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

1
Impact of Laboratory Measurements of the ClOOCl
Cross Section On Our Understanding of Polar Ozone
Chemistry

• T. Canty1, R. J. Salawitch1, R. M. Stimpfle2,
• D. M. Wilmouth2, J. G. Anderson2, M. Rex3,
• R. Schofield3, M. von Hobe4, M. Santee5,
• D. Kinnison6, M. Kurylo7, B.-M. Sinnhuber8
• 1University of Maryland, College Park, MD
• 2Harvard University, Cambridge, MA
• 3Alfred Wegener Institute for Polar and Marine
  Research, Pottsdam, Germany
• 4Institute for Chemistry and Dynamics of the
  Geosphere, Julich, Germany
• 5NASA Jet Propulsion Laboratory, Pasadena, CA
• 6National Center for Atmospheric Research,
  Boulder, CO
• 7University of Maryland, Baltimore County,
  Goddard Earth Sciences and Technology Center, MD
• 8University of Bremen, Bremen, Germany

2
A study by Pope et al., JPC, 2007 reports
measurements of the ClOOCl cross-section that
challenge our understanding of polar chlorine
chemistry.
Burkholder et al., 1990
JPL 2006
ClOOCl Cross Section (cm2)
Huder and DeMore, 1995
Pope et al., 2007
WAVELENGTH (nm)
3
Sensitivity to Treatment of Cl2 Interference
No allowance for Cl2
Largest allowance for Cl2
Intermediate allowance for Cl2
Smallest allowance for Cl2
Courtesy, J. Burkholder, NOAA-ESRL
4
ClOx Partitioning
Daytime
ClO ClO M ? ClOOCl M Rate kFORWARD
ClO2 ClOOCl h??? ? Cl ClOO Rate
J ClOOCl ClOO heat ? Cl Cl O2 2
( Cl O3 ? ClO O2 ) Net 2 O3 ? 2 O2
Observations sensitive to kFORWARD and
?ClOOCl Ozone loss occurs if ClOOCl is lost
primarily by photolysis (i.e.. T lt 210 K)
Photolysis is rate limiting step for ozone loss
Nighttime
ClO ClO M ? ClOOCl M Rate
kFORWARDClO2 ClOOCl heat ? ClO ClO
Rate kREVERSEClOOCl Net Null Cycle
Observations sensitive to kREVERSE / kFORWARD
KEQ No ozone loss Accurate measurement
of ClO and precise knowledge of KEQ allows ClOx
(ClO2xClOOCl) to be calculated
important for constraining ozone loss and for
evaluating measurements obtained during
daytime for similar conditions
5
Sensitivity of Antarctic ozone loss to the ClOOCl
cross section
Pope 2007
Huder DeMore 1994
JPL 2006
JPL 2006
Observed Ozone
Burkholder 1990
von Hobe et al., ACP, Phys., 7, 30553069, 2007
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• The Role of Halogen Chemistry in
• Polar Stratospheric Ozone Depletion
• Objectives
• Evaluate consequences of new data on the ClO
  dimer photolysis rate on simulations of
  stratospheric ozone depletion, particular in
  winter polar regions.
• Evaluate old and new laboratory results for 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, models
  linking ozone depletion to stratospheric active
  chlorine / bromine amounts.
• Implementation
• Workshop (Cambridge, UK June 15 17, 2008)
  focused on Laboratory / Theory Studies,
  Atmospheric Measurements, Modeling / Analysis
  Investigations
• Detailed workshop report in preparation
• Publications in each focus area to be assembled
  in a special journal issue (TBD) on a timescale
  suitable for use in the 2010 UNEP/WMO Ozone
  Assessment
• Organization
• Co-Chairs - M. J. Kurylo (UMBC/GEST) B.-M.
  Sinnhuber (U. Bremen)
• Steering Group

7
MOZART3/WACCM1b Column Ozone Change
0 pptv Bry
22 pptv Bry
Slide courtesy D. Kinnison
8
Aura Observations
Antarctic, 2005
Arctic, 2004-05



Mixing Ratio (ppb)
ClONO2
HCl
ClO




Inferred Cly (ppb)
ClOOCl (ppb)
JPL2006
JPL2006 ? JPL 2006 kinetics
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Aura Observations
Antarctic, 2005
Arctic, 2004-05



Mixing Ratio (ppb)
ClONO2
HCl
ClO




Inferred Cly (ppb)
ClOOCl (ppb)
JPL2006
Stimpfle 2004
JPL2006 ? JPL 2006 kinetics Stimpfle 2004 ?
JClOOCl Burkholder et al. 1990, KeqCoxHayman,
1988, KfBloss et al., 2001
10
Aura Observations
Antarctic, 2005
Arctic, 2004-05



Mixing Ratio (ppb)
ClONO2
HCl
ClO




Inferred Cly (ppb)
HuderDeMore 1995
ClOOCl (ppb)
JPL2006
Stimpfle 2004
JPL2006 ? JPL 2006 kinetics Stimpfle 2004 ?
JClOOCl Burkholder et al. 1990, KeqCoxHayman,
1988, KfBloss et al., 2001 Huder DeMore 1995 ?
JClOOCl Huder and DeMore, 1995
11
Aura Observations
Antarctic, 2005
Arctic, 2004-05



