GEOPHYSICALRESEARCHLETTERS,VOL. 23, NO. 14, PAGES 1749-1752,JULY 1, 1996
Balloonobservationsof organicand inorganicchlorinein the
stratosphere:The role of HCIO4 productionon sulfate aerosols
LyattJaegl••,2,Yuk L. Yung•, GeoffreyC. Toon3, BhaswarSen3, Jean-Francois
Blavier3
Abstract. Simultaneous
observations
of stratospheric
organic September1993. We theninvestigatethe possiblesourceof the
andinorganicchlorineweremadein September1993out of Fort missing chlorine, emphasizing a possible heterogeneous
Sumner, New Mexico, using the JPL balloon-borneMkIV
formationof HC104. Finally we discussthe implicationsof the
interferometer.Between15 and20 km, a significantfraction(20 productionof HC104 for the mid-latitudelower stratosphere
in
- 60%) of the inorganicchlorinecouldnotbe accounted
for by the contextof the high aerosolloadingconditionspresentafter
the sum of measuredHC1, C1ONO2,and HOC1. Laboratory Mr. Pinatubo'seruptionin 1991.
measurements of the reaction of C10 radicals on sulfuric acid
solutionshave indicatedthat, alongwith HC1, small amountsof Missing Chlorine: MkIV observations
perchloricacid, HC104,wereformed. Very little is knownabout
thefateof HC104 in the stratosphere
andwe usea photochemical The MklV interferometer is a Fourier Transform Infra-Red
box modelto determinethe impactof this new specieson the spectrometer(Toon, 1991), which hasflown on 7 balloonflights
partitioning
of inorganicchlorinein the stratosphere.
Assuming since 1989 (Sen et al., 1996) as well as on several DC-8
that HC104 is photochemicallystable, it is shown that in the campaigns. The set of measurementsdiscussedhere were taken
enhanced aerosol loading conditions resulting from Mr. on the flight of September25, 1993, out of Fort Sumner, New
Pinatubo's
eruption,HC104couldrepresent
a significant
reservoir Mexico. During this flight, an exceptionally clear tropopause
of chlorinein the lowerstratosphere,
sequestering
up to 0.2 ppbv allowed data to be taken nearly all the way down to the ground.
(or 50%) of the total inorganic chlorine at 16 km. The The many gasesmeasuredbetween5 and 39 km includedspecies
occurrence of this new species could bring to closure the in the families of inorganic chlorine (HC1, C1ONO2, HOC1),
2, CC12FCC1F
2, CHC1F2,CH3CI,
inorganicchlorinebudgetdeficiencymade apparentby recent organicchlorine(CC13F, CC12F
CC14),reactive nitrogen species,as well as tracers. In addition
ER-2 aircraft in situ measurements of HC1.
the Submillimeterwave Limb Sounder (Stachnik et al., 1992), on
the sameballoonpayload,observedC10 simultaneously.
Introduction
MklV measuresapproximately86% of the chlorine-bearing
source
gases. Adding to thesegasesan estimateof CH3CC13
Onceorganic
chlorine
(CCly)hasreached
thestratosphere
in
the form of halocarbons, it is converted by photolysis and basedon MkIV CFC-11 togetherwith an empiricalrelationship
reactionwith radicalsto inorganic
chlorine(Cly). Mostof the betweenCH3CC13and CFC- 11 (Elkins et al., 1996), we account
inorganicchlorinespecies
thoughtto playan importantrolein the for 99% of the organicchlorine in the troposphere(-3.8 ppbv;
stratosphere
have been detected(HC1, C1ONO2,HOC1, CIO, WMO, 1994). Furthermore,the sumC1ONO2+HCl+HOCl+C10
OCIO), anda few others(C12,C1,C1202,C1NO,C1NO2)occurat accountsfor 82-100% of the total inorganicchlorine. We also
abundancestoo small to be observablewith currenttechniques.
These compoundsrepresentonly a small subsetof the many
possiblechlorine-containing
compounds.In particular,higher
oxideslike C103,CIO4, CI 2¸, C1207,andoxoacidslike HC102,
HC103, HC104 have been characterizedin the laboratory
environment (Greenwood and Earnshaw, 1985), and their
possibleimportancefor stratospheric
chemistryis still subjectto
speculation(Sanderet al., 1989, 1995). As mostof the higher
oxidesof chlorine tend to be unstable,they could be presentin
the stratosphere
only in smallquantities,but may possiblyplay
an importantrole in the lossof stratospheric
ozone(Prasadand
Lee, 1994). On the otherhand,if any oxo acid were to be formed
under stratosphericconditions,it might be stable enoughto
constitutean importantreservoirof chlorine.
