A reconstructed view of polar stratospheric chemistry

Transcription

1 JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 104, NO. D7, PAGES , APRIL 20, 1999 A recnstructed view f plar stratspheric chemistry M. T. Cffey, William G. Mankin, and J. W. Hannigan Natinal Center fr Atmspheric Research, Bulder, Clrad Abstract. We describe a technique that uses relatively sparse bservatins frm aircraft f vertical clumn amunts tgether with a quasi-cnserved parameter, ptential vrticity (PV), t recnstruct clumn abundances n a near-glbal scale. Stratsphericlumn amunts fr a number f gases (including HF, NO, NO2, HNO3, C1ONO2, 0 3, and HC1) were measureduring airbrne field deplyments t bth plar regins in fur separate years. Functins are determined that relate vertical clumn amunts t the isentrpic ptential vrticity at tw ptential temperature levels (4 K and 520 K) at the bservatin pints. Gridded PV values, derived frm Natinal Center fr Envirnmental Predictin temperature and heights, are used t recnstruct clumn distributins fr an entire plar regin. Recnstructed fields are used t explre the usefulness f clumn bservatins t describe vertically averaged prperties f the plar vrtex and t cmpare ne year and hemisphere with anther.' 1. Intrductin Tw distinct types f bservatin have been used t help hetergeneus reactins that release active chlrine frm its reservirs. As winter ends, with increasing sunlight and warming temperature, plar stratspheric cluds (PSCs) and their understand the cnditins and prcesses affecting plar zne. assciated hetergeneus prcessing end; mixing f air, relatively In situ measurements have been made, mstly frm the NASA high in NO2, frm utside the vrtex returns chlrine and ER-2 aircraft, and remte bservatins have been made frm the brmine t their reservir frms, and zne destructin slws. grund, ballns, aircraft, and satellites. The in situ bservatins While the in situ measurements have been critical t and the assciated analyses have been especially useful in understanding the prcesses f plar zne depletin, sme key identifying and describing the cnditins and prcesses that chemical cmpnents, such as C1ONO2 and HNO 3, are nt ccur in the lwer stratsphere and belw. Remte bservatins, measured by in situ techniques. The cmplete picture f such as thse frm the NASA DC-8 aircraft and satellite-brne wintertime plar zne depletin was first cnstructed by using sensrs such as Ttal Ozne Mapping Spectrmeter (TOMS), in situ bservatins frm the ER-2 aircraft tgether with remte Micrwave Limb Sunder (MLS), Halgen Occultatin measurements frm the DC-8 aircraft. Plate 1 shws the Experiment (HALOE), Stratspheric Aersl and Gas dynamical structure f a well-frmed vrtex in the Suthern Experiment (SAGE), and Crygenic Limb Array Etaln Hemisphere tgether with typical flight altitudes f the ER-2 and Spectrmeter (CLAES) have extended the in situ descriptin and DC-8 aircraft. Instruments abard the ER-2 aircraft usually make revealed the vertical and hrizntal extent f the prcesses lcal measurements within the altitude range f the aircraft, cntrlling plar zne. which has a maximum f abut 20 km. The airbrne remte A large number f in situ and remte bservatins made sensing techniques usually prduce clumn amunts f specified during campaigns in bth plar regins have prvided an gases; differential absrptin lidar is an imprtant exceptin. explanatin f the zne destructin prcess during winter and Because f its relatively lng chemical lifetime the HALOE CH 4 spring. A brief descriptin f the situatin in plar regins is mixing rati cnturs [Russell et al., 1993] in Plate 1 shw the given here. Lng-lived halgen species, primarily general structure f a wintertime suthern plar vrtex with chlrflurcarbns, are released at the Earth's surface. After increasedescent near the ple and a mre unifrm mixing rati mixing upward these surce mlecules are phtchemically distributin pleward f 60 ø latitude. degraded in the stratsphere, leading t the frmatin f halgen The discussin here will cncentrate n clumn reservirs HC1, C1ONO2, BrC1, and BrONO2. Chlrine is measurements derived frm bservatins f infrared absrptin released frm its stable reservir in high-latitude winter, in part between an airbrne spectrmeter and the slar surce. In this thrugh reactins n the surfaces f cld stratspheric aersls, type f remte sensing, infrmatin cmes frm all pints alng prducing the mre active species C12 and HOC!. When the air the line f sight within the atmsphere; mst f the infrmatin encuntersunlight, highly reactive atmic chlrine and brmine cmes frm an altitude regin near the peak f the vertical are phtlytically prduced frm C12, HOC1, BrC1, and BrONO 2. cncentratin prfile. Fr a slar elevatin f 5 ø, typical f high- Atmic C1 and Br react in a catalytic cycle t destry zne and latitude bserving, the slant path frm an aircraft at 12 km t an prduce C10 and BrO. Reactive nitrgen, which strngly altitude f 22 km, near the peak plar HNO3 cncentratin, is regulates the available reactive chlrine and brmine, is remved abut 105 km. S mst f the infrmatin cntributing t a frm the regins f in situ bservatin by the same clumn determinatin cmes frm within abut 100 km f the Cpyfight 1999 by the American Gephysical Unin. Paper number 1998JD /99/1998JD aircraft. Since the launch f the Upper Atmsphere Research Satellite (UARS) [Reber, 1993] in 1991, fur satellite-brne remte sensing instmments (CLAES, MLS, HALOE and the Imprved Stratspheric and Messpheric Sunder (ISAMS)) have prvided

