SPARC Newsletter No

newsletter n° 41 SPARC July 2013 Stratosphere-troposphere Processes And their Role in Climate Core project of the World Climate Research Programme www.sparc-climate.org

The NASA Global Hawk being towed into the NASA Dryden Flight Research Center hanger, Edwards, California. See results from the recent ATTREX campaigns using the aircraft this issue. Photo courtesy: Tom Tschida, NASA Dryden Flight Research Center.

Contents WCRP Special Workshop on Report on the 1st SPARC Report on the 20th Session of Climatic Effects of Ozone De- Stratospheric Network for the the SPARC Scientific Steering pletion in the Southern Hemi- Assessment of Predictability Group ...... 2 sphere: Assessing the evidence (SNAP) ...... 44 and identifying gaps in the cur- Report on the Regional WCRP/ rent knowledge ...... 29 SPARC Reanalysis Intercom- SPARC Workshop with focus parison Project (S-RIP) Plan- on the Southern Hemisphere Report on the WCRP Regional ning Meeting ...... 52 and South America...... 11 Workshop on Stratosphere- Troposphere Processes And their The NASA Airborne Tropical Role in Climate ...... 35 Available online TRopopause EXperiment (AT- TREX) ...... 15 Report on the 3rd SPARC Report on the IGAC/SPARC DynVar Workshop on Modelling Chemistry-Climate Model Ini- Combined SPARC Data Require- the Dynamics and Variability tiative (CCMI) 2013 Science ments/SPIN Mid-Term Review of the Stratosphere-Troposphere Workshop - http://www.sparc-cli- Workshop ...... 25 System ...... 40 mate.org/publications/newsletter/ Report on the 20th Session of the SPARC Scientific Steering Group 27-30 November 2012, Buenos Aires, Argentina

Johannes Staehelin1, Ted Shepherd2 , Greg Bodeker3, Joan Alexander4

1SPARC Office, Zurich, Switzerland, [email protected], 2University of Reading, UK, 3Bodeker Scientific, New Zealand, 4 NorthWest Research Associates/CoRA, USA

The 20th Session of the SPARC SSG WCRP’s Joint Scientific Commit- Ted Shepherd (SPARC co-chair) (Scientific Steering Group) was tee (JSC)) provided an update of began his presentation by summa- held at SIGEN (Sindicatura Gen- WCRP activities on behalf of An- rizing SPARC’s goals and organisa- eral de la Nación) in Buenos Aires, tonio Busalacchi (JSC Chair), who tion, and then continued by mention- Argentina, from 27-30 November was unable to attend the meeting. ing SPARC’s name change (again, 2012, hosted by the ‘Centro de In- She mentioned the very successful see below for further details). He vestigaciones del Mar y la Atmós- WCRP Open Science Conference further discussed SPARC’s role in fera’, of the University of Buenos (OSC), which took place from 24- the new WCRP GCs. SPARC will Aires. 29 October 2011, in Denver, USA contribute to several GCs, includ- (http://conference2011.wcrp-cli- ing ‘Regional Climate Information’ Opening session and WCRP/ mate.org). The new WCRP struc- (led by the Working Group on Re- SPARC update ture was discussed in a short JSC gional Climate), through research meeting following the OSC, and in focusing on atmospheric circulation Greg Bodeker (SPARC co-chair) further detail at the next JSC meet- changes, and to the GC ‘Cryosphere opened the Scientific Steering ing, which took place from 17-20 in a Changing Climate’ (co-led by Group (SSG) meeting by welcom- July 2012 in Beijing, China (for CliC, the Climate and Cryosphere ing all participants, particularly more details see the meeting report project), through the Polar Climate those from South America who in SPARC Newsletter no. 401). Un- Predictability Initiative (PCPI, see joined the first session, and thanked der the new structure, six Grand below). SPARC will also contribute the local organisers. A new format Challenges (GCs) will play a criti- to the GC ‘Science Underpinning for the meeting was introduced, re- cal role, enabling the development the Prediction and Attribution of quiring the activity leaders to pro- of targeted research efforts that will Extreme Events’ (led by GEWEX), vide a short report detailing their provide successful results on 5-10 as well as to the GC ‘Clouds, Circu- main scientific achievements, an year timescales. Two new coun- lation and Climate Sensitivity’ (led outlook for the future, and any fi- cils have also been established, the by WGCM, see below), through nancial requests for the coming WCRP Modelling Advisory Coun- research focused on circulation year. These reports were distrib- cil (WMAC) and the WCRP Data analyses, upper tropospheric wa- uted to all participants prior to the Advisory Council (WDAC) (see be- ter vapour, and sulphate aerosol mi- meeting, while during the meeting low for further details). A telecon- crophysics. Together with GEWEX, brief scientific presentations were ference later during the meeting IGAC (the International Global At- then made in plenary and logisti- with Antonio Busalacchi confirmed mospheric Chemistry project), and cal aspects were discussed sepa- SPARC’s vital role in the WCRP’s other research partners, SPARC is rately in small groups with the SSG GCs. Carolina closed by discussing expected to take a lead on aerosol-re- members. This allowed more focus the emerging Future Earth initia- on coordination and logistical is- tive, to which the WCRP will con- sues. The reports have now been tribute significantly. Later, she also compiled to produce the very first presented a summary of the one and 1http://www.sparc-climate.org/fileadmin/ SPARC Annual Report 2012. a half-day local workshop, which customer/6_Publications/Newsletter_ took place prior to the SSG meeting PDF/40_SPARCnewsletter_Jan2013_ Carolina Vera (a member of the (see article later in this issue). web.pdf