In thispaper,we first presentevidenceof a discrepancy
in the
chlorinebudgetas shownby MkIV balloonmeasurements
in
'
'
'
'
I
'
'
'
"
I
*
'
'
40
'
I
'
'
'
'
I
'
: :,..•6_.:.
:,.:
•' 30
ß
•= 20
.
*
* '
'"'•"
<
10
0
0
1 10-9
2 10-9
3 10-9
4 10-9
Volume Mixing Ratio
Figure 1. MklV interferometer
sunsetmeasurements
of organic
1California
Institute
ofTechnology.
2Nowat Harvard
University.
3JetPropulsion
Laboratory,
California
Institute
ofTechnology.
Copyright
1996bytheAmerican
Geophysical
Union.
Papernumber96GL01543
0094-853 4/9 6/96GL-01543 $05.00
(CCly:•) andinorganic
(Cly:ß) chlorineon September
25,
1993 (34øN, 109.4øE). For better representation,the sum of
observed
ClyandCCly(o) hasbeeninterpolated
toa gridshifted
by 0.5 km. The solid line is the calculatedtotal chlorinebasedon
the age of the air (see text). The dashed line shows the
corresponding
CClyasderivedfromtheMkIV CFC-11using
empiricalrelationshipsdeterminedfrom in situ organicchlorine
observations
1749
aboard the ER-2.
1750
JAEGLI2 ET AL.: PERCHLORIC ACID IN THE STRATOSPHERE
include estimatesof COFC1 (Sen et al., 1996) and of COC12
(Kindler et al., 1995). The resultingtotal organicand inorganic
chlorine are presentedin Fig. 1. [A more detaileddescriptionof
these measurements
and the data reduction
used will be found in
a tbrthcomingpublicationby G. Toon].
We comparethe sumof measured
Cly and CCly to the
expectedamountof totalchlorine(CIt). C1t is a directfunctionof
the age of the air (Woodbridgeet al., 1995), which is calculated
from the MkIV SF6 measurementsbetween 12 and 21 km,
assuminga growth rate of 9% per year for SF6 (WMO, 1994).
For altitudesabove 21 km where no reliable SF6 mixing ratios
couldbe retrieved,a linearly increasingagereachinga maximum
of 5 years at 40 km was assumed.The recordof tropospheric
total chlorine documented by the World Meteorological
Organization(1994) is usedto infer C1t from the ageof the air.
Based on our current knowledgeof stratosphericchemistry,
the sum of chlorinespeciesmeasuredby the MklV interferometer
supplementedwith the otherfew speciesdiscussedabove,should
accountfor all of the chlorine. Indeed,Fig. 1 showsa remarkable
agreementbetween predicted and observedtotal chlorine over
most of the altitude range. However there is a striking
discrepancy in a layer around 17 km, where-0.3 ppbv of
chlorine
ismissing.
Goodagreement
between
MkIV CClyandin
situ organic chlorine measurementsaboard the ER-2 (Elkins et
al., 1996) yields a high level of confidencein the ability of MklV
to measuretotal organicchlorine. Also, for this sameSeptember
1993 MkIV data set, Sen et al. (1996) examined the fluorine
budgetwhich sharesmany of the speciesinvolvedin the chlorine
budget, and found very good agreementwith model predictions
for both fluorine sources and reservoirs.
On this basis, we
attributethe missingchlorineto the inorganicchlorinefamily.
ATMOSA;FLAS-3
mission
chlorine
retrievals
(Zander
etal.,
1996) and the otherMklV balloonflights madein 1992 and 1993
do not extend to altitudeslow enoughto detectany discrepancy
in the chlorine budget. In the following section, we will
speculate that the missing chlorine suggestedby the MkIV
measurementsis held in HC104, a specieswhich could be
producedon sulfateaerosols.
Perchloric
Acid and Sulfate
Aerosols
The possibilityof HC104 formation in the stratospherewas
first discussedby Simonaitis et al. (1975). They proposedthe
tollowing threebody reaction:
C103+OH+M
-->
HC104+M
[1]
C103itselfcanbe formedeitherfrom photolysisof C1203or from
OC10+O+M (Sander and Friedl, 1995). Both require OC10,
which is presentat significantlevelsonly in the polar springtime.