2 8296 COFFEY ET AL.' POLAR STRATOSPHERIC CHEMISTRY RECONSTRUCTED prfile measurements f imprtant stratspheric trace gases, such as HC1, C1ONO2, C10, HNO 3, and HF. The familiar clr cnturs f zne depletin dating back t 1978, which clearly shw the evlutin and extent f zne depletin, are ttal clumn measurements by TOMS [Stlarski et al., 1986], which has flwn n a number f satellite platfrms. Frm the perspective f ultravilet radiatin reaching the surface it is primarily the ttal clumn f zne that is imprtant. This paper will shw the usefulness f clumn measurements t describe the integrated vrtex, rather than a relatively thin layer at the lwer bundary as might be sampled by an in situ sensr. Clumn bservatins frm aircraft platfrms during fur field campaigns are used t cnstruct hemispheric distributins f clumn amunts fr a number f gases. Distributins f clumn amunts, recnstructed frm aircraft bservatins, are cmpared t satellite-derivedistributins fr gases fr which cincident satellite data exist. Cntur maps are cmpared fr different years and between hemispheres. The mean clumn amunts fr a number f gases, nrmalized fr vrtex area, are cmpared fr three prgrams. Budgets f integrated chlrine and nitrgen are prduced fr bth plar regins. 2. Observatins f Clumn Amunts < z au High-reslutin infrared spectra have been recrdeduring fur aircraft-based deplyments in wintertime plar regins. Observatins were made in the Suthern Hemisphere frm August Octber 1987 Airbrne Antarctic Ozne Experiment (AAOE)[Tuck et al., 1989] and in the Nrthern Hemisphere frm January t February 1988 Chemistry f the Plar Stratsphere (CHEOPS), January t February 1989 Airbrne Arctic Stratspheric Expeditin (AASE)[Turc et al., 1990] and January t March, 1992 (AASE 2) [Andersn and Tn, 1993]. Clumn amunts abve the aircraft flight levels were retrieved by fitting f the bserved spectra with calculated spectra. Details f the clumn retrieval methd are discussed elsewhere [Mankin and Cffey, 1989; Cffey et al., 1989]. Table 1 shws the gases retrieved in each field prgram. In additin t the gases listed in Table 1, ther gases, such as CO2, H20, CH4, N20, C2H 6, and CF2C12, are retrieved, but these will nt be used in the discussin here. Figure 1 shws clumn amunts fr a number f gases frm all fur field prgrams as a functin f the ptential vrticity n the 4 K surface. Each symbl represents the average f typically 60 s f bservatin. It is nt strictly apprpriate t cmpare clumn amunts frm nrth and suth plar regins at all the different times because many f the gases may have time variatins r interhemispheric differences in their vertical distributins. There is als a clear evlutin f the plar chemistry and changing cnditins f temperature and slar illuminatin, which must be cnsidered in cmparing ne bservatin perid with anther. Figure 1 des shw, hwever, the range f clumn bservatins during the fur prgrams. The regin f disturbed plar chemistry that develps each winter in each hemisphere cvers an extensive area; a typical diameter fr the suthern hemisphere vrtex is 7500 km. In the nrth, althugh the vrtex is usually less symmetrical than that in the suth, a typicalng dimensin is cmparable t a suthern diameter. During a 1 hur slar bservatin perid abard the NASA DC-8 aircraft in AASE 2 the aircraft cvered abut 900 km. Flight paths fr the times when clumn bservatins were made during AASE 2 are shwn in Figure 2. Als shwn in

3 COFFEY ET AL.' POLAR STRATOSPHERIC CHEMISTRY RECONSTRUCTED HALOE CH4 Sept-Oct , ',.Octber 100 "" ; July,.., Latitude ER-2 WB~57 DC-8 Plate 1. General lcatin f the Suthern Hemisphere plar vrtex as described by Halgen Occultatin Experiment (HALOE) CH 4 bservatins. Als shwn are a typical and a depleted zne cncentratin prfile and the bservatinal cverage f airbrne in situ and remte sensing techniques.

4 8298 COFFEY ET AL.: POLAR STRATOSPHERIC CHEMISTRY RECONSTRUCTED O AASE2 [] AASE I... I... I... O CHE-O: A AAOE. AASE2 [] AASE CHEOPS h AAOE I... I PV(4K) x10 s 2 O PV(4K) x10 O AASE2 [] AASE O CHEOPS AAOE AASE2 ]... 4ø I [] AASE I... ' ' ' I crams, " / " N,,OE l &,?.,. ø, O O A O %20 1 ', I... I... I... I PV(4K) x10 _,., PV(4K) x AASE2 [] AASE h AAOE AASE2 h [] AASE CHEOPS AAOE 8 12 E O a B I 0,,,, IA,,,, I,,,, I,,,, I,,,, PV(4K) x10 E 8 O ' e k,,,, I,,,, I,,, I,,,, I,,,,fi PV(4K) x10 Figure 1. Observed clumn amunts frm fur field prgrams, Airbrne Antarctic Ozne Experiment (AAOE; SH, 1987), Chemistry f the Plar Stratsphere (CHEOPS; NH, 1988), Airbrne Arctic Stratspheric Expeditin (AASE; NH, 1989), and (AASE 2; NH, 1992) versus ptential vrticity at the 4 K ptential temperature surface.

