Of the SPARG Scientific Steering Group

2001 newsletter n" l6 Morch STRATOSPHERIC PROCESSES AND THEIR ROLE IN CLIMATE A. Project of tFre \A./orld Clirnote [?eseorcl-r Proglrctrrrrfl€

Report of the Eighth Session of the SPARG Scientific Steering Group

Buenos Aires, Argentina, November 13-16, 2OOO Marie-Lise Chanin ([email protected]) f his Eighth Session ol-1he SPARC I Scientific Steering Group (SSG) was held in Buenos Aires during the week following the SPARC 2000 Gene- ral Assembly in Mar del Plata (see the Assembly report in this issue). First the Co-Chairs of the SSG offered their warm thanks to the Foreign Minister of the Republic of Argentina and the State Secretary of Science and Techno- logy who had provided very nice faci- Iities for the meeting.

The session started by reviewing the main events which took nlace in the lasl year. in particular the lasl SSG meeting, the meeting of the WCRP Joint Scientific Committee (JSC), that took place in Tokyo in March 2000, and the SPARC 2000 General Assem- Participants in the SSG in Buenos Aires, from left to right. bly. Marvin Geller first recalled the First row: P. Canziani, M. Geller, M.-L. Chanin, A. O'Neill. conclusions of the SSG meeting in Second row: V. Ramaswamy, D. Kley, R. Vincent, T. Shepherd, Ph. DeCola, J. Gille, Paris where the future SPARC overall R. Newson, S. Yoden, M. Baldwin, S. Pawson. strategy was discussed. It had been Third row: D. Karoly, K. Hamilton, Y. Koshelkov, P. Simon, T. Peter, U. Schmidt, W. Randel, concluded that, after B years of fairlv A. R. Ravishankara.

Gontents

Reporl on the Eighth SPARC SSG. by Marie-Lise Chanin ,'1

SPARC 2000 Session Reporls. by Alan 0 Neill et al...... 6

SPARC Assessement of UT/S Water Vapour, by Dieter Kley and lim Russell...... LL Detection and Attribution of Stratospheric RoIe in Climate Change, by David Karoly. .16 Internal Interannual Variations ofthe TS Coupled System, by Shigeo Yoden ef o1. .18 IGOS for Ozone and Relevant Atmospheric Parameters, by Ernest Hilsenrath el aj .22 Public Access to the NDSC Database, by Martin P. Chipperfield and Paul Newman... The evolution of the Antarctic ozone hole in 2000, by Pablo Canziani ...... 26 SOLVE-THESEO 2000 science meeting , by Neil Harris ef al...... 27 First S-RAMP symposium, by Lon Hood and Toshitaka Tsuda... 29 Fulure Meelinss. 3L focused initiatives, it was now timely to The results from the first phase of 03, NO2, HNO3, etc.) have been assem- integrate the knowledge acquired GRIPS and their scientific implications bled from NCEP, UARS and other data. across SPARC, in order to progress can be found in Pawson ef ol. (2000) in Monthly and daily stratospheric circula- towards the goal of an overall under- BAMS, Koshyk et al. (20oo) in lGR, tion statistics have been inferred from standing of all aspects of stratospheric and Amodei et al. to appear in available stratospheric analyses or re- variability and change, its interactions Annales Geophysicae. New data from analyses. Other data compiled include with the troposphere, and its role in cli- several model groups have been col- upper-level radiosonde winds from Sin- mate. This was going to be a main topic lected and their analysis will focus on gapore (as an indicator of the phase of of discussion during the present SSG forcing mechanisms of stratospheric the QBO) and statistics on tropopause meeting. Among the points raised at the variability (wave forcing and diabatic height. These data sets are now acces- JSC, M. Geller mentioned that the forcing) and involve some focused sible from the SPARC Data Centre unique quality that SPARC was brin- modei experiments (sensitivity studies (http ://www.sparc.sunysb. edu/). ging to the WCRP, the dynamics- for interactions between mechanisms ). W. Randel presented a draft of the chemistry-radiation linkage within the The second phase of GRIPS, now in technical report to be published as a stratosphere, should even be amplified progress, involves further validation of SPARC Report in 2001, describing the by a more active role in the JSC initia- out controlled data sets, comparing stratospheric cir- tive on the climate-chemistry issue led models and carrying to test parameterisation culation statistics, and quantifying by Susan Solomon. It should become experiments radiation schemes, uncertainties and interannual variabi- an integrated joint venture with IGAC schemes, including response the formulation of lity. This report entitled "SPARC on the troposphere-stratospheric climate model to problem (including S/T coupiing). mesospheric drag, and of gravity wave Intercomparison of Middle Atmo- of Other ties should be amplified with (GW) parameterisation schemes sphere climatologies" uses 10 sets (Hines' data (some including the mesosphere) CLIVAR on the possible links between first and then Mclntyre's). very UARS data from L9S2- the North Atlantic Oscillation and the Models have been shown to be and the 19S7. Randel indicated his plans Arctic Osciilation, and with the newly sensitive to different radiation W. proposed IGBP Surface Ocean and schemes. and the issue of radiation has for the near future to include the rocket- data data intercompa- Lower-Atmosphere Study (SOLAS) on become a major one to be solved in sonde in the order for models to converge. risons. Furthermore he intends to the role of the UV radiation. organise a group meeting in Goals for the third phase were defined Alan O'Neill, Chair of the Scientific spring/summer 2O01- to complete the a very successful workshop Organising Committee of SPARC 2000, during report and in particular to identify the 2000 Toronto. The main reviewed the new scientific results held in in biases in each data set, to identify the goal explain the observed variabi- presented during SPARC 2000 and the is to quantities which have high uncertain- period as a com- conclusions, which would need to be lity in the 1979-1999 ty and to discuss the strategies for and taken into account into the future bination of natural variability comparison with models. development of SPARC. He remarked perturbations due to known forcing that the SPARC 2000 General Assem- mechanisms: aerosols, solar variabili- Climate Forcing in the Stratosphere bly has started integrating the different ty, ozone change and CO2 change. As Under the auspices of SPARC, a components of SPARC and that it a further step, experiments will be run review of stratospheric aspecls of cli- should help the Project to develop a with imposed climate change scena- mate forcing had been undertaken in more holistic approach of the issues to rios for ihe period 2ooo-2o2o (using order to provide, for the use of the cli- be solved in the future. It was recogni- the best possible predictions of trace mate modelling community, the cur- sed that, in order to understand past gas concentrationsJ. rent best estimates of the relevant parameters. The work has been com- changes, one needs to understand and A new GRIPS workshop is planned for pleted and a report by David Karoly bound natural variability and its pat- February 26 to March 1,, 2oo1, in Ham- was included in SPARC Newsletter terns and look together at the observed burg, Germany to discuss ongoing acti- No. 14 (January 2000). All the reLevant fieids of several variables as well as vities and plan future work. The role data are available at the SPARC Data their simulations. of GRIPS in the planned integrated Centre. Then the leaders of the SPARC activi- SPARC acti v ity mentioned above ties provided a review of the progress needs also further thought. One of the D. Karoly, who had chaired this activi- in the projects and activities organised main output being the prediction of ty and is a Lead Author in the current under SPARC activities. future climate/ozone interactions, it IPCC/Third Assessment Report (TAR), will also be discussed at the Ioint reported on the way detection and SPARC/IOC ozone meeting in March attribution of a Stratospheric Role in Modelling stratospheric 2001 to prepare for the upcoming Climate Change has been taken into effects on climate WMO-UNEP Ozone Assessment. account in the IPCC/TAR (see the paper by David Karoly in this issue of Stratospheric reference climatology Intercomparison of stratospheric the Newsletterl. models It has been long recognised that a revi- The "GCM Reality Intercomparison sed climatology of the averages and Stratospheric data assimilation Project for SPARC" (GRIPS) has grown variances of basic stratospheric parame- At its meeting in Paris in 1999, the both in the number of research groups ters was needed for GRIPS. as well as a SPARC SSG agreed that it would be involved and the range of tasks being number of other SPARC initiatives. In useful and timely to review the status tackled. During his presentation of the the last few years, a series of monthly of stratospheric data assimilation and GRIPS highiights of the year, Steve global climatologies of temperature, specific related problems (including Pawson raised the question of what zonal winds, and various atmospheric stratospheric data availability). GRIPS should do and should not do. trace constituents (N2O, O, CH4, H2O, A. O'Neill, who was asked to report on plans on this issue, informed the SSG date of the data and of model infe- In the longer term, an extension to that a DARC [Data Assimi]ation rences, extension to the upper strato- study jointly trends in stratospheric Research Centre) has been supported sphere and mesosphere, (this later part parameters in general (including tem- and set up in the UK by the Natural in liaison with ICMA and SCOSTEPJ, perature, etc...) is foreseen by the Environment Research Council, in improved work on trends of quantities ozone trends group. view of the important role of data assi- having high uncertainties (tropopause Stratospheric and upper tropospheric milation both for the climate studies and stratopause temperatures). In paral- water vapour and the numerical weather prediction lel with this continuous activity, the This SPARC initiative, originally set (NWP). Atmospheric data assimilation need to have a more integrated perspec- out to refine the water vapour climato- will be based on the use of a general tive was recognised as temperature logy in the stratosphere and upper circulation model of the troposphere trends are closely linked with changes in troposphere (S/UT), developed into a and stratosphere, which at this stage other stratospheric parameters (ozone, comprehensive Water Vapour Assess- incorporates a parameterisation of waler vapour. dynamical acti-vily. elc.). ment, which investigated the concen- ozone chemistry. More sophisticated and activities will have to become tration, distribution and variability chemistry is incorporated in an off- increasingly integrated with other (including the long-term changes or line, 4DVAR. chemical data assimila- SPARC studies in these areas. A group trends) of water vapour in this region. tion system. The SSG supported a meeting is planned for around mid-2001. The processes controlling the present proposal to form a SPARC working What has been strongly emphasised has distribution of S/UT water vaDour group to focus on stratospheric data been the value of the SPARC umbrella have also been sludied. The Asiess- assimilation. and A. O'Nei1l has under which coherent international ment Report is now completed and agreed to pursue this. Several mee- research into stratospheric temperature will be printed as SPARC Report No. tings of potential European partners in trends can be and has been carried out 2, 2OOo (and WCRP- 113, and WMO- the group have already taken place to including the planning of future co- TD-No. 1043). It will be available early make recommendations to EU towards ordinated activities. It is viewed as in 2001. the use of the ENVISAT data. A full important to keep together the internatio- meeting of all the parties is being plan- The executive summary, printed in nal "expert" SPARC temperature trends gather this Newsletter, gives the main conclu- ned to information on current group, comprising observationalists, activities and to discuss developments sions as well as the recommendations modellers and d iagnosticians. in stratospheric data assimilation that for a further comprehensive and may be needed. This initiative will be Understanding ozone trends organised approach to monitoring closely co-ordinated with the Working After the major effort in 1998 to assess water vapour in the S/UT. A summary Group on Numerical Experimentation, the trends in the vertical distribution of the Assessment has been provided in 3 which has overall responsibility in the of ozone (SPARC Report No. 1, 1998) due time for inclusion into IPCC-TAR. WCRP for data assimilation questions. and the contribution to the Understanding Stratospheric Climate WMO/UNEP Ozone Assessment, 1999, The data assimilation initiative is Change thought had been given to the further especially important in view of the The proposal of a new integrated development of studies in this area. new streams of stratospheric data SPARC initiative, with a view towards Neii Harris (who sent his apologies for coming on line from research satellites "Understanding Stratospheric Climate absence from the SSG meeting) had in the next few years (e.g., ENVISAT, Change (1979-1998)", was discussed at informed the SPARC co-chairs about a HIRDLS, the NASA EOS series, etc.), length during the SSG meeting, under possible future workshop to be orga- as well as from operational ones. the leadership of V. Ramaswamy. It was nised together SPARC and IOC by in agreed that it should focus on the study (and conjunction with upon invitation of the consistency amongst the various Long-term changes ofl the co-chairs of the Montr6al Proto- observational data set and comoaiisons in the stratosphere col Assessment Panel. This informa- of model-simulaled resoonses 1o well- tion has been confirmed since the time Stratospheric temperature trends characlerised and known lorcings with of the SSG meeting. The goal of this observations. The project should not The original objectives of SPARC activi- be workshop is to review the scientific too ambitious to start with and should ties in this area have been well fulfilled activity on the topic of stratospheric be accomplished years. for the lower stratosphere. The results in 3 Preliminary ozone changes and their causes. This discussions about the input data and the of the first phase of this initiative have topic will be among those addressed type of models to be used took place formed the basis of the chapter 5 in the by the next WMO/UNEP Ozone latest WMOiUNEP during the meeting but should continue Ozone Assessment Assessment, whose drafting will begin (1999). A summary will be published in the future months by email in the summer of 200L and will be exchanges involving at least the SPARC in Reviews of Geophysics in February completed by the fall of 2002. This group leaders of the trends issue and of 2001. The full account of the work is workshop to be held on March 7-9 at GzuPS. This should help in preparing a also in preparation as a SPARC Report the University of Maryland, will bring workshop to be held in spring/summer to be edited by NOAA. The work car- together (upon invitation) leading ried out is aiso proving valuable input 2001,. scientists in this area of research to to the IPCC/TAR in particular for the take stock of the current state of scien- discussion of radiative forcing of cli- processes tific understanding, to facilitate the Stratospheric mate change, climate processes, and formulation of common scientific Gravity wave processes and their detection and attributiol. viewpoints, and to encourage prompt parameterisation V. Ramaswamy reported ihat the views submission of peer-reviewed publica- The construction of a stratospheric of the group are to pursue its activity tions that will form the basis of the gravity-wave climatology based on in several directions: continuous uo- 2OO2 Ozorle Assessment. high-resolution radiosonde data is proceeding as planned. Following the and Peter Haynes, will take place in counterpart within IGAC. The connec- successful Abingdon workshop in ]uly AW|I 1,7-21,, 2001 in Bad Toelz, Ger- tion with IGAC clearly needs to be 1999 the participants reanalysed their many. The SSG was asked to review strengthened on this issue. data to generate climatological and the list of invited participants. It was noted that the workshop on UV research products. R. Vincent presented A.R. Ravishankara reviewed the joint impacts, which took place at Mar del some of the highlights of the climatolo- SPARC-IGAC activities on chemical Plata, SPARC 2000 gies of wave energies and propagation following the processes in the UT/LS. On the issue General Assembly attracted about 30 directions as a function of latitude. In of Organic Peroxy Radicals, which participants from the SPARC commu- 2OO1. ft is planned to submit for publica- was reviewed in SPARC Newsletter nity. Pablo Canziani, who was the tion a series of articles describing the No. 15. a paper is now in press in organiser of this workshop, asked whe- research efforts that have gone into the The work on the quantum yield ther this issue should not become a generation of the climatologies. lGR. of ozone photolysis reactions was pre- regular part of SPARC Assemblies. The Kevin Hamilton described how the sented at the Quadrennial Ozone SSG hesitated to include the imoact planning of the internationai field expe- Symposium in 2000 and is to be sub- aspecl of UV within its themalics al riment ETCE (Effects of Tropical mitted to lGR. Such joint SPARC- the present time. Convection Experiment) is progressing. IGAC activity is judged by the SSG to ETCE is designed to investigate the gra- be extremely beneficial to both pro- vity-wave field forced by tropical jects and crucial in the evaluation of Other scientific issues convection during a six-week intensive important UT/LS reactions. chemical Dynamical coupling of the stratosphere (late observation period October-early It generates an important interaction and troposphere December 2002) over the Tiwi Islands, between the modelling and the field At the SPARC SSG Paris meeting, two north of Darwin, Australia. A detailed Iaboratory communities and brings (somewhat speculative) aspects of what plan of the scientific objectives arrd ins- new people into the process. The are thought to be manifestations of the trumentation to be deployed during the queslion oI expanding the co- dynamical coupling of the stratosphere field campaign may be viewed at: operation to other issues was discus- and troposphere were discussed, the http://www.princeton.edu / -kphlEXP2. sed. The iopic of UT/LS water vapour quasi-biennial oscillation (QBO) and and the role played by subsonic avia- K. Hamilton also described a pre-ETCE tion in the formation of contrails/ the Arctic Oscillation (AO). On the first campaign called DA\A|EX (Darwin Area topic, an extensive review of the cirrus was judged to be already recei- QBO Wave Experiment). This campaign. pro- and its role in coupling the stratosphere ving sufficient attention by the atmo- posed by EPIC/SCOSTEP and SPARC, is and troposphere was published spheric community. in 4 planned for the Austral spring 2001 arrd Reviews of Geophysics in October is aimed at characterising the wave field The other issue was the Upper Tropos- 1999, as a consequence of the SPARC in the middle atmosphere over Northern pheric Ozone (UT 03) climalology and QBO Workshop of March 1998. During Australia prior to the onset of the diur- trends. It was thought ihat SPARC this SSG session, Mark Baldwin was nal convection, known locally as "Hec- should undertake this task and ask invited to present an update on the AO tor", and during the active Hector IGAC to join, as the contribution of the and its possible link to the NAO (North period. As it only involves ground- stratosphere is important enough to be Atlantic Oscillation). He noted similari- based equipment, the preparation's time taken into consideration. A leader of ties between the NAO fNorth At]antic is much shorter than for ETCE. this new initiative has yet to be Oscillation) observed in surface pressure Lower stratospheric/upper tropo- appointed. A workshop on the role of and features of the AO (Ärctic Oscilla- nitrogen oxides is being organised for tion), which was derived as a leading spheric processes March 2001 in Heidelberg. "mode" of variability of the combined Transport and mixing in the UT/LS are I rnnos nhere-qtrA I nc n h e rc fundamental to SPARC and hold the Penetration of UV radiation into the ""r" system. He proposed that the NAO and key to many issues, e.g., the UT/LS lower stratosphere and troposphere AO were, in fact, different manifesta- ozone budget, mid-latitude water It is essential to know the actinic flux tions of the same underlying dynamical vapour distribution and tropical dehy- distribution in the lower stratosphere phenomenon, and showed evidence for dration. However, there is no and troposphere and to determine the still the apparent downward propagation of overall strategy and theoretical frame- climatoiogy of photodissociation rate the AO signal. Issues raised by these (] work for studying stratospheric- constants values) for various radicals ideas concern the mechanism for tropospheric exchange, paradigms that as a function of altitude to make mark- downward propagation of the AO can be lesled, or an obvious common ed progress in model calculations. signal, whether the stratosphere can measurement/diagnostic approach. The SSG at its 1999 meeting encoura- influence the large-scale variability of Thus, the role played by SPARC in ged a joint SPARC-IGAC initiätive on the troposphere, and whether one can this area up to now has been to keep this issue, with the obiectives of eva- predict changes of the large-scaie circu- under review the basic questions that (including luating existing data lation in the troposphere from prior need to be addressed and to bring the vaiues and actinic measure- I flux knowledge of the state of the strato- different communities involved in this ments), considering the requirements sphere. The issue was judged still too subject together in various focused for new instrumentation and organi- speculative to generate any SPARC ini- workshops. In view of the importance sing validations of computations of tiative. besides a continuation of the of the tropopause (where climate/ radiative transfer at UV wavelengths. investigation. This question of joint ozone issues come together), conside- This activity, which should well com- interest for CLIVAR and SPARC should ration has been given in the last two plement the joint SPARC-IGAC studies be raised at the next Meeting. years to planning a "tropopause work- of chemical processes in the UT/LS, fSC shop". This workshop, organised has not started yet. Paul Simon will A presentation was then given by Shi- under the leadership of Ted Shepherd contact IGAC to helo identifv his geo Yoden on "Intra-seasonal and interannual variations of the now appropriate. Hitherto, SPARC available information on relevant stra- troposphere-stratosphere (T/S) cou- initiatives have been fairly focused tospheric questions for the periodic pled system" (see article in this issue). and dealt with individually (by sub- international assessments such as those Results have been obtained from 1000- project working groupsl. Although of IPCC and WMO/UNEP. This requires year runs using a hierarchy of numeri- some of the scientific issues taken up a forward-looking approach to identify cal models assuming different types of obviously still need specific conti- new questions llrat could arise. linkages between the troposphere and nuing efforts, it appeared that it may the stratosphere. They show that the now be timely to integrate the know- T/S system is highly non-linear and ledge accluired across SPARC in order lnteractions with has large internal variability. to progress towards the goal of an other programmes overall understanding of all aspects Solar forcing and climate variability of and activities stratospheric variability and change, As requested the SPARC is by JSC, its interactions with the troposphere, As noted earlier, SPARC maintains keeping under review research on and its role in climate. strong links and/or interacts widely as solar forcing, its variability as a source appropriate and necessary with several In some areas, focussed of variations in climate and possible efforts are still other programmes. Particularly note- cleariy needed: gravity underlying mechanisms that could be wave climato- worthy is the co-operation rvith IGAC put forward. The SPARC SSG noted logy and understanding the role of GW (lhe ioinl SPARC-IGAC activity on last year that, although changes in the in stratospheric dynamics; UTi LS UT/LS chemical processes; the pro- solar spectrum are known to affect chemistry and microphysics; the tro- posed joint initiatives on the penetra- ozone, temperature and the actinic popause; solar forcing and climate tion of UV radiation into the lower flux in the middle atmosphere, there is variability. SPARC also saw the need stratosphere and troposphere, the still no consensus assess observations on whether trooo- to of stratospheric possible joint assessment of observa- spheric climale infl uenced any aerosols (jointly is irr with IGAC). Additio- tions of stratospheric aerosols). It was way by these changes. The data ana- nally. [here is a range ol specific unfortunate that neither Guy Brasseur iysis planned the European project in modelling questions such as the para- nor Stuart Penkett were able to attend SOLICE and the modelling activities in meterisation of radiation and GW, as this SSG meeting. It was decided that GRIPS and SOLICE, which are still at well as the topic of stratospheric data in view of the increasing IGAC/SPARC an early stage, should throw further assimilation. interactions, an alternative method for light on this issue. The sort of basic structure foreseen for planning is needed. In particular, it Research on links between solar for- SPARC in the future would involve was suggested that a small IGAC/SPARC liaison-planning group cing and climate variability is another integration or synthesising the under- 5 example of a cross-cutting activity in standing of stratospheric trends of be formed to plan for SPARC/IGAC the WCRP, where SPARC would be temperature, ozone and water vapour, programs. Of course, those plans involved in studying the mechanisms and solar effects through modelling would need ratification of the SPARC involving the stratosphere, GEWEX on studies. These would be particularly and IGAC SSGs. possible cloudiness variations linked aimed at elucidating UT/LS variabili- Reference was also made to the to changes in solar cosmic rays, and ty, and its role in the overall climate planned collaboration with SCOSTEP CLIVAR in a rigorous interpretation of system by building on the modelling on upper stratospheric temperature the observed climate signals. work already carried out in the strato- trends and on the issue of solar Stratospheric aerosol climatology spheric trends study and GRIPS. influence on climate. The constitution The subject of stratospheric aerosol However, additional models (e.g., two- of joint SPARC/SCOSTEP working has attracted intense work in the r:ast dimensional. chemical transport) groups on these issues was discussed. decades. bul the need l'or an organised which have not so far been exploited Possible members for these groups activity has been discussed for years in SPARC would also be required, as were discussed. The allocation of a as without any success. The SSG decided well developing the use of data assi- US$ 6,000 grant by ICSU should assist to form a group with the mandate to milation techniques. Furthermore, the WCRP and SCOSTEP funding of look at the presently existing climato- although the number of climate these joint activities. logies, identify their consistencies or models including the stratosphere is increasing, inconsistencies and contribute to a there is currently insuffi- better knowledge of the composition of cient contact between the SPARC The SPARC Data Centre aerosols. Two co-chairs will be named community and tropospheric climate The SPARC Data Centre, supported by for a two-year mandate and should modelling groups. The new SPARC NASA, has been operated by Petra together with a small group prepare a initiatives on stratospheric data assi- Udelhofen at the State University of report and eventually organise a work- milation and UV penetration could New York at Stony Brook for more shop in this time frame. help in building bridges. Within this than a year, and a significant start has framework, the main priority for been made on assembling key strato- SPARC is to continue generally to faci- spheric data sets in a readily accessible Review of overall SPARC litate research on stratospheric pro- form. New data sets have been added to strategy and status cesses and their role in climate by the original ones: High-resolution tem- providing of implementation a forum or umbrella for perature and wind data from radio- international co-operation and encou- sondes, data from the GRIPS model The SPARC SSG gave consideration to raging inter-disciplinary exchanges. intercomparison, the Water Vapour the overall strategy that has so far been SPARC will thus remain science- Assessment (WAVAS) archives. (see followed and assessing whether any driven, but, at the same time, it should SPARC Newsletter No. 15 and reorganisation of lhe programme is be in a position to provide the best http://wt'w.sparc.sunysb.edu/). The SPARC Office ADEME. A half-time position of Next SSG meeting Project scientist is opened and the As well as its regular responsibilities K. SPARC Office is looking for a post-doc Hamilton invited the SSG to meet of compiling and SPARC editing candidate. in Hawaii in 2001. The invitation was Newsletters, updating the SPARC mai- unanimously welcome. The exact date ling list, maintaining contacts with the has now b een fixe d to th e SPARC community of scientists, orga- Meeting of the SPARC 3-6 of December 2001. nising various SPARC meetings and periodically revising the SPARC home SSG perse page, particular support has been The SSG members met twice during the Reference given to the preparation of the SPARC 4-day meeting to discuss the partial Pawson, S. el o-1., The GCM-Reality water vapour assessment report. renewal of the SSG chairs and mem- Intercomparison Pro ject for SPARC Substantial efforts have aiso been bers. This was necessary as the (GRIPSJ: Scientific Issues and Initial devoted to seeking sponsors for the mandates of several members are Results, BAMS, Vol. at, No.4, April 2000. Second SPARC General Assembly, and coming to an end. Marie-Lise Chanin assisting in the arrangements for the has expressed her intention to step General Assembly. The composition of down from her post as co-chair of the SPARC Office has been chaneed SPARC. She proposes to stay as during the year. ln lune 2000 lhe airj- Director of the SPARC Office for L-2 val of Catherine Michaut, who has a years, until a new offer is made to wel- full time position of assistant engineer come the SPARC Office. The composi- at CNRS, provided an efficient mana- tion of the renewed SSG will be ger fbr the Office. In November 2000 submitted for approval to the ISC in C6line Phillips decided to leave the March 2001 and will be announced on Office for a permanent position at the web site and in the next Nervsletter. a

