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I t has been a very good year forSPARC. Having served SPARC

superbly for more than a decade in Paris(France), our International Project Office(IPO) has relocated smoothly to Toronto(Canada). Our 3rd General Assembly,held in Victoria (Canada), was a greatsuccess. Our science programme isdeveloping strongly, thanks to theefforts of an enthusiastic SPARC com-munity. And our role as a key project inthe World Climate Research Programme(WCRP) is being enhanced by strength-ening links with other international pro-jects, both within the WCRP and withinthe International Geosphere BiosphereProgramme (IGBP).

The new SPARC IPO was set up at theUniversity of Toronto in April 2004,staffed by Norman McFarlane(Director), Diane Pendlebury, (ProjectScientist) and Victoria De Luca (ProjectManager). The relocation from Paris toToronto went smoothly thanks to theirefforts, and to the unstinting help ofMarie-Lise Chanin and CatherineMichaut at the Paris office. Catherinewillingly made extended visits toCanada to help get the new office underway, helping, for instance, to producethis newsletter. There cannot be manypeople in the SPARC community whohave not had occasion to be grateful toMarie-Lise or Catherine at some time oranother. On your behalf, we warmlythank them for their commitment toSPARC and for their professionalism inrunning the SPARC IPO in Paris. We arealso grateful to CNES (Centre Nationald’Etudes Spatiales, CNRS (CentreNational de la Recherche Scientifique),and Meteo France for their support ofthe SPARC office in Paris. Luckily for

SPARC – and especially for us, the farless well-organised co-chairs – Norm,Diane and Victoria have taken overwithout a hitch.

We gratefully acknowledge the financialsupport for the new IPO given by sever-al Canadian sponsors: the Meteorolo-gical Service of Canada (MSC), theCanadian Foundation for Climate andAtmospheric Science (CFCAS), theCanadian Space Agency (CSA), theClimate Change Action Fund (CCAF)and the University of Toronto.

In August 2004, SPARC’s 3rd GeneralAssembly was held in beautiful sur-roundings (and balmy summer weather)in Victoria (BC), Canada. The scienceprogramme was structured aroundoverview talks to outline the key scien-tific issues for each session, contributedtalks, poster sessions, overarching talkswe called SPARC lectures, and a specialtalk by Prof. F. S. Rowland. The postersessions were given ample time, and(with the slight encouragement of a cashbar) were seen to be highlights of theGeneral Assembly, as the organisersintended. Some of the key develop-ments highlighted were that: (1) chem-istry-climate models have finallyreached a level of maturity for attribu-tion and prediction of long-term changesin the stratosphere; (2) process studies inthe upper troposphere/lower strato-sphere (UT/LS) demand an interdisci-plinary approach, involving models andmeasurements; (3) high-resolution(cloud-resolving) modelling will play animportant role in understanding theUT/LS; (4) connections between differ-ent timescales are important for dynami-cal variability on seasonal and climate

Contents

SPARC Newsletter n° 24

STRATOSPHERIC PROCESSES AND THEIR ROLE IN CLIMATE

A Project of the World Climate Research Programme

January

2005

News and Views from the Co-Chairs,by A. O’Neill and A. R. Ravishankara ...1

Report on the SPARC 3rd GA, by J. P. Burrows et al. ................................3

Report on the 12th SPARC SSG Meeting,by N. McFarlane et al. ...............................9

Polar Stratospheric Ozone Changes,SPARC, and IPY, by SPARC Co-Chairs ..............................19

Report on the 2nd Sower Meeting, by F. Hasebe et al. ....................................21

The Lower Arctic Stratosphere Wintersince 1952: an update, by K. Labitzke et al. .................................27

Report on the Quadrennial Symposiumon Atmospheric Ozone, by C. Zerefos ............................................28

Summary of the COSPAR 2004, A1.1, by J. P. Burrows........................................29

In Memory of T.M. Donahue,by A. R. Ravishankara ............................31

Announcement: Termination of theSTRATALERT Reports, by K. Labitzke ..........................................31

Future Meetings ......................................32

Figure 1. The structure of recently adopted SPARC activities is shown in the figure. Theactivities of SPARC, a project of WCRP, are aligned into thematic areas shown as shadedovals. The basic information for SPARC research and activities are in the form of observa-tion, process studies, and modelling, which are integral to all the three themes; they areshown as boxes supporting the themes and connecting to the specific tasks that are shown asovals below. The specific tasks are the heart of SPARC and it is through these tasks thatSPARC activities are carried out and the SPARC community is involved. This is meant to bea "living"figure in which, for example, new ovals will be added for additional SPARC activi-ties when they are established.

timescales; and (5) there is an emergingunderstanding of the nature of long-term changes (beyond trends) involvingtemperature, water vapour, ozone,methane and other chemical species.You can read more about the scientifichighlights of the General Assembly inthis newsletter (p. 3). We thank the localorganizers and the Scientific OrganizingCommittee for their excellent work.(Please see the names in the report onthe General Assembly.)

The scientific programme of the GeneralAssembly was organised around thenew structure of SPARC (Figure 1).There are three main themes: chemistry-climate interactions; detection, attribu-tion and prediction of stratosphericchange; and stratosphere-tropospheredynamical coupling. The first of these,chemistry-climate interactions, is beingpursued as a joint activity with theInternational Global AtmosphericChemistry Project (IGAC) of the IGBP.The themes are integrators of activitiesin SPARC. A critical role in SPARC isplayed by the working groups, whichfocus on specific activities that supportthe main science themes. (See the backpage of this newsletter for furtherdetails). The working groups are wheremuch of the hard work gets done. AsSPARC’s priorities evolve, the workinggroups reconstitute themselves accord-ingly.

The GCM Reality IntercomparisonProject for SPARC (GRIPS), for example,has played a leading role internationallyin identifying strengths and weaknessesof climate models that have a represen-tation of the stratosphere. The last for-mal meeting of GRIPS will be held inHawaii, March 21-25, 2005. Many mo-delling issues remain problematic, how-ever (e.g. the representation of gravitywaves). Effort will now be focused onthese issues in the context of the threeSPARC themes, such as chemistry-cli-mate model evaluation. We thank StevePawson, GRIPS leader, and his col-leagues for running GRIPS so success-fully, and for their long-standingcommitment.

We should like to mention one newworking group, in particular, which iscurrently being formed – the workinggroup on solar variability. Kuni Koderais leading this activity for SPARC, inclose collaboration with the CAWSES(Climate and Weather of the Sun-EarthSystem) project of SCOSTEP. Under-standing the impact of solar variabilityon the stratosphere, and on the rest of

the climate system remains, a very highpriority for SPARC. Such an under-standing is essential scientific underpin-ning for our theme on detection,attribution and prediction of strato-spheric change, and we very much wel-come the developing collaboration withCAWSES.

Collaborations "closer to home" withinWCRP are essential, if our knowledge ofthe stratosphere is to be brought to bearon wider issues of change in the physicalclimate system. WCRP’s strategy for thenext ten years has, as its central integrat-ing theme, the Coordinated Observationand Prediction of the Earth System(COPES). The aim is to facilitate predic-tion of Earth system variability andchange for use in an increasing range ofapplications of direct value to society.SPARC will be fully involved in this ini-tiative. We have been tasked with lead-ing WCRP efforts on chemistry-climate

interactions, in collaboration withWCRP’s Working Group on CoupledModelling (WGCM) and with IGBP’sIGAC project. Amongst other contribu-tions to COPES, SPARC will be repre-sented on the Task Force for SeasonalPrediction, on the Modelling Panel, andin the Working Group on Observationsand Assimilation (WGOA) of theClimate System. CLIVAR, a major pro-ject in WCRP, is large and multi-faceted.Although the interests of SPARC andCLIVAR overlap, previous linksbetween the two projects have not beenas strong as they should have been.There are now so many scientific pointsof contact between CLIVAR and SPARCthat forging stronger links leading tojoint activities is a priority.

During the next few years, our effortswill be directed at contributing effective-ly to future scientific assessments – thenext WMO/UNEP Ozone Assessment

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(2006) and IPCC report (2007) – as wellas participating fully in the planningand execution of scientific campaigns forthe International Polar Year, 2007-2008.If you are reading this as a newcomer toSPARC, and would like to get moreinvolved with an extremely enthusiastic,committed scientific community, pleasecontact us. We’d be delighted to hearfrom you. We also welcome commentsand suggestions from the veterans ofSPARC who have made this project sucha success.

(1) Data Assimilation Research Centre,Reading, UK (alan@met.reading.ac.uk)

(2) NOAA-Aeronomy Laboratory, Boulder,USA (A.R.Ravishankara@noaa.gov)

We thank the participation of the SSG infleshing out the themes, tasks, etc. andthe continued involvements in the work-ings of SPARC. The next SSG meetingwill be held in Oxford, England inSeptember of 2005. The venue for thenext General Assembly will be decidedat the meeting or soon after.

SPARC co-Chairs

Alan O’Neill(1), A.R. Ravishankara(2)

Report on the SPARC 3rd General Assembly

VViiccttoorriiaa ((BBCC)),, CCaannaaddaa 11--66 AAuugguusstt 22000044

JJoohhnn PP.. BBuurrrroowwss, University of Bremen, Germany (burrows@iup.physik.uni-bremen.de)

CCllaaiirree GGrraanniieerr, Service d’Aéronomie-CNRS, Paris, France (clg@aero.jussieu.fr)

PPeetteerr HH.. HHaayynneess, Centre for Mathematical Sciences, Cambridge, UK(phh@damtp.cam.ac.uk)

TThhoommaass PPeetteerr, IAC, Zürich, Switzerland (thomas.peter@env.ethz.ch)

WWiilllliiaamm JJ.. RRaannddeell, NCAR, Boulder, USA (randel@ucar.edu)

AA.. RR.. RRaavviisshhaannkkaarraa, NOAA-Aeronomy Lab., Boulder, USA (A.R.Ravishankara@noaa.gov)

TTeedd GG.. SShheepphheerrdd, University of Toronto, Canada (tgs@atmosp.physics.utoronto.ca)

Overall Structure

SPARC General Assemblies provide avenue for the exchange of scientificinformation related to SPARC researchactivities. They also provide a goodvenue for people to interact, one-on-oneand in small groups, to discuss individ-ual issues of mutual interest. They areheld only in plenary format, i.e. with noparallel sessions, with a moderate num-ber of oral contributions and an empha-sis on poster sessions. As such, they areintegrative in nature and complementthe highly focused workshops that arethe main venues for discussing some ofthe pressing questions addressed bySPARC. The General Assemblies alsocomplement the mainstream large meet-ings, such as the American andEuropean Geophysical Union meetings.The plenary approach and the format ofthe meeting allow a synthesis of infor-mation as well as discussions of thedetails of the science. Lastly, theGeneral Assemblies ensure that all theactivities that are integral parts ofSPARC have a "home" for scientificexchanges and discussions.

Even though a very large number ofresearch topics and areas form the"bricks and mortar" of SPARC science,they all contribute to one, or more, of theoverarching three themes of SPARC: (1)Stratospheric Chemistry and Climate, (2)Stratosphere-Troposphere DynamicalCoupling, and (3) Detection, Attribution,and Prediction of Stratospheric Changes.This is the new architecture of SPARCand this Assembly, the first since theadoption of this architecture, strived torepresent the science along thesethemes. To take into account the impor-tance of current research focusing on theextratropical and tropical tropopauseregions, the SPARC 2004 GeneralAssembly mapped the three SPARCthemes as follows: Day 1: Chemistry-climate coupling; Day 2: ExtratropicalUpper Troposphere/Lower Stratosphere(UT/LS); Day 3: Stratosphere-tropo-sphere dynamical coupling; Day 4:Tropical Tropopause Layer (TTL); Day 5:Detection, attribution, and prediction.

The three SPARC Lectures, each onehour long, were the venue for the "grandscale" synthesis. For each of the five

themes, the theme leader gave a synthe-sis and review of the specific theme ofthe session. Invited Lecturers alsostrived to synthesize and review infor-mation, and to offer a concise descrip-tion of the state of the science. Specificresearch issues were addressed in con-tributed oral presentations and postersessions. The half-day session on toolsand techniques provided some of the"building blocks" of the science, whichare essential for all the themes. Theyincluded laboratory studies, micro-physics, gravity waves, and data assimi-lation.

The Assembly began with a SPECIALtalk by F.S. Rowland on "EnvironmentalScience in the Global Arena: Strato-spheric ozone to megacities to climate".This presentation put the work ofSPARC in a global perspective andshowed why this work is important forthe good of humanity.

The poster sessions formed the back-bone of the Assembly. They were themain venue for disseminating thedetailed science. To ensure success of

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the poster sessions, and hence of theassembly, the posters were each up fortwo days, viewed for four 2-hour longsessions, and made more attractive bythe location, availability of ample spaceand lighting, and food and drinks tolubricate the science. The availability ofthe posters for two days in the vicinityof the auditorium allowed people tolook at posters even during times thatwere not dedicated to posters. Alltogether there were 375 presentations atthe Assembly, and roughly 340 partici-pants from 30 countries.

Building Blocks

Laboratory studies of gas phase and het-erogeneous chemical reactions, micro-physical processes, and photochemicalprocesses are crucial for understandingand modelling atmospheric chemistry.The invited talk by J. Abbatt highlightedthe key role of laboratory experiments indeciphering chemical and cloud process-es in the upper troposphere. The invitedtalk by B. Kärcher highlighted theunderstanding of detailed microphysicalprocesses and the representation ofthese processes in models. Clearly, therehas been significant progress in theseareas over the years as shown by a fewpapers on gas phase and heterogeneousprocesses, as well as better calculationsof the global warming potential of HFC-134a. However, new and interestingatmospheric observations such as theformation of large nitric-acid containingparticles in the polar winter/springlower stratosphere have elicited morestudies in the laboratory, formulation ofdetailed mechanisms for their formation,and analyses of atmospheric data.Incorporation of this information into3D chemistry models was demonstrated.The coating of atmospheric ice and otheraerosols was shown to affect the reactiv-ity and properties of the particles.Information needed to check microphys-ical models was shown to be availablevia balloon borne measurements. Onelaboratory study highlighting the prop-erties of cubic ice was presented and thisinformation will be very useful in inter-preting laboratory and field data. D. Weisenstein hypothesized that tro-pospheric SO2 from industrial sources,such as emissions from China, couldhave led to more aerosol formation inthe tropical upper troposphere, which inturn could have led to a larger numberof smaller ice particles lofted into thestratosphere. Such a temporal change inSO2 emission was suggested to be a pos-sible reason for the increase in water

vapour in the LS over the past decade.The question of how uncertainties ininput of sulphur at the tropicaltropopause influence the stratosphericaerosol budget is part of the SPARCAssessment of Stratospheric AerosolProperties, which is soon to be released.

Gravity waves (GW) play an importantrole in stratospheric climate, principallythrough GW drag which contributes tothe driving of the diabatic circulation.The "cold pole problem", which is cha-racteristic of stratospheric climate mo-dels, is attributed to missing GW drag,and the treatment of this problemthrough GW drag parameterization re-presents one of the most significantuncertainties in modelling polar ozonechemistry. J. Alexander reviewed thesubject of GWs, and emphasized the lackof consensus among the experts con-cerning key aspects of GW drag parame-terization. While one might hope thatmeasurements could be brought to bearto resolve these disagreements, the inter-pretation of GW measurements isextremely challenging because of themismatch between what is observed andwhat is needed for models (Figure 1 p. I);thus it takes great care to ensure that oneis comparing apples with apples.However, J. Scinocca showed thatdetailed differences between GW dragparameterizations may not be so impor-tant if certain bulk properties (e.g. thesource spectrum) are constrained to bethe same. This helps to narrow theuncertainty associated with GW para-meterization. On the measurement side,the availability of high-quality, high-res-olution global temperature measure-ments from GPS occultations is anexciting development for GW studies,and several papers presented resultsusing this data.

Data assimilation is the process bywhich measurements are optimally com-bined with models to produce the bestavailable estimate of the state of theglobal atmosphere at any given time.Originally developed to determine ini-tial conditions for weather forecasts,assimilated data sets are increasinglyused for diagnostic analyses and processstudies. Dynamical analyses in the stra-tosphere have been available from sever-al operational weather centres for manyyears, and have played an importantrole in understanding polar ozoneprocesses, for example. These centresare currently raising their model lidsabove the stratopause, and there is also awealth of stratospheric chemical datanow available from satellites. R. Rood

reviewed the history of these develop-ments, as well as current hopes andchallenges. He specifically noted severalfundamental challenges relating to biasand noise, especially as seen in chemicaltransport calculations which are invari-ably too diffusive (Figure 2 p. I). S. Polavarapu developed this issue ofbias and noise, both for constituents andfor dynamical fields, noting how bothbias and noise become particularlysevere in the upper stratosphere.Because this region also coincides withthe top of the observation domain (typi-cally the stratopause), special kinds oftensions arise between model and obser-vations. D. Fonteyn highlighted theremarkable development of strato-spheric chemical data assimilation inrecent years, especially as applied toEnvisat data, illustrated with severalapplications to calibration/validationand science studies.

Chemistry-Climate Coupling

The chemistry-climate coupling sessionconsisted of a session overview talk byC. Granier, a SPARC Lecture, threeinvited talks, 7 contributed talks and 74posters. A wide range of issues werediscussed in the talks and posters, deal-ing with lower stratospheric ozone, tro-pospheric ozone, aerosols and polarstratospheric clouds (PSCs), watervapour, and the impact of climatechange in the stratosphere and the tro-posphere. Results from observation sys-tems, either from laboratory, ground-based or satellite-borne platforms, aswell as results from chemistry-transportmodels and chemistry-climate models,were discussed.

The SPARC Lecture by G. Brasseurpainted the "big picture" of the role ofchemistry in the evolution of the climatesystem and the biosphere. Ozone playsa central role in this respect, as it filtersUV radiation, warms the atmosphere,and controls the lifetime of pollutants.The first invited talk, given by J. Pyle,showed that the stratosphere-tropo-sphere system is a highly coupled sys-tem, through a discussion of theresponse of tropospheric ozone to cli-mate change, to changes in stratosphericozone, and to anthropogenic emissions.In his invited presentation, R. Garciacompared results of simulations per-formed with a coupled chemistry-cli-mate model with observations of ozonevariability, and temperature and watervapour trends from 1980 to 2001. Thethird invited presentation, given by

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W. Collins described the importance ofincluding chemistry in global circulationmodels (GCMs). The talk focused on theincrease of water vapour resulting fromclimate change and its impact on tem-perature, the relationship between cli-mate and surface emissions of chemicalcompounds, and the impact of climatechange on dynamical processes.

The contributed talk given by J. Zawodny discussed the 1984-2004record of NO2 data from SAGE, whichdisplays a strong hemispheric asymme-try in the long-term changes in NO2,with a positive trend in the SouthernHemisphere (SH) and a decrease in theNorthern Hemisphere (NH), the largestchanges being in the LS. Another analy-sis of satellite data was given by M. Weber, who discussed the linksbetween planetary wave driving andtrace gas transport and chemistry usingobservations from TOMS and GOME. Aquantification of the relation betweenwinter-spring loss of Arctic ozone andchanges in stratospheric climate was dis-cussed by M. Rex, who gave an estima-tion of the additional ozone lossresulting from possible stratosphericcooling linked with climate change.

J. Austin discussed the analysis of cou-pled chemistry-climate model (CCM)simulations, looking at a set of diagnos-tics: temperature, PSCs, age of air, corre-lations between tracers, or area of theozone hole. V. Eyring discussed how aprocess-oriented validation of CCMscould complement traditional validationand increase confidence in the results ofthe models.

Within the SPARC community, transientsimulations can now be performed forlong periods of time, and analysis ofboth surface and satellite observationsand model results for various periods oftime (from a few years to about 45 years)were presented in both oral talks andposters. Several discussions regardingassimilation exercises and their evalua-tion were displayed in the posters, usingobservations from diverse past and cur-rent satellite data sets. The first uses ofthe ERA-40 reanalysis data set werereported, and preliminary results onsimulations for this period were ana-lyzed. Ozone calculations have alsobeen included in a few global forecastmodels, which have been shown toreproduce reasonably well ozone fieldsup to at least 4-5 days ahead. For exam-ple, analyses of long-record observationswere presented from surface stationssuch as the Dobson network, or from

satellite observations, for which longrecords are becoming more and moreavailable.

Simulations for future conditions werealso discussed for different sets of sce-narios. The impact of climate change onozone levels and corresponding UV lev-els were shown for different conditionsand scenarios. Solar-terrestrial interac-tions were also presented in severalposters; the impact of the 11-year solarcycle on stratospheric and mesosphericozone and global circulation was simu-lated with CCMs.

In summary, the presentations in thesession showed that since the previousSPARC General Assembly in 2000, therehave been large advances in both theavailability and analysis of global obser-vations in the stratosphere, troposphereand mesosphere, and in the develop-ment of CCMs, which are starting to bewidely used. Several discussionsfocused on the best strategies for the val-idation of these models.

Extratropical UT/LS

J. Burrows opened the oral session withan overview of some of the currentresearch issues in the extratropicalUT/LS. Experiments using measure-ments and models are currently aimedat providing a much better understand-ing of cross-tropopause transport andthe dynamics on both sides of thetropopause. D. Fahey gave the openinginvited lecture for the session. He dis-cussed the use of in situ measurementsto probe the UT/LS, providing a per-spective on the use of tracer correlations,and describing recent progress in thisfield. The latter focused on some recentaircraft measurements in the UT/LSregion. Comparison of the correlationsof HCl and CO with O3 in the UT/LSdemonstrates the need for an improvedinterpretative framework for STE. Thecommunity is well prepared to conductthe next generation of UT/LS experi-ments, which are now urgentlyrequired. In an invited lecture, H. Wernli described the key issues ofStratosphere Troposphere Exchange(STE) in the extratropics. The processesinvolved in STE and their timescaleswere discussed, with evidence for STEon many scales. Potential Vorticity (PV)streamers and cutoffs are currently con-sidered to be more significant for STEthan tropopause folds. However manyprocesses are poorly understood — forexample the importance of latent heat,

radiative processes, turbulence, anddeep convection, to name a few.