5 COFFEY ET AL.: POLAR STRATOSPHERIC CHEMISTRY RECONSTRUCTED Jan Jan Jan 1992 "50' N PV(4)= 2.5 x 10 's Km2/kg-s 22 Jan Feb Feb 1992 DC- Flight Path 17 Feb Feb Mar km 12 Mar Mar Mar 1992 Figure 2. Map f the DC-8 flight paths and the vrtex edge (defined as PV(4)=2.5 x 10-5 K m2/kg s) fr each day f AASE I I I Slar Input 65 degrees I AASE H NO3 ""-... E, AASE,,, 1989 _ c--'e 15 ' E =.. CHEOPS 1988 ( AAOE > -- HCI --. "" NO /--- '., 5 CiON02 -. /, / --,. SH Day Seasn Autumn I Winter I Spring I Summer NH Day Figure 3. Schematic f the seasnal change f NO 2, HNO 3, C1ONO2, and HC1 clumn amunts frm grundbased bservatins. Als shwn are the time perids f the fur field prgrams discussed here. (tp) Seasffal variatin f inslatin.

6 _ 8300 COFFEY ET AL.' POLAR STRATOSPHERIC CHEMISTRY RECONSTRUCTED [] [] N 02 AAOE Fit(pv4 pv520) I ß N 02, _ [] ß [] [] I PV at 4K X10 s K m2/kg s AASE ' ' ' ' I " ' ' ' I ' ' ' ' I ' ' ' ' I ' ' ' ' [] NO 2 ß N 02 Fit(pv4,pv500) 0 0,,,, I I I I, [,,,, ],, I, I,,,, z 0 I PV at 4K X10 s K m2/kg s 'E AASE 2 3, ' ' ' I ' ' ' ' I ' ' ' ' I ' ' ' ' I ' ' ' ß _ [] N O <17 Feb ß N O Fit(pv4,pv520) <17 Feb ) _ 2 [] N O >17 Feb E 2 ß NO Fit(pv4,pv520) >17 Feb = I - [] - E - - _ - _ O "0 z 0,, I,,, I,, I,,,, I,,,, I PV at 4K X10 s K m2/kg s Figure 4. Observed vertical clumn amunts f NO 2 (pen symbls) versus PV(4) fr three field prgrams. Slid symbls are calculated frm analytic fits t the bservatins as a functin f PV values at 4 and 520 K. Observatins in AASE 2 are divided int tw distinctime perids as described in the text. Figure 2 is the apprximatedge f the vrtex as defined by the flights, clumn measurements were made at a large range f ptential vrticity (PV) cntur f 2.5 x 10-5 K m2/kg s n the ptential vrticity values. Observatins f cnserved species 4 K surface. This cntur is near the peak f the gradient in ptential vrticity and is ften assciated with the edge f the vrtex. Because f the relatively large extent f the regin f frm different flights can be cmpared by relating a clumn measurement a cnserved quantity that is available glbally, such as the ptential vrticity at sme level. This has been dne perturbed chemistry assciated with plar vrtices, the cnstant fr each clumn determinatin based n the lcatin f the mtin f the vrtex, and the limited range f aircraft flights, the vrtex is nt well sampled n a given flight, but ver the range f bservatin and the derived PV field at the 4 K surface frm Natinal Meterlgical Center (NMC) temperature analysis.