Report on the 2lrd SPARG General Assembly 6 (SPARC 2OOO) 6-1O November, Mar del Plata, Argentina Conveners: A. O'Neill (Chair), S. Diaz, R. McKenzie, V. Ramaswamy, T. Shepherd and S. Yoden Chair of Local Organising Committee: P. Canziani

A summary of some of the scientific highlights Since the discovery of the ozone hole in the mid 1980s, great progress has been made in understanding the dynamical, chemical and transport pro-

cesses that occur in the stratosphere. | - I ll \.!rnrlfi :t!lll At the same time, the importance of liir Llrl {rhlr, li, t!lJtifx.\rxilrirx the stratosphere as an integral part of the climate system has come to be more fully appreciated. Through exchanges of mass, momentum and energy, the stratosphere is strongly coupled to the climate system as a whole. Relevant processes are com- monly non-linear (for instance, the dynamical coupling between the troposphere and stratosphere), and by no means fully understood. SPARC has Alan O'Neill opening the SPARC 2000 General Assembly been instrumental in promoting the science that has led to a wider appreciation of the importance of the The Scientific Organising Committee te change. The five-day meeting com- stratosphere in climate. It has also of the 2nd SPARC General Assembly prised four sessions. Session 1 empha- been active in promoting greater inte- {SPARC 2000) aimed to structure the sised fundamental processes and gration between scientific disciplines scientific meeting in a way thal interactions among processes. Session involved in the broader World Climate emphasised the importance of the stra- 2 discussed observations relevant to Research Prosramme. tosphere in the wider context of clima- these processes and indicative of climate variability and trends. Session 3 interface between the troposphere and model (H. Teyssedre), the German focused on modelling stratospheric stratosphere, so it is where exchanges KASIMA model (T. Reddmann), and processes and climate variability, and of material occur; radiative and chemi- the Utrecht model (8. Bregman). was designed to present a synthesis of cal time scales are relatively long, so Late-winter/spring polar ozone our current understanding. Session 4 transport is very important; ]ow tem- deple- tion continues to be a focus was devoted to observations and peratures imply a role for condensed of investigation. (Wegener modelling of solar ultraviolet radia- matter in the chemical balance; and M. Rex Inst., Potsdam) gave an update tion, a particularly timely topic during there is a sensitive radiative feedback on the latest results a year in which the Antarctic ozone from relatively short-lived greenhouse from the MATCH program, which identifies hole covered the greatest area yet gases (water vapour and ozone). chemical ozone loss in the Arctic on specific observed, extending for a time over the However, the entire stratosphere air parcels through the combined use of trajectory southern tip of South America. Each affects the UT/LS region. It does so of these sessions was accompanied by dynamically through "downward modelling and ozonesondes. The cove- poster sessions, the scientific quality control" and the diabatic circulation, rage is sufficiently dense that an esti- and breadth of which were outstan- chemicaliy through transport (the mate of the net ozone loss over the Arctic can be obtained ding. It is clear that the convenors of Brewer-Dobson circulationl and for the late- winter/spring season. future SPARC General Assemblies through filtering of actinic fluxes, and Antarctic ozone must be vigilant in structuring the radiatively loss was estimated in a paper by through both short wave (NIWA, meeting to give equal emphasis to orai and long-wave fluxes. B. Connor Lauder). With and poster sessions. regard to polar processes relevant to The papers in Session 1 can be grou- ozone depletion, the role of mesoscale SPARC 2000 was attended by over 300 ped into five main areas: chemistry, processes in Arctic PSC formation was scientists fiom more than 30 countries. transport, clouds and water vapour, discussed by M. Mueller (Free Univ., All Latin American countries were gravity waves, and climate variability BerlinJ using Iidar measuremenrs, represented. Attendees will remember and tropical oscillations. Because of while denitrification was identified in not only the high scientific quality of the large number of papers, only the the Arctic by H. Oelhaf (FZK the meeting, but also the warmth of salient themes are highlighted. Karlsruhe) using a combination of the reception given by our hosts in MIPAS-B measurements and model- Argentina, their hard work over many Chemistry ling, and in the Antarctic by months to make the meeting very R. de Zafra (SUNY, Stony Brook) An invited overview talk by enjoyable, and the generosity of the using mm-wave spectroscopic measu- A.R. Ravishankara (NOAA Aeronomy sponsors that enabled so many young rements of various species. scientists to attend. Lab) highlighted some of the complexi- ties of the chemistry of the UT/LS The Chair of the Scientific Organising region. He noted the unique aspects of Transport Committee, Alan O'Neili, wishes to ozone: its spatial inhomogeneity, its An invited talk by P. Haynes record here his thanks to the Scientific role in both UV and IR radiation, its (Cambridge Univ.) presented the notion Conveners for their diligent work. He production within the atmosphere, and that the mid-latitude tropopause is a extends particular thanks, on their the strong role of chemistry in its abun- mixing barrier, which emerges behalf, to the Chair the Local flateral) of dance. The complex role of NOx in the naturally in idealised studies of baro- Organising Committee, Pablo ozone budget, still not fully unders- clinic instability. In this view, the extra- Canziani, for his unstinting efforts to tood, was discussed; it was suggested tropical tropopause is the transition ensure that the meeting was a success. that the summer polar stratosphere, level between altitudes which exoe- A summary of some of the scientific being under photochemical control, is rience widespread mixing (the tropo- highlights is given below. a good place to test our chemical pause) and those which are constrained understanding. Finally, the UT was by this mixing barrier (the lowermost Session 1 : stratospheric noted to be chemically very fertile, and stratosphere). The subject of mixing and the possible role processes and their role of chloral was raised. transpofl across the extratropical tropo- The role of NOx in the UT/LS region pause was addressed in several other in climate was also discussed in the paper by papers: by E. Shuckburgh (Cambridge (Convener: T. Shepherd) S. Meilinger (MPI, Mainz), given by Univ.) and R. Scott ILaboratoire T. Peter, which emphasised the need d'A6rologie, Toulouse) Understanding the role of the strato- using analysed to distinguish carefuily between the LS sphere in the climate system interpre- winds, by A. Zahn and H. Fischer [both and the UT; e.g. for high NOx, NMHCs MPI, ting indicators of climate change, Mainz) using measurements from can have a large effect on ozone pro- the developing credible models, providing CARIBIC and STREAM aircraft cam- duction just below the tropopause. a framework for diagnostic studies, paigns, respectively, and by Y. Rao (IITM, Pune) and Y. Tomikawa and quantifying and interpreting The global modelling of chemical cli- fTokvo Univ.) using radar data. changes in UV radiation all require a mate using generai circulation models fundamental understanding of the has emerged as a major evolving area Another mixing barrier exists on either basic physical processes involved. of research. While several years ago side of the tropical stratosphere, and This was the rationale for Session 1, only a few groups were active, now there has been much interest in recent which to some extent underpinned the there is a wealth of activity in various years in quantifying the upwelling in following sessions. A major focal point countries. Results were presented on the "tropical pipe" and the associated was the Upper Troposphere/Lower the lapanese CCSR/NIES model mixing rates. M. Volk (Frankfurt Stratosphere (UT/LS), also known as (K. Sudo), the NCAR model (F. Sassi, Univ.) provided latest estimates of the the dynamical "middleworld". The D. Kinnisonl, the Canadian MAM model mixing rates using Geophysica data UT/LS is pivotal and complex: it is the (A. fonsson), the French MOCAGE from the APE-THESEO campaign, which were complemented bY a studY (Washington Univ.) attempted to asso- though this has the obvious spatial using bolh iidar measurements and ciate variability in the cold point tem- biases, it does provide excellent verti- (Adelaide modelling by H. Bencherif (R6union perature with the QBO and ENSO. cai resolution. R. Vincent paper lhe Univ.). The representation of the tropi- S. Sherwood (NASA/GSFC) examined Univ.) gave an overview on cal tape recorder in general circulation the role of conveclive overshoots. SPARC radiosonde initiative, while (DLR, modeis was found to be highly sensitive noting the existence of a transition T. Birner Oberpfaffenhofen) to the choice of numerical advection zone between the troPosPhere and reported on German results, M. Geller scheme in studies by K' Nissen and stratosphere wherein different kinds of (SUNY, SB) on US results, and I. Son V. West (both Edinburgh Univ.) and air coexist. A. Gettelman (NCAR) IYonsei Univ.) on Korean results. are beginning to show S. I. Lin (NASA/GSFC). In a somewhat noted that the diurnai cycle in tropo- These sludies different but related study addressing pause temperature (of aboul 1.5 K) links with source mechanisms. Tn rela- the origin of the tropical upwelling, over land, with a much smaller varia- ted papers, E. Pavelin (Wales Univ') experi- R. Garcia argued that a transient caicu- tion over the ocean, implicates the role studied gravity waves in a field Sato lation was required in order to account of convection, but that convection ment over Aberystwyth, while K. for the seasonal cycle of upwelling. above the tropopause is very rare, per- (Kyoto Univ.) identified long-lived haps occurring less than 1% of the layered structures in radiosonde obser- exists on the Yet another mixing barrier time across the troPics. vations over Japan. edge of the wintertime stratospheric polar vortex, and several studies were D. Kley (Juelich) Presented the Gravity waves are important in the midd- devoted to quantifying mixing across findings of the SPARC Water VaPour le atmosphere because of their effect on the vortex edge and within the neigh- Assessment Report (WAVAS), which mixing and momentum transPort. bouring surf zone. This remains an was recently completed and which D. Fritts (CRA, Boulder) reported on important issue for quantifying polar focuses on the upper troposphere and high-resolution numerical simulations ozone loss. especially in the Arctic. The lower stratosphere (see report in this directed al quanli$zing l-he generation of papers included several studies with newsletter). The report discusses the turbulence by breaking gravity waves. the French MIMOSA model bY various measurement techniques, the I. Alexander (also CRA, Boulder) deri- F. Fierli, A, Hauchecorne and data quality, limitations of data sets ved conslraints on the gravily-wave for- M. Marchand (Service d'Adronomie, and advice on how to combine them cing of the aimospheric circulation based Paris) and one by the Berlin model by (e.g. for trend studies), and the current on UARS satellite observations to infer K. Krueger (Free Univ., Berlin). A underslanding of the dislribulion and the radiative heating arrd cooling, while variety of measurement platforms are variability of waler vapour' Copies of H. Chun (Yonsei Univ.) did a similar available in the Arctic; papers were pre- the report are available from the thing based on closing the momentum sented using ILAS satellite data by SPARC Office. budget in the UKMO analYses. The H. Nakaiima (NIES, Tsukuba), L. Pan important question of paramelerising the (NCAR), and W. Choi (Seoul National Gravity waves effects ofunresolved gravity waves in cli- by D. Gibson-Wilde (CRA, mate models was addressed in papers by Univ.), An invited talk by T. Tsuda (RASC, using ALOMAR ground-based R. Tailleux (LMD, Paris) and Boulder) Kyoto) described the new GPS/MET and by C. Basdevant (LMD, Paris) M. Charron [MPI, HamburgJ. data, data set which is providing an un- using trajectory methods. precedented global view of gravity-wave activity in the lower stratosphere. The Climate variabilitY Clouds and water vapour data show stronger gravity-wave activity and tropical oscillations An invited talk by T. Peter (ETH, in the tropics than in the extratropics, It was at lhe fi rst SPARC General Zurich) addressed the question of the presumably associated with stronger Assembly in Melbourne in 1996 that composition and origin of the subvisible convective activily. and interest natural- the first resu.l ts were announced cirrus clouds located at about 17.5 km ly focuses on quantifying the con- concerning the simulation of a QBO- altitude in the tropics. They are seen nection between convection and gravi- Iike oscillation in a [simplified) high- only in certain backscatter wavelengths, ty-wave excitation. This quantification resolution GCM (by M. Takahashi). arrd sit several km above, and are appa- is of great importance for climate Since then there has been a lot of rently unconnected with, the thick cirrus modelling. Several papers investigaled progress, with QBO-like oscillations associated witl-r conveclion. Peter argued this connection: T. Kerzenmacher first simulated in more realistic but that it seems difficult to account for their (Wales Univ.) using radiosonde ana- still high-resolution GCMs, and most existence unless a rather iarge upweiling lyses, and Z. Eitzen (Colorado State recently in coarse-resolution GCMs. of about 6 mm/s, which is an order of Univ.) and Z. Chen (LASG, Beiiing) The missing ingredienl seems to have magnitude larger than the large-scale using idealised model simulations. been momentum transPort bY small- upweliing inferred on radiative ground, N. McFarlane (CCCma. Viclorial reporl- scale gravity waves, which can either can be hypothesised. Some questioners ed results from the Canadian middle be resolved (at very high resolution) wondered whether inertia-gravity waves atmosphere GCM showing that the natu- or parameterised. The latter possibili- might possibly be responsible, and this re of the convective adjustmenl scheme ty is crucial if GCMs are to include possibility was in fact discussed further had a strong effect on the gravity waves this most important mode of atmo- in a paper by F. Hasebe (Ibaraki Univ.)' (incLuding equatorial wavesl generated spheric variability, and yet run Iong The APE-THESEO campaign that obser- in the model. enough to produce climate simula- cirrus clouds was ved these subvisible While GPS/MET is providing a global tions. The locus now is on underslan- Stefanutti presented in a paper by L. view from satellites, SPARC has been ding why models produce QBO-like (CNR IROE, Firenze). co-ordinating the development of a oscillations, and whether they do so The issue of tropicai dehYdration global gravity-wave climatology from for the right reasons. There were three proved to be a lively toPic. X. Zhou hish-resolution radiosonde data. Even papers on the presence or absence of such oscillations in coarse-resolution The availability of long (-a decade or stratosphere. The plausible connection models: A. Scaife (UKMO) using the more) time series of several relevant between interannual changes in strato- UKMO unified model, C. Mclandress stratospheric parameters, as measured spheric circulation, tropospheric (Toronto Univ.) using the Canadian by satellites and ground based instru- structure and total ozone may bear on middle atmosphere model, and ments, have initiated analyses studies the causes of the observed stratospheric M. Giorgetta (MPI, Hamburg) using seeking to understand causes of the ozone and temperature trends in the the MAECHAM model. Mclandress associated phenomena. Besides ozone northern mid-latitudes. The modes of noted that the period of the oscillation which was the focus of several papers, atmospheric variability, in particular depended on the finite differencing recent observations of stratospheric involving planetary wave propagation, used to determine momentum flux water vapour have generated a lot of could have substantial implications for divergence in the parameterisation interest, in part because of the impor- climate change and detection. tance of the apparent changes for stra- scheme, suggesting that much more While the oral presentations exposed tospheric temperature trends/climate work is needed to assess the reliability several important contemporary issues and stratospheric chemistry, and in of these kinds of results. concerning stratospheric indicators of part because the basic causes are not climate change, the poster sessions pro- A large conponent of climate variabi- well understood. lity in the stratosphere concerns ozone vided the setting for amplifications on and temperature in mid-latitudes and Findings of the recently completed several of the above issues. In addition, in polar regions. Understanding this SPARC water vapour assessment (see the poster sessions reported important variability, and its possible link with also Session 1 report) suggest signifi- outcomes or anticipated results from the troposphere, is crucial for delinea- cant increases in the lower strato- several campaigns or new measurement ting anthropogenic ozone loss and spheric water vapour content over the techniques or new diagnostic methods. climate change. There were several past few decades. The details showcased the in-depth scrutiny and research underlying the papers on this topic; e.g. R. Bernardi Investigations of the long-term diagnostic analyses of observations e.9., (Univ. Republica, Uruguay) linked (-2 temperature decades or more) different kinds of problems affecting changes in the SH vortex to SST ano- the global stratosphere based trends in interpretation of observed phenomena, maLies, P. Canziani (Buenos Aires on measurements from a number of (or sampling problems and instrument Univ.) linked total ozone anomalies platforms reveal a general cooling, but 'mini-holes') to synoptic variability, uncertainties, temporal discontinuity with distinct seasonal and latitudinal difficulties, inconsistencies between and L. Hingane (IITM, Pune) linked a wide variations; however, there is various observational platforms, global the evolution of the mini-holes to the estimates for the divergence in the versus regional features, and accounting monsoon circulation. problema- mesosphere. There are some for the natural internal variability of the I the (and tic issues regarding currently stratosphere. Session 2 : stratospheric the only one) deployed AMSU satellite instruments' ability to detect cli- Nonetheless, the abiiity to synthesise indicators of climate change mate change in the stratosphere. the numerous observations available (Convener: V. Ramaswamy.) Stratospheric aerosol concentrations now, and the resulting understanding This session focussed on recent research appear to be at their lowest values now of the variations in stratospheric fea- concerning stratospheric indicators of compared to the late 1970s when such tures, have advanced considerably climate change. The subjects covered global observations were begun. The since the First SPARC General included variations and changes in utility of long-term lidar measure- Assembly and have opened up a host trace species such as methane and ments at a specific site to diagnose the of new research opportunities. other well-mixed gases, ozone, water climatology of locally present cirrus vapour, aerosols, polar stratospheric clouds was demonstrated. The tropical Session 3: modelling and and cirrus clouds; temperature; tropo- upper tropospheric and tropopause pause features; stratospheric circula- regions are generating substantial diagnosis of stratospheric tion; and forcing/ variability of research interest. Radiosonde measure- effect on climate stratospheric ozone and climate. Both ments indicate correlation between ICo-conveners: S. Yoden and tempera- the oraL talks and posters on display surface and stratospheric V. Ramaswamy) yielded new insights besides covering tures, with a cooling of the lower This session was focussed on the syn- a of technical issues related stratosphere during El Niflo events, wide array thesis of stratospheric processes in the although the sonde data quality at the to the above topics. context of climate interpretation and lower stratospheric altitudes have to (W. prediction. Issues concerning strato- The invited presentation Randel) be accounted for with some care. prominent as well as spheric climate and effects of strato- pointed out the Intraseasonal and longer-term varia- unusual features in the observations of spheric processes on the lower tions in the tropical tropopause are the stratosphere during the 1990s, e.g., atmosphere were discussed based on inferred from observations and ana- the variation in the Brewer-Dobson cir- both numerical modelling and dia- lysed fields. culation and eddy wave fluxes, the gnostic studies involving observations. accompanying varialions in melhane Diagnostic investigations, based on It was divided into four sub-sessions; and water vapour, and trends in tem- observations and modeis, have explo- (3-1) Climatology, (3-2) Internal varia- peratures especially in the northern red the possible links between strato- tions in S-T coupled system, polar regions during springtime. spheric climate, ozone and (3-3) Responses to forcings, and Besides influences due to solar cycle tropospheric features. Solar variations (a-+) Trends. Regular periodic annual and volcanoes, there is also a signifi- and their possible modulation of the cycle or intemal variations of the strato- cant coupling with the climate of the QBO could be enabling a solar compo- sphere-troposphere coupled system were troposphere. nent in the long-term variability of the discussed in the first two sub-sessions, while responses to "external" forcings fully coupled chemistry-general circula- being accepted. OnIy 10 of these were were discussed in the resr. tion models were used to investigate the given oral presentations, and it could responses. Haigh (Imperial College) be argued that greater emphasis be In the first sub-session of climatology, f. gave an invited talk on the response to given to this area in future assemblies M. Chipperfield (Leeds Univ.) gave solar variability, and A. Robock (Rut- of SPARC, since changes in UV are the an invited talk on the current status gers Univ.) summarised the impact of major driving factor for this research. of three-dimensional global chemical the 1991 Mt Pinatubo eruption based on There was a good mix of topics and transport models (CTMs) and their the Pinatubo Model Intercomparison geographical coverage: it was especial- use to understand the interaction of Pro ject. On the other hand, ly pleasing to see an excellent repre- ozone depletion and climate. V. Ramaswamy (GFDL) pointed out the sentation of the wide range of research R. Kawa (NASA/GSFC) showed the difficulty of getting statistically signifi- into UV and its impacts that is being capability of such CTMs by the com- cant results in the high-latitude winter undertaken in South America. parison with atmospheric measure- due to large internal variability as a ments on the winter of 19gg-2000 in The posters presented were of a very result of the GFDL "SKIHI" experiments. the Northern Hemisphere. We also high quality alrd the focused discussion had active discussions on the inter- The last sub-session on trends, which sessions provided an excellent forum for actions between chemistry and climate was also the last part of the assembly, informal discussion with the authors, in the focused discussion session in had an invited talk by D. Karoly despite the inclement weather fbut low which several new results with diffe- (Monash Univ.) who gave a perspective tIV) which prevailed most of the time at rent hierarchy of numerical models of the Intergovernmental Panel on Cli- the meeting. They attracted a lot of inter- (z-D or 3-D, CTM or fuliy coupled mate Change for detection and attribu- est among the atmospheric scientists as chemistry-climate (dynamics) model) tion of a stratospheric role in climate well as with the biological scientists were presented. Several other papers change. Stratospheric forcing pro- who convened the associated workshop in this sub-session dealt with the cesses include not only natural forcing on impacts ofLIV radiation on terrestrial GRIPS(GCM Reality Intercomparison variations discussed in the third sub- and aquatic ecosystems on the Saturday Proiect for SPARC) initiative. For ins- session but also anthropogenic varia- following the SPARC meeting. tance, Horinouchi (Kyoto Univ., as greenhouse gases or T. tions such in Several papers (orals and posters) focu- presented by S. Pawson of ozone. studies of stratospheric Model sed on relating ground-based measure- NASA/GSFC) gave a clear dependen- stratospheric trends in ozotre, tempera- ments of UV to satellite-derived ce of the generation of vertically pro- ture and water vapour were reported estimates of UV. Most of these compa- pagating waves in the tropics on the by several authors. For example, red of ground-based measurements of cumulus parameterisation scheme in (NCAR) showed a result of B. Boville UV with estimates using data products t0 each GCM. the climate change simulations with from the TOMS instruments. There was NCAR Climate System Model The subject of the second sub-session a general consensus that while satellite (a coupled ocean-atmosphere general was the internai variations in the products provide a useful global covera- circulation model) for the period of stratosphere-troposphere coupled sys- ge of UV patterns at the surface, signifi- 1B7O-21OO with several scenarios of tem, and the hot issue was the Arctic cant discrepancies remain. The trace gas changes. Importance of the oscillation (AO), or the annular mode. discrepancy appears to be related to modulation due to large internal dyna- More than ten papers were submitted uncertainties in allowing for tropo- mical variations was repeatedly point- on this subject. M. Baldwin (NWRA) spheric extinction (e.g. from ozone and ed out during Ihe sub-session. described the observed deep, longitudi- aerosols). At unpolluted sites differences nally symmetric patterns of low- between satellite-derived estimates of frequency variability and the down- Session 4: UV observations tIV and ground-based measurements are ward propagation of the AO signature, smaller. Improvements may be achie- while A. O'Neill (Reading Univ.) and modelling vable with a better understanding of pointed out the importance of the (Conveners: S. Diaz and R. McKenzie) regional scale differences in tropo- three-dimensional structure in the AO. The UV session invited papers on spheric extinction and with higher reso- Not only observational studies but measurement studies as well as model- lution topography and cloud imagery. several types of numerical studies were the ling studies of UV radiation in Several speakers (inciuding the invited presented on AO-like internal and at Earth's surface. the troposphere the speakers to this session Drs Bais and variations. In the invited talk of this particularly interested in We were Seckmeyer) discussed the present status sub-session, Shindell (NASA/GISS) that relate to D. receiving contributions of UV research, and the extent to which AO patterns are fre- changes ozone, showed that the changes in UV to in recent internationally co-ordinated acti- quently obtained in responses to green- and aerosols. Particular empha- cloud, vities have improved the measurement gas, solar and volcanic sis was placed on the co-ordination of house ozone, accruacy and our understanding of pro- forcing in climate change simulations. ground-based measurements of UV to cesses that affect UV radiation. One of Other variations with intra- assess the accuracy of the estimations internal these was the IPMMI (International Pho- scales since in seasonal and interannual time of UV derived from satellites tolysis Frequency Measurement and were also discussed intensively in this years to come it is expected that these Model Intercomparison) campaign, play a role UV radiation sub-session. will major in which focused primarily on actinic assessment, in the same way that satel- The third sub-session of responses to radiation. It was argued (S. Madronich) lite derived ozone has already proved into three: that the effects of air pollution can be forcings were divided [1) QBO crucial to our global understanding of and ENSO, which are, in a sense, "exter- Iarger on actinic UV fluxes than irra- ozone depletion. nal forcings" to the extratropical strato- diances and that more emphasis should sphere, (2) solar forcing with the 11-year This session attracted more interest be given to measuring actinic fluxes, cycle, and (3) volcanic aerosols. Some than expected, with over 50 papers particularly in polluted environments. SPARG Assessment of Upper Tropospheric and Stratospheric Water Vapour

