Other
Scientific paper
Dec 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011agufm.p24a..07c&link_type=abstract
American Geophysical Union, Fall Meeting 2011, abstract #P24A-07
Other
[3346] Atmospheric Processes / Planetary Meteorology, [5405] Planetary Sciences: Solid Surface Planets / Atmospheres, [5445] Planetary Sciences: Solid Surface Planets / Meteorology, [6225] Planetary Sciences: Solar System Objects / Mars
Scientific paper
We report direct measurements of the winds within Martian dust devils from HiRISE imagery. The central color swath of the HiRISE instrument has three separate CCDs and color filters that observe the surface in rapid cadence. Active features, such as dust devils, appear in motion when serendipitously captured by this region of the instrument. Though apparent movement of cloud features can be attributed to parallax from the spacecraft's motion, we determine that this is a relatively minor effect in our observations. Our image animations reveal clear circulatory motion within dust devils separate from their tangential motion across the Martian surface. Both manual and automated tracking of dust devil clouds reveal tangential winds that approach 20-30 m/s in some cases. These winds are sufficient to induce a ˜1% decrease in atmospheric pressure within the dust devil core relative to ambient, facilitating the lifting of dust particles into the Martian atmosphere. Finally, radial velocity profiles of dust devils constructed from our automated measurements test the Rankine vortex model for dust devil dynamics: the vortex consists of an interior region in solid body rotation and an outer region where tangential velocity decreases as a function of r-1. Our profiles successfully reveal the solid body rotation component in the interior, but fail to conclusively illuminate the profile in the outer regions of the vortex. One profile provides evidence for a velocity decrease as a function of r-1/2, instead of r-1, suggestive of surface friction effects. However, other profiles do not support this observation, or do not contain enough measurements to produce meaningful insights.
Choi David S.
Dundas Colin Morrisey
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