The morning session was completedwith three contributed talks. L. Pandescribed modelling of the UT/LS. Inparticular, the potential to quantify theinfluence of mixing and transport nearthe subtropical jet has been investigatedin a case study (Figure 3 p. I). The ini-tial results show that the large-scalewind fields appear to be responsible for the observed tracer behaviour. J.-P. Cammas discussed recent resultsand analyses from the European MOZA-IC project. This project, which beganback in 1992, has equipped in-serviceaircraft with instruments for measuringozone and water vapour. Recently, themeasurement suite has been extended toinclude of CO and NOy. The long haulaircraft used in MOZAIC provide someunique measurements in the UT, andvertical profiles at a series of airportsaround the world. C. Schiller intro-duced the SPURT (Trace gas transport inthe tropopause region) study, whichmade measurements of water vapourand a variety of tracer substances in thetropopause region at midlatitudes. Avariety of campaigns took place from2001 to 2003.

The afternoon session began with theSPARC Lecture by M. Schoeberl, whodescribed the satellite view of extratropi-cal STE and the UT/LS. The extratropicalUT/LS is a mix of tropospheric andstratospheric air, and the tropopause isnot well defined for trace gases (Figure 4). The concept of the age of airin the stratosphere and its applications toinvestigate the LS were thoroughly dis-cussed. Examples of useful satellite datafrom instrumentation on NASA-UARSand ESA-ENVISAT were given. The finalpart of the lecture addressed the potentialof the instrumentation aboard AURA toinvestigate the UT/LS. After this excitingreview and overview of different satelliteobservations and their applications, H. Kanzawa gave an invited lectureabout results from the ILAS (ImprovedLimb Atmospheric Sounder)-I and ILAS-II instruments, which provided infrared(IR) solar occultation measurements ofthe atmosphere from November 1996 toJune 1997 and from April to October2003. This instrument provided measure-ments of key stratospheric species in thestratosphere at high latitudes.

The last session of the day was devotedto contributed talks on current researchtopics. D. Knopf described the experi-mental measurement and theoretical

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re-emphasised the central role ofdynamical coupling. P. Haynes, as ses-sion convenor, summarized the recentdevelopments in this field and empha-sized some of the remaining uncertain-ties.

The strong intrinsic variability of the tro-posphere-stratosphere system is anessential component of any considera-tion of dynamical coupling. S. Yodenemphasized that this strong variabilityrequires a probabilistic interpretation ofthe response of the troposphere-strato-sphere system to external change, eitherchange imposed in a model as part of ascientific investigation, such as animposed Quasi-Biennial Oscillation(QBO), or change imposed on the realatmosphere, such as input of volcanicaerosol or increase in source gases. Hestressed the usefulness of a hierarchy ofmodels in studying such change anddescribed how modern computingresources (which tend to be allocated toincreasingly sophisticated coupledchemistry-climate modelling, for exam-ple) could allow very long time integra-tions of relatively simple, but usefullyrealistic, atmospheric models and hencereliable computation of probability den-sity functions and reliable assessment ofthe significance of apparent changes(Figure 5 pII).

Stratospheric sudden warmings have forthe last 50 years been regarded as aremarkable example of dynamical vari-ability and a stringent test of dynamicalunderstanding. The sudden warming inthe SH stratosphere in September 2002emphasized some of the limitations of

investigation of the nucleation of NATand NAD. It appears that current labo-ratory data are insufficient to explain theArctic denitrification. L. Poole des-cribed the first analyses of PSCs usingthe extended capability of the SAGE-IIIinstrument, which is a solar occultationinstrument operating in the UV-visibleand near IR spectral regions. Two dis-tinct types of PSCs and some large NATparticles were identified. J. Loganaddressed our current understanding ofthe interannual variability of the verticaldistribution of ozone in the UT/LS.Overall the interannual variability ispoorly understood in the 80-125 hParegion. Finally, attribution of ozonerecovery requires a detailed understand-ing of the dynamical factors influencingozone in the LS. G. Mullendoredescribed advances in modelling cross-tropopause transport in midlatitude con-vection, one of the three mechanisms bywhich tropospheric air is transportedinto the stratosphere.

The poster session addressed a widerange of topics including laboratorystudies and analyses of data from a vari-ety of platforms: ground based observa-tions, aircraft and balloon campaignsand satellite observations. In total 83posters were presented, demonstratingthe continuing and growing scientificinterest in this region.

Overall, it can be concluded that muchprogress has been made in our under-standing of the extratropical UT/LS.Currently, one large focus of researchactivity addresses the dynamics of theUT/LS region using chemical com-pounds as tracers. It is however worthreconsidering whether the elementaryhomogeneous and multiphase physico-chemical processes, which determinethe behaviour of this key region, areadequately understood. Our currentknowledge of the physical and chemi-cal processes determining the behav-iour of the tropopause region remainsof fundamental scientific interest and avery significant limitation in the accu-racy of current predictions of theimpact of climate change on the strato-sphere.

Stratosphere-TroposphereDynamical Coupling

Coupling between the troposphere andstratosphere through radiative, chemicaland dynamical effects is one of the cen-tral themes of SPARC. Recent observa-tional and modelling work has

our current understanding. T. Hirookadescribed an investigation of this sud-den warming using the Japan Meteo-rological Agency forecast model,examining the differences between fore-casts initialized on different days, andargued that deceleration of the flow inthe LS by the action of synoptic-scaleeddies may have been important inallowing the subsequent upward propa-gation of planetary waves associatedwith the warming.

M. Baldwin summarized the observedcharacteristics of the annular modes ofvariability. It has been argued that theseare evidence of dynamical couplingbetween troposphere and stratosphere.In particular, he emphasized the strongobservational evidence that circulationanomalies in the mid-stratosphere areprecursors to (but not necessarily thecause of) circulation anomalies in thetroposphere and speculated that thestratosphere acts as an integrator of highfrequency forcing from below, produc-ing long-lived circulation anomalies thatfeed back to affect the troposphere. Healso discussed the interesting possibili-ties that this picture might offer formedium-range weather forecasting andalso for understanding aspects of futureclimate change (Figure 6 p. II). B. Christiansen developed this themefurther by describing the use of strato-spheric information in statistical fore-casts of tropospheric circulation. Hedemonstrated that including lowerstratospheric winds, in particular, in sta-tistical forecasts, was an effective way ofimproving skill out to 30 days or more.

Figure 4. LACE balloon pro-files at 34°N for May 1998.SF6 and CO2 are increasing intime so older air has loweramounts. Air above the 390 Kisentrope shows distinctlyolder air (low values of SF6and CO2), air below the 350 Kisentrope shows distinctlyyounger, tropospheric air(high values), and air inbetween these two isentropesshows a mixture of tropos-pheric and stratospheric air.The tropopause and regionnear 380 K appear as transi-tion layers in trace gases.[Ray et al., J. Geophys. Res.,104, 26565-26580, 1999].

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W. Robinson reviewed the dynamicalmechanisms by which changes in thestratospheric circulation might signifi-cantly affect the troposphere. Heemphasized the observational evidencethat synoptic eddies played a very sig-nificant role in any tropospheric annularmode response but noted also strongobservational and modelling evidencefor the active role of longer planetarywaves. L. Polvani emphasized that theanomalous stratospheric events werestrongly associated with previousupward wave flux from the troposphere,but went on to present evidence (model-ling work with R. Scott presented in aposter) that the stratosphere itselfplayed an active role in determining thisupward flux. J. Perlwitz argued that thedynamical link from stratosphere to tro-posphere may sometimes be via thezonal mean circulation and sometimesvia downward propagation (reflection)of planetary waves.

Whilst the evidence for dynamical coup-ling between stratosphere and tropo-sphere has renewed interest in thepossibility of a significant modulation ofthe tropospheric circulation by the equa-torial QBO, K. Hamilton demonstratedthe difficulty of unambiguously demon-strating such modulation in limited-duration (20 years or so) GCMsimulations. There is also significantinterest in the role for dynamical coup-ling in determining troposphericresponse to stratospheric injections ofvolcanic aerosol. G. Stenchikovdescribed relevant GCM simulationsand noted modelled aerosol injections

appeared to cause both direct dynamicalchanges within the stratosphere, andindirect changes due to surface coolingin the troposphere and resulting changesin planetary waves.

Other oral presentations and manyposter presentations gave differentangles on many of the importantdynamical and dynamical couplingissues mentioned above.

Tropical Tropopause Layer

Although the importance of the tropicaltropopause as the principal sourceregion of air entering the stratospherewas pointed out by Alan Brewer in 1949,this region is still largely "terra incogni-ta" due to its inaccessibility. It was rec-ognized only recently that most of thetropical deep convection does not reachthe cold point tropopause but ceases afew kilometres lower, sandwiching theTTL, i.e. a relatively undisturbed body ofair, subject to prolonged chemical pro-cessing of air parcels which may slowlyascend into the stratosphere (Figure 7).These background issues were reviewedby T. Peter in the session overview.

The TTL session was kicked off by P. Wennberg, by asking whether deepconvection could transport short-livedhalogen species into the TTL. He pro-vided lines of evidence suggesting thatWMO estimates for stratosphericbromine could be low by 25%, and thatcalculated ozone trends are highly sensi-tive to assumptions about the existence

of short-lived brominecompounds. I. Folkinsgeneralized this aspect bypointing to the long con-vective replacementtimes making the TTLsuited for chemical pro-cessing of air with signifi-cant probability ofundergoing Troposphere-to-Stratosphere Transport(TST). The efficiency ofthese processes is deter-mined by the averageconvective detrainmentprofile, which is not wellknown. Predictions ofhow the detrainment pro-file will respond tochanges in sea surfacetemperature or in theBrewer Dobson circula-tion are presently uncer-tain. Most pronouncedmight be the effects of

such changes on H2O through implica-tions for cold point temperatures.

A. Gettelman summarized the presentparadigms of how air enters the strato-sphere, and how this specifically differsfrom water entering the stratosphere:convection up to the cold pointtropopause vs. slow radiative lifting, andmoistening/dehydration mainly as con-vective phenomenon vs. the formation ofcirrus, respectively. With particularview on the large scale, A. O’Neill high-lighted various dehydration scenarios:does the tape-recorder signal originatefrom freeze-drying in the western Pacific("Fountain" Hypothesis) associated withstrong localized convection, or fromslow, widespread up-glide associatedwith diabatic heating at the tropopause?Both speakers emphasised the impor-tance of the southeast Asian monsoon,which according to model studies con-tributes at least 25 % of the moist signalin the tape recorder.

A. Dessler presented the first satellite-borne aerosol lidar data from IceSAT/GLAS, revealing extremely high TTLclouds. Climatologies from space-bornelidars will in future become very usefulto constrain the dehydration problem.Another important aspect of the tropicalwater budget is high H2O supersatura-tion with respect to ice outside andinside cirrus clouds. This issue was pre-sented by J. Smith, showing frequentobservations of clear air supersatura-tions, evidence for very high ice nucle-ation threshold (< 200 K) and forpersistent in-cloud supersaturations ashigh as 20-30%. The in-cloud supersatu-rations remain a fully unexpected andnot understood phenomenon: they chal-lenge the conventional belief that anywater vapour in excess of ice saturationshould be depleted by crystal growthgiven sufficient time. E. Jensen present-ed detailed simulations of supersatura-tions in thin cirrus near the tropopause.Consequences are enhanced ice numberdensities, decreased crystal sizes,extended cloud lifetimes, increased ae-rial coverage of thin cirrus in the tropics,and most significantly an increase by0.5-1 ppmv in H2O entering the strato-sphere across the tropopause cold trap.This would imply that lower tropopausetemperatures are required to explain theobserved stratospheric water vapourmixing ratios than previously assumed.

Global models and detailed cloud models,such as those presented by A. O’Neilland E. Jensen, leave a gap in thedescription of mesoscale processes.

Figure 7. Schematic figure of the Tropical Tropopause Layer(TTL). The altitude of the Cold Point Tropopause (upper blackline), Minimum Lapse Rate (lower black line), and QClear=0(blue line) are shown. The horizontal motion is indicated as vec-tors in and out of the page (it also occurs along the zonal dimen-sion). Thin black arrows represent radiative heating, large blackarrows are the stratospheric (Brewer-Dobson) circulation, andblue horizontal arrows are the detrainment from convection.[Gettelman and Forster, J. Met. Soc. Japan, 80 (48), 911-924,2002].

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T. Birner presented a 100km x 100kmcloud-resolving model which allows thisgap to be bridged. The model suggeststhat the final stage of dehydration isachieved by convectively generatedbuoyancy waves.

Isotopic composition measurements ofwater can help to identify dehydrationprocesses leading to fractionation.Similarly, other compounds revealingstrong enrichments of the heavy iso-topes during photolysis or reaction withO(1D) could help to constrain the resi-dence time of air in the TTL. For the freestratosphere such techniques were illus-trated by J. Kaiser for the case of N2O.

D. Hartmann’s SPARC Lecture gave anopportunity for synopsis of fundamentalaspects governing the TTL on all spatialscales, and with particular emphasis onchanges of the TTL in a future, warmedworld. The lecture provided argumentsin support of an accelerated Brewer-Dobson circulation in a warmer world.But will this cool the tropopause? Andhow will convective overshoot change?While substantial progress has beenmade toward a quantitative understand-ing, many questions concerning thefuture TTL remain open.

In total there were 75 posters in the TTLsession. These posters offered a verybroad spectrum of TTL-related issues,from cubic ice in the laboratory, via ver-tical wind measurements in the TTL, tothe response of global climate to ElNiño.

Detection, Attribution,and Prediction

The Detection, Attribution andPrediction theme of SPARC encompass-es the overall understanding of past andfuture stratospheric changes, and acts asan integrator of the process-orientedactivities of SPARC. Accordingly, thistheme occupied the last day of theGeneral Assembly, and provided a sum-mary for the week’s activities. Themesdiscussed included updated observa-tions and interpretations of past strato-spheric changes, interactions with thetroposphere, and predictions of futurestratospheric evolution. These issueswere introduced in the session overviewby W. Randel.

There is substantial current interest inunderstanding changes in stratosphericwater vapour, and its coupling to tropi-cal tropopause temperature changes.

K. Rosenlof gave an overview of obser-vational results from different data sets,and highlighted measurement uncer-tainties in the LS that influence estimatesof long-term changes. L. Thomason dis-cussed long-term variations in strato-spheric aerosols as measured by SAGEsatellite observations. Current aerosollevels are at historic low values, allow-ing for observations of seasonal circula-tion effects on aerosols. The SAGE datado not show evidence for long-termtrends in background aerosol amounts.

Understanding the influence of naturaland forced changes on the stratosphericcirculation is a key to attribution studies.U. Langematz presented an overview ofdynamical influences on past strato-spheric changes, comparing observationsand simulations from several chemistry-climate models. A key result is thatderived dynamical responses toimposed ozone or greenhouse gaschanges vary considerably betweenmodels. M.-L. Chanin gave an updatedview of solar cycle variability (fromobservations and models), and showedsignificant spatial structure during win-ter, pointing to the importance of plane-tary waves in the solar response.Dynamical changes in stratosphericozone and temperatures were discussedin a number of presentations. New sta-tistical analyses by L. Hood quantifieddynamical influences on midlatitudeozone variability and change: the effectsof planetary wave forcing of the strato-sphere, plus synoptic-scale potentialvorticity variations in the UT, accountfor over 50% of the interannual variancein NH midlatitude ozone during 1979-2002.

Direct coupling of stratospheric changeswith tropospheric climate is an excitingactivity within several SPARC themes,and current work aims to demonstrateand quantify these effects. B. Santer dis-cussed using changes in the globaltropopause as an indicator of climatevariability and change, showing consis-tent results (increased tropopause alti-tude) from analyses of the ERA40 dataset and climate model simulations(Figure 8 p. III). N. Gillett demonstrat-ed the influence of Antarctic ozonedepletion on tropospheric and surfaceclimate using CGM simulations; themodel results furthermore show thattropospheric eddy dynamical feedbacksare a key factor for this coupling.

Studies of model-predicted futurestratospheric change were presented byseveral groups, based on chemistry-cli-

mate models. A key uncertainty in suchmodels regards changes in troposphericplanetary wave forcing of the strato-sphere under changing climate condi-tions. While past model results haveshown conflicting results, a new inter-comparison of model results by N. Butchart shows that most currentmodels predict future increase in plane-tary waves, and corresponding increasesin the stratospheric Brewer-Dobson cir-culation. This is an important result thatmust be considered in understandingstratosphere-troposphere coupling infuture climates.

There were a total of 84 posters in thefinal session, which provided moredetails on these issues.

Overall, the body of work presented atSPARC 2004 highlights the significantstrides taken by the community as awhole for understanding and quantify-ing the effects of stratospheric changes.These strides have been fueled by thedetailed understanding of stratosphericprocesses, and in integrating that under-standing for interpreting past and pre-dicting future changes.

Acknowledgements

The scientific organizing committee wasgreatly assisted in the execution of theseideas by the Local OrganizingCommittee. The success of any scientificmeeting depends on the local arrange-ments, and this assembly was no excep-tion. The arrangements workedseamlessly and facilitated excellent scien-tific interaction. The travel support andthe support of the meeting by variousorganizations is gratefully acknow-ledged.

Local Organizing Committee:N. McFarlane (Chair); M. Berkley; J. Fyfe ; J. Scinocca; D. Tubman; K. von Salzen; V. Arora (webmaster).

In addition, the efforts of the followingpeople were instrumental to the smoothrunning of the General Assembly:A. Chautard (WCRP), V. De Luca(SPARC IPO), L. Droppleman (NOAA),C. Michaut (SPARC/CNRS).

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•

Report on the 12th Session of the SPARC Scientific Steering Group

VViiccttoorriiaa ((BBCC)),, CCaannaaddaa 99--1122 AAuugguusstt 22000044

NNoorrmmaann MMccFFaarrllaannee, SPARC IPO, Toronto, Canada (Norm.McFarlane@ec.gc.ca)

DDiiaannee PPeennddlleebbuurryy, SPARC IPO, Toronto, Canada (diane@atmosp.physics.utoronto.ca)

VVllaaddiimmiirr RRyyaabbiinniinn, JSP/WCRP, Geneva, Switzerland (VRyabinin@wmo.int)

Participants of the SSG Meeting inVictoria. From left to right1st row: V. De Luca, S. Doherty, D.Conway, K. Carslaw, T. Peter, U. Schmidt,A. R. Ravishankara, C. Granier, J. Kerr, T. Shepherd, T. McElroy, N. McFarlane, R. Michaud, J.R. Drummond2ndrow: R. Menard, M. Baldwin, D. Pendlebury, K. Kodera, D. Hartmann3rd row: M.A. Geller, S. Polavarapu, S. Pawson, T. Wehr, V. Ryabinin, S. Yoden,W. Randel, V. Ramaswamy, V. Eyring, M. Kurylo, P. Canziani, L. Thomason, D. Carson, C. Michaut, A. O'Neill, K. Hamilton, J. Burrows, M.-L. Chanin, V. Yushkov

Introduction

The 12th session of the SPARC ScientificSteering Group (SSG) was held atDunsmuir Lodge near Victoria (BC),Canada, at the invitation of N. McFarlane, the Director of the SPARCInternational Project Office (IPO).

Opening the meeting, A. Ravishankara,co-chair of the SPARC SSG, emphasizedthat one of the most important tasks forSPARC and the SSG session was to fleshout the scientific content of the threemajor project themes and define waysfor their implementation. Examples ofissues of high importance for SPARC aremicrophysics modelling, TropicalTropopause Layer (TTL) chemistry,upper troposphere/lower stratosphere(UT/LS) interaction, the generation ofstratospheric indicators of climatechange, solar activity, and, increasingly,laboratory experiments. GRIPS is draw-ing to a close as a key successful SPARCactivity, and optimal organization offuture intercomparison of models is atopic of high value. In addition to fun-damental research, SPARC will continueits practice of conducting focused assess-ments, and specialists will actively con-tribute to the ongoing work of the IPCCFourth Assessment Report. SPARCmust be prepared for the new WMO

lenges facing the WCRP: -- The problem of seamless predictionover time periods ranging from weeks todecades and longer, -- Prediction of the broader climate/Earth system,-- Demonstrating the use to society ofWCRP-enabled science and predictions,-- Efficient use of new opportunitiessuch as new and increasing datastreams, growth of computer capacities,and complexity and breadth of modelsand data assimilation schemes,-- Interaction with other Earth SystemScience Partnership (ESSP) programmes(DIVERSITAS, IGBP, and IHDP apartfrom WCRP).

The main goal of COPES is to facilitateprediction of Earth system variabilityand change for use in an increasingrange of practical applications of directrelevance, benefit and value to society,and to predict the entire climate system.

Initial suggestions for COPES activitiesinclude determining the predictabilitypotential of current systems, with focuson seasonal time scales, further develop-ing and testing ensemble forecastingmethods, determining the scientific basisfor, best approaches to and current skillof projections of regional climatechange, developing well-tested chem-

ozone assessment that will start soon,and must start collecting ideas for futureIPCC assessments. SPARC must alsodecide how to maintain and foster closerconnections with projects within andoutside WCRP, such as CLIVAR andGEWEX, IGAC (IGBP), and groups likeWGNE, and how to effectively con-tribute to new WCRP initiatives such asCOPES.

WCRP Comments

D. Carson presented the new overarch-ing framework for the World ClimateResearch Programme (WCRP), entitled"Coordinated Observation and Predic-tion of the Earth System" (COPES). Hereviewed the development of the WCRPsince its formation in 1980 under thesponsorship of the World Meteorolo-gical Organization (WMO) and theInternational Council for Science (ICSU)with additional support from theIntergovernmental OceanographicCommission (IOC) of UNESCO startingfrom 1993. In the nearly 25 years of itsexistence, the main goals of WCRP havebeen to determine the predictability ofclimate and the effects of human activi-ties on climate.