Thus this processcan only contributeto very small amountsof
perchloricacid at mid-latitudes. More recently,Prasadand Lee
(1994) presentedanotherpossibility:
CIO'O3 + HO2
•>
HCIO4 + 0 2
[2]
where the CIO'O 3 radical would be formed via reaction of
CIO'O 2 with ozone. The stabilityof C10-O2is itself still subject
to discussion(Prasadand Lee, 1994) and the existenceof C10'O•
is hypothetical.
Martin et al. (1980) obtained measurements of the C10
heterogeneousreactivities on sulfuric acid. Loss of CIO was
monitored over the 240-293 K range. The following
temperature-dependent
uptakereactionprobabilitywas derived:
Thedifference
between
C1t andthesumCly+CCly
isshown
in
¾(T) = exp[- 9.361 + (3.22 + 1.43) (1000/T- 3.867)] [a]
Fig. 2. The error bars are the 1-• precisionpropagatederrors,
and do not include an estimate of systematicerrors, which are
The main chlorine containing product was found to be HC1
mainly due to spectroscopicuncertainties. Although these
(accountingfor 60-100% of the C10 lost), and, interestingly,
uncertainties
are substantial,
theyaremostlyaltitudeindependent smallamountsof HC10 4 were alsodetected(Martin et al., 1979):
and thereforedo not detractfrom the significanceof the deficit.
C10 n•,so4
>HC10
4+products
[3]
Sucha featurewasnot observedin the 1985ATMOS Spacelab3
observations(Zander et al., 1992). However, an important
C10 H,.SO4
>HC1
+ products
[4]
difference between the two observations is that the MkIV
balloon
flight took place in an atmospherewith levelsof sulfateaerosols
still high after Mr. Pinatubo's eruption in 1991, while the
ATMOS experimentflew in a relativelycleanatmosphere.The
40
E 30
• 20
Moreover,formationof HC1 and perchloricacid was seenfrom
reactionsof C1radicalsand C12moleculeson sulfuricacid. It is
unclear what mechanismwould causeHC10 4 formation in
sulfuricacid. To our knowledge,no othermeasurements
of C10
uptake on sulfuric acid have been published (note that
preliminarymeasurements
by R. Zhang(privatecommunication)
seem to suggesta slower reaction probability). Martin et al.
examinedthe possiblesignificanceof HC1 formationvia [4] for
stratospheric
chemistry. They concludedthat [4] contributesto a
slightreductionof the CI/HC1ratio at 20 km underbackground
aerosol loading conditions. The impact of [3] has not been
examined, and is an interesting possibility to consider under
volcanic aerosol levels.
<
Recent ab initio characterization of
perchloric acid (Francisco et al., 1995) have shown that the
10
molecule, under the form HOC10 3, is stable to thermal
decomposition.
If it appearsthatundersomeconditions
HC104
couldbe formedin substantialamountsin the stratosphere,
we
0
1 l0 -10 2 10©
3 10© 4 10©
Volume Mixing Ratio
needto examinethe possiblelossmechanisms
of thismolecule.
As very little is knownaboutthe stratospheric
lossprocesses
of HC104,we baseourconsiderations
on analogies
withHC1and
HOC1.The [O-HI bond is thermodynamically
more stablein
HC104thanin HOC1,if we usetheheatof formationfor HC104
Figure 2. Comparisonbetween MkIV observationsof the
chlorine deficit (ß), and calculatedvertical profile of HC10 4
(•).
A modelcalculationwhichincludeverticaleddydiffusion
andC104 calculatedby Colussiand Grela (1993). Therefore,we
is also shown (- - -).
adopteda rate constantfor reactionof OH with HCIO4 to be 5
JAEGLI• ET AL.' PERCHLORIC ACID IN THE STRATOSPHERE
times slower than that with HOC1. Photolysisexperiment of
40 04/15/92
12/15/93 04/15/92
12/15/930.6
concentrated
liquid HC104 (Huie and Peterson,1983) suggest
slowdecomposition
of HC104in thenearUV andvisible,thusits "•30
•
lossby photolysis
in the atmosphere
is probablynegligibleand
• 20
we have chosen it to be equal to the HC1 photolysisrate.
