ARCH AT THE

TO LOBALC

INSTITUTE FOR

ARCH AT THE

EAERONOMY

E. Arijs, P.C Simon, D. i'ieyejans • .:vI. De :VIaziere, C Lippens, J.Y. :\>WUer, D. Fonteyn, D. Fussell, Arnelynck, E.

~eefs,

\V. Vanderpoorien. )1. Van Roozendael, C Hermans,

D. Gillotay, D. Bolsee, A.C Vandaele Belgian Institute for Space Aeronomy

I

^t ;s evident rhat Nirhin a programme such as Global Change, 'Nhicl-] aims at "the c:r:derstane:r.g or ~he inter- aCTive physical, chemical arJd oialogical ;Jroc8sses

era:

~eguiate the :OIal Earth sysle;,,", ;he sr;.;dy of ;r-a atmos- phere should be of ;Jrimary importance

Therefore ard in response to ~he need for a study af global-scale changes ;n the 3.LrnOSp~er:c C:J!7':JCSH10:1 3-

core project wf the ir:teri:a:;oraj Ge::sp'1ere Biosphere Programme (IG8P) 'Nas s:ar;ec, ca:'ed iGi'lC

~I:-:terna!lcpal Globa! ,L\rmCS::Jhe~lc Cher:-1lstT)f:'_

The Belgl2,n Ins~tut9 for Space Aeronomy ,BiSA) was 'curded in 1964 under the imouise of P:of. M, ~jicoiet and

~as since then contr:buted signlficant:y :0 :lUi renow/edgs of the pry sics and Chemistry of our 3:mosphe:-8_ O:le of :ts major study objects is the ~i:ratosone:fL ~hrG~gh mo-

obS8Natio!:5 ar.d !aboratory \vcrk, !t ;5 :~e pur- ,Dose of this paper to gi'l9 an ClVerJ18'lJ Jf

:re

'Ncr'-<: af t3IS.A :eiated to Global Crange,

Ai!~ough stnctly spa3king IGAC is concerned ''''nth :rODosoherie research and stratospheric studies a,~ ~r~atsd within the SPARC (StratcspherlC Processes and thsir Role ;,'1 Cillnare) project oj the l/Jodd Ciimate Research P'ogramme (vVeRPj, we na\/S also sumlTaii- 2ed in tn:s paoer the work of BISA the S,ia- ios,ohere,

Mas: of this work:s Cireclly reiated the ;J20ne problem, The latter !las been the focal point of many !nlerrationai research efforts, especially since the discovenf of the ozone hole and the results of an international ozone trend study. This study provided evidence for a woridwide ozone decrease in me stratosphere of the orde~ or a few percent in 20 years and at the same :ime at"' ozone i;lcrease in the troposphere,

it is worthwhile noting ,hat these findir.gs were acrua!!y ,he very f:rst real quantifications :)f globai changes and rha! the at;nosphere :s one of the regions where the :mo3ct of man is urambiguoiJsiy shown, In tris cortext th~ decision of the Royal Swedish Acacemy of Sc;ences 10 a'<'1ar,j the 1995 Nobel Prize in to P CrUlzer.

,:)

\1. Melina and F,S, Rowland "for their work in almos- phenc ;J2rI:culady cDncsr0~rg the fQr";.,a.rion and decorroositio0 of owne" can :,e cons:de~ed as a conrrrma:;Dn of the :~portanc9 of at~cspheric -esearch TJ 9;ve 2t o'/ar'.I:ev" of the global change ;91ated iesearc~

!'"1 BiSA !he parag;aohs ;-iereaTter, 'he ha\/8 subdivided

,rce 'Nor". 'nto ti,e ;:8'd mSRsurements or aoser'/ations, aoorato:1 'Nork a^ro"71odeilng,

The fieia -;;easuranen!s ~r.ciude grour:d baSEd ~emot9 sensing. 'r:-S~LU :r192SiJremer;ts \Nlth ba:loon borne instru"

:ments ano so:..:nding of the 3TrT':Qsphe,e from space, T:-'ey ma;nly prOVide data concernrng the cO:"71position of the str2TOsprere or ir.f:Jr;"'1atior: about soiar radiation driving

~h6 chemica: ;Jrccesses in :re atmosphere.

Tr:9 sf :;--e

one s:de ex:Jen~e;,rs a~e set wO to meaSUi9 fundamental models, such as aosorp- t~00 cross sect;ans of atrn.:Jsphsr:c constituents. On the cnne^r har.d :aooratcrl exper'ments also provide data nee- ded to 'merpret fie:c measurerlents, such as for instance rate coeffiCients of ;o~l-molecuie reactions involved in chemica! ionization experiments,

F.raily :he modeling efforts '.Ise expermer;tal ard obser- varional data to describe atmosphenc processes w;thin a rnathemalical framework. The cor.parison of model results and Obse:'/ations laaes to a cant:ruous 'mprove- mert of our urde~sranoing of atmospheric precesses, H ShOL:!d also be :T:antioned that most of the scientific st'Jdies at 81SA related !o :he !GBP Globa! Ch::mge programrr:e, alSO contnbur8 to several interr.ational programmes, such as

- the ;:::wironment Programme of the European Commission (CG XII):

the ca;1t~ Observation Programme of ESA and other agenc;es (NASA. NASDA" ... );

the NetworK for ,he Detection of Stratospheric Change ii'JDSC}:

43

0 7 vVCRP:

-- tre ccr~e;atj\le measurement programf08S of several 5~~eHite·borne experimer.ts (CARS. GOrviE ar:d in future i\OEOS. ODiN and ENVrSAT-1 ;,~.nth the a~mcsprer:c instrClmems GOMOS, SCiJl.MACHY and MiPAS):

EUROTRAC, a project of EUREKA

Field measurements

Ground based observations

Grour,d-based remote sensing r.leasurements ·::Jf st'a-

tosp~eric soecies have been extensively used to increa- se'the scientific understanding of stratosoherlc processes at high and mid-!atitudes. The first t::.;ropean Arctic Stralosphe:ic Ozone Expei!ment (EASOE) co- ordinated by the European Commission (EG) during the winter 9911992 has demo'1Stratec the r,eed for a com- olemer:tary aporoach betweer. high quality 9:ou'1d-ba- sed aoservaUons. aircraft and balloon meaSLrements, eomb,"'ed With sateilite data and model caiculations.

S,:1ce 'he 19505. the Internati::mai SCientific Station of !!le JungfrauJoch (lSSJ) has been equipced 'N:th infrared soect~ofT1 etriG instruments fa r soi ar and ati71cspneric ob- Serjations, in particular by the Institut d'Ast~ophyslque of the Universite de Liege, The actual instrumemation for femme sensing in the infrared consists CJf two Fourier- Trarcsform !rfrared (FTIR) spectrom~'ers with a soectrai resciu[ion of the order of 0.0025 em , ;1 .. dditionai technl- cues ha'fe been implgmercted as, 8,0" ;j\iCrrJwave rad'o-

;'eters (Univ. of Bern), a SAOZ UVN;sible spe~roneter

!815ft .. \ 1 and others, The continUing effort

or

conbined obser;ations with a guarantee for high quality makes that the ISSJ, the ObserJatoire de Haute Provence (OHP).

and plateau de Bure together have been designated as the alpine station at northern mid-latitude of the interna- tionai Netvvork for Detection of Stratospheric Change (NDSC).