Dieter Kley, Institut fur Chemie und Dynamik der Geosphäre, Forschungszentrum Julich, Germany (d. kley@fz-j uel ich. de) James M. Russell lll, Center for Atmospheric Sciences, Hampton University, Hampton, VA, USA (james. [email protected]) Assessment co-chairs

Introduction was generously supported by many r The concentration of stratospheric organisations and agencies including An initiative to conduct an assessment water vapour in the "overworld" \ r]\4O, WCRP, SPARC, DG Environment (@ of upper tropospheric and stratosphe- > -380 K) is determined by dry air of the European Commission, NASA, ric water vapour was begun following upwelling through the tropical tropo- NOAA, NCAR, a SPARC sponsored international CNRS, CNES, FOT- pause, methane oxidation in the stra- workshop held at NCAR, Boulder, schungszentrum lülich, Imperial Colle- tosphere, and transport by the ge and other national research poleward-and-downward (Brewer- Colorado, USA, 26-28 August 1998. progrirmmes and institutions. Dobson) Two main goals for the assessment mean circulation. At the tropical tropopause, air a were identified: 1. To critically review We take this opportunity to express our is dried by complex mix of processes measurements of water vapour in the gratitude to all the scientists (authors, that act on a variety of spatial stratosphere and upper troposphere in contributors and reviewers) who and temporal scales. Water vapour in the upper troposphere order to consolidate our knowledge helped in the preparation of the assess- is controlled by local and regional cir- and understanding of its distribution ment and to the SPARC Scientific Stee- culations and seasonal and variability and 2. To collect quali- ring Group who have been supportive changes of upper a I mospheric temperature. ty assured water vapour data, in order since its inception. Our special gratitu- to make them available for indeoen- de is due to the lead authors of the o There has been a 2 ppmv increase of dent examination oI the assessmenl chapters and to Petra Udelhofen at the stratospheric water vapour since the results and to preserve such data for SPARC Data Center for setting up the middle 1950s. This is substantial given future use. data archive. Particular thanks must be typical current stratospheric values of given to Samuel Oltmans who organi- 4-6 ppmv. Methane photochemical The objectives for the assessment, the il sed the workshop oxidation in the stratosphere produces report structure and the production at NCAR, Boulder Colorado; Computational Physics Inc. approximately two molecules of water schedule were published as a White CPI, for hosting a workshop in vapour per molecule of oxidised Paper in SPARC Newsletter No. 13 Washington D.C.; methane. The increase in the concen- fKley and Russell, 1999]. Drafts of FranEois Dulac from the CNES for hosting the review mee- tration of tropospheric methane since three chapters of the assessment report ting in Paris; C6line Phillips the the 1950s (0.ss ppmv) is responsible were prepared in 1999. The first draft at SPARC Office for her co-editorship, for at most one half of the increase in report was examined by an internatio- Marie-Christine Gaucher at the SPARC stratospheric water vapour over this nal panel of peer reviewers both by office for her help in the organisation time period. It is not clear what is res- mail review and at a meeting in Paris, of the review meeting in Paris and in ponsible for the remainder of the France in 2000. During the January the final editing of observed increase in stratosoheric Paris meeting responses to the mail the report, and Catherine Michaut at the water vapour. review comments were proposed by SPARC Office for her help in editing the second peer- the chapter authors and discussed by o In the upper troposphere, no major review draft and the final draft of the the participants. This rigorous evalua- inconsistencies were found between repolt. tion greatly improved the report with existing satellite-based measurements the contribution of the reviewers being The full report is available at that would preclude their use in des- significant. A second draft report was http:www.aero.iussieu.frl-sparc/. The cribing the long-term behaviour of evaluated by mail review in August Report Summary is reproduced below. upper tropospheric humidity. The data 2000. are also of sufficient quality for climatological and process studies. Following the second review, a report: Summary . "SPARC Assessment of Upper Tropos- Upper tropospheric relative humidity (UTH) has been monitored for about pheric and Stratospheric Water Key findings Vapour" was completed and published 20 years by instruments on operational . A significant increase in the number in December 2000 [SPARC, 2000]. satellites. Assessing long-term and quality of stratospheric water changes in the UTH is difficult becau- The success in producing the Report is vapour measurements has occurred se of high variability during ENSO the result of the intensive work and over the past 25 years, particularly events, other natural modes of variabi- enthusiastic co-operation of a large with the advent of satellite observa- lity in the large-scale circulation, and number of scientists world-wide who tions. Stated accuracy of most in situ the competing effects of water vapour have worked towards improving the and remote instruments as well as and lemperalure changes on lhe UTH. quality of the measurements and our direct or indirect comparisons of coin- Although both positive and negative understanding of the observations. The cident field measurements cluster are statistically significant long-term work of the contributors and reviewers within a +10% range. changes can be found in different

l Iatitudinal bands, no striking global f""f,niqu" Range Altitude range Accuracy trend emerges from preliminary analyses. i Frost point hygrometry 101000 0.5 ppmv 5 30km 5-10% o The operational radiosonde network Lyman-a fluorescence 500 0.2 ppmv 5-35 km 6 -7% does not produce water vapour data Tuneable diode laser spectrometry > 0.1 ppmv 0-30 km 5-10% that can be used for either long-term MOZAIC sensor > 20 ppmv 11ono91!ey9 5 -7% RH middle and low analyses, process studies the Radiosonde u5%RH not assessed change in 100 troposphere upper troposphere, or for validation of Micro wave spectrometry 20 - 0.2 ppmv 20-80 km os - o.i pp.J upper tropospheric humidity (UTH) LIDAR > 4 ppmv 0-20 km 5 10To measurements. emerging However, lR and FIR spectrometry > I ppmv 5 40km 5-13% data sets from improved quality, quasi- operational aircraft and ground-based Table l. In situ and remote sensing techniques for measurements of H2O from ground- instrumentation show promise and based, balloon-borne and airborne platforms, along with their typical measurement range should be used more extensively for and overall accuracv, i.e. the sum of systematic and random errors. UTH process studies, climate analyses and satellite data validation. upper tropospheric water vapour are fic instrument implementation. listed in Table 2 along with random Horizontal resolution is typically on Instrumentation, precision and systematic error estimates for the order of s0 km to 300 km depend- and accuracy single profile observations (as opposed ing on whether the experiment is nadir to zonal or temporal averages). nr I imh rriernrino water '_."--___ö' Tropospheric and stratospheric Accuracy estimates can be obtained vapour has been measured over the past from the root-sum-square of the ran- The Microwave Limb Sounder (MLS) 50 years a large number of by indivi- dom and systematic error components. and several generalions oi High duals arrd institutions using a variety of Error estimates are given for ranges of Resolution Infrared Sounder (HIRSI and remote measurement tech- in situ verticaL levels. Since some systematic instruments on the TIROS Operational niques. Measurement results are widely error components vary randomly from Vertical Sounder (TOVS) suite of mis- the literature. Instrumenta- dispersed in profile to profile, these components sions have provided measurements of tion has steadily evolved from a small are less important for daily, seasonal, upper tropospheric relative humidity number of manually operated ln sifu ins- or zonal means. Therefore, a zonal- (UTH) from satellites. MLS relative huments to automatic devices deployed average stratospheric error profile is humidity accuracy estimates for low io on balloon and aircraft platforms, and 12 dominated by the truly systematic mid-latitudes range from 10 to 35% at more recently to high precision sensols error components, whose signs may be 1,47 hPa and 20 to 50% at higher pres- on satellites. Only limited measure- unknown and offsetting. The vertical sures. Accuracy estimates for indivi- ments of relative or specific humidity resolution of satellite instrun:rents, also dual relative humidity measurements a have using single instrument type given in Table 2, depends on the indi- made by TOVS are difficult to obtain records longer than 10 years. vidual measurement concepl (e.g. but several generations of TOVS ins- Operating principles and measurement occultation or emissionl and the speci- truments span a temporal range of specifications of most in situ research- type instruments currently use are lnstrument in Random error Systematic error Vert. Res.(km) presented in Table 1 along with their and data set estimated measurement accuracies. LIMS (version 5) 20-15% (1 -5 hPa) 31-24% (1-5 hPa) These instruments provide point mea- (Limb lR emission) 15-10% (5 - 10 hPa) 24-20% (5 - 10 hPa) -E surements in time and space with high 10% l1O - 50 hPa) 2j-37o/o i'10 - 50 hPa) vertical resolution, typically in the SAGE ll (version 5.9) 1o-57" (3 - 10 hPat 6-13%(3-7 hPa) range of a few hundred meters or better. (lR solar occultation) 5-14% l1O - 25 hPa) 13% \7 - 25 hPa) =3 Accuracy estimates range from 5 to 10% 14% (25 - 300 hPa) 3-21%\25 100 hPa based on known or estimated random 27'/" (10O - 300 hPa) and systematic uncertainties inherent in ATMOS (version 3) 9-11o/o(1 hPa) 6% \1 - 300 hPa) the instrument system, calibration pro- (lR solar occultation) -300 cedures and retrieval algorithms. HALOE (version 19) 9-t% (1 - 10 hPa) 10-14'/. \1 - 10 hPa) Remote sensing instruments deployed (lR solar occultation) 7-13% (1O - 40 hPa) 14-19'/" (10 - 40 hPa) 2.3 on ground-based, balloon-borne and air- 13% \4O - 100 hPa) 19-24'/. \4O - 100 hPa) borne platforms provide vertical profile MLS (version 0104) 4% 11 - 10 hPa) 6-9%(1- 10 hPa) measurements with stated accuracies (Limb mwave emission) 3% (10 - 50 hPa) 9-16% (10 50 hPa) similar to those from in situ instru- 3-8% (50 100 hPa) 16-50% {50 - 100 hPa) ments, although with coarser vertical MÄS 5-1O% (1 - 50 hPa) 10-15% \1 50 hPa) =5 resolution. Such vertical resolutions (Limb mwave emission) range from several hundred meters in ILAS (version 4.20) More than 10% (above 2 hPa) 30%{'1-2hPa) the case of LIDAR, a few kilometres for {lR Solar occultation) 10-5o/o (2 - 300 hPa) 30-10% (2 -7 hPal 1-2 the infrared (IR) and far infrared (FIR) 10% \1 - 300 hPa) spectrometers, and approximately POAM lll {version 2) 5%\3 100 hPa) 15' (3 - '100 hPa) 10 km for microwave instruments. (lR Solar occultation)