•
Alternatively,HC104couldbe removedby inclusioninto sulfate •g 10
aerosols.We arenot awareof anymeasurements
of thesolubility •o
of perchloricacidin sulfuricacidsolutions,
sowe estimated
its
0.9
Henry'slaw constant
frombasicthermodynamical
properties
in
0.5
0.4
0.3
0.2
o.1
o
•'•: -'
water (Colussiand Grela, 1993' Karapet'yants
andKarapet'yants,
1970)andcomparison
withHC1solubilities
in waterandsulfuric
acid (Hansonet al., 1994; Clegg and Brimblecombe,1990).
Takingintoaccountthedissociation
of HC104 to formC104- in
solution,
weobtain
a Henry's
lawconstant
of about106M.atm
4
at200K(compared
to6 x 104M.atm-1
forHC1).Thus,lessthan
1751
---
0.8
f 18
km
0.7
0.01
0.6
0.001
0.5
I).4
0
16
km
10
20
30
40
Months after eruotion
0
10
20
30
40
Months after eruption
10-2%of theHC104will be sequestered
in theaerosolphase. Figure 3. Time dependentbox model calculationsince Mt.
However,if we use ab initio calculationsof the heatof formation
of HC104(Francisco
et al., 1995),thevalueobtainedfor Henry's
law wouldbe muchhigherand a significantfractionof HC104
Pinatubo'seruption.(a) Aerosolsurfaceareaevolutionat 16, 18
and 20 km (2-D model outputby Tie et al., 1994). The solid
linesrepresentmodelcalculations
includingHC104 chemistry
could be in the aerosolphase. Direct laboratorymeasurements (seetext)for (b) HC1On/CIy,
(c)HC1/Cly,
and(d)C10/CIy.The
dashed lines illustrate the effect standard heterogeneous
wouldbe necessaryto settlethisissue.
chemistryonly (N20 s and C1ONO2hydrolysis). The arrow on
Model Description
We haveimplementedthe simpleHC104chemistryoutlined
above(usingthe upperlimit of 40% for HC104yield from CIO
uptakeonsulfuricacid)in a photochemical
boxmodel(Allenand
Delitsky, 1990). We haveassumedHC104 to be releasedto the
gasphase,whereit is lostby reactionwith OH andphotolysis.
Heterogeneous
processes
alsoincludedare hydrolysisof N205
andC1ONO2(Hansoneta!., 1994).
Given the large lifetime of HC104 (2-10 monthsin the lower
stratosphere),
we haveperformed
ourcalculations
for the3 years
tollowingMr. Pinatubo'seruptionin June1991,thustakinginto
accounttheprogressive
decrease
of theaerosolsurfacearea. The
panel(a) indicatesthetimeof theMkIV balloonflight.
This hasthe main effect of increasingthe uptakecoefficientfor
diluteaerosolsfoundin the lowerstratosphere
(yielding¾ = 0.02
at 18 km). As canbe seenin Fig. 2, the mixingratio of HC104
predictedby the modelpeaksat 16 km (using[b]), with a shape
similar to the observations
of missingchlorine,but reachinga
lower maximum.
Given the uncertainties associated with both
the chemistry of HC!O4 and this idealized calculation,we have
not attemptedto obtain a better match with the observeddeficit.
Introducingverticaleddy diffusionhasthe effect of smoothing
this profile vertically (dashedline in Fig. 2). A fasterrate for
surface area evolution as a function of altitude is based on a 2-D
HC104+OHwoulddecrease
theamplitudeof thepeakin HCIO4.
Figure 2 illustratesthe fact that heterogeneous
productionof
modelcalculation
by Tie et al. (1994)at 45øN,whichwe adjusted
to matchthe aerosolprofile measuredby the SAGE II satellite HC104is a possiblecandidateto accountfor the missingchlorine
Eventhoughthe sticking
closein spaceandtimeto theballoonmeasurement
(G. Maddrea inferredfrom the MklV measurements.
and L. Thomason,personalcommunication). The altitude coefficientfor CIO in reaction[3] is small, it could be very
profilesfor O 3,H 2¸, CH4havebeenconstrained
to theconditions effectiveat producingHC104 becauseof the assumedslow gasobservedby the MkIV ballooninstrumenton September25, phaselossof this species.
