A SPARC Success Story: The Role of Halogen Chemistry in Polar Stratospheric Ozone Depletion An Update on the Initiative Sponsored by the Stratospheric Processes and their Role in Climate (SPARC) Project of the World Climate Research Programme Initiative Co-Chairs: Michael J. Kurylo (UMBC/GEST) Björn-Martin Sinnhuber (U. Bremen) WCRP SPARC Scientific Steering Group 17 th Session Kyoto, Japan October 2009

ClOOCl Spectral and Absorption Cross-Section Data Available for the JPL 06-2 Evaluation

A Greater Problem Arises

Models Using Pope et al. Cross Sections Yield Less O 3 Loss than Observed: Antarctic simulation using CLAMS model JPL 2006 Burkholder 1990 Pope 2007 Huder & DeMore 1994 von Hobe et al., ACP, 2007 Observed Ozone JPL 2006

Figure 4-17, WMO 2007, adapted from Frieler et al., GRL, 2006 Updated to include Pope et al. cross section by R. Schofield, M. Rex, T. Canty and R. Salawitch JPL 2006 Observed Ozone Loss, Match Calculated Ozone Loss for Model Constrained by SOLVE Measurements of ClO+2×ClOOCl Modeled Ozone Loss for: GREEN DASHED: Pope et al. (2007), BrO from CH 3 Br & Halons GREEN SOLID : Pope et al. (2007), measured BrO Modeled Ozone Loss for: BLACK : JPL 02 Kinetics, BrO from CH 3 Br & Halons BLUE DOTTED : JPL 02 Kinetics, BrO x from measured BrO BLUE DASHED: JPL 02 Kinetics except Burkholder et al. (1990) cross section BLUE SOLID : Burkholder et al. (1990) cross section and measured BrO Models Using Pope et al. Cross Sections Yield Less O 3 Loss than Observed: Arctic simulation using box model constrained by observed ClO x

0 pptv Bry 22 pptv Bry Kinnison, Brasseur, Orlando, Garcia, Tilmes Pope et al. cross sections in MOZART3/WACCM1b yield half as much ozone loss as Burkholder et al. cross sections

Huder and DeMore, 1995 JPL 2006 Burkholder et al., 1990 Pope et al., 2007 ClOOCl Cross Section (cm 2 ) von Hobe et al., 2008 The UV/Vis Absorption Spectrum of Matrix-Isolated Dichlorine Peroxide, ClOOCl M. von Hobe, F. Stroh, H. Beckers, T. Benter, and H. Willner Phys. Chem. Chem. Phys., 2009, 11, , DOI: /b814373k

More Recent Published Gas Phase Spectra Chen et al., UV Absorption Cross Sections of ClOOCl are Consistent with Ozone Degradation Models, Science, 324, 781, 8 May 2009.

NASA / JPL Data Panel Interim Recommendation "Chemical Kinetics and Photochemical Data for Use in Atmospheric Studies” Evaluation Number 16 of the NASA Panel for Data Evaluation", JPL Publication 09-XX (2009). S. P. Sander, R. R. Friedl, D. M. Golden, M. J. Kurylo, P. H. Wine, J. Abbatt, J. B. Burkholder, C. E. Kolb, G. K. Moortgat, R. E. Huie, and V. L. Orkin Soon to be available at v/. v/

NASA / JPL 09: Estimated Error Limits Revised

“Chlorine- Catalyzed Ozone Destruction: Cl Atom Production from ClOOCl Photolysis” D. M. Wilmouth, T. F. Hanisco, R. M. Stimpfle, and J. G. Anderson J. Phys. Chem. (in press) Available for download on the J. Phys Chem A ASAP website: / /jp / /jp

“Chlorine-Catalyzed Ozone Destruction: Cl Atom Production from ClOOCl Photolysis” Wilmouth et al., J. Phys. Chem. (in press)

“Chlorine-Catalyzed Ozone Destruction: Cl Atom Production from ClOOCl Photolysis” Wilmouth et al., J. Phys. Chem. (in press)

“UV Absorption Spectrum of the ClO Dimer (Cl2O2) between 200 and 420 nm” D. K. Papanastasiou, V. C. Papadimitriou, D. W. Fahey, and J. B. Burkholder J. Phys. Chem. (in press)

“UV Absorption Spectrum of the ClO Dimer (Cl2O2) between 200 and 420 nm” D. K. Papanastasiou, V. C. Papadimitriou, D. W. Fahey, and J. B. Burkholder J. Phys. Chem. (in press) Comparison of wavelength dependent Cl 2 O 2 atmospheric photolysis rate coefficients, J(λ), calculated for a solar zenith angle (SZA) of 86  at an altitude of 20 km

“UV Absorption Spectrum of the ClO Dimer (Cl2O2) between 200 and 420 nm” D. K. Papanastasiou, V. C. Papadimitriou, D. W. Fahey, and J. B. Burkholder J. Phys. Chem. (in press) Upper Frame: Integrated atmospheric photolysis rate coefficients, J, calculated for Cl 2 O 2 as a function of solar zenith angle (SZA). Lower Frame: Same data relative to the values obtained using the NASA/JPL recommended Cl 2 O 2 cross section data.