Satellite and shuttle based experi- Table 2. Estimates of random errors, systematic errors and vertical resolution of strato- ments for measuring stratospheric and spheric H20 profiles derived from satellite instrumentation. SPARG Assessrnent of Upper Tropospheric and Stratospheric Water Vapour

Dieter Kley, Institut für Chemie und Dynamik der Geosphäre, Forschungszentrum Julich, Germa ny (d. kley@fz-j uel ich.de) James M. Russell lll, Center for Atmospheric Sciences, Hampton University, Hampton, VA, USA (james. russel [email protected]) Assessment co-chairs

Introduction was generously supported by many o The concentration of stratospheric organisations and agencies including An initiative to conduct an assessment water vapour in the "overworld" WMO, WCRP, SPARC, DG Environment (O of upper tropospheric and stratosphe- > -380 K) is determined by dry air of the European Commission, NASA, ric water vapour was begun following upwelling through the tropical tropo- NOAA, NCAR, a SPARC sponsored international CNRS, CNES, FOT- pause, methane oxidation in the stra- workshop held at NCAR, Boulder, schungszentrum ]ülich, Imperial Colle- tosphere, and transport by the and other research Colorado, USA, 26-28 August 1998. Be national poleward-and-downward (Brewer- programmes and institutions. Dobson) Two main goals for the assessment mean circulation. At the tropical tropopause, were identified: 1. To critically review We take this opportunity to express our air is dried by a complex measurements of water vapour in the gratitude to ail the scientists (authors, mix of processes that act on a variety of spatial stratosphere and upper troposphere in contributors and reviewers) who and temporal scales. Water vapour in the upper troposphere order to consolidate our knowledge helped in the preparation of the assess- is controlled by local and regional cir- and understanding of its distribution ment and to the SPARC Scientific Stee- culations and seasonal and variability and 2. To collect quali- ring Group who have been supportive changes of upper atmospheric temperature. ty assured water vapour data, in order since its inception. Our special gratitu- to make them available for indeoen- de is due to the lead authors of the . There has been a 2 ppmv increase of dent examination of lhe assessment chapters and to Petra Udelhofen at the stratospheric water vapour since the results and to preserve such data for SPARC Data Center for setting up the middle 1950s. This is substantial given future use. data archive. Particular thanks must be typical current stratospheric values of given to Samuel Oltmans who organi- 4-6 ppmv. Methane photochemical The objectives for the assessment, the il sed the workshop oxidation in the stratosphere produces report structure and the production at NCAR, Boulder Colorado; Computational Physics Inc. approximately two molecules of water schedule were published as a White CPI, for hosting a workshop in vapour per molecule of oxidised Paper in SPARC Newsletter No. 13 Washington D.C.; FranEois Dulac from methane. The increase in the concen- lKley and Russell, 19991. Drafts of the CNES for hosting the review mee- tration of tropospheric methane since three chapters of the assessment report ting in Paris; C6line the the 1950s (0.55 ppmv) is responsible were prepared in 1999. The first draft Phillips at SPARC Office for her co-editorship, for at most one half of the increase in report was examined by an internatio- Marie-Christine Gaucher at the SPARC stratospheric water vapour over this nal panel of peer reviewers both by office for her help in the organisation time period. It is not clear what is res- mail review and at a meeting in Paris, of the review meeting Paris and ponsible for the remainder of the France in 2000. During the in in lanuary the final editing observed increase in stratospheric Paris meeting responses to the mail of the report, and Catherine Michaut at the warer vapour. review comments were proposed by SPARC Office for her help in editing the the chapter authors and discussed by second peer- o In the upper troposphere, no major review draft and the final draft of the the participants. This rigorous evalua- inconsistencies were found between report. tion greatly improved the report with existing satellite-based measurements the contribution of the reviewers beins The full report is available at that would preclude their use in des- significant. A seconcl draft reporl was http :www. aero. jussieu.fr/-sparc/. The cribing the long-term behaviour of evaluated by mail review in August Report Summary is reproduced below. upper tropospheric humidity. The data 2000. are also of sufficient quality for climatological and process studies. Following the second review, a report: Summary . "SPARC Assessment of Upper Tropos- Upper tropospheric relative humidity (UTH) has been monitored for about pheric and Stratospheric Water Key findings Vapour" was completed and published 20 years by instruments on operational . A significant increase in the number in December 2000 ISPARC, 2000]. satellites. Assessing long-term and quality of stratospheric water changes in the UTH is difficult becau- The success in producing the Report is vapour measurements has occurred r" oi high variability during ENSO the result of the intensive work and over the past 25 years, particularly events, other natural modes of variabi- enthusiastic co-operation of a large with the advent of satellite observa- lity in the large-scale circulation, and number of scientists world-wide who tions. Stated accuracy of most in situ the competing effects of water vapour have worked towards improving the and remote instruments as well as and temperature changes on the UTH. quality of the measurements and our direct or indirect comparisons of coin- Although both positive and negative understanding of the observations. The cident field measurements cluster are statistically significant Iong-term work of the contributors and reviewers within a +10% range. changes can be found in different satellite measurements. |udicious use equator as methane is oxidised into values also appear to spread out to the of data from the MOZAIC (Measu- water vapour. Below approximately poles and into the winter hemisphere. rement of Ozone and Water Vapour by 100 hPa, the extratropical lower The horizontal transport caused by the Airbus In-Service Aircraft) project provi- stratosphere is moistened by air trans- South Asian monsoon is stronger than ded some information used in assessing ported from the tropical upper tropos- other monsoon circulations, leading to the quality of the MLS and TOVS mea- phere horizontally across the more water vapour in the upper tro- surements. To gauge their value in futu- subtropical tropopause at the location posphere during boreal as opposed to re correlative efforts. DIAL and Raman of the subtropical jet. austral summer. LIDAR systems were compared with The horizontai transport in the lower At the tropical tropopause, a complex radiosondes and frostpoint hygrometers. stratosphere has a strong seasonal mix of processes act to remove water The LIDAR results in the troposphere component (Figure 3). An absolute vapour lrom air as it enters the strato- agree to within about 10% with other minimum of the mixing ratio sphere from the troposphere below. correlative measurements, suggesting (-z.s ppmv) is centred near 20"N Within the framework of large-scale that such systems accurately measure during with the dry air mean ascent, the dehydration processes water vapour. If deployed in sufficient January-March, propagating both poleward and into probably include smaller-scale (convec- numbers, such measurements could pro- the Southern Hemisphere. Relatively tive) ascent, radiative and microphysi- vide profile data valuable for validation high water vapour values, centred near cal processes within clouds, and of UTH satellite measurements. 30'N. are observed during the wave-driven fluctuations in temperature. Northern Hemisphere summer coinci- The location, strength, and relative Spatial variability dent with the convective phases of the importance of these processes vary and seasonal changes summer rnonsoons. Similar to the seasonally. However, the observed Stratosphere, including the tropopause winter poleward propagation of the seasonal variation in tropopause-level The annuai zonal mean water vaoour dry air masses, the higher summer water vapour is influenced primarily by distribution in the stratosphere the annual variation in tropical is depicted in Figure 2. Key tropopause temperatures. Air features are sharp vertical gra- Annucrl lneern wqler Ycrpor rising lhrough lhe tropopause is dients at the tropopause and .3 marked with seasonally varying in the extratropical lower stra- (n mixing ratio, and retains these tosphere, a minimum in the I markings as it spreads rapidly tropics at or just above the 1 poleward and more slowly 40 s tropopause, and gradual upward into the stratosphere. 14 E tn- increases upward and pole- tu o D Upper troposphere ward. The water vapour distri- o o Upper tropospheric water bution can be understood as a - CL 20 vapour in the tropics and sub- balance between dry air ente- 100 tropics is strongly influenced ring via the tropical tropopause, t0 300 by the Hadley Celi and the a source of water vapour from Walker Circulation. The predo- methane oxidation in the 0 I 000 minant source tbr moisture in upper stratosphere and return 905 605 305 0 30N 60N 90N Lolitude the tropical and subtropical the troposphere via the Iq. to upper troposphere is convec- extratropical tropopause. The tion, producing, on average, general features of the distri- Figure 2. Annual zonal mean water vapour from HALOE and MLS data by height latitude. interval moist regions in the convective are by and equivalent Contour bution explained of 0.2 ppmv. The thick dashed line is the tropopause, and areas over the western Pacific, Lagrangian-mean transport via the thick solid line is the 400 K potential temperature surface. South America and Africa the Brewer-Dobson circula- (Figure 4). Moist areas also tion, wave-induced isentropic appear seasonally in the region mixing, and upward extension HA1OE woler Y.rpor 3aO K of the Asian summer nrorrsoorr of tropospheric circulations in and along the intertropical and the lowest few kilometres of South Pacific convergence the stralosphere. Nearly a1l 60N zones. The seasonality of sur- air that reaches the slratosphere face temperature and of above 100 hPa passes through 30N convection, which roughly fol- Eo the tropical tropopause where low the sun, as well as season- 'En- freeze drying at low tempera- gv al variations in monsoon tures and other poorly unders- r+ circulation. produce concomi- tood processes produce 305 tant seasonal changes in water annual mean mixing ratios of vapour in the troposphere.

-3.5-4 ppmv. Some of this 60s This relationship between dry air rises slowly in the tro- convection and upper tropo- pics. bul most spreads pole- spheric moisture changes sign ward, primarily in the lowest near the tropical tropopause, few kilometres oI the strato- Monrh somewhere between 150 hPa sphere. In addition, water and 100 hPa, so that convec- vapour concenLrations increase Figure 3. Latitude-time evolution of water vapour mixing ratio tion dries the tropopause upward and away from the near 380 K derived from seasonal cvcle fits ofthe HALOE data. region. Water vapour is also Figure 4. Annual mean Upper Tropospheric Humidity over ice (L/TH| ) {$?ä"!; averaged for 1980-1997 from HIRS instru- {x$&&,xssy} ments, in percent.

influenced by fluctuations at both shorter and longer time scales, including the quasi-biennial oscillation in the stratosphere and the El Niflo- Southern Oscillation and the Tropical Intraseasonal Oscillation in the troposphere.

Upper tropospheric water vapour at middie and higher latitudes is highly variable and can be supplied by transport from the tropics, by mesoscale convection, or by extratropical cyclones. Dry air can be transported of nearly twenty years. A linear fit of When combined with satellite-derived from the subtropics or from the extra- relative humidity from 1929 to present upper tropospheric temperature data tropical lower stratosphere. These is shown in Figure 6. The trends for which also show a small positive trend transport phenomena tend to be episo- different latitudinal bands, and espe- since 1979, the HIRS data imply a lar- dic rather than steady. cially in the deep tropics, are slightly ger positive specific humidity trend, positive but insignificant at the 99% but the combination of uncertainties in Long-term changes confidence level. these two types of measurements Stratosphere means A shorter time series of upper tropo- that the uncertainty in specific There is only one nearly continuous spheric relative humidity, 1992 to pre- humidity is large enough to hide stratospheric water vapour time series sent, exists from the MLS instrument. trends that are significant to climate. of 20 years duration, using a single ins- Figure 7 shows the MLS humidity for t5 trument type, that is available for long- centre altitudes of 147 and z1s hpa Recommendations term change determination. Although over the latitude range 30"S-30oN. For 1. Further studies, including well differences between instrument sys- the overlapping time period both data designed intercomparison experi- tems were largely determined to fall sets show a minimum in relative ments and laboratory work, are requi- within their stated uncertainty esti- humidity that occurs in 1994 although red to quantify and understand the mates, those differences are stiil too the MLS minimum is shallower. differences between stratospheric large to combine various ins- water vapour sensors. This is trument records to constmct a particularly important for in longer time 45 series. However, silu instruments. /n sifu ins- a number data sets of used in truments are critical for obtai- the assessment sampled the \ t ,\ \sotltott- ning high-resolution data for atmosphere periodically 0.00,Ä/yr \uorro, .0.10%:/yr over use in process studies of a long period providing seve- 40 water vapour transport bet- ral time series of intermediate ween the troposphere and length (B-15 '6os-6oN o.o4%/yr years). These \..r' stratosphere. Strong valida- were used in combination '105-l0N 0.10%/yr tion programs lo eslimale including cor- slralospheric relative measurements need changes. The observations are +--Jl F to be a part of water vapour consistent in sr-rggesting that = -:-1 '-..\ satellite measurement efforts. water vapour has increased at 'v./ .,/ \ l0N-30N 0.02%/yr Tn lhe upper lroposphere. a rate of about 1%/year over such validation has not been the past 45 years (Figure 5, 30 a part of the measurement p. III). The record also sug- program. Improvement of gests that this increase has not '-\ror'* radiosonde observations of been uniform but has .o.o:"a/yr varied water vapour and wider use over this period. 25 of LIDAR would aid in such 80 8l 82 83 84 85 86 8/ 88 89 90 91 Upper troposphere 92 93 94 95 96 97 validation. Iime (yeors) The longest data set of upper 2. Greater attention needs to be tropospheric humidity is one Figure 6. Annual mean upper tropospheric humidity jce paid to the continuity of mea- that is derived from the HIRS over from HIRS for various latitude bands and linear fit statistics surements fbr determination of instrumentation on different from 1980 to 1997. 60"5-60"N (solid tine),60.5-30.5 (dotted long-term changes in both the TOVS satellites. The HIRS ins- line), 30"5-10"5 (dashed line), I0"S-10"N (dot-ctash line), stratosphere and upper tropo- truments cover a time period (dash-3dots 70"N-30"N line) and 30"N-60"N (long dashed line). sphere. It is important to have complementary observations, not ments, whether satellite or in situ, planned to provide overlap with exis- relying solely on one instrument or should be combined with simulta- ting instruments in orbit. To better quantify dynami- neous methane measurements. Main- approach. 3. Process studies of upper tropospheric impact long-term current long-term in situ cal effects that can taining water vapour and convection should be stratospheric measure- measurement programs is necessary changes. all undertaken. These would include joint for any interpretation measurements of water vapour, cloud of long-term change. microphysical properties, ald chemical Stratospheric water that carr provide a history ofthe vapour should be species air. More observations of the tropical monitored in situ aI (15-20 km), by both various latitudes, and tropopause region in particular in the in situ and remote sensing methods, are presently data sparse needed in order to improve our under- tropics and Southern standing of stratosphere-troposphere Hemisphere. Satellite exchange there. sensors with a history 4. Data sets collected in the future of high quality measu- should be added to the SPARC Data rements should be Center at http ://www.sparc.sunysb.edu. included in future Valuable data from the 1940's, 1950's, sateiiite missions in and 1960's may already be lost, but 70 order to monitor long- some could and should be rescued. 60 term changes in stratospheric and upper 50 tropospheric water References 40 vapour. Upper tropo- Kley, D. and J.M. Russell III, Plan for the 30 spheric specific humi- SPARC Water Vanour Assessment l1 t992 1993 1994 dity should be (WAVAS), SPARC Newsletter 13, 5-8, 1999 monitored with a view SPARC Assessment of Upper Tropospheric to determining long- and Stratospheric Water Vapour, Dieter Figure 7. MLS relative humidity over ice. Data were term trends. To deter- Klev. Tames M. Russell III and C6line Phil- years and 30"N. The top figure averaged for 7 between 30"5 mine these trends hpi (eds), wcRP - No. 113, wMo/TD - No. represents a 3 km layer around 147 hPa and the bottom 1043, SPARC Report No.2, Paris 2000. the sequen- t6 f igure a 3 km layer around 215 hPa. Dots are daily effectively, averages and the line is a l2-month running mean boxcar ce of future satellite filter to remove the annual cYcle. missions should be a

Detection and Attribution of a Stratospheric Role in Glimate Ghange: An IPCG Perspectiwe

David Karoly, Monash University, Australia, (d.karoly@sci. monash.edu.au) (Coordinating Lead Author, Detection of Climate Change and Attribution of Causes, IPCC Third Assessment Report)

lntroduction governments of more than 120 countries . climate is expected to continue to ald its reports are approved and accep- change in the future There has been increasing scientific, ted by consensus of all Panel members. government and community interest . there are still many uncertainties over the last twenty years on the possible The main conclusions from the first The third conclusion attracted consi- IPCC Second Assess- role of human activity in global and volume of the derable attention, as it suggested for "Climate 1995" regional cha-nges to climate. The tntergo- ment Report Change the first time that there was a discer- vernmental Panel on Climate Change (Houghton e/ o1., 1996) were: nible human influence on global cli- (IPCC) was established by the World . greenhouse gas concentrations have mate. Meteorological Organization and the continued to increase United Nations Environment Program to The IPCC Third Assessment Report is . climate has changed over the past cen- cany out regular assessments of climate being finalised at present and will be rury change science, the impacts of climate released later in 2001. In this report, change, and approaches for mitigation of . the baiance of evidence suggests a there has been a greater appreciation and adaptation to climate discernible human influence on globai of the important role of the stratosphere change. It includes representatives of the climate in the climate system due to changes Nurnerical Experiments on lnternal Interannual Variations of the Troposphere-Stratosphere Coupled System

Figure 1 Seasonal variation of daily temperature at 30 hPa at the North Pole (a), the equator (b) and the South Pole (c) drawn with NCEP/NCAR re-analvsis data for 1979-1997. Thick red line is the 19-year average for each calendar day. Numerical Experiments on lnternal Interannual Variations of the Troposphere-Stratosphere Coupled System

&sF{ *6 l*F*r

Figure 2 Seasonal variation of daily temperature at 86'N and 26 hPa for 10 runs of 100-year integrations under a purely periodic annual forcing.Thetopographicamplitudeh6of zonal wavenumberl ischangedfrom0mto3000mastheexperimental parameter. Thick red line is the 10O-year average for each calendar day.

fu*sFSS *u6x I S&S m

'272.0 Jun. 0.6 '271.0 Jul. Figure 3 04 Frequency distributions of the 264.3 Aug. monthly mean polar temperature , 0.6 '255.t at p = 2.6 hPa in the two millen- 5ep' nium integrations: ho:500 m !& , 2.1 '243.7 (left) and 1000 m (right). Dashed 0d. , 4.9 line denotes 1000-vear mean , tu: the s , ',' '234.2 annual variation monthlv Nov. of the b.-'- - s.2 mean temperature, and orange L | 233.0 =r Der, shade shows the variable range. a *--"1 . 13.6 Averages and standard deviations H e, Jon. for the 1000-year data are also written on the right hand side of feb. each panel (top and bottom numbers, respectively). Frequency dis- Mor. tributions for a seasonal mean are also displayed in the bottom: ,&.,"ii Apr. spring mean for ho : 500 m and '268.7 L,zz Moy winter mean for ho = 1000 m. The l0 '; .t ' 241.5 downward arrow in the seasonal 5 Win. g.g mean indicates a threshold value 0 ' ,n*'rx**' ' for the 200 years of highest tem- 240 pe ratu re. II] II] Numerical Experiments on Internal Interannual Variations of the Troposphere-Stratosphere Coupled System

ä**a ? &SS rm Wü*äes

-* $üf *; 'n t6 *J -;. . 6ü I *d*s g \., ,; * *?,*ooot * o {.."€ j. - -, "

, ' t.. ,1, j . i.

