HR: 0800h
AN: P11A-0247    [Abstracts]
TI: The Neutral Atmosphere of Mars as Observed Through Radio Occultation Measurements With MEX and MGS
AU: * Hinson, D
EM: dhinson@stanford.edu
AF: Department of Electrical Engineering, Stanford University, Stanford, CA 94305, United States
AU: Patzold, M
EM: paetzold@geo.Uni-Koeln.DE
AF: Institut fur Geophysik und Meteorologie, Universitat zu Koln, Cologne, D-50923, Germany
AU: Simpson, R
EM: rsimpson@magellan.stanford.edu
AF: Department of Electrical Engineering, Stanford University, Stanford, CA 94305, United States
AU: Tellmann, S
EM: tellmann@geo.Uni-Koeln.DE
AF: Institut fur Geophysik und Meteorologie, Universitat zu Koln, Cologne, D-50923, Germany
AU: Tyler, L
EM: len.tyler@stanford.edu
AF: Department of Electrical Engineering, Stanford University, Stanford, CA 94305, United States
AB: Radio occultation experiments conducted with Mars Express (MEX) and Mars Global Surveyor (MGS) yield atmospheric profiles with fine vertical resolution, typically about 1 km. We are exploiting this attribute of the occultation measurements to investigate the structure and dynamics within the lowest scale height of the Martian atmosphere. Radio occultation experiments were conducted concurrently by the two spacecraft during several intervals: May to August 2004, December 2004 to January 2005, August to September 2005, and November 2005 to April 2006. Owing to differences in orbital geometry, the MEX and MGS occultations generally sound the atmosphere at widely different combinations of latitude and local time [e.g., Hinson et al., Radio occultation measurements and MGCM simulations of Kelvin waves on Mars, Icarus, in press, 2007]. Our current analysis of these observations addresses two topics. The first concerns the temperature lapse rate in the lower atmosphere and its diurnal variations. As an example of initial results in this area, the convective boundary layer extends to a height of 4--9 km at local time 17:00 in a set of MEX occultations that sounded the tropics during northern spring of Mars Year (MY) 27. The depth of the boundary layer varies significantly among these profiles, possibly in response to spatial variations in surface thermal properties and local topography. This investigation can provide valuable constraints for Mesoscale Models and Large Eddy Simulations. We are also using these observations to characterize the meridional variations in temperature and geopotential height associated with the winter polar vortex and to estimate the near-surface zonal wind speeds implied by geostrophic balance. For example, the geopotential height at 400 Pa decreases by about 3 km from equator to pole in late northern winter of MY 27. The gradient of geopotential height near 60°N implies a zonal wind speed of about 40 m s^-1.
DE: 5405 Atmospheres (0343, 1060)
DE: 5445 Meteorology (3346)
DE: 6225 Mars
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting