Formation of the Y Feature at the Venusian Cloud Top by Planetary‐Scale Waves and the Mean Circulation: Analysis of Venus Express VMC Images

Nara, Yoshiharu; Imamura, Takeshi; Murakami, S.; Kouyama, T.; Ogohara, Kazunori; Takagi, Masahiro; Kashimura, Hiroki; Sato, Naoki

doi:10.1029/2018je005779

Cited by 10 publications

(19 citation statements)

References 42 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This component is, however, almost absent in the periodogram of the brightness (Figure ). The discrepancy between the periodicities in the wind velocity and the brightness was also reported by Nara et al () and Imai et al () in the same data set. On the other periods, the periodicity associated with the Rossby wave was detected in both the velocity field and the brightness (Imai et al, ; Rossow et al, ).…”

Section: Observationssupporting

confidence: 83%

“…This photometric correction has widely been used for images of the planets covered with thick clouds including Venus (Lee et al, 2015;Titov et al, 2012). We calculated I 0 over the area with emission and incidence angle less than 80° (Nara et al, 2019).…”

Section: Analysis Methodsmentioning

confidence: 99%

“…We also deduced velocity fields at the cloud top with cloud tracking from the same data set using the method of Nara et al (). Some settings were different from adopted by Nara et al (); the size of the template was set to 8° × 8° and the search area was determined assuming that the westward velocity is between 0 and 150 m s −1 and the meridional velocity is between −50 and 50 m s −1 . Velocities were obtained every 4° in both longitude and latitude.…”

Section: Observationsmentioning

confidence: 99%

See 2 more Smart Citations

Vertical Coupling Between the Cloud‐Level Atmosphere and the Thermosphere of Venus Inferred From the Simultaneous Observations by Hisaki and Akatsuki

et al. 2020

Self Cite

View full text Add to dashboard Cite

The vertical coupling between the cloud‐level atmosphere and the thermosphere of Venus was investigated using 365 nm images obtained by the Ultraviolet Imager on board Akatsuki and oxygen atom 135.6 nm dayglow intensities obtained by the Extreme Ultraviolet Spectroscope for Exospheric Dynamics on board the space telescope Hisaki. Simultaneous observations revealed a common periodicity of ~3.6 Earth days in the cloud‐tracked velocity, the cloud brightness, and the airglow intensity. The oscillation at the cloud level is attributed to a planetary‐scale Kelvin wave. A one‐dimensional linear wave model showed that the Kelvin wave cannot propagate from the cloud level to the thermosphere because of radiative damping. The modeling also revealed that a small‐scale gravity waves having wavelengths of <1,000 km can reach the thermosphere on the dawnside and that they are strongly attenuated on the duskside because of the difference in the background winds with vertical shears. We further developed a one‐dimensional photochemical model to investigate the response of the airglow intensity to the change of the eddy diffusion coefficient, which is expected to increase with the wave amplitude. The model showed that a 3.6‐day oscillation of the diffusion coefficient with an amplitude of ~300 m2 s−1 explains the observed airglow intensity variation. A possible cause of the 3.6‐day period is the filtering of gravity wave fluxes by the Kelvin wave‐induced wind.

show abstract

Section: Observationssupporting

confidence: 83%

Section: Analysis Methodsmentioning

confidence: 99%

Section: Observationsmentioning

confidence: 99%

See 1 more Smart Citation

Vertical Coupling Between the Cloud‐Level Atmosphere and the Thermosphere of Venus Inferred From the Simultaneous Observations by Hisaki and Akatsuki

et al. 2020

Self Cite

View full text Add to dashboard Cite

show abstract

“…Smith et al () argued that the Kelvin wave could be a global mode of the Venus atmosphere and it could be generated by the cloud heating below the cloud top level. The roles of these waves in the formation of the planetary‐scale Y feature were investigated by Peralta et al () and Nara et al ().…”