100 200 300 400 500

30 t I cr ,a IC a po 20 -a a f? , r r' I urä *J ö-.o - at 9 a * ß.-u t t6rr$cl*r t tf c go - a"", *d *- .o F f, *t *, a ü3 0-3a a tc at a a .* l0

0 'l ',1 ;r i -,1 ,i'i ,-1 .10 i: .

.20 600 700 800 900 r 000 Yeot

Figure 4 Time series of the deviation of winter-mean polar temperature at p : 2.6 hPa in the millennium integration for ho : 1000 m, which is made by connecting 10 independent 10O-year integrations. The green horizontal line is the threshold value (+ 9.2 K) to select the 200 warmest winters denoted by green dots.

SPARG Assessrrent of Upper Tropospheric and Stratospheric Water Vapour ill

/ HAIOE V MRF *t Tffi-fi4& F'nFm, ßffi*-Sffi"trd . CMDI tr FIRS-2 Ö ATMOS X MKIV X NRI

Yeor

Figure 5 Water vapour time series for several instruments between 30-50"N over the pressure range 110-140 hPa. Data plotted are individual measurements with the exception of NOAA-AL Lyman-alpha (1 minute averages). lntegrated Global Obserwing Strategy (IGOS) for Ozone and Relewant Atrnospheric Parameters

310

Gtehsl Avermge ffizeüfte S#ömtuwe P"trffiFffi#

E üryr*h Frak* fSmS i rn e o 5 Figure 1 € / 6o / Observed and predicted -t\ o ton /t ozone trends; TOMS I '- -/ o / \--l (Nimbus-7, Meteor, and f4Ill predicted recovery Earth Probe) and model predictions that include lj the known chemical T catalytic processes and 280 solar cycles, but not temperature trends in llleleor TOltÄS the lower stratosohere which could further I 980 I 990 2000 201 0 2020 slow ozone recoverv.

r20'I4, 90'w 60'l/\, 30 ffi tl 36 6l 86 [ppbv]

Figure 2 Monthly mean afternoon (1 to 4 pm) surface ozone concentrations calculated for July using Harvard GEOS-CHEM model. lntergrated Global Observing Strategy (IGOS) for Ozone and Relevant Atmospheric Parameters a

INSTRUI{IENI MtsstoN 0 2 3 4 5 6 7 8 I l0 il 12 l3 t4 t5

TOMS Eorlh Probe

Quik T0M5

EPIC Iriono

0Ml E0S Auro

OMPS NPOE55

s}uu/2 NOAA I I

NOAA 14

NOAA 16

NOAA M

NOAA- N

NOAA N'

GOMT ERS- 2

IMG ADEOS

ODUS GCOM AI

ODUS GCOM A2

SCIAMA(HY ENVISA]

GOME-2 MTTOP - I

MEIOP - 2

MEIOP - 3

Figure 3a Satellite missions and instruments. which will measure total ozone, 2000 to 2015

INSIRUMENT MtsstoN 0 I 2 3 4 5 6 7 8 I t0 tl t2 l3 t4 l5

SAGE III Meleor-3M

ISS

F00

sMttEs ISS

POAM SPOT- 4

SBUU/2 NOAA- I I

NOAA 14

NOAA -I 6 NOAA-M

NOAA- N

NOAA - N'

t]Äs-2 ADEOS 2

SOFIS GCOM-AI

50Fts GCOM-42

0srRts ODIN

Microwove ODIN

A(t ftiSAT

ERS 2 GOME

GOMOS ENVISAT

SCIAMA(HY ENVISAT .:l : "., MIPAS ENVISA]

HIRDLS E0S Auro

Mt_5 E0S Auro

IES E0S Auro

0Ml E05 Auro

GOME-2 MTTOP

OMPS NPOISS Figure 3b Satellite missions and instruments, which will measure ozone and atmospheric constituent profiles, 2000 to 2015. Public Access to the Netvvork for the Detection of Stratospheric Ghange Database

VI Figure 1 - Evolution of the daily mean total column abundance of hydrogen chloride ano hydrogen fluoride measured above the Jungfraujoch station (47"N,8"E) since 1977, as part of the University of Liege commitment to the NDSC. For details see European Research in the Stratosphere (1997), and Mahieu et al., (20001. Figure courtesy of R. Zander.

Figure 2 - Monthly means of sunset (pm, blue) and sunrise (am, red) N02 slant column measurements at Lauder (45"S, 170"E) as part of NIWA's commitment to the NDSC. The right- hand scale shows approximate values for vertical column N02 based on an air mass factor of 17.5. For details see Liley et al., (2000lr. Figure courtesy of p. Johnston. The Ewolution of the Antarctic Ozone Hole in 2OOO

il*.

";,\ F' ' H29s ,r,,"i]i !,,o ,),i\ H*, 'rtffili

f,f r' ,,, ffi,"o -;l';i' Figure 1 Map of the total ozone over the Southern Hemisphere, on fi::" September 10, 2000, as seen by EP-TOMS. On this day the n'o' ozone hole reached its largest size on record. The white line vtl shows the 220 DU isoline. Values larger than 340 DU are il;, not shown.

",f":'." il*" ,ir" -- ... il:;,

t' t,:: Ji .,tl""' fH26s

--"J-- 1 ffiti m,*

r." Figure 2 il Mean total ozone over the Southern Hemisphere between October 6 and 20. Note the dis- .,"f: placement .,r.l"o;r+* of the ozone hole t,:, and how it covers at least half of Tierra del Fuego during this il"u fortnig ht. The Evolution of the Antarctic Ozone Hole in 2000

October t99O fr.oo 32s r:1 [-]3ro n 2es n 280 Fj 26s 2so m a 235 ffiR22() ffi;; ff rzs rit6o F r45 r3o I ttt Ll -60 -so Lotitude Degrees South

October 1999 f,.,, r-l 34o r"l 32s i-l 3ro 2es r-l 2l r*j 28o 26s f':l 2so vill q) @ o o mä; tl ffi ?3; H rz5 roo l-.1 r4s 1--l r 30 1tl,.' l-l t nil5 -80 -70 -60 -50 -30 b) Lotitude Degrees Soufh

October 2OOO f .uu f-l34o n 32s l- 3ro l- 2es n 28o ffi zos h# 2so ffi;; ffi zos Figure 3. ffi reo Evolution of the ozone laver between n r7s 30'and 80'S during fi roo a) October 1990, f-j rrs b) October 1999, l-lr3o c) October 2000, nils averaged between 60" and 70'W, i.e. over -70 -65 -60 -55 -50 -4s -40 -35 '30 Southern Chile and Argentina. The white Lotitude Degrees Soufh line shows the 220 DU isoline. in the structure of the stratosphere and peratures noted above are due to exter- In addition to these anthropogenic recognition of its vital role for both nal climate forcing factors or to inter- forcings, changes in natural external radiative and dynamical processes in nal climale variability. reliable climate forcings have been included in the climate system. estimates of the magnitudes and pat- this IPCC assessment. Estimates of the terns of internal climate variations are climate forcing due to changing solar required. The observational data for irradiance or due to changes in strato- The elements of detection both the surface and the lower stratospheric volcanic aerosols are based on and attribution sphere are too short to be used to esti- direct observations for the last two In decades but are based on indirect of climate change mate internal climate variability. addition, they may have been affected evidence over the last 100-200 years Here, I briefly discuss the essential ele- by the response to external climate for- and therefore have greater uncertainty. ments used in the detection and attri- cings, making it difficult to isolate the The response to these forcings must be bution of climate change, with an effects of internal variability alone. estimated from simulations with emphasis on the role of the stratosphere. The only way to estimate internal cli- climate models. The response to indi- Anthropogenic climate change, if and mate variability is to use very long viduai major volcanic eruptions seems when it exists, must occur against a simulations of climate models that to be well simulated but changes in background of natural internal climate have no variations in external forcings. volcanism appears to have played a variability and natural forced climate Such control simulations have been smaLl role in recent climate variations. variations. Detection and attribution of run with a number of different cou- The response to the direct effect of climate change is a statistical 'signal in pled ocean-atmosphere climate models changes in solar irradiance has been noise' problem. Detection is the pro- for periods of 1000 years or Ionger. simulated in climate models. cess of demonstrating that an observed They show that the observed warming However, those simulations used in change is significantly larger than over the last 100 years is very unlikely detection and attribution studies have could be explained by natural internal to be due io internal climate variabilitv not included possible changes in variability. Attribution is the process alone. stratospheric ozone associated with of demonstrating that the observed changes in solar UV irradiance. This However, such models do not provide changes are consistent with the climate coupling between ozone and climate is reliable estimates of internai climate response to a specified forcing and not likely to be important in simulating variability in the stratosphere, as they consistent with the response to other the climate response to changes in have very poor stratospheric resolution forcings. Hence, any detection and attri- solar irradiance. Another climate (Gillett et ol., 2ooo). Unfortunately, bution study needs to consider observa- forcing in the stratosphere which has no climate models with adequate reso- tional evidence of climate change, received little attention until recently l7 lution in the stratosphere have been estimates of internal climate variations, is changing stratospheric water run out for extended periods of several estimates of natural and anthropogenic vapour. While there is some evidence hundred years, which would be need- forcing factors and the climatic respon- of trends in water vapour in the upper ed to estimate internal climate variabi- se to such forcings as simulated by cli- troposphere and lower stratosphere lity on multi-decadal time scales. mate models, as well as quantitative (Kley et al., 2ooo), this observational Simulations with some simpler stra- methods to compare observed climate evidence is uncertain and the climate tospheric modeLs show iarge multi- changes with the simulated responses response even less certain. decadal variability in the stratosphere to different forcings. due to internal dynamics alone. In A number of different approaches have The longest instrumental climate addition, it is likely that the coupling been taken for the quantitative records exist for surface air tempera- between atmospheric circulation and comparison of observed and modelled tures, with data available for some chemistry plays a role in the internal climate changes due to different regions since about 1850 and adequate variability of the stratosphere. No long causes. Early studies compared the coverage to provide a reliable estimate control simulations are available fiom magniiude of variations of global mean of globai-mean temperature since about climate models with adequate strato- temperature between observations and 1900. These data show a warming of spheric resolution and interactive climate models with anthropogenic global-mean temperature by about chemistry. Hence, estimates of internal forcings. Later, fingerprint studies 0.6+0.2"C over the last 100 years. Data climate variability in the stratosphere compared the spatial patterns of for the stratosphere is available for a are uncertain. observed temperature changes with much shorter period, with radiosonde those forced by natural and anthro- If significant climate changes can be data available in the lower stratosphere pogenic forcing factors. For example, detected in the observational data, the (1996) since about 1960 and satellite data avai- Tett et a1., showed that the next step is to compare them with the lable from the 1970s (Chanin and inclusion of increasing greenhouse climate responses to different forcings gases, stratospheric ozone Ramaswamy, 1999). These data show a decreasing to identify the possible causes, both global-mean cooling in the lower stra- and increasing tropospheric sulphate natural and anthropogenic. Reliable model tosphere of about 0.2'C per decade, aerosols were needed so that estimates exist for the magnitude and the zonal mean tempe- inlerrupled by irregular warming per- simulations of patterns of changes in anthropogenic iod associated with major volcanic rature variations in the tropo-sphere forcing due to increasing greenhouse and lower stratosphere over the last eruptions. Higher in the stratosphere, gases, but there is some uncertainty in decades compared well with the cooling trends are even larger four the forcing due to stratospheric ozone observed temperature variations. Most (Chanin and Ramaswamy, 1999) changes and greater uncertainty in the recently, optimal fingerprint studies In order to assess whether the changes forcing due to changing tropospheric have compared the spatial and tempo- in surface or lower stratospheric tem- aerosols due to human activity. ral variations of the observed climate with model simulations with different o uncertainties about dynamical links References forcings. These show that the observed between the stratosphere and the tro- Chanin, M.-L., and Ramaswamy, warming over the last 40 years cannot posphere. V. (1999) Trends in stratospheric tempera- be explained by natural forcing factors The main conclusions of the IPCC tures. In Scientilic Assessment ol Ozone Depletion: 1998, WMO Global Ozone alone, such as changes in solar irra- Third Assessment Report on the detec- diance or volcanic activity, as the Research and Monitoring Proiect - Report tion of climate change and attribution No. 44, Geneva, 5.1-5.59. observed changes in these forcings of causes include that: would be expected to lead to a cooling Gillett, N., Allen M. R. and Tett S. F. B. . there stronger evidence now of a (zooo): Modelled and observed variability over this period (Tett et d1., lggg). It is is human influence on global climate; in atmospheric vertical temperature struc- only through the inclusion of increa- ture. Climate Dynamics,16, 49-61. sing greenhouse gases. increasing . paleoclimate data and model esti- Houghton, Meira Filho L.G., Callander tropospheric aerosols, and decreasing mates of natural climate variations J.T., 8.A., Harris N., Kattenberg A., Maskell K. stratospheric ozone as forcings in cli- suggest that the observed warming (Eds.J (1ss6) Climate Change 1995. The mate model that they provide simula- over the last 100 years is unlikely to be IPCC Second Scientific Ässessmenl. Cam- tions consistent with the iarge-scale solely natural in origin: bridge University Press, Cambridge, 572 observed temperature changes over the . simulations of the climate response pp. last 40 years. to natural forcing alone, including vol- Tett, S.F.B., Mitchell J.F.B., Parker D.E., canic eruptions and changes in solar Allen M.R. (t996) Human Influence on the irradiance, fail to explain the warming Atmospheric Vertical Temperature Structu- re: Detection and Observations. Science, Summary over the last 40 years; 274, LL70-LL73. Some of the difficulties in assessing . stratospheric ozone depletion has Tett, S.F.B., Stott, P.A., Allen M.R., Ingram, the role of the stratosphere in climate been a major contributor to the obser- W.J., Mitchell (1999) Causes of twen- change arise from: J.F.B. ved cooling in the lower stratosphere tieth century temperature change. -A'/afure, . poor stratospheric resolution in cli- over the last 20 years; 399,569-572. mate models used for detection and o it is likely lhal increasing green- SPARC Assessment of Upper Tropospheric attribution; house gases have made a substantial and Stratospheric Water Vapour, Dieter . limitations of simulations of internal contribution to the observed warming Kley, James M. Russell III and C6line PhiI- lips (eds), WCRP No. 113, WMO/TD - No. climate variability in the stratosphere; over the past 50 years; - 1043, SPARC Report No.2, Paris 2000. o uncertainties in solar and volcanic o the accuracy of predictions conti- forcing reconstructions and responses; nues to be limited by uncertainties in t8 . uncertainties in trends in water internal climate variability, natural vapour in the upper troposphere and and anthropogenic forcing and the cli- lower stratosphere; mate response lo exlernal forcing. o the relatively short observational Hence, there has been greater under- record for the stratosphere; standing and appreciation of the . the absence of adequate coupling important role that stratospheric pro- between stratospheric chemistry and cesses play in ciimate variability and circulation in climate models; change. a

Numerical Experiments on Internal Interannual Variations of the Troposphere-Stratosphere Goupled System

Shigeo Yoden, Masakazu Taguchi and Yoko Naito, Kyoto University, Japan, (yoden@ku g i. kyoto-u. ac.j p)