7 COFFEY ET AL.: POLAR STRATOSPHERIC CHEMISTRY RECONSTRUCTED 8301 Table 2 Cnstants in Plynminal Fits f Clumn t Ptential Vrticity AAOE 1987 Gas a b c d e R HF O88 HC NO NO HNO C1ONO CHEOPS 1988 HF HC1 NO NO2 HNO AASE 1989 HF HC1 NO2 HNO3 C1ONO , ø AASE HF HC1 <Feb HC1 >Feb NO <Feb NO >Feb NO2 <Feb NO2 >Feb HNO C1ONO See Scheberl et al. [ 1992] fr a discussin f PV determinatin in the nrth. The HNO 3 variatin shwn in Figure 3 is fr an and use as a surrgate fr measurement f cnserved species. Antarctic vrtex and wuld nt shw a large decrease in T prperly interpret the measurements f a given field midwinter in the Arctic. This is discussed in mre detail belw. prgram, ne must place them within the time frame f the Figure 4 shws NO2 clunt amunts versus PV fr the general evlutin f a plar vrtex and its changing dynamical AAOE, AASE, and AASE 2 prgrams. Fr AAOE and AASE and chemical cnditins. Figure 3 is a schematic shwing the there is nt a wide spread in clunt amunt fr a given PV seasnal change in the clunt abundance f a number f key value, especially within the vrtex regin (PV(4)>2.5 gases. The figure is derived frm surface bservatins f clunt Observatins made at different times but with the same value f amunts frm high-latitude lcatins [Keys and Jhnstn, 1986; PV are similar, allwing a fit f the clunt amunts versus PV Shibasaki et al., 1986; Pmmereau and Gutail, 1988; Murcray withut cnsideratin f the time. Plynmial fits were prduced et al., 1989; Sanders et al., 1989; Keys and Gardiner, 1991; Liu fr all the gases f Table 1. Clunt amunts were fitted t a et al., 1992; Van Allen et al., 1995], and als cmpares well with plynmial f PV at the 4 K and 520 K (500 K fr AASE) mdel simulatins f the behavir f the plar vrtex [Brasseur ptential temperature surfaces. Ptential vrticity fields fr et al., 1997]. The basic features shwn in this figure are fairly AASE (at 4 K and 500 K) and fr AASE 2 (at 4 K and 520 stable clunt amunts during summer and autunm, a brad K) were cmputed by Scheberl, Lait, and Newman f winter minimum in NO2, HNO3 and HC1, and a recvery in NASA/GSFC and Nagatani f NOAA/NMC. Data files f PV springtime. Figure 3 als shws the time perids f clunt fr each day f bservatin are included in the cmpact disk bservatins fr the fur airbrne prgrams discussed here. distributin f the prgram archives fr AASE and AASE 2. Fr AAOE was in the Suthern Hemisphere; the ther prgrams were AAOE and CHEOPS, PV fields are calculated at NCAR frm x 10-5).

8 8302 COFFEY ET AL.' POLAR STRATOSPHERIC CHEMISTRY RECONSTRUCTED 'A,SE' 2' H( i... PV(4) Day Number 8O PV(4) _ lo, I i I, [,, I, ] ] [ I J ] I J,,, I Day Number 8O 4O 3O 2O E 10 AASE 2 HNO PV(4) z 0 3: I I i i Day Number i i Figure 5. Trend in bserved clumns f HCI, NO2, and HNO 3 fr bservatins within the nrthern plar vrtex during AASE 2. The line is a linear fit t the data. NMC temperature and height fields. There is a strng crrelatin Table 2 cntains values fr the cnstants in the clumn fits between the PV values at 4 K and 520 K, s fitting tw PV fr the gases discussed here. Als cntained in Table 2 is the levels rather than just 4 K des nt make a large difference in crrelatin cefficient R (Pearsn's) calculated frm the bserved the derived functin. Hwever, differences between bserved and fitted values. This cefficient prvides a measure f the and recnstructed clumn amunts were less by a mdest amunt quality f the fitted functin, with 1.0 being a perfect fit. Clumn (typically less than 10%) fr all the gases discussed here when amunts recnstructed frm the analytic functins fund in the tw PV levels were used in the fits. The frm f the fits is fitting described abve are shwn in Figures 4 (as slid symbls) alng with the actual bservatins (as pen symbls). Variatins clumn = a + b x PV(4) + c x (PV(4)) 2 + d x PV(520) in the fitted pints f Figure 4 appear nt t lie alng a smth + e x (PV(520)) 2 curve because the recnstructed clumn amunt is pltted against

9 COFFEY ET AL.: POLAR STRATOSPHERIC CHEMISTRY RECONSTRUCTED 8303,, AAOE,, i [,,,, - 30 [] HNO ß HNO Fit (pv4,pv520) 3 20 ::,10 [] ERE] 0 I PV at 4K X105 K m 2/kg s,, - 30 [] HNO ß HNO Fit(pv4,pv500) 3 AASE i, i [ ] I, i i 20 =10,,,, I,,, I,,,, l, t,,, I,,, I PV at 4K X105 K m2/kg s,, AASE 2 ' ' ' ' I ' ' ' ' I ' ' ' ' I ' ' ' " I ' ' ' ' ::,10 0 [] [] HNO DE] 3 ß HNO 3 Fit(pv4,pv520) I,,,, I,,,, I,,,, I,,,,, I PV at 4K X10 s K m2/kg s [ Figure 6. Same as Figure 4 but fr HNO3. nly ne f the independent variables (in this case PV at 4 K). Fits als were made f clumn amunts versus an "effective PV," which was a linear cmbinatin f PV values frm eight ptential temperature levels (420, 4, 465, 520, 585, 655, 7 and 8 K) (with thanks t W. Randel and F. Wu). These fits reveal that the PV levels between 4 and 520 K are the mst influential and that using multiple PV levels des nt substantially imprve the fits. Fits were als prduced that included a term fr the height f the trppause at the lcatin f the bservatin, but these fits did nt significantly imprve the match t bservatins. A linear dependence n time (as days since equinx) was included as a parameter f the fits. N significant imprvement was bserved fr all the cases tested. Even fr NO2 during the AASE 2 prgram, which shws a relatively large increase with time (~60%/mnth) the deviatin f fitted frm bserved clumns fr fits including PV at 4 K and 520 K versus fits that als included a linear dependence n time was changed by less than 7%. The simpler functins are used here. The validity f these fits fr NO 2 in AAOE and AASE is

