Large stationary gravity wave in the atmosphere of Venus

Fukuhara, Tetsuya; Futaguchi, Masahiko; Hashimoto, George L.; Horinouchi, Takeshi; Imamura, Takeshi; Iwagaimi, Naomoto; Kouyama, T.; Murakami, S.; Nakamura, Masato; Ogohara, Kazunori; Sato, Mitsuteru; Sato, Takao M.; Suzuki, Makoto; Taguchi, Makoto; Takagi, Seiko; Ueno, Munetaka; Watanabe, Shigeto; Yamada, Manabu; Yamazaki, Atsushi

doi:10.1038/ngeo2873

Cited by 123 publications

(119 citation statements)

References 17 publications

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“…These waves have a brightness temperature contrast of about 5-6 K with the bright and dark portions corresponding to about 230 and 225 K, respectively. Surprisingly, the signature of these standing waves can also be detected at 283 nm (Fukuhara et al 2017a) and at 365 nm (less frequently compared to 283 nm) and in 2.02-µm IR2 dayside images, also after filtering (Satoh et al 2017). The detection at 2.02 µm suggests that cloud-top variations likely occur due to the wave.…”

Section: Thermal Infrared: Cloud-top Brightness Temperature Morphologmentioning

confidence: 82%

“…19) aligned almost north-south with a slight curvature which has been interpreted as a standing gravity wave triggered by surface topography (Fukuhara et al 2017a). Such waves have often been seen in Akatsuki LIR data and it has been observed that the north-south linear or bow features are seen as stationary at certain local times (3:00-7:00 PM) in the LIR data (Fukuhara et al 2017a). Further analysis of LIR data shows that these waves last as long as 2-3 weeks.…”

Section: Thermal Infrared: Cloud-top Brightness Temperature Morphologmentioning

confidence: 99%

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Venus looks different from day to night across wavelengths: morphology from Akatsuki multispectral images

Limaye

Watanabe

Yamazaki

et al. 2018

Earth Planets Space

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Since insertion into orbit on December 7, 2015, the Akatsuki orbiter has returned global images of Venus from its four imaging cameras at eleven discrete wavelengths from ultraviolet (283 and 365 nm) and near infrared (0.9-2.3 µm), to the thermal infrared (8-12 µm) from a near-equatorial orbit. The Venus Express and Pioneer Venus Orbiter missions have also monitored the planet for long periods but from polar or near-polar orbits. The wavelength coverage and views of the planet also differ for all three missions. In reflected light, the images reveal features seen near the cloud tops (~ 70 km altitude), whereas in the near-infrared images of the nightside, features seen are at mid-to lower cloud levels (~ 48-60 km altitude). The dayside cloud cover imaged at the ultraviolet wavelengths shows morphologies similar to what was observed from Mariner 10, Pioneer Venus, Galileo, Venus Express and MESSENGER. The daytime images at 0.9 and 2.02 µm also reveal some interesting features which bear similarity to the ultraviolet images. The nighttime images at 1.74, 2.26 and 2.32 µm and at 8-12 µm reveal features not seen before and show new details of the nightside including narrow wavy ribbons, curved string-like features, long-scale waves, long dark streaks, isolated bright spots, sharp boundaries and even mesoscale vortices. Some features previously seen such as circum-equatorial belts (CEBs) and occasional areal brightenings at ultraviolet (seen in Venus Express observations) of the cloud cover at ultraviolet wavelengths have not been observed thus far. Evidence for the hemispheric vortex organization of the global circulation can be seen at all wavelengths on the day-and nightsides. Akatsuki images reveal new and puzzling morphology of the complex nightside cloud cover. The cloud morphologies provide some clues to the processes occurring in the atmosphere and are thus, a key diagnostic tool when quantitative dynamical analysis is not feasible due to insufficient information.