lntraseasonal revolution, respectively. Intraseasonal response to the time variations of the and Interannual Variations and interannual variations are defined external forcings or boundary condi- as deviations from the periodic annual tions of the atmospheric system, while Time variations of the atmospheric response; generally the intraseasonal the rest is generated internaily within state have two periodic components variation means low-frequency varia- the system. Well known natural for- known as a diurnal cycle and an tion with week-to-week or month- cings with interannual time scales are annual cycle, which are responses to to-month time scales, while the inter- the 11-year solar cycle, irregular and the periodic variations of the external annual one means year-to-year varia- intermittent eruptions of volcanoes, forcings due to the earth's rotation and tion. Some part of these variations is a and interannual variations of sea- surface and Iand-surface conditions Hierarchy of Numerical consists of the zonal mean and a single (e.g.. temperalure. roughness. Models to Understand the wave components in a mid-latitude snow/ice, ...), although the last ones beta-channel. Important external para- should be considered as internal varia- Stratospheric Variations meters in the HM model are the inien- tion of the coupled system of the We have made some numerical experi- sity of the mean zonal flow forcing, atmosphere, ocean and land. The ments with a hierarchy of models over dUp/dz, and the wave amplitude at the Quasi-Biennial Oscillation (QBO) of a decade, in order to understand intra- bottom boundary placed near the tro- the zonal mean zonal flow in the equa- seasonal and interannual variations in popause level, -h6. torial stratosphere, which is basically the polar stratosphere and their dyna- Yoden (1987) showed that multipie caused by the interaction between the mical linkage to the troposphere. The stable solutions of a cold/strong polar mean zonal flow and equatorial waves importance of a balanced attack with a vortex and another warm/weak one propagated from the troposphere, could hierarchy of numerical models was may exist for the same external condi- be considered as variation of a laterai pointed out by Hoskins (roas) a long tions in a finite range of fi6, and dis- boundary of the mid-latitude strato- time ago, and his advocacy has much cussed a possible application of such sphere. In addition to these natural influenced our experimentation. concept for understanding the intra- forcings, there are some anthropogenic Numerical models can be divided into seasonal variability of the NH winter forcings such as the increases of green- three classes based on their complexi- stratosphere. Some theoretical modeis house gases, aerosols, chemical consti- degrees of freedom (number of SSW were reinterpreted the tuents related to the stratospheric ty or of with dependent variables after spatial dis- same framework of the HM model. The ozone decrease, or something else. cretisation). In the past, only simple essence of Matsuno's (rszr) theory is Responses to these anthropogenic low-order models (LOMs) with 100-2 an impulsive initiation of a wave forcings are usually called "trends". On degrees of freedom could be used in forcing in the troposphere; transient the other hand, external forcings are parameter sweep experimenls due to response to the increase oI hg lor a not so significant in the intraseasonal lime scales: fundamentally inlra- the limitation of computing resources. short time interval may cause a rapid We have to be careful with spurious transition from the state of cold/strong seasonal variation is considered as a results due to severe truncations in the polar vortex the other warm/weak result of internal processes that may to discretisation, but LOMs are exist even under constant external spatial state. Another theory of SSW is the still useful for conceptual description strato-spheric vacillation found by conditions. Such variation may be a or illustration of the basic dynamics the periodic varia- linear periodic osciilation or non-iinear HM. They showed with limited components. Nowadays it variation (periodic, quasi-periodic or tion of the stratosphere that mimics becomes possible to use full dynami- repeated occurrence of SSW events with t9 chaotic) produced in the atmospheric ca] models with L04-6 degrees of free- a period of 50-100 days may exist even system. These time variations can be dom lbr parameter sweep experiments. classified systematically with some for a time-constant -hs. The vacillation is We call them mechanistic circulation a internal variation of the simple models (Yoden, 1997). non-linear models IMCMs). Some idealisation of mid-latitude stratospheric system with Figure r (p. I) shows an example of the physical processes in these models fixed external conditions. variations in the polar stratosphere; helps us to understand the essential These two theories made a very oppo- daily temperature at the North Pole (a) dynamics. We do not need to worry site assumption on the dynamical link- has large intraseasonal and inter- about the truncation effect. For quanti- age between the troposphere and the annual variability in winter and early tative argumenls. more complex gene- stratosphere. Matsuno (tgzt) assumed spring, while large variability at the ral circulation models (GCMs) with a "slave stratosphere"; the strato- South Pole is seen in spring (c). Large 1Oa-B degrees of freedom are necessary, spheric variation is caused by the fluctuations at the North Pole are in which sophisticated physical para- variation of its bottom boundary, that direct results of the occurrence of meterisation schemes should be adop- is, the troposphere, without any stratospheric sudden warming (SSW) +oÄ l{nruorror r-. Jmeler sweep stratospheric influence on the tropo- event, which is associated with a rapid experiment with full GCMs is still sphere. On the other hand, HM assumed breakdown of the polar vortex from a limited even in the most advanced computational environment. an "independent stratosphere" in the cold, strong and undisturtred state to time variations; the stratospheric another warm, weak and disturbed variation is possible for a time- one. The difference between the two Use of Stratosphere - constant bottom boundary condition. hemispheres is quite noticeable. These intraseasonal and interannual varia- Only Models Seasonal and interannual variations of tions are also seen in the monthly Some simplified models on the inter- the stratospheric circulation have been mean temperature data. In the equator- action between the zonal mean zonal studied theoretically with some "inde- ial lower stratosphere, the QBO signal flow and planetary waves propagated pendent stratosphere" models. Yoden is dominant in the original time series from the troposphere have been deve- (r000) varied dUp/dz in the HM model of temperature, but the annual compo- loped to study the stratospheric varia- periodically with an annual component is also discernible in Figure 1 (b); tions including SSW events. Yoden nent to investigate the response to the the ]ow temperature in northern win- (1,s87, 1990) discussed the intra- periodic forcing, but did not obtain ter can be understood as a result of seasonal and interannual variability in any example of interannual variations adiabatic cooling due to the stronger the stratosphere by using LOM introdu- (i.e., deviations from the periodic upward motion associated with the ced by Holton and Mass (1976, hereafter annual response). The periodic res- wave-induced meridional circulation referred to as HMl. The HM model is a ponse, or the seasonal variation is qua- in the northern hemisphere (NH). highly-truncated spectral model which litatively different depending on hs, and the difference resembles that of those done with LOMs over a decade longer period from autumn to spring the climatoiogical seasonal march ago, with three-dimensional MCMs in and extremely large skewness is found between NH and the Southern Hemi- order to understand the T-S coupled in March. Based on these probability sphere (SH); larger ftB corresponds to variability. Taguchi et aL. (2}oo) distributions, a question can be raised NH. By using similar dynamical condi- modified an atmospheric GCM by on the usefulness of ordinary statis- tions in a hemispheric primitive- making some simplifications of physi- tical significance tests assuming a equation model, Scott and Haynes cal processes; all the moist processes Gaussian distribution. (1998) found interannual variations were taken out, the radiation code Figure a (p. III) shows the time series even for a periodic annual forcing. The was replaced by a simple Newtonian of the deviation of winter-mean polar internal interannual variability arises heating/cooling scheme, Rayleigh lemneratrrrp al n . 6 hPa in the mil- owing to the longer "memory" of the friction was used at the surface, and = lennium integration of ho 1000 m, stratospheric flow at low latitudes. A sinusoidal surface topography was = which is made by connecting 10 inde- given wind signal at low latitudes is assumed in longitudinal direction pendent 1OO-year integration. Here a less affected by radiative damping, of with a single zonal wavenumber threshold value is introduced to select which time scale is much shorter than m = 1 or 2 component. It is a spectral the 200 warmest winters denoted by a year, due to the smaller Coriolis primitive-equation model with 42 red dots. The occurrence of the warm parameter. Internai variability due to vertical levels from the surface to the winters looks like random. In some the longer memory of low latitude mesopause and its horizontal resolu- periods there is no warm winter over winds might have a role in the interan- tion is given by a triangular trunca- decades (e.g., the period around year nual variability in the real stratosphere. tion at total wavenumber 2L in 410), while warm winters appear spherical harmonics. Thus the model fre- quently in some other periods (e.g., has full dynamical process with around year 620). To test the random, Troposphere- 105 degrees of freedom. Stratosphere Coupled ness, intervals of two consecutive Under a purely periodic external warm winters are examined statis- Va riation condition of annual thermal forcing, tically. Figure 5 shows frequency dis- The stratosphere-only models described 10 runs of 10O-year integration were tribution of the interval of warm in the previous section, either "slave done with different topographic winters that is longer than the interval stratosphere" models or "independent amplitude of 0 m < ho < 3oo0 m indicated on the abscissa. The cumu- stratosphere" ones, assume no down- (Taguchi and Yoden, 2000a). The lated frequency is well fitted by an ward influence from the stratosphere to relatlve importance of the planetary exponential function A exp(-t/T) as 20 the troposphere. However, some recent waves forced by the topography is denoted by the broken line with esti- studies pointed out the coupled variabi- studied by such parameter sweep. mated T of 4.5 years. The exponential Iity of the troposphere and the strato- Figure 2 (p. II) shows the dependence distribution means that the occunen- sphere with intraseasonal and of temperature variations in the polar ce of a warm winter itself is described interannual time scales (see, e.g., Bald- stratosphere on ftp; if it is equal to by a Poisson process. That is, the win, 2000; Hartmann et 01., 2000); the zero or a small value, the interannual warm winters occur at random from Arctic Oscillation (AO) is a deep signa- variation is very small, particularly in year to year, and preferred periodicity ture of zonally-symmetric seesaw pat- winter. The variation becomes large does not exist in the present internai terns of geopotential height, alternating in spring for fto = 400 - 600 m, which i nterannual variability. between the polar region and mid-lati- looks like the variation in SH as The warm winters are directly related tudes, flom the surface to the lower stra- shown in Figure 1 (c). If ir6 is to the occurrence of SSW events. A tosphere. Such annular variability of the increased further, the variation lag-correlation (regression) analysis of polar vortex is observed in all seasons becomes Iarge in winter. The results in such intraseasonal variations shows both for ho = 700 or 1000 m look like the hemispheres and the two-way interactions in the T-S cou- troposphere-stratosphere (T-S) variation in the NH. Note that the coupling pled system. A typical preconditioning is stronger in dynamically active season, interannual variation in this experiment and "after-effect" of SSW event are namely winter in NH and spring SH. is caused only by the intraseasonal in identified. The after-effect is character- Downward propagation variations which have a random phase of the AO signa- ised by poleward and downward pro- ture from the stratosphere depending on each year. to the tropo- pagation of anomalies of the zonal sphere was noticed association with in Taguchi and Yoden (2000b) also made mean zonal wind and planetary-wave SSW events. It was also pointed out that 2 runs of 1000-year integration under amplitude, which continues for seve- the propagation route of planetary waves the same purely periodic annual for- ral months. Some signatures of the is very sensitive to the annular varia- cing. In the millennium integration's, after-effect are also seen in the tropo- tions. These studies are indicative of the statistically reliable lrequency distribu- sphere. importance of two-way interactions tions of the monthly-mean polar tempe- between the troposphere arrd the strato- rature are obtained (Figure 3, p. II). The spnere. internally generated interannual varia- Concluding remarks tion is very large during winter in the Generally, the parameter sweep expe- Internal Variations in a T-S run of fto= 1000 m, while it is large in riments are important to investigate Coupled Model spring in the run of hu = 500 m. The dis- non-linear systems because of the limi- tributions for h, = 1000 m are positiveiy tation of linear interpolation in para- Recent progress in computing facili- skewed in autumn and bimodal in meter space. Such experiments are ties enabled us to make some parame- winter. On the other hand, those for useful for understanding the dynami- ter sweep experiments, similar to fto = 500 m have positive skewness for a cal mechanism, and were done to study the internal variations of the T-S Longer dataset is quite desirable, but References coupled system with a MCM. The cou- we have no intention of insisting on Baldwin, M.P., 2000: The Arctic Oscillation pling process fundamentally a two- is the hopelessness in detecting the and its role in stratosphere-troposphere way interaction in which roles of the efTects of small-amplitude external for- coupling. SPARC newsletter, 1.4, 1.0-1.4. mean zonal flow and planetary waves cings. For example, the bimodality in Benzi, R., G. Parisi, A. Sutera and are important, and the generation of the frequency distributions gives a A. Vulpiani, 1982: Stochastic resonance in planetary waves is a highly non-linear hint of the possibility of stochastic climatic change. Tellus, 34, 10-16. (1982) process in the range of realistic topo- resonance. Benzi et al. introdu- Hartmann, D.L., I.M. Wallace, graphic amplitude .hp. Internal intra- ced a concept of stochastic resonance V. Limpasuvan, D.W.J. Thompson and seasonal and interannual variations in a system with bimodality to explain J.R. Holton, 2000: Can ozone depletion and that we obtained are large in a dynami- the glacial-interglacial cycles in paleo- global warming interact to produce rapid cally active season, that is, spring for climatic records; if relatively short- climate change? Proceedings NAS, 97, '1.41.2-L4L7. small h, while winter for large ha. term fluctuations (noises) in the These variations have some similar system have enough intensity as an Holton, I.R. and C. Mass, 1.976 characteristics of the real atmosphere, internal stochastic forcing, a small- Stratospheric vacillation cycles. J. Atmos. although no interannual variation of amplitude periodicity in the external Sci.,33,2218-2225. the external forcings is permitted in fbrcing could be greatly amplified by Hoskins, B.J., 1983: Dynamical processes in the model. regular transitions between the bi- the atmosphere and the use of models. Roy. Meteor. modal states. If we Quart. f. Soc., 109, 1-21. could regard baroclinic Matsuno, T., 1-97'L: A dynamical model of the stratospheric sudden warming. N=2OO disturbances in the tro- J. Atmos. Sci., 28, 1479-1,494. posphere as a source of 2.r0, tIl=250'7 stochastic forcing, Palmer, T.N., 1999: A non-linear dynamical T=4.5 perspeclive on climate prediclion. small changes in a bi- s =.017 J. Climate, L2, 575-59L. l.l 02 ' \ stable energy potential Scott, R.K. and P.H. Haynes, 1998: Internal ). +het nrnrlrrcoc +ho D L interannual variability of the extratropical o I bimodality might be stratospheric circulation: The low-latitude I -! qmnlifiarl h-, tho flywheel. Quart. J. Roy. Meteor. Soc., 124, stochastic resonance. 2L49-2L73. 2.1 0l l. Palmer (rosO) gave Taguchi, M., T. Yamaga and S. Yoden, a'- 2000: Internal variability another example that of the troposphere- l.l0l stratosphere coupled system in a simple 21 5 l0 15 20 shows the importance globaI circulation model. Atmos. Sci., Intervol (Yeor) J. of non-linearity of the submitted. system to appreciate Taguchi, M., and S. Yoden, 2000a: Internal Figure 5: Frequency distribution of intervals of two consecu- the effects of small- intraseasonal and interannual variations of tive warm winters in the millennium integration for amplitude external the troposphere-stratosphere coupled sys- (number) ho = 1000 m- Blue dot shows the frequency of the forcings. Again the tem in a simple global circulation model. interval that is longer than year indicated the on the abscissa. existence of bimodality Part I: Parameter sweep experiment (to be The warm winters are defined in Figure 4 as the top 200. (or, metas- submitted to J. Atmos. Sci.) The broken line is the best-fit exponential function multiple Taguchi, M., and S. Yoden, 2000b: Internal A exp(a/T), determined by the least square method. The table states) is the key intraseasonal and interannual variations of mean interval T is 4.5 vears, and the mean error t=0.017. point. He demonstra- the troposphere-stratosphere coupled sys- The scale of x is 7 for one order of frequencv. ted with LOM that the response to a small- tem in a simple global circulation model. Part II: Millennium integrations (to be sub- A large internal variability and a clear amplitude external forcing is primarily mitted to J. Atmos. Sci.) bimodality seen in the frequency dis- changes in the residence frequency Yoden, S., 1987: Bifurcation properties of a tributions of the monthly-mean polar associated with the metastable states. stratospheric vacillation model. J. Atmos. temperature in late winter (Figure 3l The external forcing does not have Sci., 44, 1-723-L733. much influence on the structure of remind us of some non-linear dyna- Yoden, S., 1990: An illustrative model of mical perspective to appreciate the metastable states. If this concept is seasonal and interannual variations of the system, effects of small-amplitude external applicable to our T-S coupled stratospheric circulation. J. Atmos. Sci., 47, forcings such as the solar cycle, erup- a perturbation run with any kind of 1 845-1853. tions of volcanoes, and so on as stated small-amplitude external forcing Yoden, S., 1997: Classification of simple in the first section. First, we should would give significant changes in the low-order models in geophysical fluid be very careful to draw any conclu- frequency distributions of the dynamics and climate dynamics. Non- sion from data with a limited length, monthly-mean temperature as shown linear Analysis, Theory, Methods & Applications, 30, 4607 -4618. either from a numerical experiment or in Figure 3. real observation, because the large Anyhow it is important to notice that internal variability may produce spu- the T-S coupled system is a typical rious "response" just due to the limi- non-linear system with large internal ted number of sampling. Longer variability and non-Gaussian fiequen- dataset would give more statistically cy distributions. We should be careful reliable conclusion, although it might not to misuse linear concepts to ana- be very difficult to get a sufficiently lyse the data obtained from such long dataset. system. a lntegrated Global Observing Strategy (IGOS) for Ozone and Relewant Atrnospheric Pararneters Ernest Hifsenrath, NASA Goddard Space Flight Center, Greenbelt, l\AD 20771, USA (h [email protected]. nasa. gov) Christopher J. Readings, ESA, European Space Research and Technology Center, Noordwijk, N L (cread [email protected]. n | ) Jack A. Kaye, NASA, Headquarters, Washington, D.C. 20546, USA ([email protected]) Volker A. Mohnen, IFU-FhG, D-A2467 Garmisch, Germany ([email protected])

lntroduction monitoring. Variations of ozone in the and ground-based (surface, balloon and troposphere and stratosphere must be aircraft) were then documented via There is an urgent need to assess the glo- understood because of the central role consultaiion with the space agencies bal consequences of industrialisation for it plays in several important environ- and the ground-based network spon- which reliable global data are essential. mental problems such as: controlling sors. From an analysis of the require- IGOS international working The fan the amounts of biologically damaging ments and measurements, a set of on Earth group linked to the Committee ultraviolet radiation that reaches the recommendations for establishing an Obsewing Satellites, CEOS) proposes to Earth's surface, its impact on air quality integrated global observing system is integrate the major satellite and ground- as an oxidising pollutant that is harm- proposed. Two levels of measurement based systems to provide highly accurate ful to biosphere, and as a "greenhouse" requirements were established and defi- global environmental observations of key gas that contributes to the Earth's radia- ned as L) Target requirements that satis- variables of the atmosphere, cryosphere, tive balance. The "Project" not only fy the needs of most (if not all) of the oceans and land in a cost effective deals with ozone, but also considers the user communities and 2) Threshold fashion (http ://r.tr,r,'w.unep.ch/earthw/igos. Iong-term measurements of source and requirements satisfy the needs of at least htm). To satisfy this objective, IGOS reservoir gases that control ozone che- one set of users. The Target require- a framework for compi- must provide mistry throughout the atmosphere. In ments are more stringent and deman- user requirements coupled with ling addition, relevant meteorological para- ding than the Threshold requirements. an overarching strategy for conducting meters and aerosols are included in the In addition, the strategy distinguishes global observations. This will allow requirements. measurements that are needed conti- 22 contribu- data providers to tune their nuously from those that are only needed The specific objective of this project is tions to the requirements, make better occasionally. A well-supported and document the requirements for decisions on the allocation of to ongoing validation program and data resources, and take advantage of better ozone measurements and those para- quality control is also considered a and co- meters needed to accurately interpret international collaboration requirement. As data sets are improved, ozone observations. Once the ordination. the planning for reprocessing arrd distribu- requirements are established, recom- the present time, ground, balloon, tion of data becomes a major goal for At mendations are directed to the obser- airborne, and space observations of the IGOS. Figur" 1 (p. IV) (from Goddard ving community that outlines the steps atmosphere are used to verify not only Space Flight Center) aptly illustrates the needed to meet user requirements after that the Montreal Protocol is in fact need for continuous ozone monitoring assessing ongoing and planned obser- working but also to gather vital data on with a long-term precision of at least ving systems. The project recognises changing global atmosphere and 1% per decade. the the need and existence of appropriate establish a solid scientific thus help physical and assimilation chemical As indicated above, an array of chemi- foundation for future policy debate and and transport models used to interpret cal species must be observed in addi- effective use action. To assure the most the observations. An initial report, tion to ozone. These include a limited resources for global observa- of available which fulfils this objective, sponsored set of long-lived source gases. reservoir tions, priorities must be established for by CEOS and the WMO, entitled the species, radicals in the major catalytic upgrading existing and/or establishing "The WMO/CEOS Report on a Strategy cycles and several closely associated new systems. IGOS will provide a frame- for Integrating Satellite and Ground meteorological variables such as tempe- for decisions to ensure 1) the work Based Observations of Ozone" (Report rature and winds measured with at least long-term continuity and spatial com- No. 140), is now in its final stages of the same spatial and temporal resolu- prehensiveness of key observations and publication by the WMO. tion as the gases. Aerosol properties are 2) the research needed to improve highly interactive with the chemistry processes so that understanding ofEarth and radiative properties in both the stra- observations can be properly inter- Requirements tosphere and troposphere; therefore preted. IGOS will build upon existing The IGOS Ozone Project solicited user their characteristics must also be measu- global observation international requirements from the scientific (GAW, red. These data are also needed for programs and identify deficiencies in SPARC, IGAC) and application {WMO, accurate trace gas retrieval algorithms. planned the current and systems. WHO. UNEPI communities. These In addition, the total and spectral solar The Ozone Project is one of six Pilot requirements were documented by the irradiances must be observed to be able Prolects established within CEOS to \MMO and GCOS and then compiled in to interpret climate and ozone changes. assess the feasibility of achieving the the "Ozone Project" Report. The exis- Concerns about air quality and trans- objectives of IGOS in the area of ozone [ing measuremenl programs from space port of pollution and its precursors on Total Lower Upper Lower Upper Strat Parameter Class Surface Column Trop. Trop. Strat. & Meso. o3 Mon./Trends A A A A o3 Oper. Met. A o3 Air Ouality A N N o3 UV Forecasts A A Temp. Met. Variable A A A Wind Met. Variable