There are now a number of new chal-

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istry-climate models (CCMs), andaddressing projections at the decadaltime scale. Formulation of specific tasksshould be made in close consultationwith the wider WCRP community.

The Joint Scientific Committee (JSC) ofWCRP will oversee COPES. The WCRPModelling Panel will coordinate model-ling initiatives across WCRP, focus onclimate system prediction, and overseedata management in modelling activi-ties. The Working Group on Obser-vations and Assimilation (WGOA) willcoordinate synthesis of global observa-tions, information and data managementacross WCRP and facilitate interactionswith other agencies, and observing sys-tems.

New challenges for the ESSP includedeveloping operational tools capable ofmonitoring and simulating the EarthSystem including the atmosphere, ocean,land, and cryosphere with physical,chemical and biological processes, andintroducing the human dimension. Thiswill require collaboration of the ESSPpartners and the establishment of aframework for the integration, intowhich existing and planned research cancontribute. This process should be driv-en by the science of global change.

The SSG exchanged views on howSPARC could contribute to COPES. Theobvious roles are providing guidance onhow to prescribe atmospheric composi-tion and to initialize the stratosphere ina range of applications, and propos-ing/implementing diagnostic studiesand numerical experiments. Concernson limited WCRP resources were raisedand a need for close coordinationbetween WCRP COPES and IGBP GAIMwere expressed. It was also noted thatthe future activities would stronglydepend on developments within theWMO and the Global Earth ObservationSystem of Systems (GEOSS).

Review of the main Eventssince the last SSG

The 3rd SPARC General Assembly(SPARC GA) was held in Victoria on 1-6August 2004, in the week prior to theSSG meeting. The main theme of theSPARC GA was chemistry and climate.A discussion on the lessons learned andconsequences for SPARC was led jointlyby T. Shepherd and A. Ravishankara,co-chairs of the Scientific Committee forthe SPARC GA, and N. McFarlane, chairof the Local Organizing Committee. The

la Recherche Scientifique (CNRS), theCentre National d’Etudes Spatiales(CNES) and Meteo France, for the longsupport given to the project while theoffice was located in France.

Presentations from the Canadian ClimateResearch Community

A half-day of the session was devoted topresentations on Canadian stratosphericresearch.

J. Fyfe, on behalf of D. Whelpdale andthe MSC, welcomed SPARC to Canadaand expressed their pleasure at beingable to support SPARC through theestablishment of the SPARC IPO at theUniversity of Toronto. The efforts of N. McFarlane and T. Shepherd ensur-ing that this opportunity became a reali-ty were recognized.

D. Conway , Executive Director ofCFCAS, reported on the role of CFCASin funding Canadian research in climatescience. The vision of CFCAS is to"enhance Canada’s scientific capacity byfunding the generation and dissemina-tion of knowledge in areas of nationalimportance and policy relevance,through focused support for excellentuniversity-based research in climate andatmospheric sciences".

Funding priorities for the 2004-2005period will be high latitude research intothe Arctic and cryosphere, extremeweather including drought, marine cli-mate and the use of technologies inresearch (remote sensing and satellites).Examples of funded projects related toSPARC are: (a) Measuring the OzoneColumn from Astronomical Archives,(b) Stratospheric Indicators of ClimateChange, and (c) Modelling of GlobalChemistry for Climate. CFCAS is also ajoint partner in funding the SPARC IPOin Canada.

R. Michaud reported on key activities ofthe CSA. The CSA was established in1989 with the goal of integratingCanadian space activities such asCanada’s contribution to theInternational Space Station, theRADARSAT and the Space ScienceProgrammes.

There are three themes in the EarthObservations branch of CSA: the envi-ronment, resource and land-use man-agement, and security and foreignpolicy. The priorities in the environ-

general agreement was that the SPARCGA was very successful. The SPARC GAweb site would remain online until latein 2004 to allow access to the GA presen-tations.

Some key developments seen in theSPARC GA are: -- CCMs have reached a high level ofmaturity, -- Modern process studies of UT/LS andTTL are of interdisciplinary characterand involve a combination of modelsand measurements, -- Detailed (e.g. cloud-resolving) model-ling is coming into the fore, -- Connections are strengtheningbetween studies of different time scales,from seasonal to climate, -- A view of coupled long-term changes,i.e. beyond trends, is emerging for temper-ature, water vapour, ozone, methane, etc.

The discussion suggested a number ofpossible future SPARC actions and ini-tiatives motivated by these develop-ments such as coupling of microphysicsand gravity waves in models, potentiallyin contact with the GEWEX CloudSystems Study; use of very high resolu-tion models for designing observing sys-tems; a need to validate numericalweather predictions in the TTL regionincluding data obtained by airplanecampaigns; inclusion of chemistry andhigher stratospheric levels in newreanalyses, etc.

The new SPARCInternational ProjectOffice (SPARC IPO)

N. McFarlane, the new Director of theSPARC IPO, reported on the relocationof the office to the Dept. of Physics at theUniversity of Toronto (Canada).Sponsorship and funding for the newIPO comes from the MeteorologicalService of Canada (MSC), the CanadianFoundation for Climate and Atmo-spheric Science (CFCAS), the CanadianSpace Agency (CSA), the ClimateChange Action Fund (CCAF), and theUniversity of Toronto (in kind). In addi-tion, the transition between the twooffices has been greatly facilitated byextended visits of C. Michaut, managerof the SPARC Office in Paris.Arrangements for the transition havegone well. V. De Luca, the new officemanager, and D. Pendlebury, the newproject scientist, were present at the SSGmeeting. Deep gratitude was expressedby the SSG to the new sponsors of theIPO and also to the Centre National de

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ment, remote sensing are: (a) betterunderstanding of the key parametersand processes of the earth-atmosphere-ocean-cryosphere and biosphere systemsand their inter-relationship; (b) impactof climate change on land, marine andatmospheric environments and the vari-ations in key factors influencing the cli-mate; (c) support to environmentalpolicy and decision-making at all levels.

The CSA has focused its efforts on smallpayloads such as the Middle Atmo-sphere Nitrogen Trend Assessment(MANTRA) high-altitude balloon, whichmeasures stratospheric composition andozone chemistry. The 3rd field campaignoccured in August 2004. Other smallpayloads include the Gravity WaveImaging and Mapping (GWIM), whichmeasures gravity wave (GW) activity inthe upper mesosphere and lower ther-mosphere with a potential flightonboard Brazil’s EQUARS scientificsatellite in 2007.

J. Scinocca reported on research activi-ties of the Canadian Centre for ClimateModelling and Analysis (CCCma). Theprimary activity is the ongoing develop-ment and application of global coupledclimate models aimed at understandingpast climate change and variability, andprojecting future climate change undervarious GHG emission scenarios.CCCma is involved in a variety of col-laborative projects with universities,most of them supported (often in part-nership) by a combination of agenciesincluding MSC, CCAF, CFCAS, and theNational Science and EngineeringResearch Council (NSERC). Theseinclude projects in Regional ClimateModelling (RCM/URANOS), MiddleAtmosphere Dynamics and ChemicalProcesses (CMAM/GCC), ClimateVariability and Prediction (CLIVAR),Clouds and Chemistry (MOC2), Car-bon Cycle (GC3M), Air-Sea Inter-action/Coupling (SOLAS), and AerosolsProcesses (CCAF project/CAFC).

The Modelling of Global Chemistry forClimate Project (GCC) is a focus for amajor part of Canadian SPARC relatedresearch activities. The two centralactivities of GCC, done in cooperationwith MSC and CSA, are the develop-ment and use of a CCM and a chemicalclimate data assimilation system. Insummarizing its activities, T. Shepherdnoted that it has several unique features.Among these is a strong team ofresearch associates, responsible to theGCC project as a whole. Another fea-ture is participation in numerous nation-

al and international collaborative activi-ties. These include the WMO UNEP 2002Ozone Assessment, SPARC/SCOSTEPMesospheric Temperature TrendsAssessment, Arctic Climate ImpactAssessment (ACIA), GRIPS (radiation,GW drag, circulation response to dou-bled CO2, and the representation ofequatorial waves), SPARC StratosphericData Assimilation Initiative, and SPARCCCM Process-Oriented ValidationInitiative.

S. Polavarapu reported on the CanadianMiddle Atmosphere Model (CMAM)data assimilation activities and the newCMAM-FDAM (Facility for DataAssimilation and Modelling). The goalof the CMAM Data Assimilation System(CMAM-DAS) is to improve the under-standing of middle atmosphere dynam-ics by confronting a climate model withobservations. A direct, rather than sta-tistical, comparison of a climate modelwith measurements creates a more solidplatform for the assimilation and helpsto optimize design parameters for mid-dle atmosphere observations and, aswell, to produce assimilated data sets forclimate studies. Comparisons of assimi-lated tropospheric and lower strato-spheric dynamical variables withradiosondes and ECMWF analyses haveproduced encouraging results(Polavarapu et al., 2004).

J. Drummond reported on the CanadianNetwork for the Detection ofAtmospheric Change (CANDAC), aninformal organization combining techni-cal facilities and highly skilledresearchers from university and govern-ment organizations. Three great chal-lenges that CANDAC will address areair quality, climate change and ozonedepletion. A primary initial focus ofCANDAC is the revitalization of meas-urements at the Eureka Arctic Strato-spheric Ozone (ASTRO) observatory.CANDAC has held three workshopsincluding one concept workshop fundedby CFCAS in support of atmosphericnetworks. It has received CFI funds forthe installation of observing equipmentat the PEARL station.

R. Menard reported on the chemicalweather prediction and assimilationcapability being developed at the MSC.This integrated system will perform realtime analysis and prediction and willfacilitate analysis for longer-term appli-cations. It couples the ADOM tropo-spheric chemistry module and theroutine weather prediction GlobalEnvironmental Model (GEM). Work in

progress includes implementation of theCMAM stratospheric chemistry packageand development of the adjoint chem-istry for 4D variational assimilation.

J.B. Kerr and T. McElroy discussed MSCUV measurement and modelling stud-ies. Despite significant advances in thepast 30 years, there are still gaps inknowledge of key processes such asnon-homogeneous scattering andabsorption by clouds and aerosols. Forinstance, satellites estimate up to 40%more surface UV than is measured byground-based instruments.

The SPARC Themes

Detection, Attribution, Prediction

W. Randel’s overview of this themeincluded discussions of: -- Key points from the Angell Workshopon Temperature Trends in the Strato-sphere (Silver Springs, November 2003,co-sponsored by SPARC and reported inNewsletter No. 22); -- Using models for detection, attribu-tion, and prediction; -- Issues regarding stratospheric temper-ature and water vapour trends; -- Needs for upcoming IPCC and WMOassessments.

The Angell Workshop reviewed updat-ed observations, model simulations ofstratospheric temperature changes andtheir interpretation, and the effects ofchanges in stratospheric variability andcirculation. Several of the issues arisingfrom this workshop were addressed inpresentations at the SPARC GA.

The observational base includes opera-tional, climatological, process study-related and experimental data sets. Keyissues for operational data are the avail-ability of long-term high quality temper-ature records in the stratosphere andmesosphere, identification of problemsand quantification of uncertainties incurrent satellite data and reanalyses,efforts to bridge data sets across theTOVS-ATOVS satellite boundary and infuture satellite datasets, inclusion ofSPARC input into future reanalyses and"climate network" designs. Key pointsfor process and experimental data setsare the inclusion of specific UT/LSmeasurements, multiple sources of data,and ensuring the quality of radiativeforcing data sets including ozone, watervapour and aerosols.

Success of modelling requires consisten-

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cy of simulations and processes, andprogress in parameterization. Consis-tency of simulations requires intercom-parison of radiation codes andintercomparison of model responses tospecified forcings. Key issues forprocess studies and parameterizationare evaluating the role of interactivechemistry in model variability, improv-ing quantification of GW parameteriza-tion effects, identifying sensitivities anduncertainties, gaining better understand-ing of dynamical coupling of the tropo-sphere and stratosphere (especiallyEliassen-Palm flux coupling and annularmodes), evaluation of model uncertain-ties in the face of interannual variability(particularly in winter polar regions),improving UT/LS physics (especiallyaerosol and cloud microphysics), andidentifying robust indicators for modelsensitivity studies. SPARC shouldactively cooperate with AMIP andCMIP, GCOS and GEOSS. The use ofPCMDI facilities for SPARC intercom-parisons, and making best practicesknown via the project website would bedesirable.

It follows from both the workshop andthe GA that the most important issuesfor the Detection, Attribution andPrediction Theme include:-- Estimating signal versus noise usingensemble runs and long control simula-tions, emphasizing the use of a proba-bilistic approach for attribution andprediction; -- Understanding sensitivity of past andfuture predictions to uncertainties inforcings; -- Testing consistency across differentindicators (e.g. temperature and radia-tive gases);-- Developing and using fingerprinttechniques based on space-time patternsof signal responses and noise; -- Understanding the differencesbetween equilibrium runs and transientresponse experiments; -- Quantifying the role of troposphericforcing of the stratosphere including theimpact of using observed versus climato-logical and observed versus simulatedSSTs; - - Developing improved diagnostics todistinguish radiative and dynamicalresponses.

Available data for middle and upperstratospheric temperature fields includeoperational satellite data (SSU/MSU/AMSU), meteorological analyses andreanalyses, lidars (several locations) andresearch satellites, i.e. HALOE. Issuesrelated to stratospheric temperature

changes are: (a) taking into accountdetails of updated SSU data; (b) compar-isons with other data (e.g. lidar;HALOE); (c) problems with reanalysesin the stratosphere; and (d) interpretingthe observed record.

Given uncertainties in quantifying andinterpreting the past record, and impor-tance for the SPARC themes and thefuture WMO Ozone Assessment, it wasproposed that a small working groupand a workshop on updating the strato-spheric temperature record be organ-ized. The workshop will be held in early2005.

Needs for upcoming IPCC andWMO assessments

T. Shepherd discussed the use of mod-els for detection/attribution/predictionof climate change. A key is the ratio ofsignal to noise. In this connection thereare several challenges. The noise is notwell characterized statistically and hastime scales overlapping with those of theforcing. Coupling between the signaland the noise is not negligible. Theremay be a need to attribute some aspectsof the noise. Models likely underesti-mate the noise and have their ownsources of errors in variability.

A number of recently published studiesaddresses these challenges, e.g., a 1000-year model run under different topo-graphic forcings shows that PDFs ofmonthly mean temperature near thepole are not Gaussian (Yoden et al.,2002). In Fioletov and Shepherd (2003),it is shown that springtime trends(1979–2001) explain the trends in othermonths of the year. This relationshipholds even better for the extratropics inboth hemispheres. Attribution needs tobe made on a case-by-case basis, forexample, for Antarctic versus Arctic tem-perature - ozone relationships (Randeland Wu, 1999).

GCM studies with imposed ozonechanges cannot account for the observedtrends in the Arctic and NorthernHemisphere (NH) midlatitudes over thepast 20 years (Shine et al., 2003). Butgiven the magnitude of the variability, itcan be argued that there is no discrepan-cy "within the error bars" (i.e. the noise),indicating that the signal is perhapsmainly natural variability. That variabil-ity may be crucial in understandingother changes, e.g. H2O or O3. CCMs arethe main tools for uncovering the coup-led chemical-dynamical variability. Thedynamical forcing is predominantly

wave drag. It is associated with (mainlyhorizontal) mixing. The planetarywave-drag (PWD) response to climatechange may be critically important, butmodel studies to date are inconclusiveon this point (Austin et al., 2003).

All CCMs show development of theAntarctic ozone hole in line with obser-vations. But the observations are nearthe lower edge of model simulations ofthe springtime minimum of total ozoneover the Arctic. Natural variability is amajor factor for the Arctic. A bettercharacterization of PWD variability andits chemical consequences is needed. Itmust distinguish between the purelyradiative response to the forcing and thePWD feedback. It should also include anunderstanding of tropospheric versusstratospheric effects on PWD.

The next round of assessments will needto build on, and improve on Austin et al.(2003). This will require improved diag-nostic characterization of the simula-tions. But before the runs begin, it isessential that they use the same forcingsand include all relevant chemicalprocesses. T. Shepherd proposed that asmall meeting of key players under theauspices of SPARC would be useful andoffered to host such a meeting inToronto in the near future.

The ensuing discussion raised a numberof questions for future consideration,including the carrying out of AMIP-likeCCM experiments under the auspices ofSPARC, and adequate use of SPARCexperience in the IPCC assessmentprocess.

C. Granier presented highlights of theQuadrennial Ozone Symposium held inKos (Greece), in June 2004, with 450 par-ticipants and 690 presentations. One ofthe key questions is whether ozonerecovery is under way. Several talksaddressed the leveling off of the chlorinecontent in the stratosphere. Is the down-ward trend in ozone slowing down in astatistically significant way? Naturalvariability and interference by other fac-tors (e.g. QBO and solar cycle effects)have to be evaluated and removed fromthe ozone record. New analyses ofozone variations based on long recordsof high quality ground based measure-ments (e.g., by Fioletov) reveal long-termchanges in variability. Trends in surfaceozone are upward in several locations,but not in all. Results from analyses ofdata from new satellite instrumentswere presented in several papers.

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Several papers on CCMs addressed thecoupling between climate and ozonechanges. Among these are climatechange impacts on stratosphere-tropo-sphere exchange. Simulations showenhancements of both the Brewer-Dobson and Hadley circulations withincreasing GHG loading.

The SSG noted that several new mem-bers have been elected to theInternational Ozone Commission (IOC).Various options for joint SPARC, IGACand IOC meetings were suggested.

V. Ramaswamy summarized the CCSP(U.S. Climate Change Science Program)Synthesis Assessment Report on temper-ature trends in the lower atmosphere.The CCSP website (http://www.climate-science.gov/Library/sap/sap-summary.htm)contains a prospectus for the report. Itsgoals are to: (a) identify cases whereuncertainties can be clarified/reduced,(b) consider context with subsequent USand international assessment reports, (c) identify aspects of uncertainty requir-ing more thorough review and assess-ment, and (d) identify strategies toreduce uncertainties.

The target date for release of the reportis in September 2005.

V. Ramaswamy reported on timelinesand the structure of the IPCC AR4 (2007)report and noted some key points fromthe IPCC Climate Sensitivity Workshopheld in July 2004 (report available at theIPCC web site: http://www.ipcc.ch). Theworkshop included reports on advance-ments in radiation codes since the lastintercomparison (presentations by Fuand Ramaswamy) and IPCC GCMradiative forcing intercomparisons (pre-sentations by Collins and Ramaswamy).The first Lead Authors meeting has beenheld in Trieste in September 2004. Allmaterial referenced in the AR4 shouldbe available by May 2005. The suggest-ed timescale for WCRP projects todirectly contribute is by the end of 2004.Some chapters may be of direct rele-vance to SPARC.

V. Ramaswamy then summarized someaspects of the radiative forcing intercom-parison. The radiative transfer calcula-tions used standard clear skymidlatitude profiles. Computations ofabsolute SW and LW fluxes and forcingsfrom line-by-line (benchmark) and GCMradiation codes were compared for spec-ified concentrations of well-mixedGHGs (present-day minus pre-industrial2xCO2 minus 1xCO2), and a case when

carbon dioxide and water vapour arechanged simultaneously). One impor-tant result is that absorption of solarradiation by CH4 bands (not usuallyincluded in GCMs) is comparable to thatof CO2.

Stratospheric Chemistryand Climate

A. Ravishankara gave an overview ofoutstanding issues, which include polarstratospheric cloud (PSC) climatology, areview of chemistry in the TTL, andmicrophysics modelling for the TTL.Cloud resolving models may be produc-tive for exploring a number of TTLissues. It was noted that Chemistry andClimate is a cross-cutting theme withinthe WCRP. The SSG agreed that over-lapping interests with the GEWEXGlobal Cloud Systems Study (GCSS)concerning microphysical processesshould be explored.

SPARC Polar Stratospheric CloudAssessment (SPA)

K. Carslaw presented a summary ofprogress in preparing for the SPA, not-ing first that the motivation for carryingout the assessment is the existence ofsignificant gaps in our understandingthat are relevant to stratospheric chem-istry, the lack of consensus on how todescribe PSCs and denitrification inglobal models, the limited and selectiveuse of PSC observations, and the risk ofinstrument-dependent climatologiessince intercomparisons are rare, as wellas the lack of a large-scale consistent andevaluated data set for model testing.

Both Arctic and Antarctic PSCs will beincluded in the assessment and informa-tion will contain their occurrence (sea-sonal, spatial, interannual and long termvariability and trends), assessment anddevelopment of understanding (modeland theory testing and consistency withlab experiments), instrument intercom-parison of primary and consistent se-condary quantities (lidar, satellite and insitu measurements), and consistencywith denitrification and dehydrationmechanisms. Excluded from the assess-ment will be heterogeneous reactionrates and PSC effect on stratosphericchemistry. The aims of the assessmentare to gather a consistent microphysicalinterpretation of all measurements andto generate a particle climatology andevaluate statistical occurence of PSCs.Understanding of the microphysicalprocesses will be examined to test

hypotheses and models, and to make re-commendations to modellers regardingpast and future changes in PSCs.

The chapter titles have been defined andthe lead authors have been chosen andaccepted. The lead authors have pre-pared chapter outlines. Co-authors haveyet to be contacted. A kick-off meetingis being arranged for early 2005, and thefirst science meeting will be held inSummer 2005. The chapters are laid outin the following way: Chapter 1 - PSCProcesses (N. Larsen); Chapter 2 -Detection and discrimination (B. Luo ,M. Fromm); Chapter 3 - Observationsand their intercomparison (T. Deshlerand L. R. Poole); Chapter 4 - Assessmentof understanding (K. Drdla, K. Carslaw);Chapter 5 - Denitrification and dehydra-tion (M. L. Santee and G. E. Nedoluha);Chapter 6 - PSCs in a changing strato-sphere (M. Rex and R. Bevilacqua).

