### Abstract

Geostrophic dynamics in the horizontally differential super-rotation of Venus are examined using f
_{A}
(the Coriolis parameter defined by the angular velocity of a basic flow in an inertial frame) and Γ (the differential rotation parameter defined by the latitudinal gradient of the angular velocity) under the conditions that vertical shear of the basic field is not considered and the intrinsic phase velocity has a magnitude comparable to that of an eddy horizontal flow. The geostrophic and quasi-geostrophic approximations are valid in the regions of weakly differential and rigid-body super-rotations; however, they are invalid in the regions of strongly differential super-rotation even when the Rossby number R
_{O}
is sufficiently smaller than unity for synoptic eddies. In a general circulation model of a Venus-like atmosphere, the horizontal divergence that results from the strong differential cannot be ignored over a wide range within latitudes ±60° and below 60 km elevation because of large Γ/f
_{A}
(≥1/2).

Original language | English |
---|---|

Pages (from-to) | 185-195 |

Number of pages | 11 |

Journal | Geophysical and Astrophysical Fluid Dynamics |

Volume | 100 |

Issue number | 3 |

DOIs | |

Publication status | Published - Jun 1 2006 |

Externally published | Yes |

### Fingerprint

### All Science Journal Classification (ASJC) codes

- Computational Mechanics
- Astronomy and Astrophysics
- Geophysics
- Mechanics of Materials
- Geochemistry and Petrology

### Cite this

**Are geostrophic and quasi-geostrophic approximations valid in Venus' differential super-rotation?** / Yamamoto, Masaru; Tanaka, Hiroshi.

Research output: Contribution to journal › Article

*Geophysical and Astrophysical Fluid Dynamics*, vol. 100, no. 3, pp. 185-195. https://doi.org/10.1080/03091920600748266

}

TY - JOUR

T1 - Are geostrophic and quasi-geostrophic approximations valid in Venus' differential super-rotation?

AU - Yamamoto, Masaru

AU - Tanaka, Hiroshi

PY - 2006/6/1

Y1 - 2006/6/1

N2 - Geostrophic dynamics in the horizontally differential super-rotation of Venus are examined using f A (the Coriolis parameter defined by the angular velocity of a basic flow in an inertial frame) and Γ (the differential rotation parameter defined by the latitudinal gradient of the angular velocity) under the conditions that vertical shear of the basic field is not considered and the intrinsic phase velocity has a magnitude comparable to that of an eddy horizontal flow. The geostrophic and quasi-geostrophic approximations are valid in the regions of weakly differential and rigid-body super-rotations; however, they are invalid in the regions of strongly differential super-rotation even when the Rossby number R O is sufficiently smaller than unity for synoptic eddies. In a general circulation model of a Venus-like atmosphere, the horizontal divergence that results from the strong differential cannot be ignored over a wide range within latitudes ±60° and below 60 km elevation because of large Γ/f A (≥1/2).

AB - Geostrophic dynamics in the horizontally differential super-rotation of Venus are examined using f A (the Coriolis parameter defined by the angular velocity of a basic flow in an inertial frame) and Γ (the differential rotation parameter defined by the latitudinal gradient of the angular velocity) under the conditions that vertical shear of the basic field is not considered and the intrinsic phase velocity has a magnitude comparable to that of an eddy horizontal flow. The geostrophic and quasi-geostrophic approximations are valid in the regions of weakly differential and rigid-body super-rotations; however, they are invalid in the regions of strongly differential super-rotation even when the Rossby number R O is sufficiently smaller than unity for synoptic eddies. In a general circulation model of a Venus-like atmosphere, the horizontal divergence that results from the strong differential cannot be ignored over a wide range within latitudes ±60° and below 60 km elevation because of large Γ/f A (≥1/2).

UR - http://www.scopus.com/inward/record.url?scp=33748577992&partnerID=8YFLogxK

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U2 - 10.1080/03091920600748266

DO - 10.1080/03091920600748266

M3 - Article

VL - 100

SP - 185

EP - 195

JO - Geophysical and Astrophysical Fluid Dynamics

JF - Geophysical and Astrophysical Fluid Dynamics

SN - 0309-1929

IS - 3

ER -