The impactof the rapid increasefollowedby a slow decrease
1993.Clywastakenasthedifference
between
totalchlorine,
C1t,
of
aerosollevelsas causedby Mr. Pinatubowouldbe a delayed
andCCly. Transport
wasnotincluded
in themodel,butthe
responseof HC104 concentrations,
as illustratedin Fig. 3. The
sensitivityof theresultsto verticaldiffusionwastested.
only time-varyinginput in our model calculationwas the aerosol
Model
Results / Discussion
loading(Fig.3a). HClO4/Cly
reaches
a maximum
of 35-45%6
monthsafter the peak in surfacearea,and thenslowly decreases
The model resultsshowthat HC104 is producedin a layer throughphotochemicalloss HC1 follows the mirror image of
between16 and22 km (Fig. 2), wheremostof the aerosolsurface HCIO4, andis reducedby 45-35% below 18 km. To distinguish
introduced
by
area is containedand the temperaturesare below 210 K. The theeffectof HC104 chemistryandtheperturbation
altitude and magnitudeof the peak dependon the assumption N20.5 and C1ONO2 hydrolysis, we have representeda model
made for C10 reactivity on aerosols,as well as on the lossterm. calculation including only standardchemistry (dashed lines).
In particular, an exponential dependence on temperature The uptake of C10 on sulfate aerosols has little effect on the
(equation[a]) yields a profile of HC104 peakingaround22 km relativepartitioningof otherchlorinespecies:productionof HC1
(not shownhere). Sincethe time of the early measurements
by via reaction [4] is slow comparedto the C1 + CH 4 reaction.
Martin et al. (1980), many heterogeneous
reactionshave been HCIO 4 mainly acts as a temporarysink for inorganicchlorine
shown to be extremely sensitive to the water content of the
sulfuric acid aerosol (Hanson et al., 1994). We have therefore
thereby
loweringtheamount
of Clyavailable
for HC1formation.
Interestingly,the increasein surfacearea resultsin a smallerand
less
prolonged increase in C10 when HC10 4 chemistry is
attemptedto fit the original measurements
of Martin et al., by
included
(Fig. 3d). Thus, volcanic eruptions such as Mt.
using a dependenceon sulfuric acid weight percent(WH2SO4)
Pinatubo's
may have the effect of temporarily reducing the
insteadof temperature.We obtainedthe followingexpression:
¾(WH2SO4)
-- 10[ 3.65-0.094
xWH2SO4][b]
availableCly for conversion
to C10, therebyrendering
ozone
moleculeslessvulnerableto lossvia chlorinecatalyticcycles.
1752
JAEGL• ET AL.' PERCHLORIC ACID IN THE STRATOSPHERE
We have attemptedto detectHC104 in the stratosphere
using
the MkIV infra-red spectra,but the large abundanceof N20 and
H20 lines in the region where we would expect to see an
absorptionfeature (Karelin et al., 1975), and the lack of high-
resolutionspectralinformation,havenot allowedus to clearly
proveor disprovethepresence
of HC104.
Francisco,J.S. et al., Ab initio characterization
of HOC103 andHC104:
implications
for atmospheric
chemistry,
J. Phys.Chem.,99, 1342213425, 1995.
Greenwood, N.N. and A. Earnshaw, Chemistry of the elements,
PergamonPress,pp. 920-1039, 1985.
Hanson,D.R. et al., Heterogeneous
reactionsin sulfuricacid aerosols:a
frameworkfor modelcalculations,
J. Geophys.
Res.,99, 3615-3625,
1994.
Huie,R.E andN.C. Peterson,
The photolysis
of concentrated
perchloric
Implications / Conclusions
acid solutions,J. Photochem.,21, 3 !-34, 1983.
In situ measurements from the ER-2 aircraft of HC1 in the
lower stratospheremade in 1992 and 1993 have revealed a
Karapet'yants,
M.Kh. andM.L. Karapet'yants,
Thermodynamic
constants
of inorganic
andorganic
compounds,
AnnArbor- Humphrey
Science
publishera,1970.
and
seriousdiscrepancy
in our understanding
of the partitioning
of Karelin,A.I., et al., Vibrationalspectraof perchloricacid-I.Gaseous
l{quid
HC104andDC10
4,Spectrochim.
Acta,3la,765-775,
1975.
inorganicchlorineat mid-latitudes:30-50% of the inorganic
chlorinecouldnot be accountedfor by the sumof measuredHCI,
C10 and inferred steady-stateC1ONO2 (Websteret al., 1994).
