### Abstract

We derive simple dynamical relationships between wind speed magnitude and meridional temperature contrast. The relationship explains scatter plot distributions of time series of three variables (maximum zonal wind speed U_{MAX}, meridional wind speed V_{MAX}, and equator−pole temperature contrast dT_{MAX}), which are obtained from a Venus general circulation model with equatorial Kelvin-wave forcing. Along with V_{MAX} and dT_{MAX}, U_{MAX} likely increases with the phase velocity and amplitude of a forced wave. In the scatter diagram of U_{MAX} versus dT_{MAX}, points are plotted along a linear equation obtained from a thermal-wind relationship in the cloud layer. In the scatter diagram of V_{MAX} versus U_{MAX}, the apparent slope is somewhat steep in the high U_{MAX} regime, compared with the low U_{MAX} regime. The scatter plot distributions are qualitatively consistent with a quadratic equation obtained from a diagnostic equation of the stream function above the cloud top. The plotted points in the scatter diagrams form a linear cluster for weak wave forcing, whereas they form a small cluster for strong wave forcing. An interannual oscillation of the general circulation forming the linear cluster in the scatter diagram is apparent in the experiment of weak 5.5-day wave forcing. Although a pair of equatorial Kelvin and high-latitude Rossby waves with a same period (Kelvin–Rossby wave) produces equatorward heat and momentum fluxes in the region below 60 km, the equatorial wave does not contribute to the long-period oscillation. The interannual fluctuation of the high-latitude jet core leading to the time variation of U_{MAX} is produced by growth and decay of a polar mixed Rossby-gravity wave with a 14-day period.

Original language | English |
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Pages (from-to) | 131-148 |

Number of pages | 18 |

Journal | Icarus |

Volume | 303 |

DOIs | |

Publication status | Published - Mar 15 2018 |

### All Science Journal Classification (ASJC) codes

- Astronomy and Astrophysics
- Space and Planetary Science