S;nce 1990, the Beigian institute for Space Aeronomy t'Jas been participating in the observations of tropospheric and stratospheric constituents wltr, the FTIR instruments and in their interpretation. HCi, CIONQ, NO, NOc., HNO:J, HF, COF2, and

0:3

total column amounts are monitored continuously; also some CFC and HCFC com- poundS are observed reguiarly. Up to now, 81SA essen- tially focused on the development af its own algOrithm for inversion of the FTIR spectra, called SFSP (SynthSPec

& FitSPec), and on the interpretation of the ozone and NOc. observations at ISSJ, This latter'Nork has been done

In coliaboration with P. Demouiin and R. Zander of the Institut d'.~strophysique of the Universite de Liege, In the SFSP method a synthetic spectrum is calculated

\'Vllh precision. In the Synthspec module the earth

ters -::f all .r1terfering gases, taker. from Ht-

TP,';0~92. arc :h9 instnj;i:ent characteristics cesired.

are taker: acco~r.L The retrieval part (F1TSiJ8C) is basao on an iterati\l8 pr8cedure, searChing fer a mini- rn;..;m 'Neighted rrf1S difference betvveen experir,gntal and synthetiC spectra, the weight being proportional to the absorption death. Recently, the procedure has been adapted

:0

perm:t a quasi-automatic retrle'/al of a ~arget s'pecfes in 3. large s8iies of spectra, ard the speed "las Jeen increased by about a ractor 30. Some preoaratory 'Nerk has been done ',\lith ~t,e purpose Of

solar ines:n U":9 5ynthe~ic spect,'"um ca!cula- rion. SF::;P nas beer: ';a:idated in Ihe ESMOSiLNDSC Infra;ed spectra! a!gorithfT"~s

exerCise 11993-199.1) BISA has aiso some expe- nence w!:h an aitemari'/9, public-domain code SFIT

P thaI was validared in the same exer-

~15eo

The ac:ua! !ong<er:'1 database oi ozone at i5SJ 312rted in ; 98'-', based an ;-i iR da!a, and ras been compierner-

ted \Vlth SAOZ cata from ,1"110-1990 on" in order to benef~t

froM ,he combined dataset, their mutuai ag;esmert

~as to !Je checked. It shou1d be noted that FTIR da:a are availabie cniy for olear-sky days, wnereas SAOZ data are taKen dally. at therefore bo~h databases are corn·

o!emenrary, The :ntercomparisor. of the FTiR and SAOZ datasets. ~p !c now tlmited ;0 1993 and the first half of 1995, resLJtsd ;n the ~c!!ow!ng f~nd[ngs {1 :

Spec~;-osc:Jpic ~aoora!ory ifJork (3) ;,as identIfied the least tempe^r3iui9 deper.dant azo~e absorption flr,es in

~VJ ; -2; 50 into account the cOribined effect of the ,ower er:ergy level of the transition ar:d rne :emperarure depender:ce 'Jf the Lorentz ha:N/ldth. The lntercOmp2[1S0n demDns:rated that the most stable FTIR r8sui!s sno the smallest r-lin-SAOl differences are ob- tained llsing several lines simuitaneo~sly in the (3039.18 - 3C40"05 ) jJ.~lindcvv in the 3\'3 band.

The intercomDarison should take intD account the fact that both instruments possibly probe diHerent air masses.

depenc:ng on the measurement lir:;e ar:d season (1). If dynamic effects of smali soatiai scaie are dominating the ozone behavlm;r. they show up as an apparent random mutual disagreement between both datasets, Such ef- fects ha'/e been observed

:f1

the winter-spring of 1993, nearby stations (Arosa. Payerne),

Although a small negative systematic offset no! ex- ceeding 5% may still exist. With the FlIR 03values being tower rhan the SAOZ ones. the agreement betweer: FTIR and SAOZ data comes very close to Ire one obtained in the most recent intercompanson among various UV,Vis spectrometers includlng SAOZ of the order of 5%

also.

For each ~eci;nique. :re ,Jf specrra i'eql;J- an 31rnospnere ~odeL Tna 993 daza -eveal a corre!atlcr: bei:\veen t!"',e :ropcpausC! aressure and ~he

as

,0

:he short-:erm fluct'-latior:s ' linear ccrrelanor r increases from A9 58 after removai

or

slow (seasonal) variations,

work studies the tropopause characteristics ana data oi meteorological nature

temperatures, etc.) at ISSJ, in Of·

oer to see whether from these parameters a model of the can be built that :Jrovides a better repre- sentation of :he -sal day-la-day variat:cns of the aim os·

cordtiors {instead of the s!ar-oa:-d models up to ror improVing the c;1utual agreernent between bolh ~atasets.

"

"

"

..

10

19a6.0 19M.O

:"5:r.9 data

i'Ci,.,ir-CL 3r.C l~:i'; 2xci:.;C:;:g ~~8 71;-S~ t;i~ester

or

^each

year tdaTa ;JC.;"'IS rs::reser:ied ':Jy Gpen GflC;lesL ~n 'Nhieh 03 var,ations OCC:';L T~e values 00(amed 'or the slrL:SCtca: '.:anatlon are cui!£! sim,iar :n beth casas . 22.3~/o

PD;f'! case i~j) as cor.-:par2;1..j to 2.5~3-::--~ ~p in case HC'v';'ever the cerived 'a,e Df 03 decrease charges from

O. t 2-; ~~:J p~er year ~ii~n ~ha 199C reiere-r:ce ·,alue 8.23',( 1 Q " rroLcm~n ::aseiⁱ {cashed to O. 1 ~ ~"per jf:.,3f ,n ", j;v,th the 1990 value aqua: 10 8.06 x ~ mo; =:Tl~ :50Ec ;;;-,ei. T'is c:fferer"ce berNeen barr trerd-'/aluessnd;catl'19 of :he tact :hat :he max:ma

the SeaSCr1a: '/ar;atrc-n were ':0;-9 ~n the ~irst

5 years of the consicered oer;cc. These 'est:i!5 are :::iose rc

tre

ones pubiiShed WMO :,;pder Similar corditlons

"

1990.0 1992.0 19904.0 1~.O

~!ie ~r;::;B CCh.H7',;: ab~VA :SSJ 93.!-~995~ ::b7.aiieC :r-. a c,:;:a..:--.wra:-:;n =-E:N2.a:-; S;S"; and the --"lns:iIt.il , The open Circles fnaicate :data :,Ntt';-:;n the :115t trrr:;;;StEf or =2ch fear~ :1'1BY are :nciuaed

line (see text),

The above ~esul!s have It shOUld be noted that these :rends ir.c!uce the 0:.; trer.d covering the

ISSJ. the reference value tal{en at the 1 The fit

low.

in~vhich \Nere particularly

Araic'Jous :a 'Jzone. Ne d!sl)cse -Jf ~NQ :ardJaSeS for NO:2 3.t rSSJ"

:r;e

der~ved from F7;R i!'1eas __ rerr;er~:s ~ror.-1 985 on. ~re :~her one derived f:-c;;; SAOZ Closer/3.:1ons s!rtce ~ic~ 199C, Aga.:0. tile~r mU'Lual agre9!T':ert is of ~he J:n~D5~ imporrance for ~xploiting ~re da~a ~cr ~he stl;\jy of the lV02 cO!l~n and C;:..;rral 'Jar:atiofl a~c lis ~org-term

evoil.:tiOrl. Sore preiir:linary res:J,ts for :he 1992-' 995 data show a rT:L:tuai agreement within 5⁰S if the SAOZ data :HS ;ss!r:cred to the usually acoered observation interval of 8 7~ to 91 :- solar zenith angle, thus of t);e same order of magr!7ude as the agreerent oQt2.ired be~.veen

var:o'Js UV Vis ,nstrUr:le;HS ,4',: the SAOZ ~eSLJts aoaear syst801atlcaHy 'ower :han t;,e ~Ti R Dnes. :n thr5 CQi71pa- nson, :he d:U:'1al v3,:at;on has been co':s;dereo. This work :s stiii progress.

Bes:de the series of sl:-atosphenc gases :Tonitmet ::ly !R solar ,:bserJai;ons. fur:r-:er rneaSurelT:ents Jf

OJ

ane ver::cal colwr:ns have beer: oer.orrr,ed 2t ISSJ since

1990. !nese ^~;ace gases are r::easured a~ in the 300-600 'liT' SOBctrai cegion. based :;n ,r-:e DOAS (Dif- rerer"riai Aosorption Spec:rosccpy ;ecnn:o"e, T:-,e role of '~eterogeneous c~ern;s~ry O~ stratcscr:eric aero50!S ha;:; '::;een corfirmed :ne ;J;c:Htoring af the stratosphere S'Jr:ng the last SiX years. Mare spec:fica\!y.

tne compou;cs partltiont'g has been s,rongly modified ewe

:0

the huge volcanic srupricr 'Ji Mt Pinatu- bo :nJune 199¹ whic:, injected L::J ;0 30 rr::i:lons ·Jf cons of sw'prc.;( diox;de into the stratasphere.

GroLi;;d~tJased measurements of :'\jO:. aCL.;[":dance ::Jve- ring onB year ')ehre amJ five years after :1'8 Mt Pira!ubo

rave

^{been car~'ed OUT} at ::oe Jr"er;;al:0f1ai Scen- t,ric: Sration at :he Jungfraujocr: (Switzeda:;c. 46:1'18:E'i and at SoCar;ky~a i:Firfand. c4 ~N. 27:') Sf. Tr:e /\J~

vertical COlumn abundance ;s rneasurea cLnng tr;e mor-

<1i:-:g and eveN'g t\vilight by application of ~ne Ciffe~emiai

absorption ... ::ethod using the sunlight sca;+ered ar zenith

if": the '/:slole range. 1>'8 avai!able lime series shows a significant reduct:on of N~ starting in winier 199¹ '992, after the eruption of the ML Piilatuoo volcano. as is visib!e In Figure 2.