I ropopause Met. Variable A Cloud Tops Met. Variable A A A Hzo Source Gas A A Nzo Source Gas A A cHq Source Gas A A N N A A CO Source Gas A A A coz Source Gas A N HCI Reservoir A A HN03* Reservoir A A BrO Free Radical N N cro Free Radical N A 19,l Free Radical A A N N A A NO" Free Radical A A N N Aerosol Pres. Met. Variable A A A Aerosol Char. Met. Variable A N N A PSCs Met. Variable A UV Met. Variable A A 23 Tablel. Atmosphericparametersthatmustbemeasuredregularlyonanearglobal scale:A=available, N:needed

regional to intercontinental scales place ground. The space missions that will measurements have been made from an even more stringent demand on measure total and profile ozone and low Earth orbit, but upcoming observations and models. Figure 2 other atmospheric parameters are missions will take advantage of new (p. IV) (from the Harvard University) illustrated in Figure 3a and b (p. V). strategic orbits such as geostationary illustrates model calculations of month- Data liom NOAA, UARS, ERS-2, Tena, and Lagrangian to observe diurnal ly mean afternoon surface ozone ADEOS, WMO-GAW and NDSC, and changes for air quality studies. concenlralions in fuly. Particularly many aircraft and balloon missions noteworthy is pollution over industrial have Ied to an understanding of atmo- Ground observations (surface, balloon, areas in the US, Europe and Asia, with spheric processes and provided a base- and aircraft) must continue and be enhancements in Asia due to burning. Iine for evaluating changes in the expanded to provide correlative and atmosphere. Upcoming research mis- validation data for the satellite mis- The combined requirements for ozone sions as well as conducting essential depletion, air quality and climate sions such as ENVISAT and Aura, and operational missions, such as METOP research observations. The networks research and monitoring are compiled and NPOESS, will provide platforms such as NDSC and WMO-GAW (e.g. in Table 1 that Iists the selected para- to continue the baseline measure- ozone sonde, Dobson/Brewer, meters that must be observed fre- ments, but will only partially satisfy ozone/aerosol lidars, and in silu sour- quently. Tables that document the the requirements. TOMS-type data sets ce gas stations) must continue to requirements, for each of these atmo- are assured until NPOESS, which will provide data as part of IGOS. Resear- spheric parameters, including spatiai continue those measurements. The ch-driven aircraft campaigns should and temporal resolution and range, next two SAGE missions are assured, continue to study processes in the accuracy, and precision (Threshold beginning in 2001, except for the third upper troposphere and lower strato- and Target) appear in more detail in platform expected later in this decade. sphere with high spatial resolution. the report. UV-VIS-NIR backscatter measurements The commercial airlines also have a will continue with GOME-2 on role for providing a platform for col- Available and Planned METOP. Follow-on ADEOS and lecting continuous data over a wide Measurements GCOM will also provide coliaborative geographic area with high spatial reso- data from space. ODIN, ACE, and lution (e.g. MOZAIC). The operation- A broad range of operationai and SABRE research missions will compli- al agencies must play a major role to research observations are underway ment the larger research and operation- insure long-term sustainability of these and are planned from space and al missions. To date chemistrv systems Calibration and Validation Recommendations below. (The SPARC community is encouraged to read the full report avai- Calibration and validation are critical As discussed above, many of the iden- lable from the WMO): assure of remote requirements will be met by the to the scientific value tified r sensing measuremenls. They are existing and planned measurements A coordinated validation activity essential for deriving climate quality from ground and space. However, the must be established which extends data sets. The space faring nations Iack of formal co-ordination among the over the entire lifetime of satellite sensors and encompasses have and must continue to allocate space faring nations to optimise the which all elements IGOS resources for calibration and valida- deployed systems and to assure com- of the system taking maximum advantage of concurrent tion of Earth science missions as is patibility for international users is a national validation activities. presently being done for ENVISAT and serious problem. In addition, there Aura. Both Europe and the United must be formal recognition and sup- . The coverage ol grou nd-based States are now planning operational port for the international community (WMO-GAW and NDSC) systems must (particularly satellite systems that will carry ozone who are providing critical data from be extended in the tropics sounders to extend the long-term ground-based systems for calibration and the Southern Hemisphere) and a record already produced by national and validation of the soace-borne carefully selected subset thereof desi- research and operational missions. systems. gnated as permanent, long-term ground "truthing" facilities. Japan is also committed to fly atmo- The CEOS/WMO report's recommen- spheric chemistry missions. However, dations emphasise the missing compo- . Sustained support for the ground net- despite the fact that the major space nents of the upcoming systems as well works must be provided by space agen- agencies have embarked on these mis- as describe what needs to be improved cies that require validation data sets to sions, no concurrent long-term valida- in the existing systems. The specific insure data availability and quality. tion program, covering the lifetime of recommendations are too detailed for o Deficiencies, revealed by the survey these missions is being planned, nor is this short summary but are highlighted of existing and planned measurements, there any assurance that existing ground-based infrastructure will be in place when they are needed. Satellite systems can only meet the established requirements if they are supported by correlative data of known quality and continually challenged by reliable 24 ground-based observations and quantitative science. Preflight Based on the experience gained from (olibrorion past satellite missions, an end-to-end approach for calibration/validation, highlighting the need for a fully integrated giobal observing system, to include both ground and space-based measurements, must be established. For satellites this approach inciudes level I the internal calibration program, post- Volidorion launch calibration employing on- board systems, external validation programs using highly controlled correlative measurements, subsequent algorithm refinements and scientific analyses of the data to ensure consistency with the best understanding of atmospheric processes and condi- Analysis tions. Figure 4 illustrates how these steps are inter-connected. The figure also demonstrates that end-to-end validation program is a highly iterative process. The magnitude of the effort demands international pooling of resources and close collaboration given the existence of parallel streams of the national operational missions, e.g. the European METOP and the US NPOESS ozone instruments and Figure 4. Steps necessary for a space-based measurement to be scientifically acceptable corresponding research missions by the user. Steps include rigorous pre and post launch calibration, validation, algorithm discussed above. and data product evaluation, and subsequent reprocessing. must be corrected by improving and/or of the user community to advise on de (beginning in 2001) (Figure 3). The providing additional measurements. calibration issues. recommendations outlined above There is a particular need for conti- r International co-operation must be attempt to identify those areas that nuous measurements in the lower encouraged in the development of remain deficient in the present and stratosphere and troposphere. algorithms employed by similar instru- planned observing systems. Data collected following the CEOS-IGOS . Validation is an iterative process, so ments and in the pooling of knowledge have the necessary resources for reprocessing data must ol- radiative transfer physics. approach will quality to enable the state of the atmo- be made available to insure that users . A body of scientists, engineers and sphere to be reliably monitored and have access to the highest quality data. managers must be established to provi- changes understood through support- de technical support to funding agen- o The synergetic use of data must be ing research thereby providing a basis cies ensure compatibility and encouraged by standardising daia to for formulating sound environmental completeness of the systems. formats, by ensuring archives are easi- policies. Iy accessible and by providing proper There is a practical incentive for swift provision for reprocessing. action as an array of satellite missions o National radiometric standards must with atmospheric instruments are be improved with the full involvement scheduled for Iaunch during this deca- a

Public Access to the Network for the Detection of Stratospheric Ghange Database

Martin P. Chipperfield, School of the Environment, University of Leeds, Leeds, UK (ma rtyn@env. leeds. ac. u k) Paul A. Nernrman, NASA Goddard, Greenbelt, USA ([email protected]) 25 lntroduction invested into instrument inter- include those obtained before the start comparison, calibration, and software of the NDSC but which have been sub- The Network for the Detection of Stra- validation. The result is a self-consistent jected to the same NDSC validation, Change (NDSC) is a set of tospheric data set suitable for addressing the clearly show the increase in the research stations extending from B0'N above aims. In order to permit the stratospheric loading of halogens due for observing and under- to 90'S) widest possible usage, all data over to the use of CFCs which has led to standing the physical and chemical two years old is made publicly stratospheric ozone depletion in both state of the middle atmosphere. Since available. This article briefly describes the polar regions and at mid-latitudes. 1991 ozone and key ozone-related the NDSC database and how to access it. Following the Montreal Protocol, and chemical species and parameters have its amendments, the increase in HCl been at this network order measured in slowed and now appears to have level- to detect and understand stratospheric Example Data led off. In the future we expect the changes and to assess the impact of The NDSC data base consists of stratospheric loading of chlorine and these changes on the troposphere and ground-based and sonde observations fluorine to decline. Continued obser- on global climate. In particular the of ozone and olher key species in vations are an essential component of NDSC aims to provide dala [or: stratospheric chemistry and climate. monitoring the rate of this recovery. . Making the earliest, possible identi- Ground-based column observations are Figure 2 (p. VI) shows column sunset fication of changes in the ozone layer Dobson, UV-visible, obtained with and sunrise observations of NO2 at and to discern their causes. microwave, and Fourier Transform Lauder (45'S, 170"E). on top of the (FTIR) The list . Establishing links between changes infrared spectrometers. diurnal and annual variations. this includes 03, HCl, in stratospheric ozone, UV radiation at of species observed data set shows long-term variations. HNo3, HF the ground, tropospheric chemistry cloNo2, clo, No, No2, Relatively low NO2 was observed and other tracers. Ozone, aerosols and and climate. around 1992, foilowing the eruption of temperature vertical profiles are also o Mt. Pinatubo. However, after allowing Tesling and improving multi- using lidar and sondes. The obtained for these aerosol-induced variations dimensional stratospheric chemical- NDSC database also includes UV flux dynamical models. and the expected increase in NO2 from at the ground and supporting meteo- increasing N2O, the clear upward . independent calibra- rological data. Providin8 an trend throughout the 1990's may be tion of satellite sensors of the atmo- Examples of NDSC data are given in larger than current models predict. sphere. Figures 1 and 2. Figure 1 (p. VI) shows These NDSC data are therefore These aims require high quality data observations of column HCI and HF at essential for comparison to models and, accordingly, since the inception the NDSC Primary station of Jungfiaujoch that test our understanding of atmo- of the NDSC, much effort has been (47"N, B"E). These observations, which spheric chemistry and transporl. Accessing the Data principally provides a link to the References public ftp database, but also includes over two years old is now European Research in the Stratosphere, NDSC data maps of the NDSC sites, instrument publicly available. Access to this data ISBN 92-827-9719-8, EC-DG XII, 1997. information, available data sets, and is available through anonymous ftp Liley, 1.B., ef a1., Stratospheric NO, varia- contact information. access to the ozone.wwb.noaa.gov ser- tions from a long time series at Lauder, ver. It is expected that users of these New Zealand, J. Geophys. Res,11633- NDSC data will consult the on-line Acknowledgements 11640,105,2000. documentation and reference articles Mahieu, E., et al., Proc. of Stratospheric Because of its world-wide dimension, Ozone 1999, 27ls to L/Lo/Lsss, St. de to fully understand the scope and limi- Jean the NDSC has been recognised as one Luz, France, Air pollution research Report tations of the instruments and resulting of major components of the inter- 73, EUR 1s340, pp. 99-102, 2000. data. Scientific users of the data are national upper atmosphere research encouraged to contact directly the program. As such, it has been endors- appropriate NDSC Principal Investiga- ed by national and international scien- tor (listed in the data documentation tific agencies, including UNEP and the on the web page) to ensure the proper International Ozone Commission (IOC) use of specific data sets. The PI can of IAMAP. It has also been recognised also be contacted if you wish to use by WMO as a major contributor to data iess than two years old. WMO's Global Ozone Observing Sys- Further information on the NDSC can tem (GO3OS) within the frame of its be obtained from the NDSC home- Global Atmosphere Watch (GAW) Pro- page (www.ndsc.ws). This web site gramme. a

The Ewolution of the Antarctic Ozone Hole in 2OOO

26 Pablo O. Canziani, Depto. De Ciencias de la Atm6sfera y los Oceanos, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires/CONICET ([email protected]).

he year 2000 Antarctic ozone hole three weeks before the climatological Figure 3 a). The year of 2000 however, event had peculiar characteris- mean timing and one week earlier than and particularly in October, the elon- tics. The most outstanding are: the 1999 event. gations were far more frequent and did not follow the "rotation" of the ozone 1. A particularly rapid growth during As can be seen in Figure 1, the shape hole. In other words the shape of the August of this ozone hole was significantly hole was not elliptic during these 2. The largest surface area on record. elliptic during most of the period. For events, but quasi-triangular. 3. The longest continued period of example, during September 15, the residence over inhabited regions of 22o DU isoline reached 50"S, over the Furthermore the hole was very much southern South America. central south Pacific. On October 12 displaced towards South America as and 1B t]ne 22O DU isoline reached can be seen in Figure 2 (p. VII), which 4. The eariiest break-up since 1991. close to 48-47'S over Southern Chile shows the mean state of the ozone The ozone hole extent began, at a and Argentina. The dynamics of the layer between October 6 and 20, 2000. rapid growth about the middle of ozone hole was significantly perturbed On the other hand, peak values above August, reaching an initial peak of throughout the period of its existence. 430 DU were observed south of Aus- 25 million kmz, i.e. about as large as the Figure 3 (p. VIII) show the mean ozone tralia. In other words the ozone distri- 1999 event, on August 2O121,, followed Ievels between B0 and 30'S averaged bution over the hemisphere was by a sudden decrease and a another for the 60-70'W longitude band, i.e. quasi-bipolar. This implies that there rapid growth until it reached the maxi- Southern Argentina and Chile, during was a very strong quasi-stationary mum extent, close to 30 million km2 1990, 1999 and 2000. 1990 was chosen wave one event. The significant eccen- on September 9/10 (Figure r, p. VII). It as an example of another dynamically tricity of the ozone hole behaviour is important to remember that the 1999 perturbed ozone hole, while 1999 coupled with important perturbations event reached its maximum extent showed a far more stable behaviour. It is and deformations of the ozone hole between September 14 and 16, 1999 clear that the year 2000 was probably resulted in a behaviour completely and the TOMS climatology shows that the most perturbed on record as can be anomalous. Indeed in previous years previous events had reached their seen in Figure 3 c). Normally as the the excursions of the ozone hole out- peak size during late September and ozone hole rotates, elongation towards side the polar region were not so early October. Hence this year's event mid-latitudes takes place, more com- prolonged in time, as can be seen in grew beyond previous recorded moniy between the South Pacific and Figure 3 for 1990. It must be noted extremes about three weeks earlier the South Atlantic. These are separa- however that because of cloud cover than in 1999 and reached its peak. also ted bv B to 16 davs, as can be seen in only during a few days ofthis very low ozone period did the surface UV levels hole begun a very .upiä, sustained break-up. Nevertheless it must be noted rise significantly above average. decrease in size, closing between that those break-ups were not separated Observations from the Servicio November 20 and 25. The size of the by so many days from those in other Meteorol6gico Nacional UV network hole during this period was within the years as was the case this time. show that during clear days UV levels TOMS climatology and far smaller than over Ushuaia (54.5'S) were equivalent the records for the '90s. This was the The reasons for the ozone hole beha- to those observed in Buenos Aires earliest break-up since 1991. viour in 2000, in particular the early [34.s'S) or Cdrdoba (32"S) during Furthermore it took place aimost a rapid growth, may be linked to the ]anuary. While such Ievels can be month earlier than in 1998 or 1999. The mean prevailing weather in the tropo- tolerated by human beings they are comparison of figure 3 a) b) ald c) and sphere. The year 2000 has been the significantly high for the local terrestrial observations of the corresponding ozone wettest in many parts of the Pampas and marine ecosystems. It must be fields show that the perturbed dynamics region in Argentina since 1860. The noted that there were reports of ofthis year's event and the excursion to winter 2000 was among the coldest sunburns in Ushuaia as well as Punta mid-latitudes with higher solar radia- and longest in recent years. Exactly Arenas from people unaccustomed to tion levels are the probable causes of what mechanisms led to this raoid such sudden changes in IfV levels. such an early break-up. The 1999 event growth and the huge size ol the hole is with a more stable behaviour and fewer currently under study. At this stage, Though the size of the hoie has signifi- deformations lasted much longer. 1990 the implications of the year 2000 event cantly decreased after the peak in and 199t, which were also significantly for the future behaviour of the ozone September, after October 20 the ozone perturbed, also had a relatively earlier hole remain uncertain.

SOLVE-THESEO 2OOO Science Meeting

Palermo, ltaly, 25-29 September 2OOO Neil R. P. Harris and Marielle Guirlet, European Ozone Research Coordinating Unit, University of Cambridge, U K ([email protected]. u k) Paul A. Nernrman, NASA Goddard, Greenbelt, USA ([email protected]) Alberto Adriani, CNR-lFA, ltaly ([email protected]) 27

Introduction These processes occurring in the The results were discussed at the joint Arctic vortex have been closely Between November 1999 and April stu- SOLVE-THESEO science meeting held died over the past decade or so and, in Palermo, Italy from September 25- 2000, two major field experiments, the qualitatively, European Commission-sponsored are fairly well under- 29 2OOO. Generous support for the stood. The Arctic stratosphere Third European Stratospheric cools meeting was provided by CNR, ENEA, during polar nighl and at sulficiently Regione Experiment on Ozone (THESEO 2000) Siciliana and the city of low temperatures, polar stratospheric Palermo. and the NASA-sponsored SAGE III Over 250 scientists partici- clouds (PSCs) form. Heterogeneous Ozone Loss and Validation pated with over 50 talks and just reactions occur on the surface of these Experiment (SOLVE), collaborated under 200 posters. Many of these are to clouds which convert relatively inacti- form the largest field campaign yet being written up for submission for ve chlorine compounds such as HCI publication mounted to study Arctic ozone loss. in two special issues of and CIONO2 into forms such as CIO or other journals. Briefly, the campaign involved research IGR in In this article which can lead to rapid chemical des- aircraft, balloons, ozonesondes, we report on some of the key findings truction of ozone in the presence of presented at the meeting and on the ground-based and satellite instru- sunlight. This CIO then gradually ments, summaries of the discussions of out- which were greatly augmented revert back to the inactive forms and by meteorological and chemical standing issues prepared by groups of the ozone destruction slows down. rapporteurs. The findings presented modeis. In all more than 400 scien- These processes largely take place in below are only a small part of those tists from the European Union, the Arctic vortex. As the vortex breaks Canada, Iceland, lapan, Norway, presented at the meeting, and we apo- down, ozone-depleted air is mixed logise in advance to those whose Poland, Russia, Switzerland and USA with mid-latitude air. results are not included. were involved. A description of the SOLVE-THESEO 2000 activities and Given the planning involved, the campaign was fortunate, from a scientific the early findings was published in Meteorology and dynamics SPARC newsletter No. 15 (Newman. perspective, to take place during a 20001. cold winter in the Arctic stratosohere As discussed in SPARC newsletter in which lhere was large ozone loss. No. 15, the Arctic stratosphere was The main aims of SOLVE-THESEO The processes involved were therefore cold during the 199S/2000 winter and 2000 were to study the processes lead- extremely weil observed, and since the the vortex was stable into mid-March ing to ozone loss in the Arctic vortex end of the campaign scieniists have at which time it was split with one and how the ozone amounts over been poring over the measurements substaniial remnant present well into northern mid-latitudes are affected. trying to understand what happened. April. The temperatures were below PSC existence temperatures from late errors were observed at lower Chemistry pressures (the uncertainties in the November until mid-March. A num- An unprecedented set of instruments anaLyses increased at pressures below ber of studies of the long-lived tracer (on aircraft, balloons, satellites and the about 30 hPa). More work is needed data collected during SOLVE- ground) observed the chemicai evolu- these uncertainties at all THESEO 2000 found that there was a to quantify tion of the Arctic stratosphere from as trajectories are such a relatively small amount of mixing in altitudes November 1999 through April 2000. tool used in Lagrangian photo- of mid-latitude air into the vortex, basic In conjunction with measurements 1O"/o ol the vortex chemical box models, identification of probably less than made in other winters over the The the origin of air masses and in ozone Past volume at around 18 km. decade or so, they have allowed stu- of mid-latitude loss studies. amount of mixing in dies of chemistry on a whole range of issue for at air masses is an important temporal (minutes to years) and spatial least three reasons. First, the chemi- Pa rticles scales (metres to 1000's of kilometres). cal reaction rates governing the acti- Stratospheric vation and deactivation processes and The long, cold winter combined with In situ measurements of long-lived the ozone loss itself are affected if advances in instrumentation, particular- tracers during SOLVE-THESEO 2000 chemically distinct air is mixed in, ly for the in situ particle measure- showed that the total organic chlorine particularly for nitrogen rich air. ments, has provided a wealth of data' (that in the form of the source gases - Second, improved quantification of There were two particularly notable CFCs, CH3CCI3, CCl4, etc.) has now the in-flow across the vortex edge is findings: (a) the first measurements of peaked in the stratosphere, some inherently valuable for understanding with a chemical composition of nitric 6-7 years after it peaked in the tropo- the mass balance of the vortex. And acid trihydrate (NAT) (Voigt et al., sphere. As in the troposphere, the third, the mixing in of air across the Science, 2gO, 1r756,2000) and (b) the early response to the Montreal Proto- vortex edge can cause errors in the discovery of PSC particles with radii col is driven mainly by the steep decli- ozone losses estimated using of 15 micron or so, much larger than ne in the relatively short-lived tracer/ozone correlations. previously thought (FaheY et al', (5 years) CH3CC13. Science, in press). The long-term context of the For the first time, simultaneous in sifu 1s99/2000 winter and the possibility The chemical composition measure- measurements of all major chlorine of long-term changes in the Arctic vor- ments showed the presence of layers species were made on the ER-2. Preli- tex were discussed at some length (see of NAT particles and layers of sulphate minary results from these were presen- also several articles in SPARC News- ternary solution particles. Some of ted which showed progress toward zö letter No. 15). The past decade has the NAT particles were present near understanding whether the chlorine certainly seen, on average, a colder, or even above their equilibrium tem- budget is balanced within the estima- longer-lived vortex, but it is hard to perature. These balloon-borne obser- ted uncertainties. Since nearly all the define the significance of these vations were made over northern major chlorine species were measured changes. The most robust change is Scandinavia in the presence of moun- by more than one technique (in situ the longer duration of the vortex tain waves. They underline the fact and remote) , it was agreed to make which during the 1990s broke uP, on that the evoLution of particles in sure that proper comparisons are made average, in March, compared to rapidly changing temperature fields to achieve a consistent data set, as is February during the 1980s and earlier. such as mountain waves is comPlex already being done for the long-lived The fundamental reason for this is and at the same time, they show that tracer data. Currently the main fea- unclear, but it does seem related to the such complex processes can be un- tures of the chlorine activation and decreased wave driving during the raveiled. deactivation in 1s99/2000 are clear, period. with a long activated period and slow January-February observations The large particLe recovery. However more detailed stu- One of the scientific foci of SOLVE- ('rocks') were made more generally dies showed that a number of quantita- THESEO 2000 was to imProve under- within the Arctic vortex from the ER-2 there standing of the formation, chemical tive issues remain. For example, aircraft. Their size, and low concentra- were reports that comparisons of impact and importance of mountain they had previously tion, meant that ozone loss caiculated from the obser- waves. A number of beautiful case as available eluded discovery most ved CIO and BrO amounts were less studies were presented which showed above a instruments lose sensitivity than the empirically determined ozone that the meteorological mesoscale few microns. The particle size also good losses. However the ozone loss calcu- modelling of these events was causes them to fall quickly through the and, further, that the new ECMWF lated by the SLIMCAT 3D chemical stratosphere, and, as they contain good agree- analyses with their improved resolu- transport model were in HNO3 and water, their sedimentation ment with the empiricallY derived tion aiso described mountain wave a lesser extent, can denitrify and, to ozone losses in 1999-2000 (Sinnhuber events well. However in such a cold vortex. This was dehydrate the Arctic ef o1., GRL, 27,3473,2000), unlike winter where PSCs were ubiquitous in showing borne out by measurements some previous winters. the vortex, the chemical imPact was extensive denitrification and some might probably not great although this dehydration in the coldest regions and Bromine compounds are significant winters where not be true in warmer enhanced nitric acid and water vapour contributors to Arctic and mid-latitude the PSC temperatures were close to amounts lower at lower, warmer alti- ozone loss. Bromine activation is now existence temperatures. tudes. However it is still not clear much better understood and there is Finalty there was a lot of discussion of what the nucleation mechanisms are good evidence that 50-80% of in- the quality of the traiectories derived for these PSCs, and there was a great organic bromine is in the form of BrO in (Arctic, from analysed wind fields. The largest deal of debate on this subject. most conditions mid-latitudes, -

