Large-Scale Traveling Weather Systems in Mars' Southern Extratropics
Abstract
Through autumn toward spring, middle- and high-latitudes within both hemispheres of Mars' atmosphere support mean equator-to-pole temperature contrasts, and an associated very strong mean westerly polar vortex. Observations from orbiting spacecraft indicate that such intense mean baroclinicity-barotropicity supports large-scale eastward traveling weather systems (i.e., transient, traveling synoptic-period waves). As on Earth, extratropical weather disturbances on Mars arising from wind-shear instabilities are critical components of the global circulation: they serve as agents in the transport of heat and momentum, and other scalar and tracer quantities (e.g., atmospheric dust, water-vapor and ice clouds). Further, such weather systems interact with other large-scale atmospheric circulation components such as quasi-stationary (i.e., forced Rossby) modes, global thermal tidal modes, continental-scale up-slope/down-slope flows, and more.
The character of Mars' traveling extratropical weather disturbances in its southern hemisphere during late winter through early spring is investigated using a high-resolution Mars global climate model (i.e., Mars GCM), one from the Agency's Mars Climate Modeling Center based at the NASA Ames Research Center. The climate model includes a complex water-ice cloud microphysics package. With such physics modules, global climate simulations present comparatively well with observations of the planet's current water cycle (Haberle et al., 2018). The climate model is "forced" with an annual dust cycle (i.e., nudged based on MGS/TES observations). Compared to the northern-hemisphere counterparts, the southern synoptic-period weather disturbances and accompanying frontal waves have smaller meridional and zonal scales, and are less intense. Influences of the zonally asymmetric (i.e., east-west varying) topography on southern large-scale weather are investigated, in addition to large-scale up-slope/down-slope flows and the diurnal cycle. A southern storm zone in late winter and early spring presents in the western hemisphere via orographic influences from the Tharsis highlands, and the Argyre and Hellas impact basins. Geographically localized transient-wave activity diagnostics are constructed that illuminate dynamical differences amongst the simulations and these are presented.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.P43K3889H
- Keywords:
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- 3346 Planetary meteorology;
- ATMOSPHERIC PROCESSESDE: 6225 Mars;
- PLANETARY SCIENCES: SOLAR SYSTEM OBJECTSDE: 5405 Atmospheres;
- PLANETARY SCIENCES: SOLID SURFACE PLANETSDE: 5445 Meteorology;
- PLANETARY SCIENCES: SOLID SURFACE PLANETS