2 SPARC newsletter n° 41 - July 2013 lated research in support of the GCs. in the mesosphere. NDMC is fo- troposphere, as well as a coupled cused on coordinating the study of ocean, such models are expected Monica Rabolli made a presen- mesospheric variability on all time- to become more common; (2) to tation on behalf of CONAE (Co- scales, as well as the coordinated compare tropospheric, stratospher- mision Nacional de Activitas Es- development of improved obser- ic and coupled chemistry-climate paciales, the Argentinian Space vation and analysis techniques models with observations, as well Agency), providing an overview and modelling of the mesosphere. as with each other; and (3) to better of the AQUARIUS satellite mis- NDMC science is currently focused coordinate stratospheric and tropo- sion, a common project between on the following topics: (1) plan- spheric modelling activities and to CONAE and NASA. The main etary waves, (2) gravity waves, (3) address specific scientific questions scientific goal of this mission is to vertical coupling, (4) inter-hemi- in the context of comprehensive improve understanding of the inter- spheric coupling, (5) infrasound, stratosphere-troposphere resolv- actions between ocean circulation, (6) climate change signal detection, ing models including atmospheric the water cycle and climate. The and (7) network intercomparison. chemistry. A CCMI website has satellite was launched on 10 June Jürgen presented some results from been created (http://www.pa.op. 2011 and provides global informa- various NDMC studies and then dlr.de/CCMI) and a 2nd workshop tion on sea surface salinity and soil finished by making proposals for was held in Boulder, USA, from 14- moisture. AQUARIUS instruments collaborations between SPARC and 16 May 2013. Veronika Eyring and also measure sea-ice concentration, the NDMC. Jean-François Lamarque act as co- rainfall rate, wind speed, water va- chairs of the activity, and a CCMI pour, cloud liquid water content SPARC activity reports scientific steering committee has and fires can be detected. These ob- been formed. servations have provided detailed Ted Shepherd presented the new information on tropical instability Chemistry Climate Modelling Initi- Claire Granier, a member of the waves, the Amazon outflow plume ative (CCMI) on behalf of Veronika IGAC Scientific Steering Commit- and hurricanes. Examples from re- Eyring. The initiative, jointly sup- tee and SPARC liaison, presented cent studies showed that it was pos- ported by IGAC and SPARC, was a short overview of IGAC’s main sible to identify hurricane Gordon discussed with the community and projects, including CCMI, to which using AQUARIUS rain rate obser- plans were approved at a work- IGAC is strongly committed. IGAC vations, while hurricane Sandy was shop that took place from 21-24 proposed that Veronika Eyring and observed using water vapour col- May 2012, in Davos, Switzerland. Jean-François Lamarque are for- umn data. Argentinian research us- The specific goals of the Davos mally recognized as co-chairs of ing AQUARIUS data will focus on workshop were to: (1) assess im- CCMI and intends to comment on the Rio de la Plata outflow plume. provements in process-oriented the CCMI leadership plan to ensure evaluation and understanding of the widest possible IGAC engage- Jürgen Scheer presented an over- Chemistry Climate Models (CCMs; ment. Allen Goldstein (incoming view of the Network for Detection extending the CCMVal approach to IGAC co-chair) was also involved of Mesospheric Change (NDMC: the troposphere), (2) identify obser- in supporting the 2nd CCMI work- http://wdc.dlr.de/ndmc/), which vations for model evaluation and shop. CCMI science will be vital to provides a framework for inter- new methods for improved compa- IGAC’s focus on air pollution and national cooperation to study the rability between models and obser- climate, which is a theme of grow- mesopause region (extending from vations, and (3) define community- ing importance for IGAC. As part 80-100km altitude). The NDMC wide simulations in support of the of the International Geosphere-Bio- was established in 2007 through an upcoming WMO Ozone and future sphere Programme (IGBP), IGAC initiative of the ICSU/WMO-World IPCC Climate Assessments, as well will be integrated into the Future Data Centre for Remote Sensing of as for process studies. The outcome the Atmosphere, which is operated of the workshop is described in fur- by the German Aerospace Centre. ther detail in a recent SPARC News- The NDMC is a global programme letter article2. More generally, the 2 Eyring et al. (2013) Overview of IGAC/ aimed at identifying and quantify- goals of CCMI are to: (1) promote SPARC Chemistry-Climate Model Ini- ing atmospheric change by moni- the use and development of global tiative (CCMI) Community Simulations in toring key parameters for the early models that include chemistry and Support of Upcoming Ozone and Climate characterisation of climate signals dynamics of the stratosphere and Assessments. SPARC newsletter No. 40

