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- Title
Solar‐Related Variations of the Cloud Top Circulation Above Aphrodite Terra From VMC/Venus Express Wind Fields.
- Authors
Patsaeva, M. V.; Khatuntsev, I. V.; Zasova, L. V.; Hauchecorne, A.; Titov, D. V.; Bertaux, J.‐L.
- Abstract
Winds derived by a digital tracking technique from ultraviolet (365 nm) images captured by the Venus Monitoring Camera (VMC) onboard the Venus Express spacecraft from 2006 to 2013 were used to study the atmospheric circulation at cloud top level (70 ± 2 km). This data set allows variations of the wind speed with both latitude and longitude to be studied and establishes their correlation with surface topography as well as local time dependence. Both zonal and meridional wind components show some correlation with topography. The minimum zonal wind speed was found at noon above Ovda Regio (10°S, 93°E), the highest region of Aphrodite Terra, one of the largest highlands in the equatorial region. The area of slow zonal wind extends to at least 30°S and shifts in the direction of superrotation in the afternoon and with increasing latitude (poleward). The observed deceleration of cloud top wind was recently attributed to the interaction of the gravity (mountain) waves generated by Aphrodite Terra with the atmospheric circulation. The present study was performed for different local time over the mountainous longitudes. The deceleration pattern in the zonal wind field is mainly conserved within a few hours around noon. Systematic longitude shift is observed in the afternoon in the direction of the evening terminator. Another area of perturbation of both zonal and meridional wind components is observed in the equatorial region around LT = 13–14 hr and may be explained by the solar tide. Plain Language Summary: Venus is completely covered with a thick cloud layer with its top at about 70 km. Surprisingly, recent observations show that the cloud level circulation is affected by the surface topography. In this paper we analyzed wind velocities derived from tracking of cloud features in the UV images acquired by the Venus Monitoring Camera onboard the European Space Agency's Venus Express orbiter during its operations from 2006 to 2013. The zonal wind at the cloud top decelerates by about 20% above the highest part of Aphrodite Terra and reaches its minimum at local noon. The zonal wind deceleration is explained by interaction of gravity waves generated by the surface relief with the atmospheric circulation. An additional deceleration occurs in the afternoon in the equatorial region and is probably caused by solar heating of the clouds. The combination of both effects results in a vast area of slow wind during the daytime. Key Points: A maximum deceleration of the mean zonal flow is observed at noon above the highest region of Aphrodite Terra, VenusThe mean zonal and meridional flows at cloud top level in the equatorial region are perturbed by a solar tide at 13–14 hrA dependence of the mean zonal and meridional flows on topography is observed from the equator to at least 30°S
- Subjects
ATMOSPHERIC circulation; WIND speed; SURFACE topography; MERIDIONAL winds; EUROPEAN Space Agency
- Publication
Journal of Geophysical Research. Planets, 2019, Vol 124, Issue 7, p1864
- ISSN
2169-9097
- Publication type
Article
- DOI
10.1029/2018JE005620