Process Based Comparison of CoupledChemistry-Climate Models

V. Eyring discussed progress onprocess-oriented validation of coupledCCMs. GRIPS has examined thedynamical/radiative state of strato-spheric GCMs. Now that CCMs aremature enough, it seems appropriate toevaluate the chemistry and transport inthese models to the same extent, using aprocess-oriented validation approachsimilar to that used for GRIPS.Measurement and process-studies com-munities, for example trajectory model-ling, need to be involved.

A detailed summary of the CCMValidation Project appeared in SPARCNewsletter No. 23 (V. Eyring et al., 2004)and a BAMS paper has been submitted.In addition, the coordinators are com-mitted to having a project publicationbefore the next WMO-UNEP assess-ment.

Individual assessments of differentprocesses are already under way; forexample a comparison of radiationschemes used in climate models, micro-physical model calculations for theSPARC Assessment of StratosphericAerosol Properties (ASAP), and the eval-uation of GW drag schemes.

Progress is being made on developmentof software packages for complex diag-nostics and further development of atable of core processes. The next CCMvalidation workshop will be held inOctober 2005.

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As the CCM Validation Project has beenbased on the experience gained in theGRIPS project and is a natural extensionof it, amalgamation and renaming of thetwo projects were proposed andapproved by the SPARC SSG. This willtake place following the final GRIPSworkshop, which will be held in Hawaiiin March 2005.

SPARC/IGAC Collaboration

A. Ravishankara introduced the topic,noting that this joint venture betweennatural partners started under the previ-ous co-chairs of SPARC. He drew atten-tion to the report from the JointSPARC-IGAC Workshop on Climate-Chemistry Interactions held in Giens(France) in 2003. It can be down-loaded from the SPARC web site:(http://www.atmosp.physics.utoronto.ca/SPARC).

S. Doherty continued the discussion.The traditional view of IGAC has beenthat SPARC represents research inatmospheric properties and processesfor the tropopause and higher, IGAC forthe free troposphere, and iLEAPS for theatmospheric boundary layer the surface.The overlap in research interestsbetween SPARC and IGAC, thetropopause layer and UT/LS region,was explored in Giens. Topics includedstratosphere-troposphere coupling, LSozone and its changes, troposphericozone and other chemically activeGHGs, aerosols and their role in climate,and water vapour and clouds. Over-arching issues for the workshop weretemporal and spatial scale mismatch (insitu vs. model vs. satellite data), andchemical kinetics and laboratory studies.

In the UT/LS region, two projects areunderway. An NCAR initiative led byL. Pan studies the coupling of large andsmall scales. It started as an internal ini-tiative inspired by NCAR HAIPER andAURA. The second is the EU ProjectSCOUT headed by J. Pyle. It has a sig-nificant component of chemical-climatemodelling with a focus on the tropics.

Stratosphere/TroposphereDynamical Coupling

M. Baldwin gave an overview of scien-tific issues in this theme. He startedwith the results of the Workshop onStratosphere-Troposphere DynamicalCoupling held in Whistler (BC), Canada,in April 2003 (see report in the SPARCNewsletter No. 22). A second workshopon stratosphere-troposphere coupling in

2006 will focus on understandingdynamics, coupling on longer (10-100years) time scales and chemical/dynam-ical coupling.

Recent work on predictability anddownward propagation of the NorthernAnnular Mode is indicative of the poten-tial importance of stratosphere-tropo-sphere dynamical coupling forlong-term prediction. M. Baldwinreported on the WCRP COPES TaskForce on Seasonal Prediction (TFSP).The goal is to determine to what extentseasonal prediction is possible in allparts of the globe with currently avail-able models and data. The importanceof the stratosphere in seasonal predic-tion was unanimously recognized at theTFSP meeting held in Hawaii (USA) inNovember 2003. The TFSP defined "sea-sonal" to begin at 7-10 days in order tobe consistent with the COPES seamlessprediction strategy. SPARC actionscould include establishing partnershipswith other WCRP projects and workinggroups, and with operational forecastingcentres to promote and facilitate theinclusion of the stratosphere in the oper-ational analysis and prediction systems.

M. Baldwin also discussed the role of thestratosphere in climate change. Mostmodels predict a stronger Brewer-Dobson circulation in a warmer climatewith increased GHGs. Recent simula-tions (e.g. by J. Kettleborough), also sug-gest a weaker polar vortex consistentwith enhanced planetary wave driving.Future changes will depend on bothchemical and dynamical stratosphere-troposphere coupling.

The theme of the stratosphere-tropo-sphere dynamical coupling was contin-ued by S. Yoden. The familiar idea thatthe troposphere affects the stratospherethrough upward propagation of waves(large-scale Rossby and also gravitywaves) goes back to the simple theory ofCharney and Drazin. It is supported bynumerical experiments with so called"mechanistic" and troposphere-strato-sphere general circulation models(GCMs) and as well by observations ofsummer-winter and interhemisphericdifferences.

Sudden stratospheric warmings, a majorperturbation of wintertime stratosphericcirculation, were a research focus fordynamics in 1970s and 1980s.Occurrence of the SH warming and"vortex split" in September 2002 hasreinvigorated interest to this topic.Despite ongoing efforts, we still cannot

point to circulation anomalies in the tro-posphere and identify them as the"cause" of a dynamical perturbation inthe stratosphere. The one-way view oftroposphere affecting stratosphere nolonger makes sense. Extratropicaldynamics is non-local in both the hori-zontal and the vertical. Changes in theLS inevitably affect the UT and viceversa. There is evidence from numericalmodelling studies, e.g. Boville (1984),and Kodera et al. (1990), that changes inthe middle and upper stratosphere affectthe troposphere and that communicationis dynamical.

Stratosphere-troposphere dynamicalcoupling is primarily through the mech-anism of planetary wave drag (as notedin the presentation of T. Shepherd). It iscurrently a major research activity, aidedby a hierarchy of models. Attention wasdrawn to several of the presentations inthe SPARC GA that dealt with variousaspects of this topic (talks by P. Haynes,S. Yoden, M. Baldwin, B. Christiansen, T.Hirooka, W. Robinson, L. Polvani, K. Hamilton, J. Perlwitz, M. Geller, andG.L. Stenchikov). Three paradigms haveemerged, supported by results of obser-vational and modelling studies: (a) thetroposphere affects the stratosphere(seasonal cycle in stratospheric circula-tion, interhemispheric differences etc.);(b) the stratosphere affects the tropo-sphere (tropospheric signal of QBO,solar cycle, volcanic aerosol, dynamicalresponse to ozone depletion); and (c) there is two-way coupling (aspects oflow frequency variability in NH winter,SH spring, response to changes in long-lived GHGs).

D. Hartmann introduced the ENSO andstratosphere theme. Recent work indi-cates that warm ENSO events are associ-ated with a warm Arctic polarstratosphere and more stratosphericwarming events in winter, while colderENSO events are associated with a coldpolar stratosphere and an enhanced vor-tex. Earlier work has also shown a rela-tionship between stratosphericvariability and ENSO. Simulations withthe NCAR WACCM model supportobservations and show that warmingevents are significantly more likely dur-ing ENSO years (Taguchi andHartmann, 2004). When El Niño andwarming events occur together, theyproduce cumulative effects over NorthAmerica. In summary, evidence hasbeen accumulating to show that ENSOevents have a strong influence on theNH stratosphere.

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CCrroossss--CCuuttttiinngg aanndd SSuuppppoorrttiinngg PPrroojjeeccttss

Assessment of Stratospheric Aerosol Properties (ASAP)

L. Thomason reported that the finaltexts of the ASAP report chapters wereto be reviewed in September 2004.Technical editing had also beenarranged and it was expected that thereport would be ready for publicationby the end of 2004. The assessment willconsist of 6 chapters: Chapter 1 - Aerosolprocesses (an overview); Chapter 2 -Aerosol precursors; Chapter 3 -Instruments; Chapter 4 - Data assess-ment; Chapter 5 - Trends; Chapter 6 -Modelling.

The report will outline several key find-ings as follows: most observations donot comprise a complete measurementset. Some parameters are derived indi-rectly from the base measurement, andduring periods of very low aerosol load-ing significant differences exist betweendata sets for key parameters, e.g for sur-face area density and extinction. It isfound that only the period from 1999onwards can be confidently identified asfree of volcanic aerosols. There is also asignificant dearth of SO2 measurements.Sedimentation plays an important rolein the vertical redistribution of aerosolthroughout the stratosphere. Under-standing of aerosols in terms of cohe-rence of measurements and modelling inthe LS during periods of low loading ispoor, although there is reasonable agree-ment during post-volcanic periods.

Data Assimilation

S. Polavarapu discussed data assimila-tion of stratosphere and climate models,noting that it could provide many bene-fits to SPARC and WCRP. An immediateresult would be the inclusion of meso-spheric data in the SPARC Data Centre.There is a wealth of current mesosphericsatellite data available from SCIA-MACHY, TIMED, OSIRIS, GOMOS,MIPAS, SABRE, and SCISAT. A similarproposal has been made within theCAWSES programme of SCOSTEP.

Links to other WCRP activities can bemade through the WGOA within theCOPES framework. GEWEX has pro-posed a new climate system reanalysisincluding chemistry, which may benefitfrom data assimilation. The COST 723action group also includes a data assimi-lation task, and the WGNE is ideal as aliaison. Possible activities for data

assimilation within SPARC are processoriented validation, the use of analysesto assess gravity wave drag parame-trizations in GCMs and CCMS, andwater vapour analysis.

An annual workshop on data assimila-tion with the focus on the middle atmo-sphere and climate was proposed. Thisis desirable since other data assimilationworkshops usually focus predominantlyon operational forecasting issues, withthe stratosphere as a side topic. Theworkshop would also bring togethernon-data assimilation people from theSPARC community with complemen-tary expertise on dynamics, chemistry,and transport. It would be possible toassess our knowledge of stratosphericwinds and quality of their analyses, andfocus on both climatologies and windsfor process studies and transport calcu-lations.

The SPARC Gravity Wave Initiative

K. Hamilton reported on the SPARCEquatorial Circulation Experiment(ECE). This initiative was inspired bythe VORCORE experiment proposed byF. Vial at the 10th SPARC SSG meetingin Kyoto in 2002. The VORCOREinvolves launching an ensemble ofsuper-pressurized balloons (SPB) thatwould fly for several months at 50 hPato 70 hPa levels in the vicinity of theAntarctic polar vortex. It receivedstrong support from the SPARC SSGwith a suggestion that a similar cam-paign would be valuable in the tropics.The SPARC ECE will be a tropical cam-paign. A working group has beenformed, co-chaired by K. Hamilton andF. Vial. VORCORE will take place in2005 as planned. ECE is planned for2006 near Darwin, and a workshop maybe held at the end of the project.Continued SPARC interest is importantfor its success.

K. Hamilton also reviewed the GravityWave Initiative, which is nearing itscompletion. A radiosonde climatologypaper is in preparation. The DAWEXcampaign took place in late 2001, and aworkshop was held in Honolulu in 2002.It was reported in SPARC NewsletterNo. 20 and a series of papers are part ofa forthcoming JGR Special Issue.

SPARC was a cosponsor of theChapman Conference, held in Waikoloa,Hawaii, in January 2004. This was a verysuccessful conference with 64 partici-pants from 11 countries (see report inSPARC Newsletter No. 23).

K. Hamilton proposed an additional,smaller workshop on convectivelyforced gravity waves, to be held in 2006,which will focus on some key remainingtheoretical questions of relevance to GWparameterization, analysis of resultsfrom, or planning for the 2006 fieldexperiment.

In discussion of the Gravity WaveInitiative, M. Geller suggested that thehigh-resolution radiosonde data usedfor the climatology could be made avail-able for general use through the SPARCData Centre.

LAUTLOS Field Campaign for Hygrosonde Comparisons

V. Yushkov presented some resultsfrom the measurement campaign of theUT/LS Water Vapour Validation Project(LAUTLOS-WAVVAP). This project isaimed at improving the knowledge ofthe role of water vapour in the atmo-sphere-biosphere system. The focalpoint of this project is the improvementof water vapour observation in theUT/LS. The LAPBIAT campaign washosted at the Arctic Research Centre ofthe Finnish Meteorological Institute, andthe participants included the CentralAerological Observatory (CAO)(Dolgoprudny, Russia), the University ofColorado (Boulder, USA), theMeteolabor AG (Wetzikon, Switzer-land), the University of Bern (Switzer-land), the Alfred Wegener Institute(Potsdam, Germany), the GermanWeather Service (DWD) (Lindenberg,Germany), Vaisala (Helsinki) and FMI-ARC (Sodankylä, Finland).

Instruments involved in the campaignwere the Lyman-alpha optical hygro-meter FLASH-B (CAO, Russia), NOASS-CMDL frostpoint hygrometer(University of Colorado), Snow Whitechilled mirror hygrometer (Meteolabor,Switzerland), FN method hygrometer(Lindenberg Observatory, Germany),Vaisala RS-92, and Microwave 22 GHzMIAWARA (IAP, Switzerland). Thecampaign consisted of 13 night-timeflights on balloons with 6 onboardinstruments (FLASH-B, NOAA frost-point, Snow White, FN, Vaisala RS-92and an ozonesonde), and 1 day and 1 night-time launch on rubber balloonswith 5 instruments on board (SnowWhite, FN, Vaisala RS-80, RS-90 and RS-92). Simultaneous measurements ofstratospheric water vapour content weremade by FLASH-B and NOAA hygro-meters.

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Coordination with OtherAgencies/Programmes

European COST 723 Action

V. Ryabinin reported activities of theData Exploitation and Modelling for theUT/LS Action group (COST 723) work-ing under the auspices of the EuropeanCooperation in the Field of Scientific andTechnical Research (COST).

Working Group 1 of COST 723 coversdata and measurement techniques.Their mandate is to gather data and tomake it available to the Action, criticallyassess the weak links in measurementcapabilities, and help identify new tech-niques and platforms to reduce thoseweaknesses. The focus is on humidity inthe UT/LS region. The inconsistency ofhumidity data sets is a most prominentissue on the global scale. It requiressimultaneous temperature data for con-version of absolute/relative humidity.

Working Group 2 focuses on assimilatedozone and humidity datasets. The task isto identify the most relevant datasets ofatmospheric constituents and other keyparameters for the UT/LS, develop andpublish assimilation algorithms, ensurequality control of observations and mod-els, analyze the benefits of combiningnadir and limb sounder information andpreliminary studies towards an assimila-tion of instrument radiances fromresearch satellites.

Working Group 3 is focusing on thestate of the UT/LS and understandingthe relevant processes. Its tasks are toassess the UT/LS climatology andtrends, study dynamical processes in theUT/LS, and quantify the anthropogeniceffects on the UT/LS. Specific areas ofstudy include ozone assessment andvariability, vertical diffusivity in theUT/LS, cirrus clouds and supersatura-tion.

COST Action 723 will host a SummerSchool at the Cargese Institute ofScientific Studies, Corsica, France, from26 September to 8 October 2005. Topicswill include UT/LS measurement tech-niques, data assimilation, and modellingstudies of the UT/LS. The school will belimited to 15 lecturers and 50-60 partici-pants.

Participation of SPARC in theInternational Polar Year 2007-2008 and

International Geophysical Year

M. Baldwin and C. Granier addressed

the issue of SPARC participation in theInternational Polar Year (IPY) and theInternational Geophysical Year (IGY)programmes. The 125th, 75th, and 50th

anniversaries of the first two IPYs andIGY will occur in 2007-2008. These mile-stones represent an opportunity to fosternew polar science research. ICSU andWMO will establish an IPO for IPY. TheIPO will support the anticipated ICSU-WMO IPY joint committee tasked withthe oversight and guidance of the IPYplanning and implementation.

SPARC participation is important; a wellidentified focus is needed. Possibleresearch areas include polar ozone, thepolar vortex, polar stratospheric andmesospheric clouds, chemistry-climateinteractions, tropospheric bromine inpolar regions, tropospheric precursors,and arctic haze.

ESA/Earth Explorer Missionsfor Implementation

T. Wehr reported on current ESA opera-tional missions. These are ERS-2,ENVISAT, PROBA, and the operationalmeteorological satellite Meteosat SecondGeneration.

ERS-2 carries the GOME instrument. Itis performing well, but a failure of thetape recorders reduces coverage. Anincreased number of ground stationssomewhat compensate for this gap indata. ENVISAT carries GOMOS, MIPASand SCIAMACHY. An ENVISAT vali-dation workshop was held in May 2004(Frascati, Italy) and an ENVISAT sym-posium will be held 6-10 September 2004in Salzburg, (Austria). PROBA is amicrosatellite with a high-resolutionimaging spectrometer (CHRIS), a high-resolution camera (HRC), a wide-anglecamera (WAC), a Space RadiationEnvironment Monitor (SREM), and adebris in-orbit evaluator (DEBIE). It hasbeen operational since 2001.

The Meteosat Second Generation incooperation with EUMETSAT continuesthe Meteosat programme with enhancedperformance and adds elements of clim-ate observing capability. It consists of aseries of at least three geostationaryweather satellites. MSG-1 was launchedSeptember 2002, and was re-namedMeteosat-8. The instruments are SEVIRI(imaging radiometer), GERB (Earth radi-ation budget), and S&R (search and res-cue transponder).

There are several future ESA missions.Details are available at the ESA web site

(http://www.esa.int/export/esaEO/index.html). Either EARTHCARE orSPECTRA will be selected this autumnfor implementation. The EARTHCAREpayload will include a backscatter lidar,a cloud profiling radar (a Japanese con-tribution), a multi-spectral imager, and abroad-band radiometer. EARTHCAREwill quantify aerosol-cloud-radiationinteractions for improvement of climateand numerical weather prediction mod-els. SPECTRA will quantify surfaceprocesses, ecosystem changes, and ter-restrial vegetation. It is a hyperspectralmulti-directional imager.

The EGPM (microwave radiometer andprecipitation radar) mission will be pur-sued with the Earth Watch programme,focused on pre-operational and proto-type operational missions.

A new call for future missions withinthe Earth Explorer Programme will beposted toward the end of 2004. This callwill be coordinated with the NASAESSP call.

T. Wehr also briefly summarized ongo-ing preparatory activities in the area ofclimate and atmospheric chemistry,stratospheric dynamics and ozone trans-port, and data assimilation.

Planned future missions of interest toSPARC are:- ADM-Aeolus: wind retrievals fromDoppler shift of UV-lidar (355 nm) lightback-scattered by aerosols and mole-cules along the line-of-sight. Launch isexpected in 2007. Additional productsare: cloud profiles, cover, heights; multi-layer clouds including cloud extinctionand optical thickness, troposphericaerosol extinction, optical thickness andstratification; wind variability and clearair turbulence.- Metop: a sequence of three polar-orbit-ing meteorological satellites with thefirst launch in 2005. Operations areexpected to continue for 14 years.Meteorological payload includes twoIASI and ESA-developed instruments;GRAS for GPS radio occultation, meas-uring atmospheric refractivity for tem-perature and humidity profile retrievals;and GOME-2, an improved version ofERS-2 GOME (maximum swath width of1920 km instead of 960 km), improvedpolarization measurements, optics andcalibration. - Meteosat 3rd Generation (MTG): to belaunched around 2015. Preparatoryactivities are ongoing. Industrial pre-Phase A is currently in preparation.Considered instrumentation is com-

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prised of imagers and sounders, includ-ing an infrared sounder (4.0 15 mm; IASI& GIFTS heritage) and UV-Visualsounder (GOME/SCIAMACHY her-itage) for frequent observations of main-ly O3, CO, NO2, SO2, H2CO (totaltropospheric column). Atmosphericchemistry is part of the current missionrequirements baseline.

The website for presenting future ESAprogrammes is located at http://www.eumetsat.de.

In discussion, J. Burrows noted thatSPARC support for the atmosphericchemistry component of MTG would bebeneficial.

NASA

M. Kurylo, in place of P. De Cola, gavea brief description of the restructuring ofNASA and presented a comprehensivereport on EOS AURA, which was suc-cessfully launched into a polar orbit onJuly 15, 2004, and flies approximately 15minutes behind Aqua. It includes fourinstruments:- HIRDLS: a UK and USA IR limbsounder,- MLS: an US microwave limb sounder,- OMI: a Netherlands/Finland visibleand UV nadir hyperspectral imager,- TES: an US IR limb and nadir high-resolution spectrometer.All four instruments view the same loca-tion within 14 minutes.

The mission is described in the paper bySchoeberl et al., 2004. Its science objec-tives are: tracking ozone layer recovery,recording the impact of atmosphericconstituents on climate, making globalmeasurements of air quality (ozone,nitrogen dioxide, aerosols), determiningpollution sources from mapping tropo-spheric trace gases, and observing influ-ences on the global oxidizing capacity ofthe atmosphere. It is expected to have asix-year lifetime. These objectivesaddress the following science questions:Is the ozone layer changing as predictedand are international protocols working?What are the roles of upper troposphericwater vapour, aerosols, and ozone onclimate forcing? What are the sourcesand distribution of tropospheric pollu-tants and their impact on environmentalhealth? How does the transport of gasesbetween the stratosphere and tropo-sphere influence ozone, climate change,and air quality?

The discussion supported a suggestionby M. Geller that SPARC should send

NASA a letter of congratulation on thesuccessful launch of the AURA mission.

CSA Activities of Relevance to SPARC

R. Michaud presented a summary of theCSA initiatives. MANTRA is a series ofhigh-altitude balloon missions (1998,2000, 2002 and 2004) to study strato-spheric composition at midlatitudes.The project is an international collabora-tion with the participation of theUniversity of Denver (USA) and Serviced'Aéronomie du CNRS (France). Anumber of instruments are involved,including several Fourier TransformSpectrometers (University of Denver,MSC/University of Toronto, Universityof Waterloo), emission radiometers(MSC/University of Toronto), Sun pho-tospectrometers, MAESTRO-B (MSC/University of Toronto), and the SAOZinstrument (CNRS).