10 8304 COFFEY ET AL.' POLAR STRATOSPHERIC CHEMISTRY RECONSTRUCTED.10 8 E 6 [] CIONO 2 ß CIONO Fit(pv4,pv500) 2 I PV at 4K X105 K m2/kg s 10-8 E 6 [] CK)NO 2 CIONO Fit(pv4,pv500) 2 AASE [ i [ i, i [] -,,,, I [,, I,,,, I,,,, I I PV at 4K X105 K m2/kg s [] CIONO AAS E 2 2 ß CIONO Fit(pv4,pv520) ' ' ' [] - [] - _ [] [] -,,,, I,, t I [,,, I,,, I,,, I PV at 4K X105 K m2/kg s Figure 7. Same as Figure 4 but fr C1ONO2. shwn by the gd agreement between the calculated clumns (slid symbls) and the bservatins (pen symbls) in Figure 4. In AASE 2 the clumns fall int tw grups, as indicated by the pen symbls, separated by a date between February 14 and 17, Within thse tw grups there is n clear sign f a tempral change in the NO2 clumns. The presence r absence f a significant change in clumn abundance may be expected fr a given gas if ne cnsiders the placement and duratin f the bserving prgrams within the evlutin f the vrtex chemistry as shwn in Figure 3. The change in clumn amunt during AASE 2 fr HC1, NO2, and HNO 3 fr bservatins made within the vrtex (PV(4)>2.5 x 10-5; the maximum f PV(4) during AASE 2 was 3.4 x 10-5) is shwn in Figure 5. As can be seen, there is a significant increase fr NO2 (~60%/mnth), a less prnunced increase fr HC1 (~20%/mnth), and a small change in HNO 3 clumn abundance (<4%/mnth). The technique described here will be mst reliable fr the gases that d nt exhibit a large change during the perid f these bservatins. Figures 6-9 shw clumn amunts fr HNO 3, C1ONO2, HC1, and HF similar t NO2 in Figure 4. Similar t NO2, tw time

11 COFFEY ET AL.' POLAR STRATOSPHERIC CHEMISTRY RECONSTRUCTED 8305 TOMS Ozne Clumn Recnstructed Ttal Clumn mlecules cm-2 10"18 14 AAOE 03 9/26/87 /10 s mlecules cm - 14 TOMS Ozne Clumn a/ 0/9 Recnstructed Ttal Clumn Dbsn units AASE2 03 Dbsn units 600 3/20/92 S O 350 3O Plate 2. Cntur maps f 0 3 ttal clumns frm Ttal Ozne Mapping Spectrmeter (TOMS) bservatins and frm the aircraft recnstructins using tw PV levels. White areas in the center and near the tp f the 1992 TOMS map represent areas f n data. Other white areas indicate values ff the end f the scale.

12 8306 COFFEY ET AL.' POLAR STRATOSPHERIC CHEMISTRY RECONSTRUCTED UARS MLS 03 COLUMN 10 " mlecules/era 14 Recnstructed Ttal Clumn Fit using tw pv levels AASE2 03 /10 a 1/ll/9 mleulea c,m -m 14 UARS MLS 03 COLUMN 3/1õ/9a l" mte le,/ m 14 Recnstructed Ttal Clumn Fit using tw pv levels AA E2 03 /10 " 3/18/92 mleules m -s 14 Plate 3. Micrwave Limb Sunder (MLS) and recnstructed 0 3 clumn amunts n tw dates during AASE 2 N data are available abve 80øN fr the MLS bservatins.

13 .. Recnstructed Ttal Clumn Fit using tw pv levels AAOE HN03 /10 ts s/22/s mlecules cm - 4O Recnstructed Ttal Clumn Fit using tw pv levels AAOE HNO3 /10 ts e/3/8 mlecules m -s Recnstructed Ttal Clumn Fit using tw pv levels AAOE HN03 /10 's 9/ 5/8' mlecules cm 'a* Recnstructed Ttal Clumn Fit using tw pv levels AAOE HN03 /10 ' mlecules cm -a 25 Recnstructed Ttal Clumn Fit using tw pv levels AAOE HN03 /10 s 9t21/e mleculem cm 'l Recnstructed Ttal Clumn Fit using tw pv levels AAOE HN03 /lo s 9/26/67 mlecule9 cm '4 Plate 4. Recnstructed maps f the HNO 3 vertical clumn fr 6 days f AAOE.

