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Findings since the 2006 Assessment

Findings since the 2006 Assessment. SAP co-chairs 7th Meeting of the Ozone Research Managers Geneva, Switzerland May 19, 2008. Outline. ClOOCl J-rate revision (Pope et al.) EESC & adjustments to CFC lifetimes Acceleration of the vertical lifting in the tropics.

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Findings since the 2006 Assessment

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  1. Findings since the 2006 Assessment SAP co-chairs 7th Meeting of the Ozone Research Managers Geneva, Switzerland May 19, 2008

  2. Outline • ClOOCl J-rate revision (Pope et al.) • EESC & adjustments to CFC lifetimes • Acceleration of the vertical lifting in the tropics

  3. ClOOCl J-rate revision (Pope et al.)

  4. Pope et al. (2007) • Ultraviolet Absorption Spectrum of Chlorine Peroxide, ClOOCl, Francis D. Pope, Jaron C. Hansen, Kyle D. Bayes, Randall R. Friedl, and Stanley P. Sander, J. Phys. Chem. A, 111, 4322-4332, 2007 ClO + ClO + M  ClOOCl + M (1a) ClOOCl + h ClOO + Cl (2) ClOO + M  Cl + O2 + M (3) 2 [Cl + O3 ClO + O2] (4) Net: 2O3 3O2

  5. Antarctic Ozone Loss Oct. 1 • Box model chemistry using JPL (2006) at 80˚S, 50 hPa • Vary J(ClOOCl) • From sondes we know that O3 is ~0 by early Oct., adopting the Pope et al. (2007) rate results in less than 50% O3 loss • Plot from Randy Kawa NASA/GSFC Polar chemistry workshop for evaluating the new Pope et al. J rate to be held at Cambridge, UK (17-19 June, 2008)

  6. EESC & adjustments to CFC lifetimes

  7. What is EESC? • Equivalent effective stratospheric chlorine (EESC) was developed to relate this halogen evolution to tropospheric source gases in a simple manner (Daniel et al., 1995) • EESC represents the levels of Cl & Br in the stratosphere that can lead to ozone loss.

  8. EESC (6-year) 6-year old air recovers in 2073

  9. Emission vs. mixing ratio forcings of CCMsLifetime problem with CFC-11 CFC-11 Emissions for 1960-2100 Global averaged surface CFC-11 mixing ratio GEOS CCM Emission & CFC-11 lifetime = 56 years 2032 2040 WMO A1 Emission & CFC-11 lifetime = 45 years Note: Assuming total CFC-11 production is the same, the difference between WMO A1 emission and model backed-out flux is due to differences in CFC-11 lifetimes and uncertainty in the remaining bank estimate. We spread the difference evenly between 2005-2100 for a modified emission estimate. Qing Liang NASA/GSFC

  10. Summary • If the new lab measurements of Cl2O2 photolysis are correct, then we must make seriously revise our current paradigm of polar ozone loss. • Our future chlorine scenarios are critically dependent on lifetimes of ozone depleting substances. Revision of the CFC-11 lifetime alone will alter our projections of recovery. • The acceleration of the stratospheric circulation is based upon model simulations, not observations. A changing circulation will affect both ozone and trace gas distributions

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