OSIRIS on Odin (2001) is composed of aUV/visible spectrograph that continuesto provide vertical profiles of ozone andother minor atmospheric species, suchas NO2, OClO and BrO, in the strato-sphere, and an IR imager whose obser-vations will be used to obtaindistributions of ozone in the upper stra-tosphere and lower mesosphere. Therehave been requests from many differentresearch groups for OSIRIS data. A neweffort to enhance the returns fromOSIRIS through collaboration with theSCIAMACHY Team in Bremen has beeninitiated, and the partner agencies(Sweden, France, Finland and Canada)have agreed to extend the mission untilApril 2005.

The Atmospheric Chemistry Exper-iment (ACE) with SCISAT providessimultaneous measurements of tracegases, clouds, and aerosols using thesolar occultation technique. The goal isto gain a better understanding of thechemical processes that control the dis-tribution of ozone in Earth’s atmo-sphere, especially at high latitudes. Itwas launched successfully on 12 August2003. The first Arctic Validation cam-paign was carried out at Eureka inFebruary-March 2004, and SCISAT hasbeen making routine sunset and sunriseoccultation measurements since April2004.

An upcoming satellite instrument forCSA is the Stratospheric WindInterferometer For Transport studies(SWIFT), which is a Canadian instru-ment designed to make global strato-spheric wind measurements both in

daytime and night-time conditions atheights between 15 and 55 km and pro-vide simultaneous co-located ozone pro-files. There is also potential forobtaining operational stratospheric windmeasurements for medium range fore-casts. SWIFT has been endorsed andPhase A studies have been performed byESA and JAXA. Unfortunately, JAXAhas re-scoped the GOSAT satellite anddisembarked SWIFT (December 2003).Currently, CSA is performing prelimin-ary studies for flying SWIFT on a smallCanadian satellite, and both CSA andESA are investigating alternative flightopportunities for SWIFT. Potential sec-ondary payloads are being considered.

SPARC support for SWIFT is consideredto be important. It was suggested thatletters of support from the co-chairsdirected to both the CSA and ESAwould be helpful at this stage. After dis-cussion this action was approved by theSSG.

Network for Detection ofStratospheric Change

M. Kurylo, in a brief report, confirmedto the SSG the commitment of NDSC tocontinue its operations. The current pri-orities are supporting the networks thathave problems, extending the systeminto the tropics working jointly withSHADOZ, replace some of the instru-ments which are already 20 years old,and to keep the validation going.

COSPAR News from the RecentGeneral Assembly

The 35th COSPAR (Committee on SpaceResearch) symposium was held in Parisfrom 20-25 July, 2004, and was attendedby approximately 3000 participants. M.-L. Chanin was the ProgrammeChair. Relevant to SPARC are Commis-sion A dealing with the Atmosphere,and Commission C on the Upper Atmo-sphere and Planetary Atmospheres.

J. Burrows was chair of the organizingcommittee for the COSPAR 2004 Session"Atmospheric Remote Sensing: Earth'sSurface, Troposphere, Stratosphere andMesosphere.“ It ran for 5.5 days with220 contributions and approximately 110speakers. A summary of the session canbe found in this issue of the SPARCNewsletter. The 36th COSPAR Sympo-sium will be held in Beijing in 2006.

M.-L. Chanin noted a number of generalissues dealt within COSPAR that arealso of interest to SPARC. It is impor-

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Coupling Processes". Theme 4: "SpaceClimatology" [co-chairs: C. Froehlich(Switzerland) and J. Sojka (USA)] withworking groups "Solar IrradianceVariability", "Heliosphere Near Earth","Radiation Belt Climatology", and"Long-Term trends in Ionospheric andUpper-Atmospheric Variability".

In addition to the themes, CAWSES runsa capacity building and education pro-gramme, co-chaired by M. Geller, S. T. Wu and J. Allen. This programmeprovides training courses and helps withcomputational and data resources forscientists from developing nations. Itwill also establish partnerships betweendeveloping and industrialized nations.An ICSU Grant Application has beenmade for such activities.

There are several national and regionalCAWSES programmes under way orplanned. The programmes for India,Germany, and Japan held an inauguralworkshop in June 2004. The 11th

SCOSTEP Quadrennial STP Symposium"Sun Space Physics and Climate" will beheld on 5-12 March 2006 in Brazil.

Solar Impact Intercomparison

K. Kodera discussed the status of theGRIPS Solar Impact Intercomparison. Asummary paper has been published(Kodera et al., 2003). A session entitled"Solar Influence on Climate ThroughMesospheric-Stratospheric Chemical-Dynamical Processes", co-organized byK. Kodera, U. Langematz and A. Smith,will be held at the fall AGU meeting(San Francisco, USA, 13-17 December2004). The SSG discussed the future andevolution of the Solar Impact Intercom-parison. It was agreed that it shouldcontinue to be supported by SPARC.With eventual merger of GRIPS and theCCM Intercomparson activities, it couldbecome part of a possible future jointCAWSES-SPARC collaboration.

SPARC Data Centre

M. Geller reported on the current statusof the SPARC Data Centre. One moreyear of funding is available, but it is pos-sible to extend the funding for anotherround. A new project scientist is beingrecruited. Previous scientists were sup-ported jointly by SPARC Data Centrefunding and M. Geller’s research funds.However, it may be useful to employ afull-time person who could work onprojects specifically for the Data Centre.

There was unanimous support for

M. Geller to continue as the Director ofthe SPARC Data Centre. A group ofmembers within the SSG have beentasked with drafting a letter fromSPARC that will convey the continuingneed for the centre. A mirror site inJapan was being considered. The groupfelt that more pressure would be put onthe centre when large amounts of chemi-cal data come onboard.

Next SSG Meeting

A. O’Neill offered to host the next meet-ing of the SSG. This invitation wasaccepted with appreciation. The nextmeeting of the SSG will be held inOxford (UK) on 26-29 September 2005.

Closure of Session

The co-chairs closed the Session in theafternoon of Thursday, 12 August 2004.The attendees unanimously thanked N. McFarlane for organizing the sessionand arranging for excellent conditionsfor its work.

References

Austin, J., et al., Uncertainties and assessments ofchemistry-climate models of the stratosphere.Atmos. Chem. Phys., 3 (1), 1-27, 2003.

Boville, B.A., The influence of the polar night jet onthe tropospheric circulation in a GCM. J. Atmos. Sci.,41, 1132-1142, 1984.

Fioletov, V.E. and T. G. Shepherd, Seasonal persist-ence of midlatitude total ozone anomalies. Geophys.Res. Lett.. 30, 1417, 2003.

Kodera, K., et al., Downward propagation of upperstratospheric mean zonal wind perturbation to thetroposphere. Geophys. Res. Lett., 17 (9), 1263-1266,1990.

Matthews K., et al., GRIPS solar experiments inter-comparison project: Initial results. Papers in Met. andGeophys., 54, 71-90, 2003.

Polavarapu, S., et al., Data assimilation with theCanadian Middle Atmosphere Model. Accepted toAtmos.-Oceans, 2004.

Randel, W. and X Wu, Cooling of the Arctic andAntarctic polar stratospheres due to ozone deple-tion. J. Climate, 12 (5) 1467–1479, 1999.

Schoeberl, M. R., et al., Earth Observing System mis-sions benefit atmospheric research, Eos Trans. AGU,85 (18), 177, 2004.

Shine, K.P., et al., A comparison of model-simulatedtrends in stratospheric temperatures. Quart. J. Roy.Met. Soc. 129, 1565, 2003.

Taguchi, M., and D. L. Hartmann, El Nino,Stratospheric sudden warmings, and enhanced cli-mate anomalies. Poster at 3rd SPARC GeneralAssembly, 2004 and submitted to Science, 2004.

Yoden, S., et al., Numerical studies on time varia-tions of the troposphere-stratosphere coupled sys-tem. J. Met. Soc. Japan, 80, 811-830, 2002.

tant for SPARC to encourage ESA andnational agencies to continue calibrationand validation activities for ENVISATinstruments, and to continue theimprovement of the ground segment,data re-processing and distribution. It isalso necessary to stress a need for conti-nuity and development of atmosphericobservation.

A number of points regarding interac-tions with the COSPAR communitywere brought forward in discussion.One suggestion (M. Geller) is to encour-age SPARC scientists to contribute to theimprovement of the COSPAR referenceatmosphere (CIRA).

SCOSTEP and Interactions withSPARC/GRIPS

M. Geller reported on SCOSTEPCAWSES activity. The mission ofSCOSTEP is to implement research pro-grammes in solar-terrestrial physics thatbenefit from international participationand involve at least two ICSU bodies.Under SCOSTEP, the Climate AndWeather of the Sun-Earth System(CAWSES) has been developed to runbetween 2004 and 2008. The CAWSESOffice has been established at BostonUniversity, with D. Pallamraju as thescientific coordinator. The first newslet-ter was published in March 2004 and thefirst CAWSES campaign organized inMarch-April 2004 in conjunction withthe CPEA Campaign.

There was a special all-day CAWSESmeeting at Observatoire de Paris on 17July 2004 and a CAWSES presentation atthe ILWS Session in the COSPAR GA.

There are four main themes of CAWSES: Theme 1 "Solar Influence on Climate" [co-chairs: M. Lockwood (UK) and L. Gray(UK)], has two working groups:"Assessment of Evidence for SolarInfluence on Climate" and "Investigationof Mechanisms for Solar Influence onClimate". Theme 2: "Space Weather:Science and Applications" [co-chairs: J.Kozyra (USA) and K. Shibata (Japan)].Theme 3: "Atmospheric CouplingProcesses" [co-chairs: F.-J. Luebken(Germany) and J. Alexander (USA)],has working groups on "DynamicalCoupling and its Role in the Energyand Momentum Budget of the MiddleAtmosphere", "Coupling via Photo-chemical Effects on Particles and MinorConstituents in the Upper Atmo-sphere”, "Coupling by Electrodynamicsincluding Ionospheric MagnetosphericProcesses", and “Long-Term Trends in

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In light of such an internationally visi-ble, scientifically important, and soci-etally relevant event of the 20th centuryin the polar region, it would be inappro-priate not to include stratospheric ozoneissues as an important theme in theInternational Polar Year (IPY). Not onlywill it clearly provide a context for IPYbut also show how international activi-ties such as IGY and IPY provide scien-tifically and societally importantinformation. It also provides a wonder-ful opportunity to describe the brief, buteventful, history of the stratosphere andbenefits, foreseen and unforeseen, ofactivities such as the IPY. We stronglyurge the National and Internationalcommunities involved in IPY to includethe polar stratosphere in the schedule.

SPARC Co-Chairs

amendments to ban CFCs, and the firsttruly international treaty to preserve theenvironment. Thus the Antarctic OzoneHole became inarguably one of the mostrecognized environmental issues of the20th century, recognized by peopleeverywhere in the world. The Arcticozone changes, though lesser in magni-tude than the Antarctic ozone hole, areby no means of lesser importance.

The science of the polar ozone losses –the atmospheric dynamics, chemistry,and radiation understanding – was and,continues to be a major theme of Strato-spheric Processes and their Role inClimate (SPARC), a WCRP project. TheSPARC community was instrumental inunderstanding the polar ozone deple-tions, and the many advances that havebeen made regarding the stratosphere todate. We in the SPARC community areconfident that this progress will con-tinue.

As a part of the grand experiment ofthe International Geophysical Year

(IGY) in 1957, ozone was measured inAntarctica using Dobson spectrometers.The aim was to measure the abundancesand variations of ozone, which wasthought to be a passive stratospherictracer in this region, to understand thedynamics of the Antarctic stratosphere.What emerged in 1985 with the publica-tion of Farman et al. (Nature, 315, p 207,1985) was the clearest picture of an enor-mous annual depletion of ozone in theaustral spring over Antarctica – the infa-mous Antarctic Ozone Hole. In less than5 years, it was proven that the ozonehole was caused by human emitted fluo-rochlorocarbons (CFCs) and since thenthe ozone hole has been a "poster child"for showing how humans can causeglobal scale changes. The discovery ofthe ozone hole, its association with theCFCs, and its continued larger and larg-er depletions were the key factors thatled to the Montreal Protocol and its

Polar Stratospheric Ozone Changes, SPARC, and the International Polar Year

Report on the 2nndd International Limb Workshop

SSttoocckkhhoollmm,, SSwweeddeenn,, OOccttoobbeerr 1111--1144,, 22000044

JJöörrgg GGuummbbeell (gumbel@misu.su.se), and JJaacceekk SStteeggmmaann (jacek@misu.su.se),Dept. of Meteorology, Stockholm Univ., Stockholm, Sweden

CChhrriissttiiaann vvoonn SSaavviiggnnyy, Univ. of Bremen, Germany(csavigny@iup.physik.uni-bremen.de)

MMaarrttiinn GG.. MMllyynncczzaakk, NASA Langley Research Center, Hampton, VA, USA,(m.g.mlynczak@nasa.gov)

Introduction

During recent years, satellite instrumentsmeasuring scattered and emitted radia-tion from the Earth's limb have becomemore and more central for studies of themiddle atmosphere. The 2nd Interna-tional Limb Workshop brought together46 scientists from various satellite com-munities to discuss limb instruments,retrievals and results. The workshopwas hosted by the Dept. of Meteorologyat Stockholm University (Sweden) underthe auspices of SPARC and IGAC.Financial support was available from theInternational Meteorological Institute inStockholm. For the detailed workshopprogramme and the list of participantssee http://www.misu.su.se/limb2004.html.

While the 1st International Limb Work-

shop (Bremen, Germany, 2003) focusedon UV/Vis limb scattering, the scope ofthe 2nd Workshop was broadened toinclude limb measurements of infraredand microwave emissions. This openednew perspectives for future collabora-tions on atmospheric results. Neverthe-less, the main focus of the workshop con-tinued to be on the important first stepsof data analysis: instrumental issues,retrieval algorithms and data validation.

The following satellite instruments wererepresented at the workshop: OSIRISand SMR (on Odin), SCIAMACHY,MIPAS and GOMOS (on ENVISAT),SABER (on TIMED), ILAS-II (on ADEOS-II), SAGE III (on Meteor-3M), ACE (onSciSat), as well as SOLSE and LORE (onthe Space Shuttle). In addition, excitingoutlooks were given towards new limb

missions ranging from the ultraviolet tothe microwave part of the spectrum.

Limb Techniques in the UV,Visible and Near-Infrared

Similar to the 1st Limb Workshop, themajority of presentations concernedtechniques and results related to the limbdetection of scattered sunlight in theultraviolet and visible. Efforts havefocused in particular on the co-analysisof various species and their interaction instratospheric chemistry. The set ofstratospheric species retrieved fromSCIAMACHY, OSIRIS, GOMOS, SAGE-III and ILAS-II is comprised of O3, NO2,N2O, OClO, BrO and aerosols.Presentations on these observations weregiven by C. S. Haley, A. Rozanov, C. Sioris, S. M. Brohede, A. Seppälä,

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D. F. Rault, E. Kyrölä, and F. Khosrawi.The solar proton event of October/November 2003, presented by A. Seppäläand G. J. Rohen, was of particular interestfor satellite-borne limb observations.Enhanced NO2 chemistry led to long-last-ing effects on ozone depletion in the upperstratosphere.

D. F. Rault and E. Kyrölä presented limbscatter results from instruments that weredesigned primarily for occultation meas-urements, such as SAGE-III and GOMOS.Instrumental issues like out-of-field scatterare particular challenges for the latter.Their analysis can provide important inputfor the general understanding and devel-opment of new limb techniques. Strato-spheric limb measurements were also pre-sented from SOLSE and LORE onboardSTS107 by D.E. Flittner and R. Loughman.These experiments serve as important stepstowards the next generation of U.S. instru-mentation for ozone-related studies.

From the OSIRIS data, exciting perspec-tives were presented by E. J. Llewellyn toretrieve mesospheric OH and possiblywater vapour from the OH (A-X) solar fluorescence at 308 nm. First highlightswere also presented by J. Sloan and G. Witt from the ACE instrument onboardthe Canadian SciSat platform.

Limb scatter techniques have becomeincreasingly important tools for the detec-tion and characterization of middle atmo-spheric aerosol layers. Near infrared meas-urements along the limb path provide thenecessary sensitivity and signal-to-back-ground ratio to detect cirrus and subvisualcirrus clouds, and polar stratosphericclouds in the tropopause region and thelower stratosphere. Presentations regard-ing these issues were given by A. Bourassa,J. Sloan, and C. von Savigny.

Progress was also reported on mesosphericclouds in a noctilucent cloud (NLC) clima-tology and particle characterization by B.Karlsson, C. von Savigny, and S. Petelina.Comprehensive NLC data sets are nowavailable from OSIRIS and SCIAMACHY,but a number of challenges need to be over-come in the study of these thin inhomoge-neous cloud layers.

Infrared and MicrowaveLimb Techniques

Techniques based on infrared and sub-mmemissions were a new feature of the 2nd

Limb Workshop. Presentations about theselimb techniques readily showed the syner-gies with data retrieved from limb scat-tered UV/Vis/IR radiation. A major pur-pose of the workshop was to provide aforum to prepare future co-analysis ofthese data sets.

On the infrared side, comprehensive non-LTE (local thermo-equilibrium) data sets

are available from TIMED/SABER, pre-sented by M. Mlynczak and C. Mertens,and ENVISAT/MIPAS presented by B. Funke. These missions provide compre-hensive information on the energy budget,chemistry, and exchange processes in themesosphere and lower thermosphere. C. von Savigny presented the retrieval ofmesospheric temperatures from the OH (3-1) Meinel band, demonstrating the abilityof SCIAMACHY to perform limb analysisof infrared emissions.

Unique limb measurements of trace gasesrelated to chemistry and transport process-es were also reported from the Odin/SMRsub-mm instrument by J. Urban, N. Lautié,and E. Dupuy. Species presented includeClO, N2O, HNO3, O3 and H2O in the strato-sphere, as well as H2O and CO in themesosphere. The large potential of sub-mm techniques has also been suggested forfuture missions such as STEAM/SWIFT(D. Murtagh, and P. Eriksson) and,JEM/SMILES (Y. Kasai).

Model Studies

Presentations about numerical tools werean important complement to instrumentand data contributions. W. Lahoz, S. Hassinen, and J. Rösevall presentedmethods for chemical data assimilation,which have in recent years provided newtools for the analysis of limb data in thestratosphere. Presentations on tools forradiative transfer modelling and limbretrievals were given by J. Kaiser, J. I. vanGent, H. Walter, A. Doicu, and P.Eriksson, and included both new theoreti-cal concepts and operational codes.

Data Comparison andTechnical Collaboration

Data comparison projects are ongoing for anumber of stratospheric species involvingseveral of the satellite instruments repre-sented at the workshop. In order to facili-tate data comparisons in the future, it hasbeen suggested that a number of case stud-ies with co-located measurements bedefined. Further details about these effortswill be made available on the Odin/OSIRISwebsite (http://osirus.usask.ca). Evidently,co-location is a very limiting requirementwhen it comes to the comparison of morethan two satellites. In a long-term perspec-tive, chemical data assimilation will need toprovide a more solid basis for the jointanalysis of individual satellite data sets.

When it comes to mesospheric limb data,comparisons between various satellite mis-sions are still at a more basic stage. Thereis a large potential for co-analysis concern-ing the chemistry and transport of tracersH2O, O3, and CO primarily from the IR andmicrowave limb instruments. A primecandidate for joint mesospheric analysisefforts in the UV/Vis is the climatologyand properties of noctilucent clouds.

As instrumental issues and retrieval tech-niques are of central importance for thisworkshop series, a number of areas of col-laboration have been defined. In order tofurther improve collaborations, it wasagreed that a data base of technical notes becreated. The following topics have beendefined as issues of particular interest:pointing accuracy and altitude reconstruc-tion, baffle effects and their quantification(out-of-field effects), quantification of albe-do and multiple scattering (in-field effects),inhomogeneity along the line-of-sight (ter-minator problem etc.), and topographictechniques.

We invite everybody to share experienceon these issues by submitting technicalnotes to a common data base. The database will be hosted by the Odin/OSIRISwebsite (http://osirus.usask.ca). Please con-tact N. Lloyd (nick.lloyd@usask.ca) withany contributions or suggestions.

ConclusionsDuring recent years, satellite instrumentsscanning the Earth's limb have provided aquickly growing data base on middleatmospheric chemistry and dynamics.Efficient networks exist for the analysis ofstratospheric data, and similar develop-ments are under way for the mesosphere.In the years to come, we can also expect adownward extension of limb techniques,contributing to important scientific issuesin the Upper Troposphere and LowerStratosphere. In this region, rapid progressin new microwave limb techniques willplay a particular role.

The 2nd International Limb Workshopextended its focus towards data compar-isons over a spectral range from the UV tothe microwave. Nevertheless, the majorobjective continued to be to provide aforum for the detailed exchange of ideas onmeasurement issues and limb retrievaltechniques. The refinement of retrievalalgorithms and validation efforts are inmany cases still ongoing. Both of thesedevelopments benefit greatly from collabo-ration between individual missions. Thiswas clearly confirmed by the fruitfulexchange of ideas during the workshop.

The instrumental and retrieval issues, andthe focus on final data products, make thelimb workshop series a valuable comple-ment to large-scale conferences. The 3rd

International Limb Workshop be held inMontreal, Canada, in the spring of 2006. E. J. Llewellyn from the University ofSaskatchewan, Saskatoon (Canada) volun-teered to organise this next meeting.

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Introduction

The Soundings of Ozone and Water inthe Equatorial Region (SOWER) was ini-tiated in the late 1990's (Hasebe et al.,1998) for the purpose of improving ourunderstanding of the distribution andvariabilities of ozone and water vapourin the tropics. A series of ozone andwater vapour sonde launches has beenconducted, together with conventionalradiosonde observations at several tropi-cal stations such as San Cristóbal,Galápagos (eastern Pacific), ChristmasIsland, Kiribati (central Pacific), andWatukosek, Indonesia (western Pacific).These data constitute a unique datasetfor the monitoring of water vapour in thetropical stratosphere and provide keyinformation pertaining to transportprocesses between the troposphere andthe stratosphere.