14 8308 COFFEY ET AL.' POLAR STRATOSPHERIC CHEMISTRY RECONSTRUCTED Recnstructed Ttal Clumn. Recnstructed Ttal Clumn Fit using tw pv levels Fit using tw pv levels AASE HN. 03. /10 le mlecules era-' AASE HN03 /10 m l/6/89 t/t4/e9 mlecules crn's 35 J Recnstructed Ttal Clumn Fit using tw pv levels AASE HNO3 /10 s 1/19/s mlecules Recnstructed Ttal Clumn Fit using tw pv levels AASE HN03. /10 is 1/29/89 mlecules cm 't 25 Recnstructed Ttal Clumn Fit using tw pv levels AASE HN03_ /10 s 2/2/89 mlecule9 cm 'a Recnstructed Ttal Clumn Fit using tw pv levels AASE HN03_ /10 is,2/ 7/89 mleculea cm " Plate 5. Recnstructed maps f the HNO 3 vertical clumn fr 6 days f AASE

15 COFFEY ET AL.' POLAR STRATOSPHERIC CHEMISTRY RECONSTRUCTED 8309 AAOE [] HCI ß HCI Fit(pv4,pv520) -,, I t, I,, t I, ],, I t, - 0 I PV at 4K X10 s K m2/kg s [ i i i i i i i i i i i i ' i [ [ ß HCI Fit(pv4,pv500) ] AASE [, [! [ _,,,, I,,,, I,,,, I,,,, I ] [, t 0 I PV at 4K X105 K m2/kg s AASE 2 I 1 [] HCI < 17 Feb ß HCI Fit(pv4,pv520) <17 Feb [] HCI > 17 Feb [] A HCI Fit(pv4,pv520) >17 Feb [] _, - ß - -,- 0 I PV at 4K X10 s K m2/kg s Figure 8. Same as Figure 4 but fr HC1. perids were fitted fr AASE 2 HC1, and nly ne fit, nt invlving time, was used fr the ther gases. ensemble versus that f the excluded day we can cnclude that the dminant surce f imprecisin is the imprecisin f the Uncertainty the retrieval f clumn amunts frm infrared clumn amunts. Fr the recnstructins presented belw, slar absrptin spectra has been discussed elsewhere [Cffey et precisin is believed t be better than 20% fr C1ONO 2, and al., 1989; Mankin and Cffey, 1989]. Generally, clumn better than 10% fr the ther species. amunts are accurate t within 10-15%, with mst f the uncertainty due t spectraline parameter uncertainty and imperfect knwledge f the vertical mixing rati shape. 3. Vrtex-Wide Recnstructin and Discussin Accuracy is less fr C1ONO2, which we believe t be within 30% f the actual value. By repeatedly fitting bservatins fr a given With an analytic relatin between clumn amunts and PV we are n lnger limited by ur relatively sparse sampling f the gas and field prgram with ne f the day's bservatins remved vrtex n a given day, althugh, as can be seen in Figures 6-9, and then cmparing the variance f bservatin minus fit fr the clumn amunts are measured at a wide range f PV values

16 _ 8310 COFFEY ET AL.' POLAR STRATOSPHERIC CHEMISTRY RECONSTRUCTED AAOE [] HF ß HF Fit(pv4,pv520) PV at 4K X105 K m2/kg s AASE '! I! ' ' ' [] HF ß HF Fit(pv4,pv500) I PV at 4K X10 s K m2/kg s [] HF ß HF Fit(pv4,pv520) - [], I,,,, I,, I,, 0 I 2 3 PV at 4K X10 s K m2/kg s Figure 9. Same as Figure 4 but fr HF. i i J i i i i 4 during each field campaign. Using calculated fields f PV at 4 K and 520 K (500 K fr AASE) we can assign clumn amunts fr an entire hemisphere and examine the vrtex as a whle. Budgets can then be cnstructed fr families f cmpundsuch as (NO + NO 2 + HNO 3 + C1ONO 2) r (HC1 + C1ONO2). Partitining within families can be derived fr the entire vlume f the vrtex. Plate 2 shws the recnstructed ttal clumn f zne fr the suthern plar regin fr 2 days during AAOE and AASE 2. T test the validity f the recnstructed zne field, we can cmpare it with bservatins f the ttal zne as prduced by TOMS. A TOMS instrument has made essentially cntinuus bservatins f the zne clumn, frm a variety f platfrms, since Plate 2 als shws the TOMS results fr the same days f 1987 and 1992 as fr the aircraft bservatins. As can be seen, the majr features f the TOMS zne distributin are reprduced by the recnstructins. The recnstructed maps in Plate 2 are frm data pintseparated by 2 ø f latitude and 5 ø f lngitude, a result f the reslutin f the PV data set. The TOMS maps in Plate 2, which shw finer detail than the recnstructins, have a

