Thermal tides and stationary waves on Mars as revealed by Mars Global Surveyor thermal emission spectrometer

Don Banfield, Barney Conrath, John C. Pearl, Michael D. Smith, Philip Christensen

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Abstract

Atmospheric temperature retrievals from thermal emission spectrometer (TES) observed radiances make possible the most complete separation of the constituent wave modes evident in Mars atmosphere to date. We use all of the data from the first aerobraking period as well as the science phasing orbits, which affords good sampling of the diurnal tides and stationary waves. TES retrievals of atmospheric temperature on a grid of pressure levels are the fundamental data set in this study. We then fit this data to selected Fourier modes in longitude and time for altitude, latitude, and Ls bins. From this we have identified the amplitudes and phases of the diurnal and semidiurnal tides, the first few (gravest) stationary waves, and a few modes which arise because of couplings between sun-fixed tides and topography. We also retrieve estimates of the zonal and time of day mean temperature meridional cross sections and their rates of change. The zonal and time of day mean temperature meridional cross sections agree with those of Conrath et al. [this issue] to within 1 K where we can reliably retrieve this mode (90°S to ∼20°S). Heating rates of up to 2.4 K/sol were observed around three scale heights above 60°S-90°S during the Ls = 310° - 320° dust storm. Diurnal tide amplitudes of greater than 8 K were observed during the Noachis and Ls = 310° - 320° dust storms. From Ls = 255° - 285° an unexplained phase reversal at two scale heights was observed in the diurnal tide from 60°S-80°S. Convective penetration above the unstable boundary layer may explain anomalous (180° out of phase with the sun) diurnal tide phases between 0.5 and one scale height above the subsolar point. Semidiurnal tides are of order 2 K throughout the southern extratropics. A stationary mode of wavenumber one was observed with amplitude 1-4 K in the southern extratropics. Topographically coupled tidal modes were also quantified.

Original languageEnglish (US)
Article number1999JE001161
Pages (from-to)9521-9537
Number of pages17
JournalJournal of Geophysical Research E: Planets
Volume105
Issue numberE4
DOIs
StatePublished - Apr 25 2000

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ASJC Scopus subject areas

  • Geophysics
  • Forestry
  • Oceanography
  • Aquatic Science
  • Ecology
  • Water Science and Technology
  • Soil Science
  • Geochemistry and Petrology
  • Earth-Surface Processes
  • Atmospheric Science
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Palaeontology

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