The identification of the tropicaltropopause region has changed drastical-ly since the introduction of the TropicalTropopause Layer (TTL), leading to sev-eral new hypotheses on the dehydrationof the stratosphere. Existing satellitedata enables the study of long-termtrends in water vapour, and with thelaunch of EOS/AURA in July 2004, highquality constituent data are becomingavailable. A large observational cam-paign in the equatorial region has beenproposed by the United States to supportthe satellite programme, and the SOWERTeam is also preparing an intensive cam-paign in the western tropical Pacific inthe coming northern winter. In view ofthese programmes, we believe it is quitetimely to have a focused scientific dis-cussion on the dehydration process inthe TTL, following the first of such meet-ings in October 1997 (SOWER, 1998).

The scientific sessions were divided intothe following subjects: (i) Developmentof observational techniques; (ii) Obser-vational descriptions of UT/LS watervapour; (iii) Atmospheric processesinfluencing stratospheric water vapour;(iv) The role of UT/LS water vapour inclimate; (v) Hypotheses on the dehydra-

Vapour Experiment (AWEX) at theARM/CART site near Lamont, OK(USA) to evaluate the performance of theradiosonde sensors, as well as the SnowWhite Hygrometer. Comparisons showvery good agreement between these sen-sors.

M. Fujiwara reviewed the performanceof the Meteolabor Snow White Hygro-meter, which is a low-cost, chilled-mirrorhygrometer for radiosonde applicationsprovided by Meteolabor AG, a Swisscompany. SOWER began testing thissensor for possible tropical tropopausewater vapour measurements in 2000, andhas since collaborated with Meteolaborto improve it. Snow White was found tobe an appropriate reference sensor forradiosonde humidity sensors in the tro-posphere (Fujiwara et al., 2003a, Wang etal., 2003); however, the limited coolingstrength of the device provides a lowerdetection limit of 6 to 8% relative humid-ity (Vömel et al., 2003). The optimizationand sensitivity of the controller circuitmay also need to be improved for meas-urements above the tropopause.

Observational Descriptionsof UT/LS Water Vapour

S. J. Oltmans and H. Vömel presented are-evaluation of the long-term watervapour record at Boulder. This 25-yearrecord has shown an increase in watervapour from the tropopause up to analtitude of ~28 km; however, a recentcomparison between the Boulder profilesobtained with a balloon-borne hygrome-ter and HALOE has shown discrepanciessince 1997 (Randel et al., 2004).

Removal of contaminated profiles, and asmall correction to the instrument cali-bration after 1990, produced a time seriesthat is in better agreement with theHALOE record after 1997 (see Figure 1).The increase over the 25-year period inthe 18-22 km layer is 0.75 ± 0.2 %/year,with lesser increases in this layer since2000, making the change since 1991 smallin both the balloon record and the

tion mechanism in the TTL; (vi)Observations of dehydration processes;and (vii) Modelling of stratosphericwater vapour and dehydration processes.

In addition to the scientific discussions,ozone and water vapour sonde launcheswere demonstrated during the meetingfor those not familiar with radiosondeprocedures. Other highlights of themeeting were the presentation of NASAawards to M. Agama, J. Cornejo and F. Paredes in recognition of their contri-bution to the Southern HemisphereAdditional Ozonesondes (SHADOZ)programme, and a special talk on themeteorological observation network inEcuador was given by L. Poveda. A spe-cial presentation in memory of James R.Holton was given by A. Gettelman andK. Rosenlof. For details of the meetingsee http://sower.ees.hokudai.ac.jp/.

Development ofObservational Technique

H. Vömel reviewed the accuracy andperformance requirements for frost pointhygrometers, noting the limitations ofmeasurements of stratospheric andupper tropospheric water vapour. Incooperation with CIRES at the Universityof Colorado (CU), a new CryogenicFrostpoint Hygrometer (CFH) wasdeveloped. It is based on the NOAAfrostpoint hygrometer, but overcomes itslimitations and at the same time reducespower consumption and weight, trans-lating to a corresponding saving inweight and balloon size. Therefore, it iseasier to use and to obtain high qualitydata.

CU-CFH sondes are regularly launchedat San Cristóbal (Ecuador), Hilo, HI(USA), and Boulder, CO (USA). CFHsondes were also used during the LAP-BIAT Upper Troposphere Lower Strato-sphere (LAUTLOS) experiment inSondankylä, (Finland), and during theSOWER Bandung (Indoniesia) cam-paign. This instrument was used as thereference sonde during the AIRS Water

Report of the 2nndd International SOWER Meeting

SSaann CCrriissttóóbbaall,, GGaallááppaaggooss,, EEccuuaaddoorr,, 1100--1155 JJuullyy 22000044

FFuummiioo HHaasseebbee, Hokkaido University, Sapporo, Japan (f-hasebe@ees.hokudai.ac.jp)

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HALOE measurements.

A. Gettelman, on behalf of W. Randel,presented changes in stratospheric waterobserved in HALOE data which showsan interannual tape recorder of anom-alies that propagate vertically and latitu-dinally in the stratosphere. Since 2001,stratospheric water vapour has been per-sistently low (by ~0.5 ppv; Figure 2).These low values spread from the trop-ics, and are also seen in POAM datawhich is correlated with HALOE obser-vations. The changes in HALOE H2O arealso correlated with tropopause temper-ature anomalies throughout the record.The most recent values of water vapour(to April 2004) are still low, as aretropopause temperatures. These temper-ature anomalies are centred in a narrowlayer just above the tropical tropopause.

Tropical ozonesondes also show lowozone from 16-18 km after 2001, with thelargest changes centred around, or justbelow the tropical tropopause.Ozonesonde anomalies are similar tosatellite (SAGE II) ozone anomalies overthis period, and SAGE II ozone datashow that the anomalies are centred inthe tropics.

Temperature and ozone changes are con-sistent with an increase in tropicalupwelling (the Brewer-Dobson circula-tion), however there is not conclusiveevidence of increases in extratropicalplanetary wave forcing. Other mecha-nisms which can explain the recentchanges include persistent changes intropical convection or ozone decreasesleading to cooling.

K. Rosenlof examined theobserved drop in watervapour at the end of 2000seen in both the CMDL andHALOE records at midlati-tudes. This drop is also seenin the HALOE and SAGE IIdata sets in the tropics, and,albeit delayed by a fewmonths, in the POAM satel-lite Northern Hemisphere(NH) water vapour data athigh latitudes. The timing ofthis drop corresponds to asignificant drop in NCEPtropopause temperatures,and a drop in the cold pointtemperature as measured byoperational radiosondes, in-dicating a possible change invertical stability in the uppertropical troposphere.

The reasons for the dramatic

drop in temperatures are not known, butit is likely that enhanced uplift near thetropopause is responsible. If this contin-ues, it will likely result in a decrease instratospheric water at upper levels overthe next few years, especially since a cor-responding increase in surface methaneis not occurring at this time.

A. Gettelman gave a historical overviewof satellite observations of water vapourin the TTL, starting with LIMS in thestratosphere, and HALOE and MLS inthe TTL (Kley et. al., 2000). Satellites suchas HALOE and SAGE have helped revealthat there are significant instances of sub-visible cirrus clouds in the tropics (Wanget al., 1996), which may account for a sig-nificant amount of dehydration in theTTL. In addition, the ATMOS instru-ment on the space shuttle measureswater vapour and water vapour isotopesfrom space.

New instrumentation promises a moredetailed picture of TTL water vapourfrom space. Many of these sensors are ona series of NASA satellites called the "A-Train", which will observe the same loca-tion on the Earth at the same time. Auracontains both HIRDLS and MLS limbsounding instruments measuring TTLwater vapour. On the Aqua satellite, tro-pospheric water vapour (up to 200 hPa)is measured by the AtmosphericInfraRed Sounding (AIRS) suite, andTTL cloud properties are determined bythe Moderate-Resolution Imaging Spec-trometer (MODIS) radiometer with highspatial and moderate spectral resolution.

The future challenges will be to integratethe data from these various instruments,together with cloud data and data fromother instruments, to estimate long termvariability in the TTL.

H. Vömel presented results from watervapour and ozone soundings taken atSan Cristóbal and other tropical sites.These results have revealed a wide vari-ety of processes that control the watervapour content in the TTL. Convectiveprocesses can dry air rising within cumu-lonimbus clouds to well below the meanstratospheric water vapour mixing ratio.The outflow of these convective eventshas been observed both in the WesternPacific region as well as over SanCristóbal. This process is highly season-al for any given geographic location. AtSan Cristóbal this process also shows aclear dependency on the El Niño phase.Non-convective drying through cirrusclouds, which form at a cold tropopause,has been observed frequently at SanCristóbal during the austral winter andspring months.

During the Austral summer and earlyfall, when the tropical tropopause is typ-ically much warmer, little dehydrationhas been observed over San Cristóbal. Inone case, some indication of dehydrationin the upward phase of a Kelvin waveevent was observed, which may consti-tute an important dehydration mecha-nism during the warm season. The geo-graphic pattern of the tropopause tem-peratures also reflects the importance ofthese regions for dehydration. AtJuazeiro do Norte (Brazil) for example,

no dehydration was observedduring the season of coldtropopause temperatures,since in this region, the meantropopause temperature isgenerally too warm to con-tribute to the dehydration inthe TTL.

The tropopause temperaturesover San Cristóbal showed aclear cooling in 2000, and coldtemperatures continue in 2004.Therefore, it is to be expectedthat the geographic region ofthe eastern Pacific continues toplay a role in dehydration,even though it is generallylocated outside the region ofcoldest tropopause tempera-tures.

K. Rosenlof presented resultsfrom the January 2004 Pre-AVE WB57-F Aircraft Expe-riment based in San Jose

Figure 1. Time series of the water vapour mixing ratio in the 18-22 kmlayer over Boulder, Colorado (USA) from the balloon profile measure-ments and HALOE satellite observations.

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(Costa Rica). These flightswere part of a test missionto ready an instrumentsuite and demonstratecapabilities for validationof the Aura satellite,launched in July 2004. Oneof these flights wasdesigned to be a compari-son with the CMDL frostpoint balloon launchedfrom San Cristóbal. Signi-ficant differences are seenbetween the aircraft andballoon measurements,with the aircraft measure-ments approximately 1ppmv higher at the altitudeof the water vapour mini-mum. The net result of thelarge differences betweenthe aircraft and balloonmeasurements translatesinto large differences inestimated saturations withrespect to ice. In particular,the aircraft data show largesupersaturations with res-pect to ice that are not evi-dent in the frost point data.Statistics on numbers of points showinghigh supersaturations with respect to icediffer between the CMDL and aircraftdata sets, with the aircraft data showinga higher frequency of supersaturationwith respect to ice than the frost pointballoon.

The differences noted in the comparisonare consistent with those reported in theSPARC water vapour assessment (Kleyet al., 2000). These differences are of con-cern, because uncertainties in the watervapour measurements as based on com-parisons between techniques/platformsare large enough to preclude makingconclusions as to what processes controlthe stratospheric entry value of watervapour. The reasons for the differencesnoted are not yet known. Determiningwhy large differences exist betweenthese WB-57F aircraft instruments andthe balloon frost point instrument at lowwater vapour values is a significantproblem that requires close examination.Before using either set of data for satellitevalidation, these differences should beunderstood.

T. J. Dunkerton presented evidence for a"trimodal" distribution of extreme valuesof ozone and water vapour concentrationin NH summer, using HALOE data from1991-2004. Low values of ozone andwater vapour concentration are foundnear the equator in the western tropicalPacific (as in NH winter), but over the

major monsoon regions of NorthAmerica and South Asia there exist highconcentrations of water vapour, presum-ably due to moistening by deep convec-tion, while ozone is low over Asia buthigh over North America. Evidently theAsian monsoon circulation is strongerand somewhat deeper than the monsooncirculation over North America, causingair within the Tibetan anticyclone to berelatively isolated and depleted in ozone,due to transport of ozone-poor air fromthe troposphere.

Since September 1999, weekly ozone-and radiosondes have been launched atParamaribo station (Suriname) (5.8°N,55.2°W), on the northern coast of SouthAmerica. Since October 2002, more accu-rate water vapour balloon observationshave been made with the Snow Whitehygrometer, installed at a receiving sta-tion through a collaboration betweenKNMI, Kyoto University and HokkaidoUniversity (Japan). P. Fortuin, G.Verver, P. Dolmans, M. Fujiwara and H.Kelder presented an analysis of thewater vapour observations from 16 ofthese launches over the period October2002-June 2003 (11 launches) and March-April 2004 (5 launches).

Observations suggest a steady ascent ofmoisture-rich air through the TTL aboveSurinam, although additional evidence isneeded since the humicaps observationsat these high altitudes are unreliable.

The coinciding recurrence ofinertial instability in the UTduring the South AmericanMonsoon is also analyzed, aswell as the possible role thismight play in the redistribu-tion of water vapour. This isdone on the basis of a casestudy with ECMWF analysesand shows a stacked verticalcellular flow (Fortuin et al.2003) confirming the theoryof symmetrical inertial insta-bility.

N.O. Hashiguchi presentedan investigation of seasonaland interannual variations ofthe cold point tropopause(CPT) temperature, based onoperational rawinsonde dataover Indonesia and the sur-rounding region (90°-140°E,15°N-15°S) from 1992 to1999. The cold point temper-ature has an annual variationwith a maximum/minimumin northern summer/winter,which is the same as thatobserved at other tropical

stations, and the peak-to-peak differenceis about 6 K at all the stations. In latitu-dinal distribution, the cold point temper-ature is the warmest over the equatorand decreases with respect to latitude forboth JJA and DJF. This is because theanalysis region is located in the uppertropospheric warm anomaly region, onthe west side of the Matsuno-Gillresponse, and the latitudinal structure inthe section is opposite to a zonal meanstructure presented by Seidel et al. (2001).The CPT temperature is also the warmestover 100°E and decreases to the east withrespect to longitude.

During the non-ENSO period from July1992 to April 1997, the CPT temperaturewas decreasing over the entire analysisregion without changing the longitudi-nal inclination. In this period, activationof convective clouds in OLR andstrengthening of the upper troposphericwind of local Hadley circulations werealso seen. It seems that these tropo-spheric changes lead to cold CPT tem-peratures through adiabatic cooling inthis period.

Atmospheric ProcessesInfluencing Stratospheric

Water Vapour

N. Eguchi and M. Shiotani presentedresults from MLS and CLAES data,which suggest a direct effect of convec-

Figure 2. Time series of near-global (60°N-60°S) anomalies in lower strato-spheric (82 hPa) water vapour derived from HALOE satellite measurements.The data have been de-seasonalized; the circles show monthly mean values, andthe error bars denote the monthly standard deviation. The solid line is aGaussian-weighted running mean (using a Gaussian half-width of 12 months).[This is an update from Randel et al., 2001].

23

tive activity on wet anomalies up to aheight of 146 hPa, but an indirect effectby the dynamical response to the convec-tive heating at 100 hPa. Dynamical struc-tures around the tropopause level arecharacterized by equatorial temperatureanomalies (Kelvin wave response) andby subtropical anticyclonic gyres (Ros-sby wave response). Between the twogyres, the easterly wind blowingthrough the equatorial cold region maycause dehydration, along with the for-mation of cirrus clouds. As the northerngyre intensifies, tropical dry air is trans-ported to the subtropical Pacific andeventually to the equatorial Pacific. It issuggested that the temperature and flowvariations due to the coupled Kelvin-Rossby wave structure play an importantrole in dehydrating air in the tropical andsubtropical tropopause region.

M. Fujiwara presented a case study of anUpper Tropospheric Inversion (UTI) andjet in the tropics. Ship-board radiosondemeasurements revealed a persistent tem-perature inversion layer at 12-13 km overthe tropical eastern Pacific, which waslocated at the top of a very wet layeroriginating from the ITCZ to the north(Fujiwara et al., 2003b). Radiative trans-fer calculations suggested that this UTIwas produced and maintained by stronglongwave cooling in the wet layer.

A strong easterly jet stream was alsoobserved at 12-13 km, and was in ther-mal wind balance with the meridionaltemperature gradients produced by thecloud by radiative processes in the ITCZand the wet outflow. The jet in turnacted to spread inversions further down-stream through the transport of radia-tively active water vapour. This feed-back mechanism may explain theomnipresence of temperature inversionsand layering structures in trace gases inthe tropical troposphere. Examination ofhigh-resolution radiosonde data at othersites in the tropics indicates that similarUTIs often appear around 12-15 km. TheUTI around 12-15 km may thus be char-acterized as one of the "climatological"inversions in the tropical troposphere,forming the lower boundary of the TTL.

N. Nishi, M. Yamamoto, A. Hamada, J.Hashiguchi and S. Fukao presented thevertical wind distribution in and aroundupper tropospheric cirriform clouds,obtained by using the VHF radarEquatorial Atmospheric Radar (EAR)wind data at Sumatra Island (Indonesia)(0°N, 100°E), and GOES IR data inNovember 2003. It was found that themost dominant variability in the middleand upper troposphere is a high frequen-

cy oscillation with vertically standingphase structure, with a period slightlylonger than the Brunt Väisällä frequency.The amplitude is sometimes more than30 cm/s. However, in some cases duringlate November, strong upward motionwas detected not only in the lower half ofthe domain, but up to 15 km for clusterswith the same cloud top as earlyNovember. Large scale conditions suchas wind shear, stability and humiditymay effectively control the vertical winddistribution in the tropical cirriformclouds in large scale cloud clusters.

Y. Kasai, J. Urban, M. Lautie, D.Murtagh, P. Ricaud, and the Odin/SMRgroup presented results of the watervapour isotopes observed by the Sub-Millimetre Radiometer (SMR) onboardthe Odin satellite, which is a satellitefunded jointly by Sweden, Canada,Finland and France, and was launched inFebruary 2001. In aeronomy mode, theSMR dedicates various target bands toobservations of trace constituents rele-vant to stratospheric/mesospheric chem-istry and dynamics, such as O3, ClO,N2O, HNO3, H2O, CO, as well as iso-topes of H2O and O3.

The global distribution of water vapourisotopes and its seasonal variation wereobtained for the first time by Odin/SMRmeasurements. The δD value of watervapour in the stratosphere agrees withthe past measurements and a model(Ridal and Siskind, 2002). It increaseswith altitude from the TTL to the strato-sphere. The methane contribution to theincrease of δD was discussed and the δDvalue overhead of the TTL was estimat-ed.

Role of UT/LS Water Vapour in Climate

A dominant component of climate sensi-tivity is the size of the water vapour feed-back; the change in water vapour con-centrations in response to increasedgreenhouse gases, and the associatedradiative impact. However, understand-ing the water vapour feedback in thetropical troposphere is limited by ourunderstanding of what processes drivechanges in tropical water vapour concen-trations. Sources and sinks of watervapour are complex; the tropical tropo-sphere is moistened by detrainment ofnear saturated air and by evaporationfrom falling precipitation. Water vapourconcentrations are reduced, locally,mainly by downward advection of drierair from higher levels. A further compli-cation is that the budgets of mass and

water vapour are strongly coupled in thetropics, since most upward motion arisesfrom condensation, while downwardmotion arises from radiative and evapo-rative cooling.

Coupling of the mass and water vapourbudgets can be used to put constraints onthe sources and sinks of water vapour.For example, in the mid-troposphere (5-10 km), it can be shown that the majorsource of water vapour is evaporation offalling ice. This evaporation also drives adownward descent that must be offset byvertical motions occurring within cloudsand by clear sky subsidence. I. Folkinsshowed that, in a tropical mean model,the enforcement of vertical mass flux bal-ance gives rise to a constraint on thetropical mean relative humidity profilein this height interval which is wellobeyed in the current atmosphere.

Y. Tsushima presented changes inUT/LS water vapour and clouds mod-elled by the CCSR/NIES GCM 5.7bunder global warming scenarios, withdifferent climate sensitivities and differ-ent treatment of the temperaturedependency of the phase of cloud andfall speed of melted cloud ice. The tem-perature changes in 2 x CO2 experimentsranged from 4.0 K in the low sensitivitymodel to 6.4 K in the high sensitivitymodel. In the control climate, both ver-sions showed much higher concentra-tions of water vapour and clouds in theupper troposphere than expected fromobservations. In the low sensitivitymodel, the fraction of high thin cloud islarger and high thick cloud is smallerthan in the high sensitivity model.

The equilibrium states of the control runand the 2 x CO2 run show decreases inthe upper tropospheric water vapour inboth models, leading to a significantdecrease in high cloud, although thischange is much more significant in thehigh sensitivity model. The role of highclouds in the radiation budget of theearth-atmosphere system depends onoptical depth; high thin cloud acts towarm the atmosphere, while high thickcloud cools. Thus, the decrease in highclouds can reduce both the warming andcooling effect to the system. In these par-ticular experiments, the reduction ofcooling seems to dominate and strength-en the magnitude of the warming, with amore significant response in the highsensitivity model. For further discus-sion, evaluation of the distribution ofcloud and water vapour in the upper tro-posphere in the current climate, usingthe observational data, is necessary.

24

Hypotheses on theDehydration Mechanism

in TTL

A. Gettelman and C. Webster highlight-ed some recent work using water vapourisotopes to understand dehydration inthe TTL. The process of fractionation ofheavier isotopes of water (HDO), due totheir lower vapour pressures and prefer-ential partitioning into condensed phas-es, is temperature dependent. Lifting aparcel from the surface and removing thecondensed phase water (a so-calledRayleigh curve) results in a loss of up to95% of HDO relative to the surface abun-dance, however observations indicatethe stratosphere is only about 65%depleted in HDO. Recent observationsindicate significant variability in the TTLbelow the tropopause, with values intotal water (including ice) of no deple-tion (0%) to 95% depletion (Webster andHeymsfield, 2003).

An analytical microphysical model wasdescribed which calculates water vapourand condensate along a trajectory,accounting for condensation, evapora-tion and sedimentation of ice, and frac-tionation of water isotopes. The model isable to reproduce observations of HDOin the TTL, with a similar range of vari-ability. Depletion due to individual con-vective events, and in situ cirrus forma-tion are well captured. Isotopic observa-tions and the model are consistent with(1) convective transport and mixing upto the level of main convective outflow,(2) mixing of air with ice detrained fromconvection (the evaporation of convec-tive anvils) and (3) slow ascent undersupersaturated conditions into the stra-tosphere, with the final dehydrationoccurring in cirrus clouds. Climatologic-al experiments with the same model andensembles of back trajectories indicatethat more depletion is expected aroundregions of deep convection, such as theWestern Pacific.