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Section: Thermal Infrared: Cloud-top Brightness Temperature Morphologmentioning

confidence: 82%

Section: Thermal Infrared: Cloud-top Brightness Temperature Morphologmentioning

confidence: 99%

Venus looks different from day to night across wavelengths: morphology from Akatsuki multispectral images

Limaye

Watanabe

Yamazaki

et al. 2018

Earth Planets Space

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“…Note, however, that a surface-fixed source of "lightning," even associated with a surface feature interpreted to be volcanic, is not a guarantee that active volcanism is occurring. A correlation could emerge in another way, for example, in that atmospheric motions that manifest near the Venus cloud tops are now known to occur in a surface-fixed reference frame, due to gravity waves excited by topography (e.g., Fukuhara et al 2017).…”

Section: Lightning and Volcanosmentioning

confidence: 99%

Lightning detection on Venus: a critical review

Lorenz

2018

Prog Earth Planet Sci

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Claimed detections and nondetections of lightning and related electromagnetic emissions on Venus are qualitatively contradictory. Here, motivated by the commencement of observations by the Akatsuki spacecraft and by studies of future missions, we critically review spacecraft and ground-based observations of the past 40 years, in an attempt to reconcile the discordant reports with a minimal number of assumptions. These include invoking alternative interpretations of individual reports, guided by sensitivity thresholds, controls, and other objective benchmarks of observation integrity. The most compelling evidence is in fact the first, the very low frequency (VLF) radio emissions recorded beneath the clouds by all four of the Veneras 11-13 landers, and those data are re-examined closely, finding power-law amplitude characteristics and substantial differences between the different profiles. It is concluded that some kind of frequent electrical activity is supported by the preponderance of observations, but optical emissions are not consistent with terrestrial levels of activity. Venus' activity may, like Earth's, have strong temporal and/or spatial variability, which coupled with the relatively short accumulated observation time for optical measurements, can lead to qualitative discrepancies between observation reports. We note a number of previously unconsidered observations and outline some considerations for future observations.

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“…12a, b should locate at least between 51 and 55 km and probably is close to 51 km. Figure 14 shows an image of the 10-μm camera showing a bow-shaped structure with a latitudinal scale of almost 10,000 km (Fukuhara et al 2017). This feature was seen for the first time on the day of successful Venus's orbit insertion on December 07, 2015; such a large latitudinal structure had not been previously seen and reported at infrared wavelengths.…”

Section: A Dayside Example On May 07 2016mentioning

confidence: 99%

Initial products of Akatsuki 1-μm camera

Iwagami¹,

Sakanoi

Hashimoto

et al. 2018

Earth Planets Space

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The status and initial products of the 1-μm camera onboard the Akatsuki mission to Venus are presented. After the successful retrial of Venus' orbit insertion on Dec. 2015 (5 years after the failure in Dec. 2010), and after a long cruise under intense radiation, damage in the detector seems small and fortunately insignificant in the final quality of the images. More than 600 dayside images have been obtained since the beginning of regular operation on Apr. 2016 although nightside images are less numerous (about 150 in total at three wavelengths) due to the light scattered from the bright dayside. However, data acquisition stopped after December 07, 2016, due to malfunction of the electronics and has not been resumed since then. The 0.90-µm dayside images are of sufficient quality for the cloud-tracking procedure to retrieve wind field in the cloud region. The results appear to be similar to those reported by previous 1-μm imaging by Galileo and Venus Express. The representative altitude sampled for such dayside images is estimated to be 51-55 km. Also, the quality of the nightside 1.01-µm images is sufficient for a search for active volcanism, since interference due to cloud inhomogeneity appears to be insignificant. The quality of the 0.97-µm images may be insufficient to achieve the expected spatial resolution for the near-surface H 2 O mixing ratio retrievals.

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Large stationary gravity wave in the atmosphere of Venus

Cited by 123 publications

References 17 publications

Venus looks different from day to night across wavelengths: morphology from Akatsuki multispectral images

Venus looks different from day to night across wavelengths: morphology from Akatsuki multispectral images

Lightning detection on Venus: a critical review

Initial products of Akatsuki 1-μm camera

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