### 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 |

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### All Science Journal Classification (ASJC) codes

- Astronomy and Astrophysics
- Space and Planetary Science

### Cite this

**Dynamical relationship between wind speed magnitude and meridional temperature contrast : Application to an interannual oscillation in Venusian middle atmosphere GCM.** / Yamamoto, Masaru; Takahashi, Masaaki.

Research output: Contribution to journal › Article

}

TY - JOUR

T1 - Dynamical relationship between wind speed magnitude and meridional temperature contrast

T2 - Application to an interannual oscillation in Venusian middle atmosphere GCM

AU - Yamamoto, Masaru

AU - Takahashi, Masaaki

PY - 2018/3/15

Y1 - 2018/3/15

N2 - 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 UMAX, meridional wind speed VMAX, and equator−pole temperature contrast dTMAX), which are obtained from a Venus general circulation model with equatorial Kelvin-wave forcing. Along with VMAX and dTMAX, UMAX likely increases with the phase velocity and amplitude of a forced wave. In the scatter diagram of UMAX versus dTMAX, points are plotted along a linear equation obtained from a thermal-wind relationship in the cloud layer. In the scatter diagram of VMAX versus UMAX, the apparent slope is somewhat steep in the high UMAX regime, compared with the low UMAX 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 UMAX is produced by growth and decay of a polar mixed Rossby-gravity wave with a 14-day period.

AB - 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 UMAX, meridional wind speed VMAX, and equator−pole temperature contrast dTMAX), which are obtained from a Venus general circulation model with equatorial Kelvin-wave forcing. Along with VMAX and dTMAX, UMAX likely increases with the phase velocity and amplitude of a forced wave. In the scatter diagram of UMAX versus dTMAX, points are plotted along a linear equation obtained from a thermal-wind relationship in the cloud layer. In the scatter diagram of VMAX versus UMAX, the apparent slope is somewhat steep in the high UMAX regime, compared with the low UMAX 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 UMAX is produced by growth and decay of a polar mixed Rossby-gravity wave with a 14-day period.

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U2 - 10.1016/j.icarus.2017.10.012

DO - 10.1016/j.icarus.2017.10.012

M3 - Article

AN - SCOPUS:85035068060

VL - 303

SP - 131

EP - 148

JO - Icarus

JF - Icarus

SN - 0019-1035

ER -