
        • Simplified and Intermediate Complexity GCMs
      • Evening : Free discussion
    • Nov. 30 (Thr)
    • 12/1(Fri.) Seminar
      • 09:00 - 11:00 Seminar 1-a Seminar 1-b pdf document
        Research Seminar : Equatorial Waves and Superrotation in the Stratosphere of a Titan General Circulation Model
        We investigate the characteristics of equatorial waves associated with the maintenance of superrotation in the stratosphere of a Titan general circulation model. A variety of equatorial waves are present in the model atmosphere, including equatorial Kelvin waves, equatorial Rossby waves, and mixed Rossby-gravity waves. In the upper stratosphere, acceleration of superrotation is strongest around solstice and is due to interaction between equatorial Kelvin waves and Rossby-type waves in winter-hemisphere mid-latitudes. The existence of this ‘Rossby-Kelvin’-type wave appears to depend on strong meridional shear of the background zonal wind that occurs in the upper stratosphere at times away from the equinoxes. In the lower stratosphere, acceleration of superrotation occurs throughout the year and is partially induced by equatorial Rossby waves, which we speculate are generated by quasigeostrophic barotropic instability. Acceleration of superrotation is generally due to waves with phase speeds close to the zonal velocity of the mean flow. Consequently, they have short vertical wavelengths which are close to the model’s vertical grid scale, and therefore are likely to be not properly represented. We suggest this may be a common issue amongst Titan GCMs which should be addressed by future model development.
  • Bibliography
  • Snapshots of the lectures
  • Snapshots of the reception (participants only)