A maximuor: cecrease of about 35% is observed in Ja- nuary 1992 at both stations. T08 contimJed time series of observations show a similar bei-:aviour a coth ratJluces.

i.8, the recovery of the N02 column until August 1994.

These results are compared with 2-D chemical model calculations ;~c!'Jdirg the effect af heterc:;er,ecu3 ""e2C-

tions using Mt Pinatubo aerosols parameters as obser- ved by iidar in the Alps (Figure 3). In generai the modeled N02 coiumr:s agree aualitatively with the obser-/ations althlJugh the amplitude of the seasonal variation !s un- derestimated. possibly due to 'nterlla! lim:ta:ions or ;he model which e.g. does not inc'ude diurnal changes. The obser/ed and calculated

NCk

perC8f1t char:ges are in good agreerTler,( Which confirms qcantitative!y the ir7103ct of the heterogeneous cher.-:'stry C~ s:ratosQheric

NC?.

heter::::genecus iJrocesses can be oeser-jed at

;at;tudes 'Afr:en levv stratospj~er:c ~e~~era-

~:....res a"e 2:~coL.r;tered, asscc:2~ed il:th the d!splaceme~'L

of ::-:2 ;Jo!a:- '/cr:ex during jNu"',ter and early spring -n the

~or;i'>;rn he;T!Spner8. O\Jrrng the v.Jinter 1 '394-1995. :~e

'owes; stratospheric :e:-:lDeratures observed so far ,vere experlencec in the Arctic in January ~ 995, leading to chior!19 actpJa~;on by p:ocesses similar to those respon- s'ble 'or the ozone ifo:e in Antarctica. OZ8r-:e de:>ietion

;-ates cornoarabie ~o !hcse cbsarved during t:-re aus~~al 3Gr~d:g nave cesn observed ~Lt :J8C211Se of !he

'Ji "~e oalar vo:-:ax :iI :re Arctic. ~he conotr:ons to de'/9Iop an oZ:Jre ~ole In ~he ;:orthern ~er71jspher9 are not ;-;-Ie:

tJur;rg a sLfflc;enriy

Desp;~e the !nternat:araj effort 3.r,d the ;fi1portant :9SJ!tS cbta:red d'.mng the first Arctic 3na AntarctiC campa:gns.

58'19r31 sc!ertific issues mainly "eiated to ozone cepletior:

::J<.JrSice the pOlar ~eg,c:ns. remain controversial due :0 the c07,pⁱex CCGo!1ng between chemis:ry and dy:;arr,[cs, 50e-

In ~~2 r;ortrerr her'1isphere. In order to 3tLdy tt-e cG~~ectiQn ::;erNeer: ;he lo,rctlc and the mid latltuee ran- gss ar:C tc ;Gprove cur :"navviecge on tr,ese iss'~as, a Secoi:c E;,.;ropean Stratospner!c .Arctic ard rv1la~L~t::L.de

Experims'it iSESA~/E) 'Nas implementea by the EC, It was decidec ,0 expand :he groG:-'d-baseo measure.T:ents for stratospher~c

gecgraphlcai gap ~er\veen

tre

observing sltes situatec oeycro ;he ArC;iC cirde a,"10 ,he mid-latitc:de A:p:ne sta:;cr:s situated arourd 4S:'N 2!id that contribut2 to ~he

NerNQrk fOi th~ ;)ete::lor, cf St:-atosphenc Char.ges (NOSe T;"'8 serecred oDserv!ng srtes Gould be 3.~ 8f ;-:60.1

:r,8 edge of the pClar vortex !jJ!'"ing , .. Vlnter in craer iQ

ceterrrii18 rhe 9xt9fii of .:hemicai:y-inducec ~as5 :;f 3i:ra~

'r'::~"!Cl"'" ozone and investigate transport frcrn ~ljgh

;aT;7ude, during late 'IJlfltermear!y sprin';j. Ti:e ob- servatiOns '.vera based on r.NO r.1ain techniquest t;""18 F'J1J~

rier :rans;orm spectroscopy in the :nfrared \FT1R) and [he UV -ViSible differential absorolio'l spectroscopy

Tc,ese m83Sc;femen:s ,nclude total amOUnTS

or

severa!

reserJorf species (FTIR) With ozone, nitrogen dioxide and OCIO UV -V;SL in tOt21, ,;;rounc-based :nstrumerts v./ere

oper3~9d a: aOOl..;t 35 sites, maInly in EIJ~ope,

81S4~ performed UV--'/~3jble rneasurements of CC;IO.

NO?

a~d

OJ

-::o!umn amounts al Hares;ua. 60'N dunng the Ninters 1993/1994 and 1994/1995 corresponding respectivelY to the ohases I and II! of SESAME A :are~ul !ab(J~-3rcrJ" ·:harac:erizat~on as well as 1:he daveioomer! of a ~e'N anaiysis soitNare significantly improved the instrumentation. Its sensitivity for the detection of ;:1Qody abundant constituenrs like OCJO and NC'2 in ,atitLJde winter condi:ions was increased 3S compared :0 the first measurements made dUring the EASOE campaign (8). in addition, a mobJie Fourier trans- ferm spectrcrr:eter was used for the first time for similar meas'crements;n the visibie range during ~he 1995 Winter (phase iii of SES,A,ME).

C\I

..-

E u

-

^Q.)

^u

o

t.'"l

E

c

::J

o u

o

C\l

Z 7

6

5

4 3 2 1

o

8 7

6 5 4 3 2 1

o

(a) ^67°

~i _'0

6 ,

^I

1

series ;:i ;:1cr~h!v 3\-erSJ;;e

N

y

1991

~O( 3ach month, al1 average T.Cf;-nng anc

anc NQz amounts are averages

1

iTleaSiJrernents between 87~ and 91' SZ,"" 'Soiar ZeGi~n 1;1 the case or the direct Sl.n data cbta:r,ed fr:::;n

to March 1995 with the FTS !Ils;rumertt is made between 83' ar!d 88'; SZA thiS zenith-aor;J!e difference which have some imoact on the comD3nson due to the diurnal 'Jaria"

tion of NQz, the agreement between the direct Sun and results is qUite

The time series shows the we!P~nown seasor~a!

var:ation due to the in :llumination. In addition.

NCk

column amounts are ((,ueh lower in

February 1995 lh3n the same in 1994. ThiS

temperatures thiS are bet!eved to

favo:;r /VOx converSion to their resar;oirs as weil as

J ;

\I

morn,ing

, ,

evening ,0,

^,---r$ I

,J..',..

~

.7~ ^I ...

¢ ""

1994

r"'""1 f,

'oiI"i

i :

0 ..

... ,

~

1 '

....,

....

1995

~"r"'r'''r'~ 3.!~d '0: ,a: :r~ :0~S'-~--2::Cf'72t Sc;e~i/ic S(at::m at tile 7ha jert:cai ;jc:-r3d ~i;\-8 ;hc:cates :he day tr;e

,:JoSS:!::ie cer:~Inf;catjor: of the polar der:satlOr. of nithc acid on potar

Cor::;j!ary, the OCiO conter:ts ;nside the polar vor1ex dUring January ~995 are Quite as compared January 1994 indicating 'arger ch!orlne activation in January 1995. Mos! OC:O observations are obtained inside or at the edge of rhe Doiar vortex which indicates that the aC:lvatlon IS ilrT:neC the vortex region.

