HR: 0830h
AN: P21F-04    [Abstracts]
TI: The Mars Polar Vortex: 2003-2004
AU: * McConnochie, T H
EM: thm9@cornell.edu
AF: Cornell University, Space Scienes Building, Ithaca, NY 14853 United States
AU: Conrath, B J
EM: barney.j.conrath@gsfc.nasa.gov
AF: Cornell University, Space Scienes Building, Ithaca, NY 14853 United States
AU: Banfield, D
EM: banfield@astro.cornell.edu
AF: Cornell University, Space Scienes Building, Ithaca, NY 14853 United States
AU: Gierasch, P J
EM: gierasch@astro.cornell.edu
AF: Cornell University, Space Scienes Building, Ithaca, NY 14853 United States
AU: Smith, M D
EM: Michael.D.Smith@nasa.gov
AF: NASA Goddard Space Flight Center, Code 693.0, Greenbelt, MD 20771 United States
AB: The winter season, westerly circumpolar flow of the martian atmosphere, like that of the terrestrial stratosphere, is concentrated into a jet which lies near 60 degrees latitude. This jet is known as the polar vortex. Polar vortices are of interest because they act as a barrier, inhibiting energy transport and potentially preventing the mixing of aerosols and chemical species. Thus, they control the response of winter polar processes to climatic forcings, both short term and long term. We have used the Mars Global Surveyor Thermal Emission Spectrometer nadir-pointed data set to generate a gridded time series of vertically resolved temperatures, and from this time series we estimate the horizontal wind field using an adaption of the "balance winds" methodology suggested by Randel (1987, J. Atmos. Sci, 44). From the wind field we calculate Ertel potential vorticity (PV), which is a conserved quantity for adiabatic flow and therefore acts as a dynamical tracer for evaluating the extent of mixing into the winter polar region. Animations of these PV maps are an important tool for visualizing the polar vortex's behaviors. The Mars polar vortex in the northern winter of 2003 shows a variety of interesting structures and behaviors, some of which appear to be characteristic of the martian polar vortices, and some of which are unique to that year and season. Characteristic features of the martian polar vortex include: 1) Rossby number of order 1, and often exceeding 1 in northern winter, in the core of the circumpolar jet; 2) a local maximum in PV on the poleward flanks of the jet, giving the potential vorticity field an annular shape and suggesting the possibility of barotropic instability; 3) a well organized northern hemisphere polar vortex that persists past L_s 330 into early 2004, and which we expect acts as an effective barrier to mixing over time scales less than the PV conservation time scale of 10 days. One notable event unique to the 2003 northern winter is a major displacement of the polar vortex, greatest on December 15, 2003, which was associated with a concurrent increase in global dust opacity. The polar vortex returned to its normal symmetric configuration by December 27.
DE: 5409 Atmospheres--structure and dynamics
DE: 5445 Meteorology (3346)
DE: 5462 Polar regions
DE: 5464 Remote sensing
SC: Planetary Sciences [P]
MN: 2005 Joint Assembly