Section: Introductionmentioning

confidence: 99%

Planetary‐Scale Variations in Winds and UV Brightness at the Venusian Cloud Top: Periodicity and Temporal Evolution

Imaï¹,

Kouyama²,

Takahashi

et al. 2019

JGR Planets

Self Cite

View full text Add to dashboard Cite

Planetary‐scale waves at the Venusian cloud‐top cause periodic variations in both winds and ultraviolet (UV) brightness. While the wave candidates are the 4‐day Kelvin wave and 5‐day Rossby wave with zonal wavenumber 1, their temporal evolutions are poorly understood. Here we conducted a time series analysis of the 365‐nm brightness and cloud‐tracking wind variations, obtained by the UV Imager onboard the Japanese Venus Climate Orbiter Akatsuki from June to October 2017, revealing a dramatic evolution of planetary‐scale waves and corresponding changes in planetary‐scale UV features. We identified a prominent 5‐day periodicity in both the winds and brightness variations, whose phase velocities were slower than the dayside mean zonal winds (or the super‐rotation) by >35 m/s. The reconstructed planetary‐scale vortices were nearly equatorially symmetric and centered at ~35° latitude in both hemispheres, which indicated that they were part of a Rossby wave. The amplitude of wind variation associated with the observed Rossby wave packet was amplified gradually over ~20 days and attenuated over ~50 days. Following the formation of the Rossby wave vortices, brightness variation emerges to form rippling white cloud belts in the 45–60° latitudes of both hemispheres. An ~3.8‐day periodic signals were observed in the zonal wind and brightness variations in the equatorial region before the Rossby wave amplification. Although the amplitude and significance of the 3.8‐day mode were relatively low in the observation season, this feature is consistent with a Kelvin wave, which may be the cause of the dark clusters in the equatorial region.

show abstract

“…VEX has observed equatorial clouds but has had minimal wave analysis due to the orbital configuration. Nara et al (2019) utilized observations from VEX Venus Monitoring Camera (VMC) to explore the connection between the planetary-scale ultraviolet contrast and the wind field. They were able to observe 4-days and 5-day periodicities in the brightness variations.…”

mentioning

confidence: 99%

Planetary‐Scale Wave Impacts on the Venusian Upper Mesosphere and Lower Thermosphere

et al. 2021

View full text Add to dashboard Cite

The Pioneer Venus Orbiter (PVO) and Venus Express (VEX) have been the two longest missions to orbit Venus and provide the largest collection of measurements. These observations have also been supplemented with observations from shorter duration orbiters, fly-bys, and ground based observations. Certain observed features have enough data to create averaged profiles or even statistical averaged maps, such as temperature, density, and nightglow emissions. Limaye et al. (2017) have organized the available thermal profiles of Venus, from ground-based observations to probes to orbiters (VEX being the latest one). Their work is in support of upgrading the original empirical models (Venus International Reference Atmosphere and VTS3); based mainly upon PVO observations (Hedin et al., 1983; Keating et al., 1985). The observations cover altitudes from 40 to 180 km and were binned into five latitude bins and three local time bins with the assumption of hemispheric symmetry.

show abstract

Formation of the Y Feature at the Venusian Cloud Top by Planetary‐Scale Waves and the Mean Circulation: Analysis of Venus Express VMC Images

Cited by 10 publications

References 42 publications

Vertical Coupling Between the Cloud‐Level Atmosphere and the Thermosphere of Venus Inferred From the Simultaneous Observations by Hisaki and Akatsuki

Vertical Coupling Between the Cloud‐Level Atmosphere and the Thermosphere of Venus Inferred From the Simultaneous Observations by Hisaki and Akatsuki

Planetary‐Scale Variations in Winds and UV Brightness at the Venusian Cloud Top: Periodicity and Temporal Evolution

Planetary‐Scale Wave Impacts on the Venusian Upper Mesosphere and Lower Thermosphere

Contact Info

Product

Resources

About