Thesemeasurements
were madein the northernhemisphere,in
the presence of high aerosol loading resulting from Mr.
Pinatubo'seruption, and, as evidencedin Fig. 2, could be
consistent
with heterogeneous
formationof HC104.
More recent in situ observationsby this same instrument
Kindlet, T.P., et al., The fate of atmosphericphosgeneand the
stratospheric
chlorine
loadings
of itsparentcompounds:
CC14,
C2C14,
C2HC13,
CH3CC13,andCHC13,J. Geophys.
Res., 100, 1235-1251,
1995.
Martin, L.R., et al., Heterogeneousreactionsof CI and CIO in the
stratosphere,
J. Geophys.Res.,85, 5511-5518, 1980.
Martin,L.R., et al., ChlorineatomandC10 wall reactionproducts,
Int.J.
Chem.Kinet., 11,543-557, 1979.
Prasad,S.S. and T.J. Lee, Atmosphericchemistryof the reactionC10 +
0 2 <:>C10.O2:whereit stands,whatneedsto be done,andwhy?,J.
indicateda recoveryof HC1,with mixingratiosslowlyincreasing
as a functionof time as the aerosolloadingis decreasing(C.
Webster,privatecommunication).This progressive
recoveryof
the
in situ
HC1
observations
between
15 and
20
km
is
qualitatively
consistent
witha slowrelease
ofthesequestered
Cly
possiblyin the form of perchloricacid, as predictedby the box
model calculation.
Geophys.Res., 99, 8225-8230, 1994.
Sander,S.P., et al., Rate of formationof the C10 dimer in polar
stratosphericchemistry:implicationsfor ozone loss, Science,245,
1095-1098, 1989.
Sander,S.P. and R.R. Friedl, Experimentaland theoreticalstudiesof
atmosphericinorganicchlorinechemistry,Advancesin Physical
Chemistry,in press,1995.
Sen, B., et al., Balloon-borne observations of mid-latitude fluorine
In this paper, we have proposedthat perchloricacid, given
abundance,
J. Geophys.Res.,101,9045-9054, 1996.
certain assumptionson its chemistry, might sequesteran Simonaitis,R. and J. Heicklen, Perchloricacid: a possiblesink for
stratospheric
chlorine,Planet.SpaceSci., 23, 1567-1569,1975.
importantfraction of the inorganicchlorinein the presenceof
Stachnik,
R.A.,
et al., Submillimeterwave
heterodynemeasurements
of
high levels of sulfate aerosols. This hypothesisprovides a
stratospheric
C10, HC1,0 3,HO2: firstresults,Geophys.
Res.Lett., 19,
qualitativeexplanation
for the imbalancein thechlorinebudget
1931-1934, 1992.
observedby the MkIV instrument,andmightprovidea possible Tie, X., et al., Two-dimensional simulation of Pinatubo aerosols and its
explanationfor the low HC1 aircraft measurements.More robust
conclusionsawait laboratory determinationsof the possible
productionand lossmechanismsoutlinedin thispaper,as well as
possibledetectionof the speciesin the stratosphere.
effect on stratospheric
ozone,J. Geophys.Res., 99, 20,545-20,562,
1994.
Toon, G.C., The JPL MkIV interferometer,
Opticsand PhotonicsNews,
2, 19-21, 1991.
Webster,C.R., et al., Hydrochloric
acidandthe chlorinebudgetof the
lowerstratosphere,
Geophys.
Res.Lett., 21, 2575-2578,1994.
Woodbridge,
E.L., et al., Estimates
of totalorganicandinorganic
chlorine
in the lowerstratosphere
fromin situmeasurements
duringAASE II,
Webster,R. Martin, J. Francisco,and S. Martin for helpfuldiscussions,
J. Geophys.Res., 100, 3057-3064, 1995.
X. Tie for providinghis 2-D modeloutput,andR. Stachnikfor making
World MeteorologicalOrganization,ScientificAssessment
of Ozone
his dataavailablebeforepublication.Partof the researchdescribedin this
Depletion:1994, GlobalOzoneResearchandMonitoringProjectpaper was carried out by the Jet PropulsionLaboratory, California
Acknowledgements.
The authors would like to thank S. Sander, C.
Instituteof Technology,undercontractwith the NationalAeronauticsand
SpaceAdministration
(NASA). Thisresearch
is alsosupported
in partby
NASA grantNAGW-413 to the CaliforniaInstituteof Technology.
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