Modeling Mars Cyclogenesis and Frontal Waves: Seasonal Variations and Implications on Dust Activity

Details Modeling Mars Cyclogenesis and Frontal Waves: Seasonal Variations and Implications on Dust Activity Modeling Mars Cyclogenesis and Frontal Waves: Seasonal Variations and Implications on Dust Activity

Dec 2011

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011agufm.p24a..02h&link_type=abstract

American Geophysical Union, Fall Meeting 2011, abstract #P24A-02

Physics

[3346] Atmospheric Processes / Planetary Meteorology, [3364] Atmospheric Processes / Synoptic-Scale Meteorology, [5405] Planetary Sciences: Solid Surface Planets / Atmospheres, [5445] Planetary Sciences: Solid Surface Planets / Meteorology

Scientific paper

From recent global imaging and remote-sensing instruments onboard spacecraft at Mars (e.g., MGS TES/RS/MOC) ample evidence exists for the frequent occurrence of large-scale, synoptic-period weather systems (i.e., transient baroclinic/barotropic waves) within its extratropical atmosphere. The weather systems and frontal waves occur during specific seasons on Mars, and in both hemispheres. The northern hemisphere (NH) disturbances are significantly more intense than their counterparts in the southern hemisphere (SH). Further, the NH weather systems and accompanying frontal waves appear to have significant impacts on the transport of tracer fields (e.g., particularly dust and to some extent water species (vapor/ice) as well), and regarding dust, they appear to be key agents in the lifting, lofting, organization and transport of this atmospheric aerosol. Frontal waves can also serve as a mechanism for the inter-hemispheric exchange of dust between northern and southern latitudes (i.e., so-called "flushing" dust storms). Ascertaining the nature of extratropical weather systems via carefully-chosen numerical experiments with a highly-sophisticated Mars global circulation model, and making comparisons with observations from recent Mars spacecraft, can improve our understanding of the roles such disturbances play in Mars' dust cycle, and their overall effect on the present climate of the planet. Here we extend our initial work on modeling Mars' cyclogenesis and frontal-wave development, and its effects on atmospheric dust [Hollingsworth and Kahre, 2010] by performing thorough analyses of a small suite of annual, high-resolution simulations utilizing the NASA ARC Mars general circulation model (GCM). In the climate model, dust is fully "interactive"; that is, it is lifted from the surface via a stress-based dust lifting scheme, and once lofted into the atmosphere it is radiatively active. We focus on NH seasonal assessments of the model's synoptic-period extratropical wave activity (e.g., dominant zonal wavenumbers, phase speeds, and surface pressure amplitudes), and the accompanying frontal-wave ramifications on the lifting, lofting, organization and transport of atmospheric dust. Comparisons with global imaging are made. It is found that during late autumn, late winter and early spring, the simulated synoptic weather systems are most intense and they have the largest zonal scales (s = 1-3). There is a significant relative minimum in synoptic-period wave activity close to NH winter solstice, even though the background baroclinicity is at its peak and extends vertically over several scale heights. Extratropical surface stress fields associated with the weather systems are the greatest and more spatially coherent (i.e., long-lived) at seasons bracketing the winter solstice period, and they often exceed the dust lifting threshold value. At winter solstice, maximum surface stresses frequently occur over the western hemisphere highlands and are associated with significant upslope/downslope flows. We adapt frontal wave circulation diagnostics to examine the nature of Mars' cyclogenesis, frontal wave intensity and correlations between dust lifting/lofting, organization and transport.

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