Dynamical Structure of Venus' Middle Atmosphere Constrained by Direct Wind Measurements

Details Dynamical Structure of Venus' Middle Atmosphere Constrained by Direct Wind Measurements Dynamical Structure of Venus' Middle Atmosphere Constrained by Direct Wind Measurements

Sep 2006

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006dps....38.1902w&link_type=abstract

American Astronomical Society, DPS meeting #38, #19.02; Bulletin of the American Astronomical Society, Vol. 38, p.515

Astronomy and Astrophysics

Astronomy

Scientific paper

Dynamical study of Venus' mesosphere from Venus Express will largely rely on temperature measurements, cloud motion tracking and the structure of non-LTE O2 and CO2 emissions. However, direct wind measurements can only be provided using high spectral resolution (105-107) ground-based facilities measuring Doppler shifts in CO and isotopic 13CO rotational millimeter lines (95-115 km), solar Fraunhofer (67 km) and CO2 5ν3 lines (74 km), or O emission line at 557 nm (100 km). Following our observations in 2001 and 2002 [1], we report new wind measurements using OHP 1.5-m/Aurélie (R 120,000) in April 2006. We measured drastic time variability of the lower mesospheric zonal wind field over a 24-h period, sometimes on the hour time scale, with equatorial zonal velocities about 0-20 ms-1 in CO2 lines on Apr. 22 (about 30 ms-1 in solar lines) and 125-195 ms-1 in CO2 lines on Apr. 23 (95-115 ms-1 in solar lines). The difference of altitude estimate probed by the two sets of lines, near 67 km for the solar lines, and about 74 km for the CO2 5ν3 lines, indicates that the general agreement between wind values inferred from the two types of lines support the case for a negligible wind shear over two scale heights near and above clouds top. Although the characteristic timescales of zonal wind variations in the visible lines are the same as those measured in CO millimeter lines [2], the vertical gradient of zonal wind appears negligible in the visible but reveals a strong vertical shear in CO data over 95-115 km. Future coordinated observations at various wavelengths from the ground, will investigate the dynamical coupling between different altitude levels and provide independent wind measurements at various altitudes.
[1] Widemann et al, 2006, Planet Space Sci., in press.
[2] Clancy et al. 2005, BAAS. 37, n°3, 54.04

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