SPARC newsletter n° 41 - July 2013 3 Earth initiative, but this will not af- SOLARIS-HEPPA activity (SO- Karen Rosenlof reported on the fect IGAC’s commitment to CCMI. LARIS: SOLAR Influences for WAVAS-2 activity (WAter Vapour SPARC, HEPPA: High Energy ASsessment 2), which focuses on Paul Newman presented the ‘Life- Particle Precipitation in the Atmos- two main topics: (1) super saturation times of Halogen Source Gases’ phere) on behalf of Katja Matthes and in situ measurement data qual- activity. This SPARC activity is the and Bernd Funke. She started by ity, and (2) upper troposphere and first re-evaluation of the lifetimes of presenting results from a joint study stratosphere climatologies, trends ozone-depleting substances (ODSs) looking at recent solar spectral irra- and radiative effects. As part of top- since 1998 (WMO/UNEP Ozone diance variability and its impact on ic 1, controlled, refereed, blind in- Assessment, 1999) and first in-depth climate modelling4. The main un- tercomparisons of the principal air- modification since 1994 (Kaye et certainty in spectral solar irradiance borne field instruments were made al., 19943). Results show that dif- lies in the 220-400nm wavelength using the AIDA chamber, and strict ferent approaches result in differ- range, where substantial differences quality checks of in-situ aircraft ent lifetime estimates, but overall between different satellite measure- observations of relative humidity there is good consistency, and un- ments remain. While the number of showed that many of the highest certainties have been significantly numerical simulations taking into relative humidity values (except reduced, through, for example, the account spectral solar irradiance is at very low temperature) are ques- re-evaluation of photochemical increasing, comparisons of availa- tionable (AquaVIT White Paper, data. The lifetime estimates of cer- ble model simulations are hampered 20095; Krämer et al., 20096). This

