HR: 14:45h
AN: A53B-06    [Abstracts]
TI: Evidence for the End of the Decline in the Stratospheric Ozone Layer
AU: * Newchurch, M
EM: mike@nsstc.uah.edu
AF: UAH, Huntsville, AL
AU: Yang, E
EM: yes@eas.gatech.edu
AF: Georgia Tech, Atlanta, GA
AU: Cunnold, D
EM: cunnold@eas.gatech.edu
AF: Georgia Tech, Atlanta, GA
AU: Salawitch, R
EM: rjs@caesar.jpl.nasa.gov
AF: JPL, Pasadena, CA
AU: McCormick, P
EM: pat.mccormick@hamptonu.edu
AF: Hampton U, Hampton, VA
AU: Russell, J
EM: james.russell@hamptonu.edu
AF: Hampton U, Hampton, VA
AU: Oltmans, S
EM: Samuel.J.Oltmans@noaa.gov
AF: CMDL, Boulder, CO
AU: Zawodny, J
EM: j.m.zawodny@larc.nasa.gov
AF: LaRC, Hampton, VA
AB: Observations indicate that we have seen the end of major declines in the thickness of Earth's protective ozone layer at low and middle latitudes. Time series of stratospheric ozone measured by the SAGE and HALOE satellite instruments are consistent with total ozone columns obtained from the ground-based Dobson/Brewer/filter networks and with the merged TOMS/SBUV satellite measurements. Results derived from the worldwide network of ozonesonde measurements also provide consistent evidence for a slowdown of ozone depletion. Statistical analyses confirm that these changes in ozone loss rates are significant above the 2-sigma confidence level. Regression analyses with Effective Equivalent Stratospheric Chlorine (EESC), and photochemical model calculations, constrained by satellite data, demonstrate that the declining levels of ozone depletion between 18-25 km altitude are consistent with a leveling off of stratospheric abundances of chlorine and bromine due to the Montreal Protocol and its amendments. Ozone changes in the lowest part of the stratosphere (tropopause to 18 km) are also significantly improving, but the dramatic changes in that layer are not primarily a result of halogen decreases. Throughout the entire stratosphere, ozone trend have changed from -7.6ñ1.0 DU/decade to -0.3ñ2.0 DU/decade. Recent observations were obtained during a period of unusually low levels of stratospheric aerosol loading. Present understanding suggests that should a major volcanic eruption occur, chemical reactions initiated by volcanic aerosol that reach the stratosphere will likely lead to short periods of decreased ozone due to anthropogenic halogens.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0340 Middle atmosphere--composition and chemistry
DE: 0341 Middle atmosphere--constituent transport and chemistry (3334)
SC: Atmospheric Sciences [A]
MN: 2005 Joint Assembly