HR: 15:30h
AN: A53A-07    [Abstracts]
TI: Polar Stratospheric Clouds Observed by Lidar in Antarctica and the Effect of Polar Vortex
AU: Huang, W
EM: wentao@colorado.edu
AF: Cooperative Institute for Research in Environmental Sciences, University of Colorado at Boulder, 216 UCB, Boulder, CO 80309, United States
AU: * Chu, X
EM: xinzhao.chu@colorado.edu
AF: Cooperative Institute for Research in Environmental Sciences, University of Colorado at Boulder, 216 UCB, Boulder, CO 80309, United States
AU: Simpson, S E
EM: simpson1@uiuc.edu
AF: Department of Electrical and Computer Engineering, University of Illinois at Urbana- Champaign, 1308 West Main street, Urbana, IL 61821, United States
AU: Nott, G J
EM: Graeme.Nott@dal.ca
AF: Physical Science Division, British Antarctic Survey, High Cross, Madingley Road, Cambridge, United Kingdom
AU: Espy, P J
EM: pje@bas.ac.uk
AF: Physical Science Division, British Antarctic Survey, High Cross, Madingley Road, Cambridge, United Kingdom
AB: The University of Illinois Fe (iron) Boltzmann temperature lidar was operated at the South Pole (90°S) from November 1999 to October 2001, and afterward at the Rothera Station (67.5°S, 68.0°W) from December 2002 to March 2005. This lidar operates at two UV wavelengths, 372 and 374 nm. By combining the Boltzmann and Rayleigh lidar techniques, it is capable of measuring the middle and upper atmosphere temperature, Fe density, polar mesospheric clouds (PMCs), and polar stratospheric clouds (PSCs). The observations of PSCs at Rothera are the first ground-based lidar observations there and also the first in West Antarctica. Overall PSCs were observed in the range of 12-28 km during the seasons from May/June to September/October. The derived PSC mean peak backscattering ratio, centroid altitude and RMS width are comparable at both locations. However, from May to October PSCs occurred much less frequently (~24.8%) and in shorter periods (June 16th to October 5th) at Rothera comparing with the South Pole (~65.4% and May 28th to October 8th) by our observations, which is reasonable given the longer persistence of the lower temperature favorable for PSC formation at the South Pole. And the PSC occurrence is strongly correlated with local temperature. We calculated the Ertel's potential vorticity of southern hemisphere on 450K isentropic surface in 2003 and 2004 from NCEP temperature and wind data, and derived the relative distance between Rothera and the calculated polar vortex edge when the vortex is stable (from June to September). The relative distance correlates well with the local temperature (at 50 mbar level) and the PSC occurrence. When the vortex edge approaches Rothera closer (< 5 degree latitude difference) or crosses it further from the south, temperature drops and PSC occurs when the temperature is below 194K. An unusual case occurred on August 18th 2003. With 190K temperature and 2.5 degree inside the vortex, no PSC was detected. This may be caused by the vortex edge acting as a barrier to tracer gas transport preventing type I PSC formation.
DE: 0319 Cloud optics
DE: 0320 Cloud physics and chemistry
DE: 0340 Middle atmosphere: composition and chemistry
DE: 3334 Middle atmosphere dynamics (0341, 0342)
DE: 3360 Remote sensing
SC: Atmospheric Sciences [A]
MN: 2007 Joint Assembly