JPL 09 Recommendation & Most Recent Lab Studies

Conclusions The ClOOCl cross section has been perhaps the largest source of uncertainty in our description of polar ozone loss. The laboratory measurement of the ClOOCl cross section by Pope et al. (2007) fell outside the range of uncertainty defined by prior laboratory studies, leading to much discussion, deliberation, and debate within the atmospheric chemistry community. The community met in Cambridge, England (June 2008) to examine our understanding of polar ozone loss (laboratory, theory, field observations, and modelling) in light of the Pope et al. study. A detailed report from that workshop is available electronically at: Several subsequent laboratory studies (published or about to be published) have failed to reproduce the Pope et al. ClOOCl cross sections and provide strong support for our understanding of chlorine-catalyzed ozone loss in the polar stratosphere. The SPARC Initiative played an important role in fostering this new work!

JPL-09 Recommendations on the ClO + ClO  ClOOCl Equilibrium Constant "Chemical Kinetics and Photochemical Data for Use in Atmospheric Studies” Evaluation Number 16 of the NASA Panel for Data Evaluation", JPL Publication 09-XX (2009). S. P. Sander, R. R. Friedl, D. M. Golden, M. J. Kurylo, P. H. Wine, J. Abbatt, J. B. Burkholder, C. E. Kolb, G. K. Moortgat, R. E. Huie, and V. L. Orkin Soon to be available at

Lab Data Used in the JPL 2009 Recommendation for K EQ Over the Temperature Range 180<T/K<300

Lab Data Together with Various Fits for K EQ Over the Temperature Range 180<T/K<300

JPL 2006 and JPL 2009 Recommendations for K EQ Together with Various Fits from 180 < T/K < 225

Salawitch / Canty Analysis of Field Data Filtered for SZA > 105 Displayed on the Previous Plot

“Constraining the ClO/ClOOCl Equilibrium Constant from Aura Microwave Limb Sounder Measurements of Nighttime ClO” M. Santee, S. Sander, N. Livesey and L. Froidevaux (to be submitted to PNAS Special Issue on Atmospheric Chemistry)

Acknowledgements NASA/JPL Panel for Data Evaluation –esp. D. Golden & J. Burkholder New Lab Studies –D. Wilmouth & J. Anderson (Harvard U.) –J. Burkholder (NOAA-ESRL)

Interface between Laboratory Kinetics and the 2010 WMO/UNEP Ozone Assessment Lifetimes for Long-Lived Compounds and VSLS’s for Chapters 1 and 5 Based on the most current JPL 2010 and IUPAC Evaluations "Chemical Kinetics and Photochemical Data for Use in Atmospheric Studies” Evaluation Number 17 of the NASA Panel for Data Evaluation JPL Publication 10-XX (2010). S. P. Sander, R. R. Friedl, D. M. Golden, M. J. Kurylo, P. H. Wine, J. Abbatt, J. B. Burkholder, C. E. Kolb, G. K. Moortgat, R. E. Huie, and V. L. Orkin Available Spring 2010 at

Influence of JPL 09-XX Recommendations on Model Simulations of NO y and O 3 Charles Jackman and Eric Fleming September 29, 2009 GSFC Fully Coupled 2-D Model Computations of Constituent Diurnal Cycles 1) Compare with UARS odd nitrogen (NO,NO 2,HNO 3,ClONO 2 ) 2) Compare with Total Ozone Measurements ( ) 3) Total Ozone (1980, 2000, time series)

1) Compare with UARS odd nitrogen (NO, NO 2, HNO 3, ClONO 2 ) NO+NO 2 at Sunset; HNO 3 +ClONO 2 for 24-hour average Model with JPL-09 higher than with JPL-06 [due to increased N 2 O + O( 1 D)  2NO reaction]

2) Compare with Total Ozone Measurements ( ) Total Ozone average Model with JPL-09 lower than with JPL-06 Largest impact in polar spring, especially SH [~One-half of change due to increased N 2 O + O( 1 D)  2NO reaction] -15 DU -10 DU

3) Total Ozone (1980, 2000, time series) Model with JPL-09 has less ozone than with JPL-06 (higher Cl sensitivity in polar regions with JPL-09) Ozone recovery delayed by ~1 year