# Presentation: 327799

## Impact of Recent Laboratory Measurements of the ClOOCl Absorption Cross Section On Our Understanding of Polar Ozone Chemistry 

- T. Canty1, M. Rex2, M. von Hobe3, R. Salawitch1,
- K. Frieler2, R. Schofield2,R. Stimpfle4, D. Wilmouth4
- 1University of Maryland, College Park, MD
- 2Alfred Wegener Institute for Polar and Marine Research, Pottsdam, Germany
- 3Institute for Chemistry and Dynamics of the Geosphere, Julich, Germany
- 4Harvard University, Cambridge, MA

## A recent study by Pope et al., JPC, 2007 reports new 

- measurements of the ClOOCl cross-section that
- challenge our understanding of polar chlorine chemistry.

- ClOOCl Cross Section (cm-2)

## Balance of ClO / ClOx and ozone loss rate are governed by:

**ClO****x**

**3**

**2**

**1**

**4**

**Step (1): Forward Reaction**
- ClO + ClO + M → ClOOCl + M
**Step (2): Thermal decomposition**
- ClOOCl + heat → ClO + ClO
- Null Cycle
**Step (3): Photolysis**
- ClOOCl + h → Cl + ClOO → Cl + Cl + O2
- Rate = **J ClOOCl** x [ClOOCl]
- O  O bond reformed here  **rate limiting step for ozone loss**
**Step (4): **Cl + O3 → ClO + O2:
- Regeneration of ClO

**Balance of ClO / ClO****x**** and ozone loss rate are governed by:**

## JPL 2006

## Antarctic, 2005

- Arctic, 2004-05

- Mixing Ratio (ppb)

- ClO

- ClONO2

- HCl

**Aura Observations**

- Antarctic, 2005

- Arctic, 2004-05

- Mixing Ratio (ppb)

- ClO

- ClONO2

- HCl

- Inferred Cly (ppb)

- JPL2006

- ClOOCl (ppb)

**JPL2006 ****→ ****JPL 2006 kinetics**

**Aura Observations**

- Antarctic, 2005

- Arctic, 2004-05

- Mixing Ratio (ppb)

- ClO

- ClONO2

- HCl

- Inferred Cly (ppb)

- JPL2006

- ClOOCl (ppb)

- Stimpfle 2004

- JPL2006 → JPL 2006 kinetics
**Stimpfle 2004 ****→ ****J****ClOOCl**** Burkholder et al. 1990, K****eq****=Cox&Hayman, 1988, K****f****=Bloss *****et al.*****, 2001**

**Aura Observations**

- Antarctic, 2005

- Arctic, 2004-05

- Mixing Ratio (ppb)

- ClO

- ClONO2

- HCl

- Inferred Cly (ppb)

- JPL2006

- ClOOCl (ppb)

- Stimpfle 2004

- Huder&DeMore 1995

- JPL2006 → JPL 2006 kinetics
- Stimpfle 2004 → JClOOCl Burkholder et al. 1990, Keq=Cox&Hayman, 1988, Kf=Bloss *et al.*, 2001
**Huder & DeMore 1995 ****→ J****ClOOCl****  ****Huder and DeMore, 1995**

**Aura Observations**

- Antarctic, 2005

- Arctic, 2004-05

- Mixing Ratio (ppb)

- ClO

- ClONO2

- HCl

- Inferred Cly (ppb)

- JPL2006

- ClOOCl (ppb)

- Stimpfle 2004

- H&D1995

- Pope2007

- JPL 2006 → JPL 2006 kinetics
- Stimpfle 2004 → JClOOCl Burkholder et al., 1990, Keq=Cox&Hayman, 1988, Kf=Bloss *et al.*, 2001
- Huder & DeMore 1995 → JClOOCl  Huder and DeMore, 1995
**Pope 2007 ****→ J****ClOOCl**** ****Pope et al., 2007**

**Aura Observations**

## (1) Direct mechanism:ClOOCl + X →  Cl + Cl + O2 

- Potential mechanisms fall into three categories:
**(1) Direct mechanism:**ClOOCl + X →  Cl + Cl + O2
- 	 Species X must be a “daytime species”, varying in a UV dependent manner similar to JClOOCl Burkholder
**(2) ClOOCl is weakly bonded and can absorb out to 1.3 to 1.6 ****μ****m**A photolytic process involving visible or near IR light
-        could be the missing sink for ClOOCl
**(3) Formation of an unknown nightime reservoir (Cl****NIGHT****)**ClOOCl + Y → ClNIGHT + ... ClNIGHT + h →  ... → Cl + Cl + O2 + Z