Ozone column amounts 'N8re determined SESAME ahases , and III from and direct Sun observa- tions. Low

Oi

cOfUmn amoLints

term

comparee to the

to the lang and phase J!I above Harestua

These ,'l1easure:71ents are cOlIs:stent \vfth of

·F

c E

::::J

o

(J

o

N

Z c

Q)

OJ c .c ro u

40

20

o

-20

AO

~60

J990 1991 1992 '993 1994

Figure J Comparison between e)(perimenlal and modelled results for the momhly average NO:! [eLa; arnC'-',~1 changa ala) 3cdanky!a ~nd ~b} at ~~e intarr'arionai Sl;:an:rtic Statier! at ~he ";L.;!igfrauioc~, The ex~e;;r;;er,taj ;-8st.dts are :;2sed on ~rose Dr8sei:~d ;i!

figure 2. 7:"19 '-.I8rtical dCl1ed iine ;ndicar2s the day of the Mr, Piraiubo er;.JOVOr..

chemica! dBsiruction inside the polar vortex in March 1994 3i'd1995, reported from other SESAME obsen/ing sites, Lmver stratospheric temperatuies were experienced du- ring SESP.,ME phase III 25 compared ~o phase !, espe- Cially from mid-December until the end of January when the norther:-: hemisphere minimum temperature remai- ned close to or below the limit af PSC type II (ice) forma- tion, Two Significant inside-vortex episodes were monitored during phase I and p.r,ase III, both yea,s at the era oi January and mid-March.

The good agreemer;1

at

.he first FTS measurements with the classical DOAS grating instrument results demons- tr3res the feasibility of the stratospheric UV-vislble

48

measurements as a r:ew application of

ere

FQur!e~ trans- form spectroscopy in :hat spectral rarge.

Balloon borne measurements

A:though a long term global study of the struCH.:re and composition of the Earth's atmosphere requires regular and long term observations with satellite oorne instrj- ments. stratospheric bailoons S1ill play an important role in s)(perimental aeronomy, They are not only appropriate for t~e study

or

iocalized ohenomena but are a necessarv too! for experiments req'uirlng an in situ sampling of

at-

mospheric species such as ion mass sDectromerry, Stra- ,ospheric balloons are also excellent platforms tor the d8\/e!opment of space ~nstruments.

:;'03 Beigian Institure for Space

sX;::Jerience in bailoonirg and nas nlCmerQL!S exper'meniS with b3l1oons w'th a VOi_~e ~ang;['1g from 30,800 rn³ to 1 ,OOO~OOO ^m:3.

P~esently rhe bailcor-: experir71ems of 3iSA are focusec on acti'Js chemica! ionlzaticn mass spectrometry (,.l,CIMS) aiming at tre detec,ion of trace gases such as i-ttVOJ and 1'11205, wr;ch playa major ~ole ,n the ozone depletion, This method, developed by ,Arnolc and co-workers :9i of the Max-Planck-Instlt:.:! fUr Ke:~Dhysik Heidel- berg (tv1P(H), relies Jpon the reactiors of at~ospher~c trace gases With ions produced by an ex:erna! ior source, :noGf1ted :n front of a balloon borne mass speC7iOmeter, Th:s leads

,0

^speCific produC7 ions, Fror: the re'alive abundance of the slI:;nals of :he prec:crsor ard produc:

ions in ,he obtained mass spec:ra, the rrlXlng ratios of the reactive trace gases can De dete~'T:r:ed,

In t;ie MACS1MS (Measurerre:l[ of ,:l..t-ospher;c Consti-

~Lients through SelecTIve Ionization Mass Specrrometr{

project wnicn is a '::Jiiaborarfon tlecNsen the Belgian rs:itute for Space Aeronomy i,Brusse!s, ceig:umL the

"Laooratolre de Pr,ys;que et Chimie de ;'E:wironremenr de; CNRS" (Or:ears, F,ance;

ant

the "Physikaiisches inst:tlit" of the UniverSity of Bem (Switzerland) 3i'd 'tihiCh :s oar!ia:ly financed by ~he Eurooean CC:Tlmission, a new balloon borne inslrc;cnem has 'Jeer' ceveopeo ror the l'":easurement of s"atosphe~ic trace gases such as l-INOJ, N20s and C/OND2,

The ACIMS method developed by tbe r,APIH grouc :5 based upon tne iOl1'zation

or

the amorer, air by a high frequency high voltage discnarge, ThiS Te:;-:oc pr'Jcuces CC3 ions and Its clus:ers 3S prec'Jr50r ior:s, which react 'With HNOJ to produce N03 ions, The innovarion of our methoG lies in tre fact that in the "vlACSI\lS instru- ment a selective io;:ization is usea, obta:r:ed through a DC discharge in gases, which are normally no! present the stratosphere, These gases are ;megrated in the payload in small sree! bottles, Through the use of gas cnixtures slJch as Ar C/2 ana AcCHJr Cr;., and

r

^source

'ons can be produced. The selective 'eaC1:ons of these ions can Iren be used for the derivation of trace gas cO'lcentrations,

Furthermore Ihe use of a new balloon borne Mattauch- Herzog mass spectrometer with simultaneous ion detec- (ian ;:;apaOriities \_IJ) shoula ailo·/w a n~gh alt,tuoa resolution in the bailoon measuremerts,

Recently nitric acid profiles have beer, determined in the st,atospnere In the altitude range 30 to 20 Km, from reslJi~s of balloon flights with the MACSIMS instrument (11 using the reaction

chat lons :prCCLlced by ~ DC dlsc;":2rge

reac:~on

r -

^{:he rnix~rg rate C7 pen-}

~ox!de COUld be ':1e:e;;-nir:ec. ~ecent ,2ooratorl 5rucies (12) have s~own that ·Nlth this ;nethod ~o distlnc::on (;ar be made berN8ar /\;zCs ar,d C;·ON~<

T:-:erefore new deve:comer:cs, such as :he adci,ion of a third source iOr.. or :he cnoice of a net: ion ;Jarem gas wiil be reqllirecL Theaoora;crl studies and new :nsiru- mental de'J9Iop~"ln:s rsquired ror cbs ourpcse will be p9r7ormeCl .'J thin

7re

"t4,CS:~,1S II arc SiMLJliCN ;:;ro- jec:s,

Observations from space

The grifie spectrometer experiment on board the ATLAS1 mission

Space-borne exper;ments :Joard tre NASA Shuttle have the advantage of large soatia: coverage of the Earth. bUI have a :ir~it9d tiM-2 d:.;ratioi :Jer miss:on, TGB latter disac'/antage "as bee" ::;v8icorre by :;,e cOf"cept Qf ~egularjy ;;paced ;-9~f:fgr.tS '':; the 5a:T9 experimerts on

boa~d successive .T:ssions, /!,TLAS, A!i~DSpberlc Labo- ratory' for i~op~icat;or.s and Sc"snce.

ras

been cQ0ceived aiong the same ,ceas : the Tr!ssion's obJective

;5

^the

if1vestigat;or; or tne E:afLh-s at0Gspherg, :fimat9 ard solar relat:onshlDs, and effects en them of ,he prccucts ot jndustnal cQr:lpiexes a~d ag~lcw!tural 2c~ivitie5, through a senes of : 1 flighis :asting .:lbout 10 days each that are c:stnbuted J'Jer a ;er:od of one solar cycre, lV'1sr6over, they succeed the 3pace!ab ~:ssions s:arrwg in ; 983 ClP to '985 the: already s:=;rr:ed Gr: tleard sene of !h:=:.4 T:"AS 8xpenment5.

T~e GrHie 5pectrome~er has been developed ard !Jpera~

Ted as a lOll;! Frencn-3e:gian axperlrner~ ;ONERA LPM.Ll, and :lISA)', First deployed from SlralGSpher:c balloors in the seventies, i! pa~iclpated in the Soace!ab-' mission in December 1983 and the first .ATLAS fTIission in 1992, lIS objectives are the study of tre vertical composition of t/1e Eanh's lower slratos:Jhere up to the iO'Ne~ !her·

rr:osohere by means of Infrared solar Gccultatron absorp- tion spectroscopy, With focus on measurements of the fOilowing 10 molecules, in the 2,5 to 10 11m spectral ~ange : CO, CO2, NO, ND2, fJ-z,O, H:zO, CH4, 0:;, HC!. and l-IF (J 3). The retrieval of the Gnlle! ATLAS 1 data has been performed i:ldeper:dently by at least +:ON':! different ;nver- sian algorithms, one being a least-squares giobal tit method, the other one an optimized Mili's inversion algo- rithm (20) : as such, the quality of the results ,'las been assessed -e1iab!y, Whenever poss!ble, the results nS'Je been comoargd to correlative data from ATMOS on board the same mission or 'rom HALe;::: on board U,,l,RS, Global resL;lts of the Spacelab-1 flight. Inc!udir:g a pre- sentation a: the instrument and ihe occultation technique, are summarized by Girard at aL (14 ). DlJring ihe ATLAS1

.~\i1ar,:h 24 to ~, ; resuits :lZlve cbta!i'ed in :ha iatitudlnai beit r2ng~ng frCiT ~he ec!..;ator :Jp [0 55;S. for Cl-i.l, CO ar:d l\JO

