HR: 1340h
AN: A13D-0963    [Abstracts]
TI: Twenty Years of Ozone Profile Measurements Above McMurdo Station, Antarctica During Austral Spring
AU: Mercer, J L
EM: mercer@uwyo.edu
AF: Department of Atmospheric Science, University of Wyoming, 1000 E. University Ave., Laramie, WY 82071 United States
AU: * Deshler, T
EM: deshler@uwyo.edu
AF: Department of Atmospheric Science, University of Wyoming, 1000 E. University Ave., Laramie, WY 82071 United States
AU: Kroger, C
EM: C.Kroger@gns.cri.nz
AF: Institute of Geological and Nuclear Sciences, 69 Gracefield Road, Lower Hutt, 6007 New Zealand
AU: Nardi, B
EM: nardi@ucar.edu
AF: UCAR, P.O. Box 3000, Boulder, CO 80307 United States
AU: Johnson, B J
EM: Bryan.Johnson@noaa.gov
AF: CMDL, NOAA, 325 Broadway, Boulder, CO 80305 United States
AB: Balloon-borne ozonesonde measurements from 0 to ~35 km above McMurdo Station, Antarctica (78°S) have provided vertical profiles of the development of the ozone hole between late August and late October each year since 1986. Here, we present the twenty-year history of these measurements and discuss long-term trends occurring in the periods prior to the onset of major ozone loss and during major depletion. In late August, prior to significant ozone loss, column ozone averaged ~250 DU from 1986 to 1998, dropped below 230 DU from 1999-2001, and has stayed above 250 DU since 2002. During the same period, column ozone minima as well as ozone between 12-20 km, the region of maximum loss, show a similar trend. During the period of major depletion above McMurdo (15 Sept-15 Oct), maximums, minimums and averages of total and 12-20 km column ozone show a steady decline from 1986 until the mid-1990s. Record minimums were observed in 1993, two years after the eruption of Pinatubo, and again in 2001. In the 12-20 km region, minima reached zero in the mid 1990s. The thickness of the region of complete ozone destruction grew from 4 km, in 1995-1997, to over 6 km, in 1998-2001, and persisted for over a week, suggesting a vortex-wide feature. These observations are consistent with predictions and observations of peaking halogen abundance in the lower stratosphere around 2000. Similarly large ozone depletion was thus expected for another five years with a slow decline thereafter. Ozonesonde measurements in 2003 and 2004, however, do not support this. Averages of total and 12-20 km column ozone in late August and between 15 September-15 October show less depletion than in the late 1990s, and are approaching values observed in the early 1990s. The cause of this lessening in ozone loss during the last few years is puzzling. Is it a result of extended anomalous stratospheric dynamics, or indicative of a larger scale trend? These observations, including the 2005 measurements (currently in progress), will be presented and discussed in the context of recovery expectations.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0340 Middle atmosphere: composition and chemistry
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005