tropics, all seasons). The overall A number of modelling studies inves- the temperatures at which PSCs can understanding of the stratospheric tigated the ozone loss at mid-latitudes, form, with higher water vapour levels bromine budget has also i.mProved including the impact of the Polar raising the PSC existence tempera- (i.e. putting the uncertainties associated ozone loss. The interannual variabili- tures. It may well be the radiative vapour with the tropospheric sinks and sources ty in dynamics causes the export of air effect of the increased water vortex to to one side). A decadal increase in BrO fiom the vortex to mid-latitude to vary which is causing the Arctic lead to consistent with tropospheric increases greatly in amount and timing, so that cool. If these conditions also and to more seems to have occurred, and there is even for a given chemical ozone loss enhanced denitrification will the strong evidence for a source of bromine inside the vortex, the effect on mid- stable vortices, how much in the very low stratosPhere from latitudes will also vary. Modelling effect of the declining halogen levels water vapour shorl-l ived compounds. studies are now realistically quanti- be offset by the increased fying this effect. Chemical transport and cooling stratosphere? There are model calculations also showed how many uncertainties in such trains of Ozone Loss polar processes vary from year to year, thought - equaliy they are plausible furlher. Ozone loss in the 199S/2000 winter and they additionaily showed how the and need to be investigaled in the contribu- was large and extensive. At altitudes importance of changes Further details on the SOLVE-THESEO chemical loss around 1Bkm, 60-7ook of the ozone tions of the different 2000 campaign can be found at: All models showed that a was destroyed between lanuarY and cycles. http ://www.nilu.no : B0/Pro jects/ vortex has little mid-March, slightly larger that the pre- strong, long-lived theseo20O0/ until it starts to vious record loss which occurred in effect on mid-latitudes http ://cloud1. arc.nasa.gov/solve/ was true dynamically 1995/96. The column ozone loss inside break up. This http ://www.ozone-sec.ch.cam. ac.uk/ the column was 2o-25o/o in 199s/2000, (no export of ozone-poor air) and che- and on the SOLVE-THESEO 2000 (no perturbation at less than the previous record years lar- mically chemical science meeting, including the rappor- mixing out or gely because the vertical extent of the mid-latitudes without teurs'reports at: Ioss was less than in those activation outside the vortex). ozone http ://hyperion. gsfc.nasa. gov/Personnel/ There was reassuringly good years. people/Nlewman,-Paul-A./speaker.html agreement between the estimates of General ozone loss found by several techniques We thank a1l scientists and technicai using measurements from a number of A number of related issues came uP support staff involved in SOLVE- instruments. A number of technical several times during the meeting. THESEO 2000 for their magnificent issues about the various techniques Chief among these was one of the main efforls during the last year. We also 29 used to estimate ozone were discus- driving forces of SOLVE-THESEO thank all those who helped in organis- sed. However, once the differences 2000 - how will climate change affect ing the meeting at Palermo, including resulting from the different time per- the future stratosphere? Or, more dra- Dr Adriani's team at CNR-IFA, iods considered were taken into matically, will there be an Arctic Rebecca Penkett, Kathy Wolfe and her account, it seemed as though these ozone hole? The interaction of climate Ieam. and Georgios Amanatidis were not that imPortant in the change with the stratosphere and with (EC Research DG) and Mike KurYlo 1999i2000 winter because the ozone lhe ozone deplelion Processes is com- (NASA HQJ. loss was iarge and because the vortex plex and will be a major area of resear- was strong and well isolated. As men- ch in the future. As one examPle, tioned above, there was good agree- there is a clear need for a Sreater ment with the loss calculated by the understanding of stratospheric water SLIMCAT 3D CTM, there was Poorer vapour for dynamic, radiative and che- agreement with other models. Further mical reasons. In the polar vortices, work is needed to understand the the water vapour concentration will be causes of these differences' one of the factors which determines I

First S-R/AMP (STEP Results, Analysis' and Modelling Phase of the Solar-Terrestrial Energy Program) Sapporo, Japan, 2-6 October' 2OOO

T*he fi rsl inlernalional S-RAlvlP Solar-Terrestrial Physics) in 1998-2002 The SRAMP slmposium was sPonsored ! svmoosium consisted of 19 sub- in order to consolidate and integrate by the Ministry of Education, Science, ry-pärii and three workshops' The results fiom the many disparate STEP Sports and Culture, Japan (Monbusho) ("http://wvw.ngdc'noaa' S-RAMP project has been promoted by (Solar-Terrestri al Energy Program) and SCOSTEP SCOSTEP (Scientific Committee on campaigns in 1990-1997. gov/stp/SCO STEP/scostep.html" )' Symposium S17: The middle Symposium S18: Solar variability upper stratosphere. Simulations with atmosphere including response effects upon the lower the Berlin climate model had not com- to forcing from above atmosphere and climate menced by the time of the meeting but the model was outlined in a ooster dis- Marwin Geller and Toshitaka Conveners: Lon Hood and Austin Conveners: Tohn play. Tsuda ([email protected]). ([email protected]. edu) A number of other potentially impor- This symposium was devoted to the Most of the papers were observational- tant issues were addressed. In a plena- dynamics and chemistry of the middle ly based, with a strong emphasis, on ry lecture preceding the symposium, atmosphere, particuiar empha- the interaction of solar cycle forcing with E. Friis-Christensen suggested that sis on wave forcing, having their with that by the equatorial wind QBO. Galactic cosmic ray (GCR) fluxes, sources in the troposphere and to K. Labitzke showed updated results which are modulated by the 11-year chemical changes from natural and lrom the data set compiled at the Free solar magnetic activity cycle, may be anthropogenic causes. Because the University of Berlin, which now indian additional contributor to solar for- middle atmosphere is also subject to cate an 11-year solar signal in lower cing of climate through effects on forcing from the variable sun and stratospheric geopotential height cloud nucleation processes. energetic particle effects, the chemis- extending over at least 4 solar cycles. K. Georgieva pointed out that the try, energetics, and dynamics of the effects of GCR's on terrestrial climate response to analysis of the US National middle atmosphere in Additional may depend on whether the northern these forcings were also key subjects Centre for Environmental Prediction or the southern solar hemisphere of this symposium. (NCEP) data set, which includes the is more magnelically aclive. Southern Hemisphere, was also pre- The main topics in dynamics were O. Troshichev noted that an empirical sented. K. Mohanakumar reported radar/optical/in-situ observations, separation of energetic particle effects evidence for an influence of the tt- modelling and theory of the general on the middle and lower atmosphere year cycle on temperature in the circulation, generation and propaga- from those of spectral irradiance varia- mesosphere (6-8 % per 100 units of tion of various atmospheric waves, bility may be facilitated by analysing 10.7 cm solar flux) and in the tropos- and their interactions and instabilities. data lrom the polar night. He presen- phere (1-2% per 100 units) using a Topics in chemistry included observa- ted correlative evidence for effects of combination of radiosonde data, rocket tional analyses, laboratory and model- short-term fdays to weeks) GCR varia- data, and the NCEP reanalysis data. ling of gas phase and heterogeneous bility on pressure in the stratosphere H. Nakane also applied the NCEP re- photochemical processes, as well as and troposphere at the Vostok station analysis data from 1959 to 1997 to studies of transport and mixing of in Antarctica. K. Boyarchuk pointed investigate properties of the northern 30 minor constituents. The coupling bet- out that the solar output varies on a polar vortex. It was found that proper- ween chemistry, radiation and dyna- number of time scales, including a ties of the vortex, including strength, mics was also an important subject of small-amplitude periodicity near the duration, radius, and stability, depen- this symposium. period, and that this periodicity on the phase of the 11-year solar QBO ded may influence GCR access to the A total of 41 papers were presented: 23 cycle as weli as that of the A QBO. atmosphere on the same time scale. presentations, inciuding seven solici- similar theme was pursued by Y. Naito ted papers, were given orally in two who showed that the "Holton-Tan D. Knipp investigated the heat budget sessions on October 3 and 5, and 18 Oscillation" in which polar tempera- above the stratosphere and showed were displayed as posters. The first tures are forced entirely by the QBO that solar UV radiation accounts for oral session treated tropospheric pro- has a different phase dependence 7O-BO % of the heating while auroral cesses, where M. A. Geller talked on under solar maximum conditions as zone currents and particle deposition the QBO and ENSO influences on the compared to solar minimum condi- account for another 1,5-25 %. tropical cold point tropopause, folio- tions. M. Salby suggested that some T, Kuznetsova analysed terrestrial wed by a summary report of the aspects of the QBO itself (equatorial Carbon 14 data (an inverse proxy for SPARC/SOWER campaigns in 1998- westerlies below 30 hPa and equatorial solar activity through effects on GCR 2000 by F. Hasebe. Then. in a session easterlies above 30 hPaJ may vary fluxes reaching the ground) for a 4500-

nn v'rv"||uUJ nhpmiclrrr and lrancn^rf slightly with the 11-year solar cycle. year period and discussed two maxi- S. Hayashida described the behaviour ma, one of which coincides with the Austin presented the results of gene- of the polar stratospheric clouds f. Maunder sunspot minimum. She sug- ral circulation modelling in which the (PSCs) observed from space, and gested that global temperature may primary forcing is variations of several M. Takahashi showed the results on correlate inversely with Carbon 14 percent in the UV part of the solar ozone variations seen in chemical cli- and that extrapolation of the available spectrum. Comparisons of the model mate models. record using Fourier harmonics provi- time scale response on the solar cycle de a forecast of climate change. processes ozone In session on the in the with satellite observations of B. Zieger investigated the behaviour Mesosphere and Lower Thermosphere and temperature changes were presen- of Schumann resonances (SR) in the (MLT) region, R. A. Goldberg talked ted. M. Takahashi presented a range Earth's ionosphere which are associa- on a study of polar summer mesosphe- of results from the CCSR/NIES climate ted with lightning discharges. re with rocket, radar and lidar (DROPS model. These included investigations program). N. f. Mitchell discussed the of the 11-year solar cycle, which gave coupling of tide and planetary waves, very similar results to those of Austin. and |. F. Kafkalidis described the pla- In particular, the model results were netary scale variations in the night- significant improvements over 2D glow structures seen by UARS/HRDI models in the Iower stratosphere, satellite. while a discreoancv remains in the a Future SPARC and SPARG-related Meetings

6-B March 2001: Lidar Measurements in Latin America Workshop, Camagüey, Cuba

(http : i /climate. envsci.rutgers. edu/antuna/workshop). ag-22 March 2001: Workshop on Nitrogen Oxides in the Lower Stratosphere and Upper Troposphere, Heidelberg, Germany (http://www. ozone-sec.ch. cam.ac.uk).

25-30 March 2001: EGS XXVI General Assembly, Nice, France: ([email protected]). (http ://www.mpae. gwdg. de/EGS/egsga/nice0 1/nice01.htm).

2-4 April 2001: Global Atmosphere Watch, GAW 2001, WMO, Geneva. Registration information: Liisa Jalkanen (Jalkanen [email protected]). 2-6 |uly 2001.: 2nd Workshop on Long-term Changes and Trends in the Atmosphere (IAGA/ICMA/SPARC), Prague, Czech Republic: Convener: ]an Lastovicka ([email protected]), http ://www.ufa. cas. czlhtml/climaero/Trend200t.html.

10-13 |uly 200L: Global Change Open Science Conference (IGBPA/VCRP/IHDP), Amsterdam, The Netherlands (www.sciconf.igbp.kva.se). Parallel session: "The Atmosphere and Global Change". Conveners: M. Geller and G. Brasseur.

L0-L8 fuly 200L: IAMAS 2001, Innsbruck, Austria (http://iamas.org). . Symposium "Middle Atmosphere Dynamics", 7 days, Lead Convener: K. Hamilton, Co-conveners: T. Hirooka, B. Lawrence, F.-J. Luebken, L. Hood (turbulence, GW, planetary waves, tides, forcing of mean circulation, long-term variability, mesospheric Iayered phenomena, MA aspects of climate change). . Symposium "MA Chemistry, Transport and Radiation", 6 days, Lead Convener: A.R. Ravishankara, Co-convener: N. Harris, V. Fomichev, D.W. Waugh (observations, models, transport relevant to understanding chemistry, aerosol microphysics, MA climate-chemistry interactions, energy budget of the MlT-layer). JI . Workshop "Solar Cycle Forcing of the Stratosphere and Troposphere", 1 day. Convener: L. Hood (possible mechanisms: solar UV variability, energetic particle precipitation, etc.).

August 2001: IAGA-IASPEI 2001 foint Scientific Assembly, Hanoi, Vietnam:

(http : //www.IAGAandIASPEI. org.vn/pta.htm). G2.O4. Solar Activity Effects on the Middle and Lower Atmosphere. Convenor: E.S. Kazimirovsky, Institute of Solar Terrestrial Physics, Russian Academy of Sciences, PO BOX 4026,664033, Irkutsk, Russia. Fax: +7 3952 462557, emaii: [email protected]. Co-convenor: S. Sofia. G2.O5 Propagation of Tidal and Gravity Waves and Planetary Signature Into and their Effects on the Mesosphere, Thermosphere, and Ionosphere. Convenor: J.M. Forbes, Department of Aerospace Engineering Sciences, Campus Box 429, University of Colorado, Boulder, CO 80309-0429, USA. Fax: +1 3O3 452 7881, email: [email protected]. Co-convenors: K.P. Hamilton (USA), A.D. Aylward (UK), D. Pancheva (Bulgaria). G2,09 Long-term Trends in the Mesosphere, Thermosphere, and Ionosphere Systems. Convenor: G. Beig, Indian Institute of Tropical Meteorology, Dr. Homi Bhabba Road, Pashan, Pune-411 008, India. Fax: +91 20 5893825, email: [email protected]. Co-convenor: J. Lastovicka (Czech Republic).

19 August-01. September 2001.: Cargese International School, Cargöse, Corse, France: (http://cargese.univ-corse.fr). . Dynamical barriers, stirring and mixing in geophysical flows - Mathematical model and applications. . Application deadline: March 15 (http://gershwin.ens.fr/geomix).

20-24 August 2001: Workshop on Atmospheric Chemistry and Climate Interaction during the Climate Conference 2001, Utretch, The Netherlands. http://www.fys.ruu.nl/-www.imau/cc2001.html

24-27 September 2001. Network for the Detection of Stratospheric Change : NDSC 200L Symposium "Celebrating 10 years of Atmospheric Research" , Arcachon, France.

(http : //www. observ.u-bordeaux. fr/public/ndsc. symp).

25 September-October 5,?OOL. School on the Physics of the Equatorial Atmosphere, ICTP, Trieste, Italy (http://www.ictp.trieste.it/cgi-bin/ICTPsmr/mklinks/mklist?smr132B). Deadline for student applications: May 31, 200L. I Network for the Detection of Stratospheric Ghange NDSC 2OO1 Syrnposiurn "Gelebrating 1O Years of Atmospheric Research"

24-27 September 2OO1, Arcachon, France Goals: to emphasise scientific results from NDSC data and to generate discussions/collaborations among NDSC working groups. Scientific Programme Committee (SPC): Chair: Prof. G6rard M6gie. Organising Committee: Chair: J6rome de la Noe, Tel: +33 557 77 61 56. Fax 61 55. The NDSC 2001 Symposium will be structured around six oral and two poster sessions, as well as a final " Sympo- sium Summary and Discussion session ". Oral sessions include invited reviews and presentations of some posters selected by the SPC. The sessions cover primarily: a - Intra- and inter-seasonal variability and trends; b - Validation and assimilation of ground- and space-based data; c - NDSC data and models; d - Stratosphere-troposphere -climate interactions; e - Prospects: new stations, techniques, databases, network synergies. Short abstracts (one page maximum) submission by 30 April 2001, registration fee (120 US $) by 30 June, final manuscripts by 15 December 2001.

http : //www. observ.u-bordeaux. filpublic/ndsc. symp, http ://www.ndsc.ncep.noaa;gov/, http ://www.nilu.no

f 2ncl Workshop 32 "Long-1srm Changes Base and Trencls in the Atrnosphere" of Atrnospheric"o..artrt#'a"r Gonstituents

I Prague, 2-6 July 2OO1 A new data base containing about 1200 spectra and spectra The workshop is focused on trends in the mesosphe- data sheets of about 120 atmospheric constituents is avai- re, thermospshere and ionosphere, but includes also lable free-of-charge to all interested scientists. stratosphere and troposphere. Among the goals: to You will find it at www.science-softcon.de/uv'vis. information (observations, models) sum up current If you need more information or a short description of for various parameters; help distinguish trends in to the data base, please contact: between trends of anthropogenic and natural origin. Dr. Andreas Noelie, Science-softCon, E-mail: For information: contact Tan Lastovicka andreas,noelle@science-soft con.de, ([email protected]). htto ://www.science-soft con. de http : www.ufa. cas.czlhtml/climaero/Trend2001.html

SPARC Scientific Steering GROUP Composition of the SPARC Office Co-Chairs Director: M.-L. Chanin Project Yu. P. Koshelkov, M.-L. Chanin (F) scientist: Michaut M. Geller (USA) Manager: C. M.-C. Gaucher Members Ex-Officio members Secretary: C. Granier (F) GAW/UVB :P. Simon (BJ K. Hamilton (USAI WMO/GAW :I. Miller [CH) Edited by the SPARC Office D. Karoly (A) COSPAR Service d'Adronomie, CNRS, BP 3 V. Khattatov (R) SCOSTEP : R. Vincent fAl 91371 Verriöres-le-Buisson cedex. France P. Mc Cormick [USA) ICAC S. Penkett (UK) Tel: +33- L 64 47 43 L5 A. O'Neili (UK)) Fax: +33- 164 47 43 1,6 T. Peter (D) Email: sparc.office@aerov. jussieu.ft http : //wr,r,'w. aero. j ussie u.Irl- sparc/ U. Schmidt (D) T. Shepherd (C) Published by M6t6o-France - Direction commerciale et de la communication S. Yoden (I) ISSN 1245-4680 - Ddpöt l6gal 1'trimeste 2000