15. 0.17,'

could be drawr from a of He: measi.lred W!tG :hQse deter"iined :11 1985 1 The He!

on board the same mIssion 12,! in comoar:son w:th the mean 1985 He! volume mfx'''g ratio

~bove

50 km of

ppbv measurerj by ATMOS the celao·3 misSion

increase of

60

40

the present value cemons:raIes an ,5:::0.05; opbv.'yr (aHas scmewhar ,es5

silghtiy higher ;!'.an mccei

~3

1f

1995

and

f'efe;e~c:?s

The

dataset ::Jresented here :5 !CO

ORA

em

EURECA

The ORA prO)8C! :5 a coilaooration between 'he institute of Space and

.Atmosphepc. Oceanic and 'fersity cf Oxfo~ct ~t has a ~Nofoid ,s a s:rLltaneOt;S :ileaSLfement

NOz.n 'he m:eds atmOSp"er9 order to contrlbl..ra ;0

\NhicM ::ecame obvious Since t;-:2 :;i5~

-ccve:~' c~ the Ar·t:irctic

iha secor'!d (",r"..,,'"'''''''' IS to ~ea' :;~re ~he 'Nater vapour cor::e:llraHO~ !n tile mesospherg

'Nit); Ire aim of the d2L3.fied baiance of ~oper

'Nater var:;o:..:r, \r\'hic~ is sti:·f :lot

un- cerSio::c

:28}

'85->'92

3,0 VMR (ppbv)

s

T1e ORA P]ccuitation FI.ad:omelerL 'Nnlc:-' -:as been de-

\/e;oped fer tre EUREC.Ac \t:Uiocean P,E:i:e'labie CAr~

r~er; aile '..'lJnlC;l S desc;~bed in ,~cre ce:.a:! e!s9'/Jne .... e

~esjgned to meaSGre \Na~er vapeur ard carbon aio.=dd8

\NaS used for iorai dersity ce!ei;7';raricns; \NaS deiivered by ere Oxford team

The UV-visible de!iv9-:sd by 3iSA. '1ia.S designed to :7leasure OZQ;:sJVD2. water vapour a::d ae~Gso!s.

absorp~ion rr:easurements in elser-ate '.vave- in the ,r-eglon af ~r~ solar scectrL~ frCHTi 250 to 1020 rlr:1. it ccns;sts of 8 modules

Gr

sirnda;-design. each 3. CljanZ \lvindo¹N. ar. :rner.er2nce f[:ter i,O :sciate the apprcpriote INavele0QIh darla::. a simple ap-

~ics to :lmit tne f;e!d of vie\v to =2'.' and a CBI8ctcr i either a Sdicon phOTCdtode or a GaHiu!T~Phosphide diode, de- pending

on

the 'Na'.!8fe-rgth). The ';'Vave!engih of rna d!f~

feren! UV~visib!e crannefS toget~er w!~h :~9 major ilght absorbers is in Table 1

Table! :f :he dIfferent

259 385

Predorninar:t neutrals

NOZ

ment ;:md !T12na'ger;-em 'N!th ESA.

The ORA inst,umenc. was !!own Of' the ~UREC:;A miSSion 1993) and oerformed its me3sure- menr.:; ihrough ~he ;Jccuitatlon technique or :irr,o tomogra- method. which allows to derive an absolute Quantity, namely [he slant path opticai tric"ress iron a reiattve :r~nS;TH5siofi measurement

FrOrl the EURECA car~;er. vvhich had an erbit of 508 km a!t~tude and 28:: inc!inat:on. and I,Nnrch \N8S a sun pointing satef1ite, measuremer:ts of the atenuation of solar radia- tion through the atmosphere over a cericd of about 9 months were obtained.

T:l6 oaia or in8 ;r.rrared ~rit C.<fcrd grou;J, we will limit ourselves here to the resul~s obtained with the UV-visible unit

Durmg 9 months (frcm ,C;ugust 992 u;;til May; 993) of continuous operarions more than 6QOO sunsets and sun- hses ~vere r8CQrded ~n the Vv'3veiength channeis ShO\Nn in Table 1.

The ra\N data as obtained from the instruiiler:t are ~UNes

r80rssentlng ~ha intensity as a function OT rime, wnicn

:JV8r :~e Qctica~ across ~he

'ntegr3~;cn aver :he a~carenr solar disc are r1'gr j ~'"'on jjnea~ \;nc~icr:s Df

rna

'ceal -3xt1f:C:;C.~

To retrieve to:al absorptlon Jroriles ;r8IT1 :~9se Sigf12iS at

~he Lsed wavBler,gths. a new r:-;e~hcd r-9fer:'"ed to 35

;'JOPE ; f\JaU_JaJ Ortho~Crial Proffis de\/8!Cped in BL3A.

has Deer

of tre ~;.(tir:c[;on ::rofi1es 3: "Q 1 J 1m, 'N;---;ch dr3 'llaiGiy causec by aerCSG1s. The ;~9-sant ,:!ata set ci8a.r1y sho\vs ;~oortan~ differsrces bSPNeen the ~etrie\.'ed tc!al extinc~jons and ~he oneS ~cr 5tar:c2 ~d atmosonere '::Jndi- tions. oL;e :0 the presence ;Jf vOlca~;c a2fosois

:r;tD the 5~rato5phere ;he Pir:2E..:JO erupI:on. The 2e~

resal ioaaing fl'"c~ rhe :\1:. ?!narubo erGDtion ;s 5.

3

2e~oscj "erose! ^3ercsol

NO]

8efoj~

GUe:o

,38iDSC;S as Cbt2;r:eC 't/ith 'JU( da:a. :")ei\veer abcut i.!O:f\·l and 40;S a vahiatlon JT ~:'le ca:a S8~ sho:.)'.] be serfcr~

:ned. T~:s va;lcarle::. \lJ~;Cn Gcns:sts ORA resu lts ',,-v~th the

It (Stra:;Jspner~c AerosOl and (:;23 is no\.;v in process and ShDVIJ5 a good agrear"19nt ~etvveen tr.e data of both sateilite expehrr;e:'lts ard confirms the

nature

Dr

the huge data set obrair:8c tre C)R,'; instr:.Jment.

Laboratory measurements

Halocarbon radiative forcing

The "LaboratoirEl de Ch:mie Physique Moleaulai'El" from Tt16 liLB rnaaa a veri rmponant cont;iOuiion, o-virh tne coil abo ration of BIS.A., to ire know'edge of IR absorption cross sections oi man-made haiccarbO:lS. with an origi- nal and comprehensive study of a variety or so-called a!r2rflatjve halccarbons to be used mainly in replacement of the current CFCs \v:;;cn vvdl be phased~cut in 1996.

according to :he fv10ntreaf protoccf and ~ts a.nlendments.

The IR cross section measurements were performed using a Founer IR spec~rometer (FTIR)' a ::)et\veen :3QQ and 1500 and

51

depth at 1013 nm

fit

, "

:-..

~ ,

. ^'.

" ,

. : .. fIB II

",,,,",. :""~ '""

".: ... "' ..

"

.. ","'"

¥ ' " • .... e"' ....

..c: 0.06

c. aJ

1:J

.=

co 0.05

^"

.'

.S:!

...

l i

0 0.04

^:..

0.03

0.02

.

^'

, "

. ..

,

.

...

.. .. : ... :'", ....

!- •

..

^'

..

_,

_.

.. .. ,,"' ....

,

.

"

.

"

"

" , ~

'.

.",,"

.'

. _:. .

" ,I

" J

"

y=0.065"exp( -xi272) 0.01

0 0 50 100

5 . GOtiC2! cepth me23' ... rec ~y

:,,=:A

a: i J -:;r. from 2 rela.x!!:g 'Nlth a time :c.~s:art of aoou! 270 cays.

at three temperatures, name,y 287, 270 and 253K. Inte- grated cross sedans have been introdLced into a two- dimenSional radiatil/e-chemical-dynamic model from NCAR in order to calculate the Global Warming Potentiais (GWPS) of each gas. These calculations show that for three compounds (HCFC22, HCFC142b, HFC125) the GWPs (relative to CFC11) are higher than unity for a 5- to 10- year period. Moreover, these com- oOIJ'lds mai'ltain a s"ong GWP for a 'J8ry long time. Therefore. taking into aCcoUflt the fact that for »ame industrial applications larger quantities of CFC alternati- ves are sometimes needed to replace the current CFCs in order to obtain an equivalent effic:ency, their contribu- tion to the GWP may remain important. These results will help In the definition of future regulation. considering the current estimate of radiative forcing by halocarbons.

