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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 111, D17309, doi:10.1029/2005JD006371, 2006

Attribution of recovery in lower-stratospheric ozone

Eun-Su Yang

School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA


Derek M. Cunnold

School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA


Ross J. Salawitch

Jet Propulsion Laboratory/California Institute of Technology, Pasadena, California, USA


M. Patrick McCormick

Center for Atmospheric Sciences, Hampton University, Hampton, Virginia, USA


James Russell III

Center for Atmospheric Sciences, Hampton University, Hampton, Virginia, USA


Joseph M. Zawodny

NASA Langley Research Center, Hampton, Virginia, USA


Samuel Oltmans

Global Monitoring Division, NOAA Earth System Research Laboratory, Boulder, Colorado, USA


Michael J. Newchurch

Atmospheric Science Department, University of Alabama, Huntsville, Alabama, USA


Abstract

Multiple satellite and ground-based observations provide consistent evidence that the thickness of Earth's protective ozone layer has stopped declining since 1997, close to the time of peak stratospheric halogen loading. Regression analyses with Effective Equivalent Stratospheric Chlorine (EESC) in conjunction with further analyses using more sophisticated photochemical model calculations constrained by satellite data demonstrate that the cessation of ozone depletion between 18 and 25 km altitude is consistent with a leveling off of stratospheric abundances of chlorine and bromine, due to the Montreal Protocol and its amendments. However, ozone increases in the lowest part of the stratosphere, from the tropopause to 18 km, account for about half of the improvement in total column ozone during the past 9 years at Northern Hemisphere midlatitudes. The increase in ozone for altitudes below 18 km is most likely driven by changes in transport, rather than driven by declining chlorine and bromine. Even with this evidence that the Montreal Protocol and its amendments are having the desired, positive effect on ozone above 18 km, total column ozone is recovering faster than expected because of the apparent transport driven changes at lower altitudes. Accurate prediction of future levels of stratospheric ozone will require comprehensive understanding of the factors that drive temporal changes at various altitudes and partitioning of the recent transport-driven increases between natural variability and changes in atmospheric structure perhaps related to anthropogenic climate change.

Received 15 June 2005; accepted 21 April 2006; published 9 September 2006.

Keywords: stratospheric ozone layer; ozone recovery; ozone trends.

Index Terms: 0340 Atmospheric Composition and Structure: Middle atmosphere: composition and chemistry; 0341 Atmospheric Composition and Structure: Middle atmosphere: constituent transport and chemistry (3334); 1610 Global Change: Atmosphere (0315, 0325); 3305 Atmospheric Processes: Climate change and variability (1616, 1635, 3309, 4215, 4513).

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Citation: Yang, E.-S., D. M. Cunnold, R. J. Salawitch, M. P. McCormick, J. Russell III, J. M. Zawodny, S. Oltmans, and M. J. Newchurch (2006), Attribution of recovery in lower-stratospheric ozone, J. Geophys. Res., 111, D17309, doi:10.1029/2005JD006371.