## Solutions?

- BrO+ClOOCl → BrOCl+ClOO

- OH+ClOOCl → HOCl+ClOO

- ClOOCl + ice → products

- ClOOCl + Vis or Near IR light

## Solutions?

- If fast enough to affect ClOOCl,
- would have seen in lab (K. Bayes and
- S. Sander, priv. comm.)

- If fast enough, BrOCl becomes dominant
- daytime reservoir of BrOx.  Inconsistent
- with atmospheric observation of BrO

- New rate constant much too slow
- (J. Hansen, priv. comm.)

- Inconsistent with EUPLEX observations
- of very high ClO at ~205 K, after recent
- PSC processing

- ClO+ClOOCl → ClOCl+ClOO

- BrO+ClOOCl → BrOCl+ClOO

- OH+ClOOCl → HOCl+ClOO

- ClOOCl + ice → products

- ClOOCl + Vis or Near IR light

- Inconsistent with diurnal variation of ClO

## Rapid equilibrium between ClOOCl and ClClO2 (              )?

**Rapid equilibrium between ClOOCl and ClClO****2**** (              )?**

- ~10% of Cl2O2
- in the form of ClClO2 leads to “Burkholder like“ photolysis of the mixture
- Temperature dependent equilibrium could explain SOLVE / EUPLEX differences in ClO

- e.g. by:	ClOOCl + ClO → ClClO2 + ClO
- 	ClClO2 + ClO → ClOOCl + ClO

- Antarctic, 2005

- Arctic, 2004-05

- Mixing Ratio (ppb)

- ClO

- ClONO2

- HCl

- Inferred Cly (ppb)

- JPL2006

- ClOOCl (ppb)

- Stimpfle 2004

- H&D1995

- Pope2007

**Aura Observations**

- JPL 2006 → JPL 2006 kinetics
- Stimpfle 2004 → JClOOCl Burkholder et al., 1990, Keq=Cox&Hayman, 1988, Kf=Bloss *et al.*, 2001
- Huder & DeMore 1995 → JClOOCl  Huder and DeMore, 1995
**Pope 2007 ****→ J****ClOOCl**** ****Pope et al., 2007**

- Antarctic, 2005

- Arctic, 2004-05

- Mixing Ratio (ppb)

- ClO

- ClONO2

- HCl

- Inferred Cly (ppb)

- JPL2006

- ClOOCl (ppb)

- Stimpfle 2004

- H&D1995

- ClOOCl isomerization

**Aura Observations**

- JPL 2006 → JPL 2006 kinetics
- Stimpfle 2004 → JClOOCl Burkholder et al., 1990, Keq=Cox&Hayman, 1988, Kf=Bloss *et al.*, 2001
- Huder & DeMore 1995 → JClOOCl  Huder and DeMore, 1995
**ClOOCl isomerization ****→ J****ClOOCl**** ****Pope et al., 2007 + ClClO****2**** ****chemistry**

## SOLVE

- A value of β=1 indicates good agreement between observations and models

- First measurements of ClOOCl from the ER-2 during SOLVE/THESEO-2000
- (Stimpfle *et al., JGR*, 2004)

## SOLVE

- N

- Trolier *et al.*, 1990

- JPL2000

- Bloss *et al.*, 2001

- JPL2006

- Boakes *et al.*, 2005

- JClOOCl=JPL06

- Kf

## SOLVE

- N

- Trolier *et al.*, 1990

- JPL2000

- Bloss *et al.*, 2001

- JPL2006

- Boakes *et al.*, 2005

- JClOOCl=Burkholder *et al*., 1994

- Kf

## SOLVE

- Trolier *et al.*, 1990

- JPL2000

- Bloss *et al.*, 2001

- JPL2006

- Boakes *et al.*, 2005

- JClOOCl=Pope *et al*., 2007

- Kf

- N

## SOLVE

- N

- Trolier *et al.*, 1990

- JPL2006

- Boakes *et al.*, 2005

- JClOOCl=Pope *et al*., 2007, ClOOCl isomerization

- Kf

## Cly

- Cly

**Modeled ClO**

- Time (utc)