They were included in the last WMO-UNEP Assessment of Ozone Depletion, 1994 published in 1995 (chapters 8 and 13 of reference

52

150 elapsed days

abC\1i3 :ne :rOPQ02,,",se to space, "'f"'~e aercsoJ loaGl::g of M~ ~'r;a:,Jou

lon-molecule reaction measurements

In order to study some of the ion-molecule reactions which are used in bailoon borne active chemical ioniza- tions instrument MACSIMS, a flow tube of the classical design (34) coupled to a quadrupole mass spectrometer was bu iit in BISA. With this instrument the reactions of HNC>:, with Gin and rn (n = have been studied at raOi:":

(35).

The reaction rates for Grn + HNC>:, for n=2 and 3 ha'Ie been determined relative to the known reaction rate for Gr + /-IND:,. It was found thai nitric acid reacts fast with Gfj, resulting mainly in the product ion The product ions of the siower two reaction of

GFi

cou:c not be determined unambiguously, but most probably NGi as well as NGi.HClare formed. For the study cf

r:, ...

^HNCs, (he ~ncwn reaction was uSed -as a r9fe~ence, No reactior: ~3S been zbseried fer

in addition rate ccr-srants or upper "mits for 'ate COr'S'

tants were determined for the reactions of nrtrlc ac:d Wiln

Vi.i-fN03 and ,f../Oj.,'-!CI,

The reaction rates obtainedr theSE; studies were used to derive the mIne ac.d Cor:cEwtra!ron in the stratospr.ere with the mentioned MACSIMS

;;;s!rumern ^~< 11)

irradiance monitoring at the Earth's surface

An UV irraciance !1"Qf'iroring stations Brusseis, at BISA since the end C' March

-3utomatic station CQ'1s:sts af two GOLD!e mcnochrcma~

,ars based en the available Jobin-'{'Ion

model H10D.

:0

meet the :eou~:-e~

mems necessary lor such a difficult meas"remerL It orovides soectral measurements of the rota: soiar Irra- dia'ice (eirect and diffuse absolute radio- metric urlts, with a field 01 view of 2;: steraCiars, and ,1-,8 diffuse irradiance of the zenith sky '.v:tn a field of view of 10' The wavelength range covered by these

teis is well oelow :he atmospheric ozone cut-eff around 29Q-300nm and exoands to :he visioFe range up :0 680nm, Spectra are :neasured every 15 ITllnutes.

solar zenith SMaller tnan 100', These 'nstrwmer:ts hav'" '"''''coo rnaracterized ana are cali-

bra!~;~ith abso~te

transfer standards i:l the 31SA !abc- and their stability is checked means

of a Lamp develo-

ped at BISA fer quality conrrol of iJV ;nstru- marts (1pnl(lVF!C

The station is by three br::ad-band radiome-

UV~8 meter (280-315 n~), an UV-A meter and

a tot~!

pyrometer

nm -

3.5

J,lmJ.

irradiance measurements,

A 1 O-channel filter radiometer has recently been instaJied to measure the direct sorar irradiance between 300 nm ar:d ~m and to deter:ni0e the ozone and atmcs~

pherid Direct measureme'1ls of soiar lrraciance are iJlanned in a near future.

Tne uncertainties 01 the meaSUf9ments in Brussels are less than 5%, The current of the data has clearly demonstrated the anti-cor~e!ation be- tween the ozone !olal amount and the UV -8 (280-31 radiation dose. vah.:es hav8 been me3sured in average in Brussels when . Ozone decreases have been observed. Further worK is needed to maKe a

Modeling

Tropospheric modeling

:S a recent

988. in close oollabo-

research is to and ~se sta~e~af~the-a;t !T',)t1"I"':n

that:an he:; JS to Jr:ders!and the varr' intricate climate, and human ac~

tlvilies. T"e is on scale modeiin';j, since

!ccaiized De:iurba:ions can af7ect even the rnost remote carts of tte atmos:::Jhere, 'JWing to the wird transport

or

. The C2i"itral cOr;"'oonern .::f ehe·

:nt'S,r" a:

31SA IS

a

three-dir;J.;"nsionai cnerrll- ca:; tia1)58Gn mccel. naMed irv1AGES

MOdel fer

,ne

An'-!.;,,' arc ,31ooal Cf':)iutiOr: of

The role man ;s

::::emorsi;ated

~rs cOniri- burions :ha er;-"ss!cns 'J1

:race

gases: e,g" between 50 a;ld SC"';' of :te 50urces of

sucl1 as the nitrco;en OX!Ce5. sulfur dioxide, carbon mo- noxide 3r:d methane are dv:: to or a; :east comrolled by human act¹vities. fsssil fue ,and ~'Vc-od

nd:..:stnal activities. 'Naste activities.

deroresta:~cn. etc. ,A, deta,!s(j

Once 9rr:rtted, trese trans-

formation and

range bet'Neen hours and years. When a liferir.te is t can be transported over very long distances and reach almost any par. of the 'en", IS",

Pe of the trace gases Is one

of the C2rtS of any model. The atmos- phere is divided the mocel into many boxes. Their

size is SOC km in :he horizontal and 1 km in the vertical. We use the analyzed winds from the

Weather Forecast

transport 01 trace gases, As the

1 ... , ;t:!"'a""",c- """-T,,", off"::"Ct \f,i~~

Vaj-.j~s r:ll c.: ell ... i "!J"";;:;;' t i l e ...-1;"' ... t " ' ....

at time scales smaller than a ITlonth must be as adirrusion process, The diffusion coefficients are calculated from ECMWF wind var'an- ces. Other transport components that are not

taken ir.io account when monthly

averaged winds are the in the

layer

vertical tr3i'Sport assccialed'.vilh cumulus clouds,

53

-;-~:?se c::--::;Ci'errs s.re tre.:i:ed seCara:2;y :: "~e j~.L~­

GE3 T:cce"

::rder :0 :ss~ tre '7'ccej :;erO'"f71ar-ce "Nrtr ~es::ec: :J

",S'5SI0[,5 ,,-nd radioac:;ve :i:e:ime, arC are ;T:eastJredn

T any ;Jar:s ~f t;,e wo-ie. The agraesent of '"'Gee: resuits :he ~cse0Jations 1S very good.

~O~ us. :J8ifutantS swch as r:i:rcger; ,3.r;C SU;fL.:

are tOXiC at h!gr

'2<1915: do -at acc;"StJ!ar8 ^'f: the a~:-;ospner-9

pr:otc·::t;ernicai ~eactlc;-S ,nitia:ec LO :;reak a

\I~ :he UV SpeCHUrT:, Photcdissociallon gives ilse to ~ production of ,r18 so-ca,led 'adieals ;';en; ;as,-'eaetirg mc;ecules' 'Nhlch can theli :iuack ott~er rnolec:..;les. The rlost ;~pc--:ar:t rac;ca~ jn :r;::pcsphenc cher1srry is Ihe r,t::rOXYi "ac:'cal ~r5 c9r.cef"'t;a~ior: 5 \i8ry ~O'N

:ne .~rCc'" of 1 !"-;;Gi8CL!ies em..J), bL~. :rar:ks :0 its h!g:

arc versa~:-e reactiV!ty. OH S =8spons:o;e fo~ :~e cher.;~

ca! degrac27,on CJT a 'arge ~~r;lber of ~c;iutarr:s The ,::rl -:he-:;"ljstry -5 '/ery c:);---,;piex 2;,G ;ts caⁱc:";:alⁱors r ,-:;ocei.:;

!"eq~;res :r:2 ,nclUStcn of te;:s

Dr

spsc:es and :""'L.f1creds

J:

reac~:Qn5, ::JH ;s baSically producea as a Gorsaq'Jence lr-,,,tl,t;GES ::ak9S ;nto ~ccount ~ost proces- ses ::hat aie reievart to OH a.rd ozor;e s~e~;siry.