Observations ofDehydration Processes

Vertical profiles of ozone and watervapour obtained by radiosondes at sta-tions in the tropical Pacific have shedlight on the role of vertically propagatingatmospheric waves in the dehydrationprocesses taking place in the TTL(Hasebe et al., 2001, Fujiwara et al., 2001).On the other hand, the idea emphasizingthe role of horizontal advection as a keyprocess in determining the water vapourconcentration in the stratosphere (Holtonand Gettelman, 2001) is becoming wide-

ly accepted (Randel et al., 2001,Hatsushika and Yamazaki, 2003, Eguchiand Shiotani, 2004).

To enable us to identify the mechanismdetermining the long-term trend ofstratospheric water vapour, it is neces-sary to quantify the contribution of eachprocess. The Lagrangian descriptionfrom the modification of the air quality ismade possible by the introduction of the"match" method. This method has prov-en effective in describing the ozone lossin the polar vortex (Rex et al., 1998), andmany questions can be answered byapplying it to the dehydration in theTTL.

F. Hasebe and the SOWER Team pre-sented calculations of air trajectories inthe TTL in northern winter, which showdependence on the phase of the El Niñoas shown in Figure 3 (p IV), which illus-trates those of possible "match" pairsbeing caught by existing stations for thecases of December 1998 (non-El Niño)and 1997 (El Niño). The first trial ofwater vapour "match" is being plannedfor the northern winters of 2004-2005 and2005-2006, with the aid of these analyses.Preliminary analysis of data taken dur-ing the December 2003 campaign atBandung and Tarawa (Kiribati) indicatessome dependence of water vapour con-centration of the air parcels on their tem-perature history during horizontaladvection.

M. Niwano presented a study examiningthe global occurrence of cirrus cloudsand dehydration in the TTL in terms ofshort term variation, based on upper tro-pospheric data from HALOE andSingapore rawinsondes.

HALOE data for the period of January1993 exhibits the global occurrence oftenuous cloud (TC) and its sedimenta-tion, which is synchronized with down-ward- and eastward-propagating coldanomalies of the equatorial Kelvin wavecoupled to the Madden-JulianOscillation (MJO) convection. To the eastof the MJO, TCs occur up to the 100 hPalevel through adiabatic cooling due tolarge scale upward motion of the MJO-coupled Kelvin wave. To the west of theMJO, TCs are spread by downward andwestward motions of the MJO-coupledKelvin wave, and disappear due to sedi-mentation and evaporation. Apart fromthe MJO convection, a layered TCappears over Singapore with a thicknessof ~2 km and a fall speed of about 10µm,which can be accounted for by sedimen-tation of cloud particles with a radius of10 µm. On a global scale, the occurrence,

transport, and sedimentation of TCs arecontrolled by the MJO-coupled equatori-al Kelvin wave, which is inseparablefrom spreading from anvil and large-scale upwelling.

S. Iwasaki presented observations ofsubvisual cirrus clouds (SVC) using a1064 nm lidar, a 95 GHz cloud radar andradiosondes launched every 3 hours, at2°N, 138°E for a period of one month(Iwasaki et al., 2004). The observed sedi-mentation rate of SVCs was 3 cm/s, thesame as the theoretical terminal velocityof ice crystals, and the average effectiveradius was estimated to be 10 µm. Theresult shows that sedimentation isimportant for dissipation of SVC.Moreover, the SVCs did not appear tocorrespond to negative temperatureanomalies as expected, but rather theydissipated corresponding to positivetemperature anomalies, ∆T>1.5°C, sug-gesting that the relative humidity isimportant to their formation as discussedby Jensen et al. (2001).

Modelling of StratosphericWater Vapour and

Dehydration Processes

H. Hatsushika and K. Yamazaki pre-sented a modelling study of the strato-spheric drain over Indonesia and dehy-dration within the TTL using air parceltrajectories to diagnose results from anatmospheric general circulation model(AGCM). The AGCM has strongupward motions in the lower part of theTTL over the maritime continent and thewestern tropical Pacific, correspondingto the stratospheric fountain region, anddownward motions in the upper part ofthe TTL over Indonesia, representing thestratospheric drain. In the TTL, strongeasterlies prevail, and the cold ascentregion tilts eastward. Upward motionover areas of deep convection is sup-pressed by longwave cooling.

Tropospheric air parcels are advectedupward to the bottom of the TTL mainlyfrom the stratospheric fountain region. Apair of anticyclonic circulations in thetropical western Pacific entrains airparcels, which then pass through theequatorial cold region during the slowascent in the TTL. This slow spirallyascending motion brings about lowhumidity in the stratosphere, despite thelocal downward motion over Indonesia.In addition, transient disturbances, par-ticularly low-frequency disturbancessuch as Kelvin waves and the MJO (Moteet al., 2000), produce intermittent upwardmotions over the fountain region, result-

25

ing in effective dehydration of the air.The spiral ascent and transient mecha-nisms are key factors in the dehydrationprocess in the TTL.

It is also found that air in the tropicallower stratosphere is more dehydratedin La Niña years, than in El Niño years.

Acknowledgements

We are grateful to M. Agama and themembers of the Aerological Station atSan Cristóbal for their help in organizingsuch a stimulating meeting, and to ElParque Nacional Galápagos for provid-ing the meeting facility. This meetingwas partially supported by the Grant-in-Aid for Scientific Research by JSPS, theGlobal Environmental Research Fundfrom the Japanese Ministry of theEnvironment, Kyoto University ActiveGeosphere Investigations for the 21st

Century COE Programme, and theDispatch of Researchers OverseasProgramme by MEXT of Japan.

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Fortuin, J. P. F., et al., Inertial instabilityflow in the troposphere over Suriname dur-ing the South American monsoon. Geophys.Res. Lett., 30 (9), 1482, doi:10.1029/2002GL016754, 2003.

Fujiwara, M., et al., Water vapour control atthe tropopause by equatorial Kelvin wavesobserved over the Galapagos. Geophys. Res.Lett., 28, 3143 3146, 2001.

Fujiwara, M., et al., Performance of theMeteolabor “Snow White” chilled-mirrorhygrometer in the tropical troposphere:Comparisons with the Vaisala RS80 A/H-Humicap sensors. J. Atmos. OceanicTechnol., 20, 1534–1542, 2003a.

Fujiwara, M., et al., Upper-troposphericinversion and easterly jet in the tropics. J.Geophys. Res., 108, 2796, doi:10.1029/2003JD003928, 2003b.

Hasebe, F., et al., SOWER/Pacific is to bestarted on a campaign basis. SPARCNewsletter N°10, 32, 1998.

Hasebe, F., et al., Initial results fromSOWER/Pacific 1998-2000 campaigns.Proceedings of the 2nd SPARC GeneralAssembly, CD-Rom 1, 2001.

Hatsushika, H., and Yamazaki, K.,Stratospheric drain over Indonesia anddehydration within the tropical tropopauselayer diagnosed by air parcel trajectories. J.Geophys. Res., 108, doi:10.1029/2002JD002986, 2003.

Holton, J. R., and Gettelman, A.,Horizontal transport and the dehydrationof the stratosphere. Geophys. Res. Lett., 28,2799–2802, 2001.

Iwasaki, S., et al., Subvisual cirrus cloudobservations using a 1064-nm lidar, a 95GHz cloud radar, and radiosondes in thewarm pool region. Geophys. Res. Lett., 31,L09103, doi:10.1029/2003GL019377, 2004.

Jensen, E. J., et al., A conceptual model ofthe dehydration of air due to freeze-dryingby optically thin, laminar cirrus risingslowly across the tropical tropopause. J.Geophys. Res., 106, 17237–17252, 2001.

Kley, D., et al., SPARC Assessement ofUpper Tropospheric and StratosphericWater Vapour, WCRP 113, WMO/TD-No.1043, 0, SPARC Report No. 2, 2000.

Mote, P. W., et al., Intraseasonal variationsof water vapour in the tropical upper tro-posphere and tropopause region. J.Geophys. Res., 105(D13), 17457–17470,10.1029/2000JD900158, 2000.

Randel, W. J., et al., Seasonal variation ofwater vapour in the lower stratosphereobserved in halogen occultation experi-ment data. J. Geophys. Res., 106,14313–14325, 2001.

Randel, W. J., et al., Interannual changes ofstratospheric water vapour and correla-tions with tropical tropopause tempera-tures. J. Atmos. Sci., 61, 2133–2148, 2004.

Rex, M., et al., In situ measurements ofstratospheric ozone depletion rates in theArctic winter 1991/1992: a Lagrangianapproach. J. Geophys. Res., 103, 5843–5854,1998.

Ridal, M., and Siskind, D. E., A two-dimen-sional simulation of the isotopic composi-tion of water vapor and methane in theupper atmosphere, J. Geophys. Res.,107(D24), 2002JD002215, 2002.

Seidel, D., et al., Climatological characteris-tics of the tropical tropopause as revealedby radiosondes. J. Geophys. Res., 106,7857–7878, 2001.

SOWER Project Team, SOWER Proposal,Workshop Report, Earth Science andTechnology Organization, 97POA1-D007,61 pp, 1998. http://wwwoa.ees.hokudai.ac.jp/people/f-hasebe/SOWER/Report.pdf

Vömel, H., et al., The behaviour of the“Snow White” chilled-mirror hygrometerin extremely dry conditions. J. Atmos.Oceanic Technol., 20, 1560–1567, 2003.

Wang, P. H., et al., A 6-year climatology ofcloud occurrence frequency fromStratospheric Aerosol and Gas ExperimentII observations (1985-1990). J. Geophys. Res.,101, 29407–29429, 1996.

Wang, J., et al., Performance of operationalradiosonde humidity sensors in direct com-parison with a chilled mirror dew-pointhygrometer and its climate implication.Geophys. Res. Lett., 30, 1860,10.1029/2003GL016985, 2003.

Webster, C. R., and Heymsfield, A. J. ,Water isotope ratios d/h, 18o/16o,17o/16o in and out of clouds map dehy-dration pathways. Science, 302, 1742–1745,2003

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•

Figure 1. Time series of the monthly mean temperatures (°C) at 30 hPa over the North Pole inMarch, 1956 to 2004. Linear trends are given for three different periods: 1956-1979, 1979-2004and 1956-2004 (Labitzke and van Loon, 1999, updated). Data: Free University Berlin (FUB)(open dots), ECMXF (full dots).

The Lower Arctic Stratosphere in Winter since 1952: an Update

KKaarriinn LLaabbiittzzkkee, Freie Universität Berlin, Germany (labitzke@strat01.met.fu-berlin.de)BBaarrbbaarraa NNaauujjookkaat, Freie Universität Berlin, GermanyMMaarrkkuuss KKuunnzzee, Freie Universität Berlin, Germany

Four years ago we published a tablewith monthly mean temperatures

(ºC) at 30 hPa over the North Pole([Labitzke and Naujokat, 2000], hereafterLN). These data started with the winter1955/56, i.e. 45 winters were available.One point of interest in the paper wasthe fact that there was a period of 7 win-ters without Major Warmings: NorthernHemisphere winter 1991/92 to 1997/1998. We pointed out that during lowsolar activity the winters in the westphase of the Quasi-Biennial Oscillation(QBO) tended to be cold and stable(Labitzke and van Loon, 2000) and thiscombination existed during 4 out of the7 winters.

Here, we would like to give a follow upon the North Pole temperatures and onthe characteristics of the last four Arcticwinters by supplementing Table 1 of LN.After the extremely cold winter of1999/2000 (LN), we observed four high-ly disturbed winters with a total of fiveMajor Warmings (Table 1). Two of therecent winters belong to the winters inthe west phase of the QBO and high solaractivity, and they are expected to be con-nected with Major Warmings.

Particularly interesting was the winter of2001/2002 when two Major Warmingsoccurred in December and in February(Naujokat et al., 2000). This has beenobserved only once before, during thewinter of 1998/99.

Compared with our earlier results (Table 1 in LN) the overall trend has notchanged much during early and mid-winter. The trend over the Arctic lowerstratosphere is clearly negative inNovember and practically zero fromDecember till February.

Major Midwinter Warmings are connect-ed with the breakdown of the polar vor-tex, much reduced activity of planetarywaves, and weak transport of energy.This leads often in late winter to the re-establishment of a persistent cold polarvortex and to the so-called late wintercooling, which is clearly visible in theArctic temperatures during March andApril, especially in the 2003/04 winter

Table 1. RJ is the monthly mean of the sunspot numbers in January; in the column marked QBOthe phase of the QBO is given (determined using the equatorial winds between 50 and 40 hPa inJanuary-February); FW gives an indication of the timing of the Final Warmings which are thetransitions from the winter to the summer circulation. CW stands for Canadian Warmings and *indicates the occurrence of a Major Mid-Winter Warming. The long-term mean and the standarddeviation are based on the period 1955/56 to 2003/04. The values of the linear trend are for the fulldata set, n=49 years. C stands for a cold monthly mean (about half a standard deviation or morebelow the long term average; see discussion in LN). [Data: Free University Berlin (FUB) until2000/01, ECMWF afterwards]

27

Labitzke, K. and B. Naujokat, The lower arcticstratosphere in winter since 1952. SPARCNewsletter, 15, 11-14, 2000.

Labitzke, K. and M. Kunze, Stratospheric tem-peratures over the Arctic: Comparison ofthree data sets. Submitted to Meteorolog.Zeitschrift, 2004.

Naujokat, B., et al., 2002: The early majorwarming in December 2001—exceptional?.Geophys. Res. Lett., 29 (21), 2023,doi:10.1029/2002GL015316, 2

The Earth’s Protective Ozone Layer still Remains Vulnerable

Report on the Quadrennial Symposium on Atmospheric Ozone, Kos, Greece, 1-8 June 2004

CChhrriissttooss SS.. ZZeerreeffoos, University of Athens, Greece (zerefos@geol.uoa.gr)

The XX Quadrennial Symposium onAtmospheric Ozone coincided with the20th anniversary of the discovery of thespringtime Antarctic ozone hole. It alsomarked two decades of intensified glob-al atmospheric monitoring, and basicresearch in atmospheric chemistry andphysics. The progress in our understand-ing of the impact of human activities onthe chemistry and physics of the globalstratosphere since the previous Qua-drennial Ozone Symposium was pre-sented among the 690 research papers atthe XX Quadrennial Ozone Symposium,which was attended by 450 scientistsfrom 60 countries. For the papers pre-sented and the proceedings of theSymposium see http://www.QOS2004.gr.

Among the important topics discussed atthe Symposium were recent research onpossible ozone recovery, results from anexpanded network of satellites andground-based stations, ozone-climateinteractions, modelling and chemistry,results from monitoring of the globalcomposition of the troposphere fromsatellites, and measurements of UV-Bsolar radiation reaching ground level,among others.

Evidence was presented that ozone inthe past few years has been a little high-er than expected from earlier projectionsbased on sensitivity of ozone to influ-ences of aerosols, halogen compoundsand the solar cycle. The data may indi-

cate the beginning of a recovery; an issuethat is complicated by a number of fac-tors among which is the prominent roleplayed by changes in meteorology,greenhouse gases and in the radiationbalance, not excluding the observedrecovery of the ozone layer from its per-turbation by the volcanic eruption ofPinatubo in the early 90s. The evaluationof future ozone recovery in a changingclimate and the effect of ozone on thatclimate has shown the importance offeedback mechanisms between watervapour content and a warmer planet.

The need for the continuation of well-cal-ibrated instruments and measurementswas discussed extensively, and emphasiswas given to the use of satellite andground-based data (e.g. NDSC and theGlobal Ozone Observing System) to eval-uate models and ozone loss, and itsexpected recovery.

Numerous chemistry/climate modelswere presented at the conference. Theyaddressed the problem of how changesin meteorology or climate interact withchanges in the chemistry of ozone. Oneproblem is how changes in meteorologyover the last 25 years may have con-tributed to observed ozone changes andfeedback mechanisms. Models can thenbe used to extrapolate that knowledge towhat may happen in the future with theexpected increase in methane, nitrousoxide, and carbon dioxide.

Significant new work that combinessatellite and in situ observations withmodel calculations was presented at theSymposium, providing an insight intothe budget of nitrogen oxides and arange of halogen species, which areindispensable to our understanding ofthe global carbon and hydrologicalcycles. Water vapour presents a particu-larly important challenge. Satellite datashown at the meeting is not consistentwith trends from previous ground-baseddata. Understanding the feedback mech-anism between water vapour content,ozone, and polar stratospheric clouds iscritical to the evaluation of predictions ofozone in a future warmer global atmo-sphere.

Important progress was made in moni-toring the tropospheric ozone budgetwith the development of new observa-tional techniques from satellites, com-bined with models of tropospheric com-position. It turns out that the key factorsinfluencing the tropospheric ozonebudget (precursors, long-range transportin the troposphere and intrusions fromthe stratosphere) make the determina-tion and attribution of troposphericozone trends difficult.

Long-range transport of troposphericpollution and its coupling to climate wastargeted in a number of studies using cli-mate/chemistry models. Other studieshave shown the importance of long-

28

(Table 1). In all four winters the FinalWarmings were late.

Figure 1 shows the time series of the 30 hPa North Pole temperatures (ºC) forMarch, an update of Figure 1 in LN. Theoverall trend for 49 years is weakly neg-ative, but depending on how one dividesthe data, the trend can be positive, as inthe first half of the data set or negative, asin the second half of the data. The changein the sign of the trend between the twodifferent periods is, however, confirmedby the re-analyses of NCEP/NCAR andby the ECMWF-ERA-40 data (Labitzkeand Kunze, submitted).

Acknowledgements

FU-Berlin: http://strat-www.met.fu-berlin.de/products/cdromNCEP/NCAR: http://wesley.wwb.noaa.gov/reanalysis.htmlERA40: http://www.ecmwf.int/research/era

RReeffeerreenncceess

Labitzke, K. and H. van Loon, The Strato-sphere: Phenomena, History, and Relevance.New York: Springer, Berlin Heidelberg, 1999.

Labitzke, K. and H. van Loon, The QBO effecton the global stratosphere in northern winter.J. Atmos. Sol. Terrest. Phys., 62, 621-628, 2000. •

Summary of the COSPAR 2004 - Session A1.1 PPaarriiss,, FFrraannccee,, 2200--2255 JJuullyy 22000044

John P. Burrows, University of Bremen, Germany (burrows@iup.physik.uni-bremen.de)

range transport of pollutants to maintainregionally high background levels of tro-pospheric ozone. For example, NASAsatellites and balloons reveal that season-al episodes of high ozone over the southAtlantic begin with pollution sourcesoriginating thousands of miles away.

Future UV-B levels for 2000-2019 are pre-dicted to decrease in all seasons but thetrends are typically not statistically sig-nificant, except during spring over bothhemispheres. UV-B trends are causedmainly by total ozone trends because inthe future cloud, changes are predictedto be small in the coupled chemistry cli-mate models used in these results.Nonetheless, there is a region over west-

ern Europe which is predicted to showan increase in UV-B due primarily to adecrease in cloudiness. The complexityof interference of cloud and other physi-cal parameters in influencing UV-B lev-els at ground level was targeted in sever-al papers.

The main conclusion drawn from theindividual oral and poster presentationsof the Symposium is that the detection ofozone recovery requires patience. Westill have a long way to go to understandthe complex system of interactionsbetween ozone and a globally changingenvironment. The best tool we have atpresent is the continuation of qualityobservations of global coverage both

from the ground and space. UV-B levelsin the coming decade are predicted todecrease for all seasons except duringspring over high latitudes of both hemi-spheres.

Acknowledgements

The author is indebted to P.J. Crutzen, R.Stolarski, I. Isaksen, S. Godin, H.Kelder, A. Matthews, T. McElroy andseveral of the conveners of theSymposium for fruitful discussions onthe outcome of the Symposium.

The system comprising the sun, theatmosphere and the earth is complex,having many non-linear feedbacks.During the past three decades the role ofanthropogenic activity has becomeincreasingly recognised as being one ofthe most important sources of changingemissions to the atmosphere. Under-standing the behaviour of the Sun-Atmosphere-Earth system requires adetailed understanding of the physical,biological and chemical processes, whichdetermine its nature and behaviour. Bothnatural phenomena and anthropogenicactivity result in changing atmosphericcomposition, which impacts on theEarth’s radiation balance and its chem-istry. Knowledge of the distribution ofatmospheric constituents and parametersis required to test and improve ourunderstanding of the Sun-Atmosphere-Earth system, whose conditions areessential to the maintenance of life onearth.

Session A1.1, "Atmospheric RemoteSensing: Earth’s Surface, Troposphere,Stratosphere and Mesosphere”, ofCOSPAR 35 Scientific Assemblyaddressed our current ability and futurepotential to objectively measure atmo-spheric parameters of relevance toatmospheric chemistry, global climatechange and numerical weather predic-tion. The focus of the session was remotesensing from space but in additionground based, aircraft and balloon bornemeasurements also featured prominent-ly. This is a relatively young research

area and is being driven by the need tounderstand the changing composition ofthe Earth’s atmosphere and its conse-quences for global climate change.

As part of the evolution of the needs ofCOSPAR, following the HoustonCOSPAR 34 Assembly in 2002, Commit-tee A overhauled the structure of its ses-sions. In this context Session A1.1 wasdesigned to be one continuous sessionrunning throughout COSPAR 35 on top-ics of relevance to the remote sensing ofthe atmosphere and the Earth’s surface.This approach amalgamated sessions,which at previous COSPAR ScientificAssemblies had been independent fromone another, and focused on differentsubregions of the earth-atmosphere sys-tem. The new structure enabled atten-dees researching the different regions ofthe atmosphere to obtain a holistic viewof current research throughout thismulti-disciplinary area. In particular, thereporting of research in the overlap areasbetween different regions of the atmo-sphere, such as the planetary boundarylayer, the tropopause, the stratopauseand the mesopause, which in the pasthave often fallen between different ses-sions, benefited from this new approach.