17 COFFEY ET AL.' POLAR STRATOSPHERIC CHEMISTRY RECONSTRUCTED AASE 2 [] AASE ß AAOE T(50mb) K O Figure 10, Nitric acid vertical clumn amunts versus the temperature at 50 mbar. bservatins (latitude f >60 ø) are included. Only high-latitude reslutin f 1 ø f latitude and 1.25 ø f lngitude. Other stratspheric gases are mre difficult t validate by using glbal CLAES t be f insufficient accuracy t prduce a clumn apprpriate t the vertical extent f ur bservatins. bservatins f the clumn. Since the launch f UARS in September 1991, HALOE has measured HC1, HF, NO, and NO 2, MLS has measured C10, 03, Plates 4-6 shw recnstructed ttal clumns f HNO 3 fr AAOE, AASE, and AASE 2, respectively. A number f days f aircraft bservatin are shwn. The recnstructin is nt limited and HNO 3, CLAES has measured HNO 3, HC1, N20 5, C1ONO2, t the bservatin dates but nly t days with an available PV and 0 3, and isams has measured HNO 3, NO, NO 2, N20 5, and 03. Each f these instruments made bservatins during the perid f the AASE 2 field campaign, frm January t March T keep the same side f the UARS platfrm pinted at the Sun, the satellite rientatin is changed by 180 ø apprximately every 36 days. In mid-january 1992 the viewing analysis; hwever, the reliability f the plynmial fits is best within the perid f the bservatins. The same clr scale is used fr the HNO 3 cnturs in Plates 4-6. Nte the dramatically different character f HNO3 clumn amunt in the Suthern Hemisphere vrtex as cmpared t the nrthern vrtex. Lwlatitude HNO 3 amunts are cmparable fr the three directin changed frm the Nrthern Hemisphere (up t 80 ø) t measurement perids with a value near 1.5 x 1016 the Suthern Hemisphere. UARS bservatins returned t the NH in mid-february AASE 2 bservatin days fr which there is a ptential verlap f UARS bservatins are marked in Table 1; nt all the experiments mentined abve (HALOE, MLS, CLAES, and ISAMS) reprted measurements fr each f these days. HALOE bservatins, using a slar ccultatin technique, did nt cver high nrthern latitudes during the AASE 2 perid, and ISAMS data are nt available fr mst f this perid. Vertical mixing rati prfiles frm the UARS data archive have been used t derive clumn amunts fr sme days in January and March 1992, when cincident bservatins were made by MLS and CLAES n UARS and by ur experiment n the NASA DC-8 aircraft. MLS prfile data are reprted at pressure levels dwn t 464 mbar with a vertical spacing f abut 2.5 km, and CLAES prfiles are reprted dwn t 100 mbar. mlecules/cm2. In the Antarctic vrtex there widespread decrease in the HNO 3 clumn. This is believed t be caused by the cndensatin and freezing f gaseus HNO 3 nt the surfaces f PSC particles. These particles eventually fall frm the stratsphere, effectively remving large amunts f HNO 3 frm the system. The SH vrtex minimum is less than ne third the lw-latitude value, substantially in agreement with grund-based HNO 3 bservatins [Murcray et al., 1989]. In the Arctic vrtex, HNO 3 clumns are enhanced with respect t lwlatitude values. During the 1989 AASE campaign, HNO 3 clumn amunts in the vrtex were 60% higher than thse in lw latitudes. AASE 2 HNO 3 clumns in 1992 were 30% larger than clumns during AASE. Figure 10 shws measured high-latitude HNO 3 clumn amunts versus temperature the 50 mbar pressure level fr the Plate 3 shws cntur plts f nrthern hemispheric 03 clumn lcatin f the bservatins. Belw abut 195 K the HNO 3 amunts frm MLS and recnstructed clumns frm aircraft clumn is substantially reduced by cndensatin and bservatins. The magnitudes and general distributin f 0 3 clumns are similar between the MLS and NCAR maps but excellent agreement is nt btained. There are even mre significant differences between clumn measurements f ther sedimentatin, as described abve, especially in the SH vrtex. Lwer nitric acid clumn amunts are clearly linked t lwer stratspheric temperatures [Tn et al., 1994]. The 50 mbar temperatures during AASE 2 in 1992 were in general abut 10 K gases (e.g., HNO 3) by MLS and CLAES and the recnstructed warmer than thse during AASE in On the basis f gas maps frm ur bservatins. We fund the HNO3 data frm the lwer-level (belw abut 100 mbar) bservatins f MLS and phase kinetics alne this increase in temperature shuld nt substantially increase HNO 3 amunts but wuld tend t enhance is a prnunced,

18 8312 COFFEY ET AL.' POLAR STRATOSPHERIC CHEMISTRY RECONSTRUCTED 4 ß 3 q: 2 ß AAOE 1987 ß AASE 1989 ß AASE ß ß ß ß ßß ßß 1 3: NH 0 0 $ 80, I,,, I, t, I,, t I, Day Number i loo 28 lo ß AAOE 1987 ß AASE 1989 ß AASE mm ß z NH S 80 ',,, I t I t t I t I,,, 0 2O 4O 6O 8O Day Number loo 28 I i i i _ 30 ßßßß ß ßßß ß ß 20 '. 10 AAOE 1987 ß ß AASE 1989 ß ß ß mm ß,- ß <1: ß AASE O 0 z NH m SH Day Number Figure 11. Mean clumn amunts f HC1, NO 2, and HNO 3 cntained within the plar vrtex bundaries fr AAOE, AASE and AASE 2. NO 2. The mst likely cause fr enhanced HNO 3 in 1992, and fr analytic relatin between clumn amunt and PV(4) and the warmer temperatures, is the presence f substantial amunts PV(520), at each lcatin where PV is calculated. The sum f vlcanic aersls frm the 1991 eruptins f Munt Pinatub, accunts fr the area assciated with each clumn, which which enhance the cnversin f NO2 and N20 5 int HNO 3 depends n the latitude. By summing all the HNO3 clumns [Cffey and Mankin, 1993, Cffey, 1996]. Sulfate vlcanic within the 2.5 x 10-5 K m2/kg s PV(4) cntur we can find aersls als may change the cmpsitin f ternary slutins the ttal HNO 3 amunt in the vrtex. The mean clumn amunts (H2SO4/HNO3/H20), which are believed t be precursrs f type fr HC1, NO2, and HNO 3, nrmalized fr the vrtex area, fr the 1 b PSCs. three bservatin prgrams discussed abve are shwn in Figure We may calculate the ttal amunt f HNO3 cntained within 11. Nte that the mean vrtex clumn f NO 2 is nt significantly a plar vrtex by assigning a clumn amunt, based n the different frm 1989 t 1992 fr similar perids f winter