- Time (utc)

- Total O3 Loss Rate

**Meas ClO**

- Mixing Ratio (ppb)

- SZA

- EUPLEX, 030130

**JPL 2006 ****→ ****JPL 2006 kinetics**

## Cly

- Cly

**Modeled ClO**

- Time (utc)

- Time (utc)

- Total O3 Loss Rate

**Meas ClO**

- Mixing Ratio (ppb)

- SZA

- EUPLEX, 030130

- Black curve = JPL 2006

**Stimpfle 2004 ****→ ****J****ClOOCl**** Burkholder et al., 1990, K****eq****=Cox&Hayman, 1988, K****f****=Bloss *****et al.*****, 2001**

## Cly

- Cly

**Modeled ClO**

- Time (utc)

- Time (utc)

- Total O3 Loss Rate

**Meas ClO**

- Mixing Ratio (ppb)

- SZA

- EUPLEX, 030130

- Black curve = JPL 2006

**Huder & DeMore 1995 ****→ J****ClOOCl****  ****Huder and DeMore, 1995**

## Cly

- Cly

**Modeled ClO**

- Time (utc)

- Time (utc)

- Total O3 Loss Rate

**Meas ClO**

- Mixing Ratio (ppb)

- SZA

- EUPLEX, 030130

- Black curve = JPL 2006

**Pope 2007 ****→ J****ClOOCl**** ****Pope et al., 2007**

## Cly

- Cly

**Modeled ClO**

- Time (utc)

- Time (utc)

- Total O3 Loss Rate

**Meas ClO**

- Mixing Ratio (ppb)

- SZA

- EUPLEX, 030130

**ClOOCl isomerization ****→ J****ClOOCl**** ****Pope et al., 2007 + ClClO****2**** ****chemistry**

- Black curve = JPL 2006

## Conclusions

- 1. New measurements of the ClOOCl cross section by
-     Pope et al., 2007 reduce both modeled ClO and polar O3
-     loss,leading to large discrepancies with observations.
- 2. A process that converts ClOOCl into a species that
-     undergoes fast photolysis and re-creates the O2 bond
-     can potentially resolve both discrepancies.
- 3. A focused effort of laboratory experimentalists and theorists,
-     field measurement investigators, and modelers is needed to
-     reconcile theory and observation of polar ozone loss.

## Acknowledgements

- Derived Meteorological Products for MLS were calculated and provided by Gloria Manney and William Daffer, with support from the MLS team at NASA's Jet Propulsion Laboratory, California Institute of Technology.
- We appreciate *very much* numerous, extremely helpful conversation with Kyle Bayes and Stan Sander.

## SPARC Workshop / Study: The Role of Halogens in Ozone Depletion

**Purpose**: This new SPARC Initiative will have three principal objectives:
- Evaluate the consequence of new data on the photolysis rate of the ClO dimer on simulations of stratospheric ozone depletion, particular in winter polar regions.
- Evaluate old and new results from laboratory studies of the photolysis rate and the type of further studies that are necessary to resolve current differences.
- Assess qualitative / quantitative evidence from the laboratory, field observations, and models that links ozone depletion to stratospheric active chlorine / bromine amounts.
**Deliverables:** A white paper describing the first two objectives and a peer-reviewed manuscript addressing the third objective.
**Timeline**: Next 6-8 months for the workshop; 12-18 months for deliverables.
- 	The completion date for objective #3, in particular, is critical to the 2010 UNEP/WMO Ozone Assessment (expected to begin in late 2008 / early 2009)
**Participants**: Laboratory Experimentalists and Theorists, Field Experimental Investigators (Ground, Balloon, Aircraft, Satellite), and Modelers.
**Venue**: TBD (possibly multiple)
**Organization:**  Co-Chaired by Michael Kurylo (NASA) & Björn-Martin Sinnhuber (U. Bremen); a Steering Committee is being assembled; announcement to be issued soon.
**Please let us know of your interest in participating (you might be invited anyway)!**
**  ****michael.j.kurylo@nasa.gov       bms@iup.physik.uni-bremen.de**

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