Tra ox[da~:c:. ot ~2::Jcn morc,~:de ar:d hydrscaroQns Ori ;s tl:e s:a~jng p.::'rnt of a c::nptax 02chanl5;n vVhii:;:h

car

91tre^r ?rod~:ce

ozore a:

suffic;erlt:y nnroge~

OX1::::e ;e\/.:;,s; Qr deSTroy QZO'lB, Huma;; acnVi:t9S ~er.d :0 ir;c'ease -"e pote,,~:al 0 1 :ne atrnosprere to oroduce Gz0ne. Th:s species:5 nC\iV c~nSldered as a K2y

8cca~se of its (d9f7l0nstratec during :he vJe;;~

Kr.o\<vn "SfTcg episodes" over lndustr;anzed areas} and because ::m::ne is radiatively active. it also concributes to the so-cal!2d "greenhouse e:'fect" i.e. the warming of th2 Ear;:,1 due ~o :he :rapping af :e~restr[al (adi2t~cn inrra- 'se absorb.t1g molecules. Me:hane:s another example Of

cremistry-controlled greenrcuse gases: its ii7e~ime cf aDcut 10 years is controlled b~l the abundar.ce of thE radicaL Ths means ~nat any ~erturbatton Dr the OH source, sink balance is SU5cept;b:e to the abundance of atmospheric methane.

T'le degradation of oollutarts by reactlon w:th radicals ar;d phowCissceiation ultimately prOduce species that ca;] be removed to the Earth's surface. either by wet deposition (i.e., absorption !n cloud or :a.in droplets rollo- 'Ned by preCIpitation) or dry deposition (direct s~jcking of the gas to the stJrface) This process explains, for eX~n1ple~ ~he increased acidity of precipita~;cn at our ia;ludes, as rain is t:~e major nrocess respor;s'bie for the rerr.oval of sulfUriC and ni:rie acid, Nitrogen

54

~""e ~\iAGcS :-:1cce' s ro,c'/, DP2(3tJOr:c> a:-'c is 88;:"'g usee fC:-~2ny c;~erenr ·crcs of 3lL:dteS, The "!cdei ;:=5:..;jtS are

·:::;r:pared i'rth ava::acle cbseriatrOi'S orde:" :0 Shec~

:he/aiid:ty of its assumptions ana par3meten:::Hier:s T~IS 2!!OWS ::-:e mcceiers to

r:rC

^~e'-tJ d;rections ::cr future research. :-!eterogeneous proo:::sses : .e., gas-ic;uid or gas :0 p3J!!c!e conv-:?rsior and reac71cn the C8rcer:sec pras9L c!olJd ~;ans;::cr:. 8icger:;c em:ss:or:s f~l1X2S 3.re a fe'll amorg ~any :H2ceSS6S NntCr

~::sr:ncn r :~e rut:...,re,

'"equ;rss ~ore

T-:6 '!lode! s also :::;:e Jf E~e 083t tools availabie n oreer :0 :';sIimare :re irroact of ~L.L;~an acr;c;it;es Dr ::;!imate C:lange an atmosoreriC com~o5itlcr., ECCS~lstefi rncde- ll:-g fer ~he :Jrssent-day Climate and fer :Qndjt~ors of tne Las: ,31ac:2l ~1axiGwr.-: ailov/8C :.;s to eS:lf'nate :1'"'8 chan~

gas 'n eccsystef'!'l ,::ls~ribu!lon and e:;-,:ssu.Jrs

Ira:

a:e

aSSOclatec :0

^:arge c!irna!ic '/2r-:2i!OnS 391.

T~e ,;;-iP2C:: Jf ;~C~s:ra!izatriJn 5:;:·:e ~~s ast cer::jri na,3

jeer"' estir,a.:ed 'I"'!:~ :he rrcceL a~d 2g~ees \i'.I;t~ Qbse"--

\ja~'cns ;n :~e esLr;:2t:C!i of ~;t!~ace c::·,--:e ;rcre2.s~ ·Jver

f,.1o:"9 !"9C9r~lv. :I-'Ie ;:odei ,s also being \~s2d in :1'8 frame~

vvcrk of ar! ,':'r;lerican assessmenT ·")T the 'mpact

Jr

su:;sc-

;,;C 3.ircraf:s or. tr9 atmosprere. liv1AGES ~as beer:

chosen NASA;r Drde; to ceterm:ne :r:e ma.jor SCientific

;5S\....95 ant ~ncei73. ~ties rr-:e cortex: of the airc:-aft

of rr:ocej OL~:~l for tr-:!S study·

j~ ;3p^t-ase r ts ~he change (in ~!":i) in n:trJgen 8X:C9S cor-

Ce:~~r3tJon 3£ an lsoba;ic level Jt 250 r:b 10 Kr!1 alri1'Jds}. it appears !hat 2i^rc!"ahs are Ti3Jcr sources of nl~rogar: ox:des in ~r:e upper rrapaschere at fJur tempe- rate !ar!rL!ces. The ozor6 changes, ho~vever. ;:;eaK at

8bc~~ -5~'o. Ti:ese ~stimates are, hQ'.v9ver. stii! orelim:- na;y, as suffer ~rom rrany ilnpoGant uncef!ainties.

Trese uncertaintIes 'NiH be t~e subject of "Jur fa..;h .. re worK.

Stratospheric modeling

The mair. Objective of thiS mOdeling study '.\las 1:0 resolve i!"lCof's;stenC!8S between theory and oosen/anors abou!

~he ozone cepietion at global 'evel and ,n the polar re- gions. Moceis or ;~e composition of the stratosphere

only gas phase che,mstrf de ,101 explain i;,e trend in SU'T'mer but underpredict it in Winter. Heter:;ge- necus effec~s are saL:ra!ed w:lh respect to aerosol SL:f-

face! either sujfate or Polar Stratcsph9i!C Clouds) in the se'lse that a large ;nc~eaSe in the latter is :lot acco~pa*

r:ied by a .~"'oporto~a! effect 8n the cher.!stry.

t995. co. 4]-53

r~"""'nl"""lo v~;\...;! ,\~ ...

-I

(07\ ,,-i,:;::>

\. /0 J '-" '- '--.; ^f1'

'"",:, '_I

r·'-" r-.f', U ...

Figl.Jre

a .

Ca:=~;al2d char".;e in rltrogen 8X!CeS corce'-';,.!zwon ; :r ;:;er:ent2ge; ~: 3~ ,5c:carrc e' .. ~e!:J~ 25:) '7ib (:~m;:L.! 4 0 ~rn J:t!t:";C2) due

~o 3.: reran efT'~SS!0ns.

'illS non-[inearit'f also shows as an hysrerssis effect 'Nhen a decrease ,n the aerosol load is nm followed a return to condilicr's eXisting betore the aerosol :ncrease.

The mathematical tools developed for these studies con- Sist Of a r.vo dimensional model of the composition of the stratosphere [alti!Uoe versus latitude}, a :hrse aimensio- qal model of the :ower stratosphere, and a modei of the formation of Polar Stratospheric Clouds {40j.

The 2-D model allows climatological studies to be perfor- med. This model is based on a zonally and monthly averaged temoerature climatology of the atmosphere, in an isentropic framework. The model inciudeS all relevanI chemical reactions. All relevant processes taking piace on aerosols (either sulfaie or Poiar Stratospheric Clouds) are also taken into account A detailed model of the formation of PSCs is incluced in the model, thus haVing a PSC climatology consistent with model climatology including effects such as denitrification and dehydrifica- ':on. This model with PSCs coupled represents very well the PSC ciimatolcgy as observed by SAM·!I (41). The

N S T, '/Oi

source ;;2.58S can have SG~3Ce cor:centratlons to reflect specific ,:onditions.

The mecei simUlates well tne Antarctic ozore hoie, Very low oZema values are found ;rorr: mid-September un;!I mid-October in the lower stratosphere, from 5 to 25 km.