Session A1.1 was comprised of sub-ses-sions that were dedicated to the follow-ing topics: a) Troposphere: Surface andAerosol - Parts I and II; b) Troposphere:Cloud and Weather; c) Troposphere: TraceGases, d) Stratosphere, e) Mesosphere, and f) Instruments and Missions.

During the first four and half days, con-tributions were primarily about currentspace missions and the exploitation ofthe existing data, and the developmentof new techniques. The final day wasfocused on the development of and theplanning for new missions by the agen-cies. In addition to the A1.1 Session it-self, one of the A1.1 community (P. J. Crutzen) gave an invited interdisci-plinary lecture on "ENVISAT: firstresults" and the A1.1 community partici-pated in the relevant panel events.

Session A1.1 was comprised of approxi-mately 220 contributions with roughly 50 %, being given as oral presentationsand about 50 % in the complimentaryposter session. The posters were hungfor the entire week and individualposters were highlighted in the relevantsub-session. The attendees welcomedthis approach to the A1.1 Poster Sessions.The attendance at each of the sessionswas typically about 60 to 70 people, withover 200 COSPAR associates taking partover the week.

The session was opened with introducto-ry remarks by J. P. Burrows and P. Schluessel. The members of the pro-gramme committee for Session A1.1, the COSPAR 35 Local OrganisingCommittee and the Overall ProgrammeCommittee were explicitly thanked fortheir support. The duration and wideranging nature of the A1.1 Session result-ed in additional work for these commit-tees, compared with that required at

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previous COSPAR Scientific Assemblies.

The session started with the remote sens-ing of the troposphere. The first sub-ses-sion was devoted to aerosol and surface.Both active and passive remote sensingtechniques were described. Results fromsuccessful ground based, airborne andspace based LIDAR experiments werepresented and discussed e.g. LITE, GLASand the forthcoming Calypso andCloudSat missions. Retrieval of aerosolparameters from the measurements ofAVHRR datasets from various platformsprovides a long data set of information.Aerosol retrieval from passive remotesensing over the ocean is less difficultthan over land. However, significantprogress has been made, with the deriva-tion of aerosol parameters over land sur-face now becoming feasible fromalgorithms applied to the data measuredby the sensors POLDER, ATSR-1, -2,AATSR, MODIS, MISR, MERIS, SeaWifs,and TOMS. The surface spectralreflectance and its applications were alsodiscussed in this part of the meeting.

The sub-session Troposphere: Cloud andWeather addressed remote sensing of rel-evance to the hydrological cycle andweather prediction. A wide range of pre-sentations described passive and activeremote sensing by means of microwave,infrared and visible/ultraviolet spec-troscopy; both absorption and scatteringbeing the source of information aboutcloud parameters and water vapour dis-tributions. Algorithms, exploiting the O2absorption bands in back-scattered solarradiation, and infrared emission, for theretrieval of cloud parameters weredescribed. These offer many potentialadvantages for improving our under-standing of clouds and improving thepredictive capability of models.Measurements of water vapour in thetropopause region, which are of greatsignificance for understanding strato-sphere-troposphere exchange, werereported from aircraft measurements.There were also several contributionsabout the observation of cirrus and sub-visible clouds.

The detection of trace gases in the tropo-sphere has been an area of growth in thelast 10 years. The sub-session Tropo-sphere: Trace Gases focused on this topic.The results of retrieval studies using datafrom the nadir looking sensors MOPITTon NASA TERRA, GOME-1 on ERS-2and SCIAMACHY on ENVISAT wereprominent. In addition, presentations onthe retrieval of limb sounding instru-mentation to probe the upper tropo-sphere presented interesting new results.Considerable progress has been made onthe retrieval of trace gases of relevance toair quality such as CO2, CO, NO2, and

formaldehyde, HCHO. The advantagesof the different approaches to retrievewater vapour were also discussed.Inversion of back-scattered solar radia-tion has been shown to yield tropospheric water vapour columns overland.

The retrieval of tropospheric con-stituents remains an area of growth forthe research community. The retrievalpossibilities for tropospheric con-stituents by means of UV and visiblespectroscopy with the current generationof instruments have made considerableprogress, and these data have beenexploited in a variety of interesting ways.Observations of solar near infrared (NIR)and short wave infrared (SWIR) spectralregions are being exploited for the firsttime. In this context, SCIAMACHY datais yielding the distributions of the atmo-spheric columns of greenhouse gases(GHGs), CO2 and CH4 , from space. Thisis a first step of limited accuracy in theassessment of the sources of GHGs,which the NASA OCO instrumentintends to improve upon for CO2.

The capabilities of the sensors aboard theNASA Aura satellite, which was success-fully launched the week before COSPAR,were also presented in both the tropo-spheric and stratospheric sub-sessions.In the stratospheric session, there was anoverview of the first 25 years of theNASA TOMS measurements. Thisinstrument along with the BUV instru-ments have not only provided a uniqueview of global ozone, and the develop-ment of the ozone hole, but also provid-ed measurements of sulphur dioxide,SO2 from volcanoes, and the ultravioletabsorbing aerosol. Similarly, anoverview of sounding the atmospherefrom balloons was a highlight of this ses-sion. Both TOMS and the balloon meas-urements have been two of the mostproductive sources of information aboutthe stratosphere in the last 25 years.

The discussion of the results from theENVISAT sensors MIPAS, GOMOS andSCIAMACHY and the ODIN sensorsOSIRIS and the microwave limb sounder(MLS) dominated a large part of thestratospheric sub-session. The firstresults were shown from the CanadianSCISAT mission, which has two solaroccultation instruments on it, an ACEand MAESTRO. Exciting results from thelong duration mission SAGE-II and thenew SAGE-III were discussed. Calibra-tion and validation of the sensors wasdiscussed and results presented. Themeasurements of stratospheric con-stituents during the anomalous warmingof the stratospheric vortex above theAntarctic in spring of 2002 were also dis-cussed. The ENVISAT data have provided

some unique insight into this surprisingstratospheric event. Interesting newresults have been obtained about thedevelopment of polar stratosphericclouds, and their role in the catalyticdecomposition of stratospheric ozone.

The session about the mesosphere wasdominated by results from ENVISAT,ODIN, and SABER. The observations ofmesospheric OH and polar mesosphericor noctilucent clouds and the determina-tion of mesospheric temperature werehighlights. The measurements of theinstruments during the Solar ProtonEvents of October and November 2003have provided some unique insight intothe interaction between the eruptionsfrom the sun and their impact on themesosphere and stratosphere. The cur-rent missions observing the mesosphereand above are providing a wealth of newinformation about these regions withinthe Sun-Atmosphere-Earth System.

The final day of the meeting was dedicat-ed to the plans of the agencies for futuremissions of relevance to this community.Unfortunately, the future after ENVISATand Aura for atmospheric chemistryresearch from instrumentation on space-based platforms is unclear. However, theoperational satellites from EUMETSATand the NPOESS system will providesome valuable data. The further develop-ments of the NASA OCO, which aims toextend and enhance the measurement ofCO2 from space by using the NIR andSWIR absorption bands of CO2 was dis-cussed. Of interest were the studies ofinstrumentation and the potential bene-fits for tropospheric research and appli-cations of passive observations fromgeostationary orbit. Teams in Europe,America and Japan presented their con-cepts. New concepts for instrumentationfrom LEO were also presented. Whetherfrom GEO or LEO, researchers haverecognised the need for synergistic use ofdifferent spectral regions to probe tro-pospheric composition.

The session closed with thanks to all theparticipants, who had made this a mem-orable meeting. The future of theresearch of the Sun-Atmosphere-EarthSystem depends on the continued effortsof this community, which would not bepossible without support from the spaceagencies and their governments.

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P rof. Thomas M.Donahue, The

Edward H. WhiteII DistinguishedUniversity Profes-sor Emeritus ofPlanetary Scienceat the University ofMichigan, diedOctober 16, 2004.

Tom was a pioneer in advocating satel-lites and spacecrafts to explore andunderstand the atmospheres of Earthand other planets in the solar system.We are indebted to Tom for making thesatellite and space shuttle measurementsof atmospheric constituents possible inthose early uncertain days through histireless work and dedication. But for hisefforts, the data on the Earth's atmo-

sphere that we use in the SPARC com-munity would have been much sparser.

Tom was deeply involved in the issue ofanthropogenic destruction of strato-spheric ozone in the early 1970s. Hisinterest in stratospheric ozone changesnaturally gravitated him towards GlobalChanges and climate. These issues stillare at the heart of SPARC activities.

Tom Donahue really understood thepower and need for atmospheric chem-istry in solving issues, be it Earth’satmosphere or that of another planet.Even till his last days, he was thinkingabout the isotope enrichment in variousplanets and how it could be detectedand used for interpreting the workingsof those atmospheres.

Tom not only provided scientific know-ledge to the community but also leader-ship. His quick mind and vastknowledge always allowed him to criti-cally evaluate any hypotheses and knowwhat is feasible and what is not, what isgood science and what is not.

We are sure that other scientists in plan-etary science will have similar things tosay about Tom from their perspective.We in the SPARC community are happythat Tom was interested in the Earth’satmosphere. We will miss him greatly,but are grateful for the rich legacy he leftbehind.

A. R. Ravishankara

In Memory of Thomas M. Donahue

TTeerrmmiinnaattiioonn ooff tthhee SSTTRRAATTAALLEERRTT RReeppoorrttss

KKaarriinn LLaabbiittzzkkee, Freie Universität Berlin, Germany (labitzke@strat01.met.fu-berlin.de)

In the 1960s the stratospheric midwinter warmings were regarded as an exciting and interesting research problem. Theobservations taken during a warming were scarce but in great demand, and a much desired aim was to launch meteorologi-cal rockets when a warming was developing above a station. For this purpose an advisory system was necessary, such as hadbeen established in the international geophysical community for other phenomena (GEOALERT). Charged by the WorldMeteorological Organization (WMO), the Stratospheric Research Group of the Freie Universität in Berlin (Germany) gottogether with their colleagues of the American Weather Bureau and developed a warning system, which was namedSTRATALERT. It was introduced in 1964 when the IQSY (International Year of the Quiet Sun) began.

The Berlin group was at first responsible for the European space, and later for the whole Northern Hemisphere. It issued aSTRATALERT report every day during winter, and a GEOALERT when needed. The alerts were disseminated through theGerman Weather Service's international net and reached all interested parties. The STRATALERT reports were an essentialsource of information about what was going on in the stratosphere; information which at that time would not otherwise havebeen available to many scientists interested in current conditions. Because of this information it was possible to time experi-ments, for instance, with meteorological rockets, to take place under desired conditions, and local observations could beassimilated and interpreted on the background of a wider field. This information system has served as a basis for decisionsmade in many large-scale field experiments.

A review and classification of stratospheric warmings can be found in SPARC Newsletter No. 15, Labitzke and Naujokat, 2000(http://www.atmosp.physics.utoronto.ca/SPARC/News15/15_Labitzke.html).

The 2003/2004 winter was the last year for STRATALERT. After 41 years we are sorry to announce that we cannot continuethis timely warning system in its old format and we could not find a successor. However, those interested in the daily devel-opment of the stratospheric circulation can find analyses and different stratospheric parameters based on the ECMWF-dataon the FUB web site. (http://strat-www.met.fu-berlin.de/winterdiagnostics). The general evaluation is, however, left to theuser.

Additional available data links are (amongst others):

US National Centers for Environmental Prediction (CPC/NCEP):http://www.cpc.ncep.noaa.gov/products/stratosphere/index.html. Japan Meteorological Agency (JMA): http://okdk.kishou.go.jp/products/clisys/STRAT/index.html

AAnnnnoouunncceemmeenntt

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200518-22 April: 4th WMO International Symposium on Assimilation of Observations in Meteorology and Oceanography, Prague,

Czech Republic (http://www.chmi.cz/dasympos/index.html). Co-chairs: R. Brozkova (radmila.brozkova@chmi.cz), M. Zak (michal.zak@chmi.cz,)

24-29 April: EGU General Assemby, Vienna, Austria (http://www.copernicus.org/EGU/ga/egu05/index.htm)AS0: Open Session on the Lower, Middle, and Upper Atmosphere - Convener: M. JukesAS1.08: Clouds, Aerosols and Radiation - Convener: U. LohmannAS1.10: Solar UV - Convener: P. WeihsAS3.01: Past and Future Changes in Mid-Latitude Ozone - Convener: S. Godin-BeekmannAS3.05: Polar Ozone - Convener: G. BraathenAS3.07: UT/LS Dynamics and Chemistry - Convener: J.P. PommereauAS4.01: Dynamics of the Middle Atmosphere - Convener: M. Juckes

07-13 May: Global Chemistry for Climate (GCC) Project Summer School on "Hierarchy of Models", Banff, Alberta, Canada (http://www.atmosp.physics.utoronto.ca/MAM/summerschool05.html).

09-14 May: SCOSTEP 11th International Symposium on Equatorial Aeronomy, Taipei, Taiwan, China(http://csrsddc.csrsr.ncu.edu.tw/isea-11.html)

23-27 May: AGU Spring Meeting, New Orleans, Louisianna, USA (http://www.agu.org/meetings)

23 May-03 June Seasonal to Interannual Climate Variability: its Prediction and Impact on Society, Gallipoli, Italy(http://www.ecmwf.int/staff/alberto_troccoli/nato_asi/index.htm

13-17 June: Joint AMS Conference on the Middle Atmosphere and Atmospheric and Oceanic Fluid Dynamics, Cambridge,Massachussett , USA (http://www.ametsoc.org/meet/anncall.html)- 17th Conference on Climate Variability and Change, Cambridge, Mass, USA

20-24 June: 5th International Scientific Conference on the Global Energy and Water Cycle Experiment, Orange County, CA, USA (http://www.gewex.org/5thconf.htm). Chair: S. Sorooshian

18-29 July: 10th Scientific Assembly of IAGA, Toulouse, France (http://www.iugg.org/IAGA/toulouse2005.htm). Chair: M. Blanc

02-11 August: 9th Scientific Assembly of IAMAS, Beijing, China (http://www.iamas2005.com)

22-26 August: IAG/IAPSO with IABO Joint Scientific Assembly, Cairns, Australia (http://www.gfy.ku.dk/~iag, http://www.iugg.org/iapso)

Director: N. McFarlaneProject Scientist: D. PendleburyManager: V. De Luca

SPARC IPODepartment of PhysicsUniversity of Toronto, 60 St. George StreetToronto, ON M5S 1A7 - CanadaTel: (1) 416 946 7543 - Fax: (1) 416 946 0513Email: sparc@atmosp.physics.utoronto.cahttp://www.atmosp.physics.utoronto.ca/SPARC/index.html

Design and Layout: C. MichautEditing: D. PendleburyProduction: V. De Luca, C. Michaut

Printed and bound by: University ofToronto Incorporated - Canada

ISSN 1245-4680

Future SPARC and SPARC-related Meetings

.. Climate-Chemistry Interactions: C. Granier (France), T. Peter(Switzerland), A. R. Ravishankara (USA)

.. Detection, Attribution, andPrediction of Stratospheric Change:M. Baldwin (USA), S. Yoden (Japan)

.. S t r a t o s p h e r e - T r o p o s p h e r eDynamical Coupling: W. Randel (USA),T.G. Shepherd (Canada)

.. Gravitiy Waves: K. Hamilton (USA),R. Vincent (New Zealand)

.. Data Assimilation: S. Polavarapu(Canada)

.. GRIPS: S. Pawson (USA)

.. CCM Validation: V. Eyring (Germany),N. Harris (UK), T.G. Shepherd (Canada)

.. Laboratory Studies joint with IGAC: A. R. Ravishankara (USA), R. A. Cox(IGAC)

.. PSC Climatology: K. Carslaw (UK), K. Drdla (USA)

.. Solar Influences joint with SCOSTEP:K. Kodera (Japan)

Co-Chairs

A. O’Neill (UK)A. R. Ravishankara (USA)

SSG Members (2004)

J.P. Burrows (Germany)P.Canziani (Argentina)C. Granier (France)K. Hamilton (USA)D. Hartmann (USA)T. Peter (Switzerland)U. Schmidt (Germany)T.G. Shepherd (Canada)S. Yoden (Japan)V. Yushkov (Russia)

Ex-Officio Members

COSPAR: J. Gille (USA)IGAC: D. Parrish (USA), K. Law (France)NDSC: M. Kurylo (USA)SCOSTEP: M. Geller (USA)WMO/GAW: L. Barrie (Switzerland)

SPARC Scientific Steering Group Themes and Group Leaders

Composition of the SPARC Office

JSP/WCRP: V. Ryabinin (Switzerland)

Liaison with WCRP

Edited and Produced by the SPARC IPO

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Report on the SPARC 3rd General Assembly

> Figure 2The distribution of particles50 days after the beginningof a back trajectory calcula-tion of parcels initialized at20 km and the equator. Thelower (upper) thin whiteline shows the zonal meanaltitude of the tropopause(380K isentrope). Zonalmean temperature is indi-cated by the colour con-tours and particles areshown as white dots.Results are from the Met.Office Data AssimilationSystem analysis (UKMO),the NASA Data Assimi-lation Office (DAO) analy-sis, and for a GCM. The Diabatic method, using smoothed heating rates, has reduced vertical dispersion, while theKinematic method, using analysed vertical winds, has both considerable vertical and horizontal dispersion. The GCM showsvery little dispersion, regardless of the method used (only the Kinematic method is shown), while the assimilated fields areexcessively dispersive. The percent of particles remaining in the stratosphere is indicated in each figure. [Schoeberl M. R., et al., J. Geophys. Res., 108 (D3), 4113, doi:10.1029/2002JD002652, 2003].

< Figure 1Probability of observation effects: An intermittent source (e.g.time-varying heat source) will produce gravity waves (GW) ofdifferent frequencies and vertical wavelenghs. The verticalgroup velocity of GWs is much faster for high frequency andlong vertical wavelengths (represented by the royal blue pac-ket), than for lower frequency waves with short vertical wave-lengths (green packet). The result is that the low frequencywaves remain in the height range of observations longer thanthe high frequency waves, making observation of the low fre-quency waves more probable. [Adapted from Alexander et al.,JAS, 59, 1394-1404].

> Figure 3Result from POLARIS 970710 showing theconcentration of ozone and CO with height.The tropopause is shown in panel A by thedashed line. Air with low ozone and high COis found in the troposphere, while air withhigh ozone and low CO is found in the strato-sphere. Air with intermediate values is foundat the tropopause. [Pan, L. et al., JGR, in press,2004].

> Figure 5Frequency distributions of the monthlymean temperature at 90°N and 2.6 hPa inthe two millennium integrations: ha=500(left) and ha=1000 m (right). The brokenline denotes the 1000-yr mean seasonalmean, and shading shows the range ofvariability. The two numbers for eachmonth denote the 1000-yr mean (top) andthe standard deviation (bottom). Frequencydistributions for a seasonal mean are alsodisplayed in the bottom panels: springmean for ha=500 m and winter mean forha=1000 m. The downward arrow in theseasonal mean indicates a threshold valuefor the 200 yr of highest temperature.[Taguchi M., and S. Yoden, J. Atmos. Sci., 59(21) 3037-3050, 2002].

< Figure 6 Timescale of the NAM as measured by the e-foldingtime (in days) of the autocorrelation function. Dailyvalues are a time average of Gaussian weightingwith a full-width at half maximum of 60 days. (B) Same as in (A) but for the SAM, normalized tounit standard deviation. The horizontal blue linedenotes the approximate level of the tropopause.The contour interval is 3 days up to a value of 30days, and 10 days for higher values. [Reprinted with permission from M. P. Baldwin, D.B. Stephenson, D. W. J. Thompson, T. J. Dunkerton,A. J. Charlton, and A. O'Neill, Stratospheric memoryand skill of extended-range weather forecasts,Science, 1 August 2003; 301: 636-640. Copyright 2003AAAS].

Report on the SPARC 3rd General Assembly •

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Figure 8

Time series of global mean, monthly mean anomalies in tropopause pressure. Model results are from seven different ParallelClimate Model (PCM) ensemble experiments, five using only a single forcing (G, A, O, S, or V) and two involving combined forcingchanges, whether in natural forcings (SV), or in all forcings (ALL). There are four realizations of each experiment. In (B), only low-pass filtered ensemble means are shown. In (A), both the low-pass filtered ensemble mean and the (unfiltered) range between thehighest and lowest values of the realizations are given. All model anomalies are defined relative to climatological monthly meanscomputed over 1890-1909. Estimates from NCEP and ERA were filtered in the same way as model data. The SUM results are thesum of the filtered ensemble-mean responses from G, A, O, S, and V. [Reprinted with permission from B. D. Santer, M. F. Wehner, T. M. L. Wigley, R. Sausen, G. A. Meehl, K. E. Taylor, C. Ammann, J. Arblaster, W. M. Washington, J. S. Boyle, and W. Brüggemann, Contributions of anthropogenic and natural forcing to recenttropopause height changes, Science, 25 July 2003; 301: 479-483. Copyright 2003 AAAS].

<

Report on the SPARC 3rd General Assembly •

III

Figure 3

370 K isentropic trajectories for December 1997 (left) and December 1998 (right) that are considered as "match" between thestations shown on the map. Calculations are based on ECMWF operational analyses and illustrations are color coded by satu-ration mixing ratio of the air parcel along the trajectories.

Participants of the SOWER meeting (from left to right)

First row: I. Folkins, M. Shiotani, Y. Kasai, K. Rosenlof, Y. Tsushima, S. Iwasaki. Second row: P. Fortuin, T. Dunkerton, M. Niwano, S. Oltmans, M. Fujiwara, A. Gettelman. Third row: L. Poveda, F. Hasebe, K. Yamazaki, N. O. Hashiguchi, C. Teran, N. Nishi, H. Vömel

Report on the 2nd International S0WER Meeting

IV

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