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Integration of MGS TES FFSM eddies and MOC-observed dust storms, MY 24--26
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  • John Noble,
  • Alison Bridger,
  • Jeffrey Barnes,
  • Robert Wilson,
  • Melinda Kahre,
  • Jeffery Hollingsworth,
  • Robert Haberle,
  • Bruce Cantor
John Noble
San Jose State University

Corresponding Author:johnnoble.mars@gmail.com

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Alison Bridger
San Jose State University
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Jeffrey Barnes
Oregon State University
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Robert Wilson
NASA Ames Research Center
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Melinda Kahre
NASA Ames Research Center
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Jeffery Hollingsworth
NASA Ames Res Ctr
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Robert Haberle
NASA Ames Res Ctr
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Bruce Cantor
Malin Space Sci System
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Abstract

Mars Global Surveyor (MGS) orbiter observed a planet-encircling dust storm (PDS) in Mars year (MY) 25 from Ls=176.2-263.4°. We present an examination of Mars Orbiter Camera (MOC) dust storms and transient baroclinic eddies identified from Fast Fourier Synoptic Mapping (FFSM) of Thermal Emission Spectrometer (TES) temperatures for the first two phases of the storm: precursor, Ls=176.2- 184.7°, and expansion, Ls=184.7-193°. FFSM analysis of TES 3.7 hPa thermal data shows the presence of eastward traveling waves at 60° S with a period of about three sols. We hypothesize that these waves are transient baroclinic eddies that contributed to the initiation of precursor storms near Hellas. Integration of FFSM and MOC MY 24, 25, and 26 data shows interesting temporal and spatial associations between the evolution of eddies and storms, including: 1) comparable periodicities of travelling waves and pulses of storm activity, and 2) concurrent eastward propagation of both eddies and storms. These results suggest a causal relationship between baroclinic eddies and local storm initiation. Based on our analysis of these MGS data, we propose the following working hypothesis to explain the dynamical processes responsible for PDS initiation and expansion. Six eastward-traveling transient baroclinic eddies triggered the MY 25 precursor storms in Hellas during Ls=176.2–184.6° due to the enhanced dust lifting associated with their low-level wind and stress fields. This was followed by a seventh eddy that contributed to expansion on Ls=186.3°. Increased opacity and temperatures from dust lifting associated with the first three eddies enhanced thermal tides which supported further storm initiation and expansion out of Hellas. Constructive interference of eddies and other circulation components including sublimation flow, anabatic winds (daytime upslope), and diurnal tides may have contributed to storm onset in, and expansion out of Hellas.