19 COFFEY ET AL.: POLAR STRATOSPHERIC CHEMISTRY RECONSTRUCTED 8313 Recnstructed Ttal Clumn Recnstructed Ttal Clumn Fit using tw pv levels Fit using tw pv levels HNO3 l0 mlecules cs-' AASE21/22/9 AASE21/14/9 / HNO3 / 0 ' mlecules cm -t Recnstructed Ttal Clumn Fit using tw pv levels AASE2 HN03 /10 is Recnstructed Ttal Clumn Fit using tw pv levels mlecules cm 't AASE2 HN03.. /10 s -- 2/22/92 mlecules cm øl Recnstructed Ttal Clumn Fit using tw pv levels HNO3 AASE2 3/1 0/9/10i mlecules cm - Recnstructed Ttal Clumn Fit using tw pv levels AASE2 HN03 /10 ' 3/18/92 mlecules cm -a Plate 6. Recnstructed maps f the HNO 3 vertical clumn fr 6 days f AASE 2.

20 8314 COFFEY ET AL.' POLAR STRATOSPHERIC CHEMISTRY RECONSTRUCTED Recnstructed Ttal Clumn Fit. using tw pv levels AASE2 NOYB /10 t z/4/ mlecules cm O Recns[ructed T[al Clumn Fit using tw pv levels AASE2 CLOYB /10 t mlecules cm - 10 Plate 7. Recnstructed distributin f Cly = (HC1 + C1ONO2) and NOy = (NO+NO2+HNO3+C1ONO2) fr a typical day in AASE 2.

21 _ ß COFFEY ET AL.: POLAR STRATOSPHERIC CHEMISTRY RECONSTRUCTED AAOE '- 20 E 10 ClONO 0... i i i i i i i i i i J i i! i i i i i PV(4K),., _.e 30 E HNO 3 = 10 ClONO NO, -'"T' ,... I I.... "r... r...! ' PV(4K)... i... i... E 30.. E 10 ClONO ' E 2 0 NO... i i i i I i i, i,,,,, i,,, PV(4K) Figure 12 Partitining f NOy species during AAOE, AASE, and AASE 2 versus PV(4). bservatin. The change in vrtex NO2 and HC1 between January and March 1992, as discussed earlier and shwn in Figure 5, is clear in the average clumns. The step near day 45 is due in part t fitting tw separate time perids but als reflects a rather abrupt change in the vrtex cmpsitin near that timeø The vrtex mean clumn f HNO 3 is 30% larger in NH winter 1992 than in NH 1989 and is 4 times larger than the mean SH winter clumn f Having an analytic methd t prduce wide-scale distributins f stratspheric gases, we can cnstruct a distributin f ttal reactive nitrgen NOy=(NO+NO2+HNO3+C1ONO2+2(N205)), missing nly the N20 5 clumn, which, in the presence f abundant aersls and sunlight, is much reduced. Likewise, we may calculate the chlrine reservir distributin Cly=(HCl+C1ONO2). Plate 7 shws the NH NOy and Cly distributins fr ne day in Figure 12 shws the partitining f reactive nitrgen species during three field prgrams. In cnclusin, a technique has been shwn that utilizes relatively sparse bservatins in the plar vrtex t recnstruct distributins n a scale encmpassing the vrtex. Cmparisns have been made between cincident glbal bservatins by ther sensrs (MLS and TOMS) and clumn distributins recnstructed frm aircraft bservatins. Vrtex-wide distributins f sme key chemical cmpnents (HNO 3, NO2, HC1, and 03) have been cmpared fr 2 years in the Arctic and between the Arctic and Antarctic plar regins. References Andersn, J. G., and O. B. Tn, Airbrne Arctic Stratspheric Expeditin II: An verview, Gephys. Res. Lett., 20, , Brasseur, G. P., X. X. Tie, and P. Rasch, A three-dimensinal simulatin f the Antarctic zne hle: Impact f anthrpgenic chlrine n the lwer stratsphere and upper trpsphere, J. Gephys. Res., 102, , 1997.

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