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M. Allison (NASA/GISS), F. Ferri (CISAS G.Colombo - University of Padova), M.K. Bird (Radioastronomisches Institut - Universitat Bonn), M. Fulchignoni (LESIA - Observatoire de Paris), S.W. Asmar (Jet Propulsion Laboratory), D.H. Atkinson (University of Idaho), G. Colombatti (CISAS G.Colombo - University of Padova), G.L. Tyler (Center for Radar Astronomy - Stanford University)
The highly resolved vertical profiles of wind and temperature in Titan's atmosphere afforded by the Huygens Atmospheric Structure Instrument (HASI) and Doppler Wind Experiment (DWE) have been analyzed as profiles of wind shear and buoyant static stability, using a variety of smoothing methods. Above the boundary layer, the regions of strongest vertical wind shear, as smoothed over half-scale height intervals, occur within the most statically stable regions of Titan's lower stratosphere. We have computed vertical profiles of the Richardson number (Ri), representing the squared ratio of the Brunt-Vaisala frequency to the vertical wind shear. As evaluated over small vertical difference intervals, Ri appears to approach the limiting value of 1/4 (for Kelvin-Helmholtz instability) within localized regions both near the surface and above 100km altitude, possibly indicative of wave breaking there. As evaluated for smoothed fits to the shear, Ri is as small as ~2-5 over roughly half-scale height layers between 70 and 90 km altitude, but is generally large at lower levels. These results have important implications for the setting of the latitudinal distribution of angular momentum and velocity by efficient eddy mixing of potential vorticity.
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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.