The ozor:e cotu:r:n content has va!lies as to'llJ as j 50 Dobson units, which is in V<'3ry goad agreement with obserJal:ans,

With the eruption of Mount Pinatubo, oiher heteroge- neous processes have been studied and found to be important as well. These heterogeneous processes on sulfate aerosol oar:icies have a less eificient ozone-des- truction capacity, but due to volcanic eruptions their effect can be enhanced. The low ozone values in the Northern Hemisphere 1992 and 1993 winter can be attributed to heterogeneous processes on sullate particles as a result from the 1991 Me. Pinatubo volcanic eruption, Taking ail these effects into account. our model studies simulate the obServed global ozore decline for the last decade (42) very weiL

55

SinC9 tr,8 mace! IS a 2-D

;n~erar';'iJal cifiererces.

ar clouds during Northern He;:;jspner~ N;n-

:ers ;:ar not tie simuiated, In the Nor!herr! Hernisphere, ,heres evidence for a 5-8% decrease for :he 'ast decace n ~ctai czone, vv!rh the !2rgeSt dep!etion at ~,he higG9st

!atituces durir.g winter and sprrng. There is aburdant direct evidence for per.u~bed ::;hemjst~y ;n :he Arctic ^51-

~ilar to that of Antarctica {43), bt..;t the cOld temperatures,

"':ece5sary for poiar stratosphenc c:ouC formation. are gel"19f3.iiy nSI;l-;er as w'despreaa :ior as ierg :asting a5n

~he sw;lng season ~n Antarctica. Thls ';]raater mereorcio- glca! Janabdity has importarH cor:secuences for the PSC formation. A 2-D moae! study is r,Qt adequate 'or Simu- iatH'g PSC arc consequenily a 2·D mocei stLdy or Nor::h- ern Hemisphere polar Cher:11stry is ve,:] difficult to :nteroret. Therefore, we developed a three dimensional mode! of the :ower stratosphere :hat :akes into account a reaiis::c meteorological variaoliiry, As of today :11iS '710- de!" ariy caicu!a~es aerosol e\iC~Lit~On {.either St..;!rate or Porar StratoSoherlc Ciouos). Its a ;Jar. Di 7he ongoi"g moce!ing 'lforts TO denve a N.H. PSC .:;:imatoiogy from :he 3-D '1lode! calculations as ;r,:Jl.It ;rto ~he 2~D rnocei,

Acknowledgements

The aurhors would like to thank for financial support to their research.

- The Belgian National Science Foundation (NFWO : Natianaal Fonds vaor Wetensci"rappefijk Onderzoek and FNRS : Fonds Nat/ana/e de Recherche Scienti·

fique);

- The Federal Office for SCientific, Technical and Cultural Affairs,

- The FKFO-MI . Fonds vaor Kolfektief Fundamenteel Onderzoek op Ministeriee! Initiatief;

- The European Commission (DG XJl) for several contracts within the Environment and Climate Pro- gramme.

Note

ONERA Office National d'~tuces at ce Rec;'erc;',es Aeraspariaies. Paris; LPMA Laboraioire de :::hysique MOi9CU- laire et Applications, Univ. P. et M. Curte, Paris: 51SA . Belgian ins!!tClt8 for Space Aeronomy.

References

1 OE MAZIERE M" HENN2N O. VAN ROOZENDAEL M ..

DEMOUliN P .. l.4NDER R., HAMDOUNI A., 3ARBE A., Multi- ple ozone measurements at the Jungfraujoch ar, '....lpda~e after optimrzed retrieval from FiIR measurements" in t:Jroceedrngs lJf rna T/;!rd ,A,r⁷nual Syrnposium on POlar St;'atosphe:rc Ozone, (SChiiersee, 3avar;a;, September 1935. press.

56

2, Z.!l:'~C=,~ ~" ~:NSL...-\NO C:,P., CEl\t~OUL;~J P" AJriiAi"-i 3.?, 3~J;_:J~1AN A" :V1.";H!~d'::, 393\, '·ES~ .. 'C'S!!j~JDSC-;;-:-

3: 3,.1.R5c,l .. ~AI,IOOLNI H .. ?LA. TEAUX J.J .. DEMOL!U'J P ..

:'A.~JOE;:; R.. OEL3DUILLS :.. .. ROLAND G. (1993), "Re:"eval ::i total Gzc:r.e ;~t12~nty frc;m hIgh resoiution :~frared specr;a . i'f!uerce J! SP':?C:icsc!Jpic arc physical pa.:--ar;:sters"j !n Aunas- ::;henc S,cecrrosccpy AppJic8tICnS WQrksl~cp, (ASA Fleim5L p, 35.

.!; '-l:ll;GHAN (3. 9t 21. (~995~. "An tn~e!"C:QfT'panscn of grGulid~

:asec U\/-\):5io;e sensorS:)T ::':::::Jr:e arc :VOi'. J Gecp/:ys =ies.

5) "SC12r~!lFc asse$srr~ent of czane c.epletio.~ 1994" ~ 995,.

Ncr;a Me:ecr-;:iegcai Organ:Bnon Reeer! 37

61 ;jA"~ ;:::lCOZENJA:::~ M. DE Mil.lIER:: M, H::RMA~,S C.

SIMc"J :J.C. PCMMERE.t\'..; J.P. GOUTAIL :=., TIE xX.

3RASSELR G .. i3?ANIER C. ^j 1 995), ·'Grounc·based ObSerJ3- :;or.s 2~ 3trato.siJr:enc t"JD2 a! ~igh ane ;-!lic-latltcdes :n c:Jrcpe ahar \.1t P1ratuno e-r:..:ption. J Seopi7ys. Pas .. subm:t!ed

-j 'J,~~,~ ?,:JCZ=:NC,.\c.L ~\i1., i-iEFit'JtLl,NS C .. K,A28ACJ y" ~Atv1- 3E,:::rT ';,C., \/A~·;C,';:=L~ A,Cq SIMON P.C .. C,.l,qLE~H :VL.

::;Ul~~'1QT J}vL. COLiN r:t -: 9951, "Gr'Jur.a-basea measure-

~9:-':S of OC:'C, /\jC*2 ar,d OJ at ~arest~a,

Ju;"!n9 S=5.~~1c" ~ Proc2':?d1!-:gs :Jf : 2th ESA on

£:Jrcae2,'"7 Plcck8r and 3aJ/oor; Programmes 3.t!d F?e!ated Pa- saar-c.n, ESA~SP-3::-"C, {L.~ne::3rnmer NorNay j, ~ 2J~-13.:1. =S.~, ,Jwre.

3: \,',,!N ~O()ZENDAEL ,\1 . FA,YT G,. eOLSEE 0" Sirv1CN ?_C ..

.3 L ~vt , YE~~ \1.. C'!.CHO .. 1. '\ ~ 39.!.L "Ground~tasec strayoSph8-

-:c :\h~ 'T'::rrtOf:r-g at r<evla>;;;":, ,1c'3iand} c:u:--irg ~,A.SOE·· Gec~

::;:"'/5. Pies, L2~ .. 2~ 137"9-: :382.

g} ,,,l,R.'HJLO F=" t<.NOP G. 198?}. 'Stratos:Jhenc [raca gas C2t=C::O;; ..;s,ng 2i '""2W :;aEoon·borr:e i"Cl~.i1S :'71etnc,d,'J, into J

,~,(!a5s Soec;r, fon p ... oc, a1, 33-J-4.

.10) :VICeR R., KDPP EO., JENZER U .. RAMSEYER H ..

'Nf..:::LCi-'!,) U ... l\RIJS E., NEvEJANS 0, lNGE:L.S J., i=USSEN D" BARASSiN A. REYNAUD C. 9S9i.'A souoie fccussing Tass spectrorlistB( tor simultaneous ;on rne25urernents in [he ,:st:-atcschere", Prccaed/ngs of ESA~PAC Syrnposium on Euro~

cean 2cc:~er and 8a!:ccn Pr'.Jgrammes and aelaTed F1eseatch.

=SA·SP-21;. rLahl1sre:n, FRG), 129-134, ESA. Aoril.

, ~ 1 f AMEL YNCK C, 'j ANDERPOORTEN W. NEEFS E, ARUS E .. RE!NHp-,i:m H., KOPP E., GUiM9,A.UD C .. BARASSIN A. {1995}, "New rr,e~hod for the derivation of stratospheric nitric acid and dinitrogen penroxicte. based on balloon borne active

·.::hernica.i ionization :nass spectrometr/. Method, instn.!ment ji:";':;:;;.Ji:~w[~ ar;j ,::s;;rnjoar,- ,-95wltS'·, in Geophysics a.r~cf :Jie Environmem. I.IUGG. ed.), (University 01 Colorado, Boulder, 'JSA). ;:I. A285, International Urian Of Geodesy and Geophy·

SiCS. XXI General A.sserrbly.

2j HUEY L.G .. HANSON C.R., HOWARD C.J. (19951. "Reac- tions of 5·"'3 and rNilh with armospheric irace gases". J.

Chern., 99, 5GC1-5008.

13) CM .. W·PE.vR!::T C. ?AP!NEAU N .. ARMANTE. fl ..

ACH,t,RD V, 3ESSON J" '.t1UU .. ER C DE MAZIER!:: M.

UPPENS C., '1Ei1CHEVAL J ... ACKEi=lMAN M., FRIMOUT D.

"" 5 T