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List of Abstracts 84study the decline and projected recovery, over the course of the 21st century, of stratospheric ozone. Adescription of tropospheric chemistry has been recently added to CMAM to produce a seamless simulationof atmospheric dynamics and chemistry from the ground to 95 km. An overview of the model and anassessment of the simulation of present-day tropospheric chemistry fields will be presented. Results from apair of simulations covering 1950 to 2000, one with evolving concentrations of halogen-containing ozonedepleting substances (ODSs) and one with constant ODSs, is presented to explore the effects of decreases instratospheric ozone on ozone in the troposphere.P-Chemistry Climate.50 ID:4158 15:35How do future changes in stratospheric ozone and climate influence tropospheric ozone and itsbudget?Guang Zeng 1 , Olaf Morgenstern 1 , Peter Braesicke 2 , John Pyle 21 National Institute of Water and Atmospheric Research, New Zealand2 University of Cambridge, UKContact: g.zeng@niwa.co.nzWe assess the impact of future stratospheric ozone recovery and climate change on tropospheric ozone andits budget, separating the effects of climate change and stratospheric ozone recovery. Stratospheric ozonechanges between 2000 and 2100 are calculated with a stratospheric chemistry climate model (CCM), and areused to prescribe lower stratospheric ozone in a tropospheric CCM. The calculations show that largeincreases of stratosphere-troposphere exchange (STE), due to stratospheric ozone and circulation changes –an intensifying Brewer-Dobson circulation – lead to significant increases of ozone in the troposphere,especially at middle and high latitudes. Compared to the climate-change only scenario, stratospheric ozonerecovery significantly contributes to increases in Southern Hemisphere surface ozone during austral winter;by 2100, the effect is about equal to that caused by climate change only. In the Northern Hemisphere,however, climate change dominates the changes in surface ozone.P-Chemistry Climate.51 ID:4400 15:35Stratospheric background aerosol from COS oxidationChristoph Bruehl 1 , Kirsty Pringle 2 , Jos Lelieveld 1 , Holger Tost 1 , Paul Crutzen 11 Max Planck Institute for Chemistry2 University of LeedsContact: christoph.bruehl@mpic.deThe modular atmospheric chemistry circulation model EMAC with the aerosol module gmXe has been usedfor multiyear simulations of stratospheric background aerosol. The model was extended by gas phasestratospheric sulfur chemistry and evaporation of sulfate particles. Lower boundary conditions are observedconcentrations of COS and long-lived source gases at the surface and emissions of shorter lived gas andaerosol species. We show that photochemical oxidation of COS explains about 50 to 70% of the observedstratospheric background sulfate aerosol mixing ratios (Junge layer, e.g. SAGE data) and most of theobserved profiles of SO2 in the stratosphere. The study will also include a superimposed volcanic eruptionand some discussion of radiation effects.iCACGP-IGAC 2010 12 July, 2010