Mariner 9 and Viking spacecraft observations during the 1970's have provided
evidence for planetary-scale wave-like disturbances in the Mars atmosphere. It has
been suggested that possible sources of the wave activity are dynamical instabilities
(e.g., barotropic and/or baroclinic instabilities). An other candidate source is forced,
quasi-stationary planetary waves. In connection with Mars' enormous relief, both
mechanical forcing and large-scale thermal contrasts due to spatially varying surface
thermal-inertia and albedo patterns should provide a strong source for planetary-wave
activity.
In this thesis, we attempt to model aspects of the observed wave activity, focusing
on forced planetary waves in the wintertime atmosphere of Mars. Our approach is
to apply two dynamical models: a linear primitive equations model and a quasi-linear
'wave, mean-flow' model. Both models have spherical geometry and represent deviations
from zonal symmetry in terms of Fourier modes. The former model permits
a separation of responses to different elements that make up the total forcing mechanism,
whereas the latter is used principally to investigate the role forced planetary
waves may play in the Mars polar warming phenomenon.
Basic states representing relatively 'non-dusty' and 'highly dusty' conditions
near winter solstice allow wavenumber-1 and -2 disturbances to propagate meridionally
and vertically into the winter jet. Higher wavenumbers are strongly vertically
trapped. Stationary waves in the northern and southern extratropics differ strongly
in amplitude, phase and horizontal wave pattern.
The possibility for near-resonant, long-period modes in Mars' winter atmosphere
is also examined. For several wave-amplitude measures and dissipation strengths,
dusty low-frequency responses are an order of magnitude larger than non-dusty ones.
Wave, mean-flow simulations using wavenumber-1 or -2 forcings indicate north
polar warmings can occur for the dusty basic states. The sensitivity (magnitude, location,
and time scale) of a simulated warming to the wave forcing and the dissipation
strength is investigated. / Graduation date: 1993
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/29267 |
| Date | 05 June 1992 |
| Creators | Hollingsworth, Jeffery L. |
| Contributors | Barnes, Jeffrey R. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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