Mixing Ratio (ppb)
ClONO2
HCl
ClO




Inferred Cly (ppb)
Pope2007
HD1995
ClOOCl (ppb)
JPL2006
Stimpfle 2004
JPL 2006 ? JPL 2006 kinetics Stimpfle 2004 ?
JClOOCl Burkholder et al., 1990, KeqCoxHayman,
1988, KfBloss et al., 2001 Huder DeMore 1995 ?
JClOOCl Huder and DeMore, 1995 Pope 2007 ?
JClOOCl Pope et al., 2007
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Rapid equilibrium between ClOOCl and ClClO2 (
)?
e.g. by ClOOCl ClO ? ClClO2 ClO ClClO2
ClO ? ClOOCl ClO
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
13
Rapid equilibrium between ClOOCl and ClClO2 (
)?
e.g. by ClOOCl ClO ? ClClO2 ClO ClClO2
ClO ? ClOOCl ClO
While the isomer is more thermally stable than
the dimer, there are several reasons this
chemistry is unlikely Ab initio study does not
support the formation of a complex from which
ClClO2 can be formed from this
reaction. J. Hansen A re-analysis of ER-2
observations during SOLVE puts an upper limit on
ClClO2 that is MUCH smaller than required for
this chemistry to be noticeable D. Wilmouth
R. Stimpfle ClClO2 would not photolyze in a
manner that would lead to re-formation of O-O
bond.
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
14
A new study by von Hobe et al., RSC, 2008 (in
review) reports measurements of the ClOOCl
cross-section in matrix isolation that agree with
results from the Huder and DeMore, 1995 study.
Burkholder et al., 1990
JPL 2006
ClOOCl Cross Section (cm2)
Von Hobe et al., 2008
Huder and DeMore, 1995
Pope et al., 2007
WAVELENGTH (nm)
15
Aura Observations
Antarctic, 2005
Arctic, 2004-05



Mixing Ratio (ppb)
ClONO2
HCl
ClO



Inferred Cly (ppb)
Pope2007
HD1995
ClOOCl (ppb)
JPL2006
Stimpfle 2004
vonHobe 2008
JPL 2006 ? JPL 2006 kinetics Stimpfle 2004 ?
JClOOCl Burkholder et al., 1990, KeqCoxHayman,
1988, KfBloss et al., 2001 Huder DeMore 1995 ?
JClOOCl Huder and DeMore, 1995 Pope2007 ?
JClOOCl Pope et al., 2007 vonHobe 2008 ? JClOOCl
von Hobe et al., 2008
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SOLVE
First measurements of ClOOCl from the ER-2 during
SOLVE/THESEO-2000 (Stimpfle et al., JGR, 2004)
A value of ß1 indicates good agreement between
observations and models
17
SOLVE
Kf
JClOOClBurkholder et al., 1994
Trolier et al., 1990
JPL2000
Bloss et al., 2001
JPL2006
Boakes et al., 2005
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SOLVE
Kf
JClOOClJPL06
Trolier et al., 1990
JPL2000
Bloss et al., 2001
JPL2006
Boakes et al., 2005
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SOLVE
Kf
JClOOClHuder and DeMore, 1995
Trolier et al., 1990
JPL2000
Bloss et al., 2001
JPL2006
Boakes et al., 2005
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SOLVE
Kf
JClOOClPope et al., 2007
Trolier et al., 1990
JPL2000
Bloss et al., 2001
JPL2006
Boakes et al., 2005
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SOLVE
Kf
JclOOClvon Hobe et al., 2008
Trolier et al., 1990
JPL2000
Bloss et al., 2001
JPL2006
Boakes et al., 2005
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Case Study Segment of 2 February 2000ER-2
Flight Over Russia
SLIMCAT MODEL
(ClOxClONO2HCl)/Cly
2xClOOCl/Cly
ClO/Cly
HCl/Cly
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Model Constrained by Measured ClO
JPL 2006 Chemistry
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Model Constrained by Measured ClO
Stimpfle Chemistry Bloss kF Burkholder
?ClOOCl Cox Hayman (1988) KEQ
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Model Constrained by Measured ClO
JPL 2006 Chemistry except Pope et al. (2007)
?ClOOCl JPL 2006 KEQ
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Conclusions (SPARC Polar Ozone Chemistry
Workshop) 1. Quantification of Cl2 present in
laboratory cell needed to reduce
uncertainty in the ClOOCl cross section 2.
Chlorine isomer chemistry unlikely to be
atmospherically relevant no other missing
chemistry/silver bullets have yet been
established 3. Numerous observations of ClO
and/or ClO ClOOCl shown to be inconsistent with
Pope et al. cross section and no other change to
model chemistry 4. Accurate knowledge of KEQ
combined with night time ClO can be used to
calculate ClOx (ClO2ClOOCl) ? If ClOx is
known, constraints can be placed on JClOOCl
from measurements of ClO when the air
mass experiences sunlight ? Measurements
of night time ClO not consistent with recommended
value of KEQ
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Thank You!
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Thank You!
New Boss
October 25, 2008