Wind Vertical Gradient Above the Venus Clouds on the Dayside : Search for Latitudinal Variation

Details Wind Vertical Gradient Above the Venus Clouds on the Dayside : Search for Latitudinal Variation Wind Vertical Gradient Above the Venus Clouds on the Dayside : Search for Latitudinal Variation

Oct 2010

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010dps....42.1505w&link_type=abstract

American Astronomical Society, DPS meeting #42, #15.05; Bulletin of the American Astronomical Society, Vol. 42, p.974

Astronomy and Astrophysics

Astronomy

1

Scientific paper

The wind regime near 80 km can only be measured in the Venus CO2 absorption features using the ground-based visible Doppler technique (Widemann et al., 2007). This region is of particular interest between the stable, zonal retrograde circulation at cloud top and the highly variable mesospheric winds probed by 13CO and 12CO absorption lines in the mm/submm range. Winds at cloud tops near 70 km are well constrained using space-borne or ground-based visible Doppler, and will be retrieved over longer continuous sequences using data from the UVI and LIR cameras on board VCO/Akatsuki.
On observing runs in July, Sept. 2007 and Feb. 2009, the dayside of Venus was observed at R = 80000 using Canada-France-Hawaii's ESPaDOnS spectropolarimeter. The instrument allows simultaneous acquisition of the entire 0.35-1.05-micron range. It was operated at phase angle 107-110 deg at a spatial resolution of 570-600 km on Venus, displaced over the dayside hemisphere across latitudinal range +/- 55 deg. The ≈ 7k Fraunhofer lines scattered by upper cloud aerosols in co-motion with atmospheric circulation measure cloud top winds, whereas a number of CO2 absorption features (in particular near the strong 869.83 nm bandhead) probe the zonal wind shear one scale height above cloud top, hence the cyclostrophic balance latitudinal extent and the coupling with the lower thermosphere. First analysis indicates evidence for a strong vertical shear with best-fit values of about 9 m/s/km, and a time variability of CO2 Doppler winds near 80 km of about 10 m/s/hour. Results over constant latitudinal bands and comparison with thermal field measurements will be presented at the meeting.
Widemann et al. 2008, Planet. and Space Sci., 56, 1320-1334
Widemann et al. 2007, Planet. and Space Sci., 55, 1741-175

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