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| Titel |
Characterization of gravity waves at Venus cloud top from the Venus Monitoring Camera images |
| VerfasserIn |
A. Piccialli, D. Titov, H. Svedhem, W. J. Markiewicz |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250065664
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| Zusammenfassung |
| Since 2006 the European mission Venus Express (VEx) is studying Venus atmosphere with a
focus on atmospheric dynamics and circulation. Recently, several experiments on board
Venus Express have detected waves in the Venus atmosphere both as oscillations in the
temperature and wind fields and as patterns on the cloud layer. Waves could be playing an
important role in the maintenance of the atmospheric circulation of Venus since they can
transport energy and momentum. High resolution images of Venus Northern hemisphere
obtained with the Venus Monitoring Camera (VMC/VEx) show distinct wave patterns at the
cloud tops (~70 km altitude) interpreted as gravity waves. Venus Monitoring Camera (VMC)
is a CCD-based camera specifically designed to take images of Venus in four narrow
band filters in UV (365 nm), visible (513 nm), and near-IR (965 and 1000 nm). A
systematic visual search of waves in VMC images was performed; more than 1700 orbits
were analyzed and wave patterns were observed in about 200 images. With the
aim to characterize the wave types and their possible origin, we retrieved wave
properties such as location (latitude and longitude), local time, solar zenith angle, packet
length and width, and orientation. A wavelet analysis was also applied to determine
the wavelength and the region of dominance of each wave. Four types of waves
were identified in VMC images: long, medium, short and irregular waves. The
long type waves are characterized by long and narrow straight features extending
more than a few hundreds kilometers and with a wavelength within the range of
7 to 48 km. Medium type waves have irregular wavefronts extending more than
100 km and with wavelengths in the range 8 – 21 km. Short wave packets have a
width of several tens of kilometers and extends to few hundreds kilometers and
are characterized by small wavelengths (3 – 16 km). Often short waves trains are
observed at the edges of long features and seem connected to them. Irregular wave
fields extend beyond the field of view of VMC and appear to be the result of wave
breaking or wave interference. The waves are often identified in all channels and are
mostly found at high latitudes (60–80ºN) in the Northern hemisphere and seem
to be concentrated above Ishtar Terra, a continental size highland that includes
the highest mountain belts of the planet, thus suggesting a possible orographic
origin of the waves. However, at the moment it is not possible to rule out a bias
in the observations due to the spacecraft orbit that prevents waves to be seen at
lower latitudes, because of lower resolution, and on the night side of the planet. |
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