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| Titel |
Limb Altitude and the Southern Hemispheric Vortex Observed by Venus Monitoring Camera on VEX Orbiter |
| VerfasserIn |
Sanjay Limaye, Robert Krauss, Wojciech Markiewicz |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250082504
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| Zusammenfassung |
| The Venus Monitoring Camera (VMC) on European Space Agency’s Venus Express orbiter
has been collecting almost daily images at four wavelengths (365, 550, 980 and 1050 nm)
since June 2006 with a few gaps during solar conjunctions. These data provide a nearly
continuous record of the southern vortex (Limaye at al. 2009) that spans the entire
hemisphere and reveal a dynamic, constantly evolving structure and showing a range of
dynamical instability features in the central region. These instability features are also seen in
the near infrared observations from the VIRTIS instrument on Venus Express (Luz et al.
2011).
Some similarities between the Venus hemispheric vortex and a tropical cyclone have been
previously noted (Suomi and Limaye, 1981; Limaye et al., 2009; 2011) and more have been
discovered from the VMC observations. While the details of the spatial structure of the vortex
is easily observed from the imaging observations at ultraviolet (VMC) and near infrared
wavelengths (VIRTIS), the vertical structure is more difficult to determine from Venus
Express.
Here we present inferences about the vertical level obtained from the visible limb of the
planet in VMC images. The altitude of the limb has been measured using full or near full disk
images and depicts the altitude of the Venus cloud cover which comprises the vortex
circulation. By precisely locating the limb location by fitting each limb profile in the VMC
images, the average latitudinal profile of the limb altitude has been estimated. Although the
pixel size of the images used is ~ 30-45 km, the large number of images (> 25,000) provides
a very large sample of limb altitude determinations at each latitude between the
equator and about 60Ë S latitude enabling sub-pixel variations of the limb altitude.
The latitudinal profile of the limb altitude is similar to that inferred from the near
infrared observations from VIRTIS (Ignatiev et al., 2009; Cottini et al., 2012) –
high in low latitudes and low in polar latitudes and is consistent with the vortex
structure.
References
Cottini, V., N.I. Ignatiev, G. Piccioni, P. Drossart, D. Grassi, W.J. Markiewicz (2012),
Water vapor near the cloud tops of Venus from Venus Express/VIRTIS dayside data, Icarus,
217, 561-569.
Ignatiev, N.I., D. V. Titov, G. Piccioni, P. Drossart, W. J. Markiewicz, V. Cottini, Th.
Roatsch, M. Almeida, and N. Manoel, (2009), Altimetry of the Venus cloud tops from the
Venus Express observations, J. Geophys. Res., DOI:Â 10.1029/2008JE003320.
Limaye, S.S., J.P. Kossin, C. Rozoff, G. Piccioni, D.V. Titov, W.K. Markiewicz (2009)
Vortex circulation on Venus: dynamical similarities with terrestrial hurricanes, Geophys.
Res.Lett., 36, L04204, doi:10.1029/2008GL036093.
Limaye, S., R.J. Krauss, D. Santek and W. Markiewicz (2011), Global Cloud
Organization and Motions on Venus from the Venus Monitoring Camera on Venus Express,
EPSC Abstracts, Vol. 6, EPSC-DPS2011-1230, 2011.T@
Luz, D., et al., "Venus’s Southern Polar Vortex Reveals Precessing Circulation", published
online on Science Express, 7 April 2011. DOI:10.1126/science.1201629.
Suomi, V. E., and S. S. Limaye (1978), Venus: Further evidence of vortex circulation,
Science, 201, 1009– 1011. |
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