Astronomy and Astrophysics – Astronomy
Scientific paper
Oct 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007dps....39.6107c&link_type=abstract
American Astronomical Society, DPS meeting #39, #61.07; Bulletin of the American Astronomical Society, Vol. 39, p.539
Astronomy and Astrophysics
Astronomy
2
Scientific paper
Employing sub-millimeter 13CO and 12CO line observations from the James Clerk Maxwell Telescope (JCMT), we have mapped the nightside distributions of winds, temperatures, and CO abundance profiles across the Venus mesopause region (90-110 km) over timescales ranging from < 1 hour to years (2001-2007). Analysis of our measurements prior to 2007 indicates that the typical circulation of this region is strong retrograde zonal flow (-150 m/sec). However, the global circulation within this transition region of Venus atmospheric dynamics is also extremely variable, exhibiting transitions from predominately zonal retrograde flow to predominately subsolar-to-antisolar (SSAS) flow on timescales as short as several days. Even shorter timescale variations (< 1hour) are apparent over individual beam positions on Venus, which appear to be related to substantial vertical motions (meters/sec) over thousands of km horizontal scales. Temporal changes in nightside CO and temperature distributions are also observed to be significant. The nightside CO distribution exhibits a post midnight CO peak that is typically less than 100% in magnitude but was several times that in January 2006 observations, which also presented unusually large (20 K) nightside temperature variations. JCMT measurements over January to August 2007 provide our first opportunity to obtain partial dayside coverage and cotemporaneous coverage with Venus Express measurements. The diurnal variations of temperatures and winds above 90 km are observed to vary sharply across the evening terminator. We have not observed the very large temperature maxima apparent in SPICAV stellar occultation measurements at 100 km altitudes [Bertaux et al., Nature, in press]. This research is enabled by grant support from the NSF Planetary Astronomy program (AST-0607493).
Clancy Todd R.
Moriarty-Schieven Gerald H.
Sandor Brad J.
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