tain species, for example CCl4 and by slightly different experimental work shows that at very high rela- CFC-11, have changed significantly setups, motivating new coordinated tive humidities even state-of-the-art since the last WMO Ozone Assess- SOLARIS-HEPPA simulations. Us- instrumentation introduces uncer- ment. The third draft of the report ing measurements from the SORCE tainties that are too large, and thus has been completed and reviewed, (SOlar Radiation and Climate many field measurements indicating and work on the final report is in Experiment) satellite instrument supersaturation may not be reliable. progress. The lifetimes recommen- leads to simulated atmospheric There is therefore a strong need to dations will be finalized in mid- temperature responses being up to improve current field instrumenta- 2013 and new ODS scenarios will three times larger than when using tion. The shifts in aircraft measure- be completed for the CCMI activity other data. Julie also reported on ments generally preclude their use after this finalization. Results from the HEPPA-II coordinated inter- for trend analyses. However, com- this activity will also be included in comparison study, which suggests parisons with a stable satellite re- the upcoming 2014 WMO/UNEP that the proton forcing (i.e. direct cord may be useful for verifying or Ozone Assessment. influence of solar proton events) is discounting extreme aircraft cam- well represented in the participating paign anomalies. The second focus Julie Arblaster presented the models and should be considered of this activity has been recently re- in all models. In contrast, electron organised and now falls under the forcing data constraining ionization leadership of Gabrielle Stiller. This below 100km remains uncertain. topic aims to analyse and combine 3Kaye, J. A., S. A. Penkett, F. M. Ormond Ongoing efforts are focused on con- long-term satellite observations of (eds.) (1994) Report on Concentrations, structing an observations-based en- stratospheric water vapour for use Lifetimes, and Trends of CFCs, Halons, and ergetic particle precipitation (EPP) as model boundary conditions, as Related Species. NASA Reference Publica- NOy source parameterization for well as for model comparison. They tion 1339, Washington, D.C. models with lids below 100km. In are currently aiming to produce a 4Ermolli et al., 2013: Recent variability of 2013, the SOLARIS-HEPPA activ- satellite climatology using SAGE the solar spectral irradiance and its impact ity aims to publish a white paper, II, HALOE and Aura MLS obser- on climate modelling. Atmos. Chem. Phys., continue the HEPPA model-meas- vations. Gaps in this data set may 13, 3945-3977 urement intercomparison study, be filled with ACE, SAGE III and 5https://aquavit.icg.kfa-juelich.de/ evaluate the solar cycle signal in the possibly other, shorter period sat- WhitePaper/AquaVITWhitePaper_ CCMI hindcast simulations as well ellite records. Ultimately, the aim Final_23Oct2009_6MB.pdf as in satellite observations, and pro- is to perform trend and variability 6Krämer et al., 2009: Ice supersatuarations vide recommendations for includ- analysis on these data, and to carry and cirrus cloud crystal numbers. Atmos. ing EPP indirect effects in low-top out an assessment of uncertainties. Chem. Physics, 9, 3505-3522 models. An authors’ meeting is to be held in

4 SPARC newsletter n° 41 - July 2013 Boulder, USA, in 2013, to finalize a ellite observational records from as of 1 January 2013) presented review paper covering super satura- the past decade, producing long- progress of the SPARC gravity tion and data quality issues. term merged satellite data series, waves activity. Gravity waves influ- data quality assessment of long- ence global circulation and climate Michaela Hegglin and Susann term ozonesonde records, and the through changes in gravity wave Tegtmeier presented progress on analysis of long-term ground-based momentum forces in the strato- the “Data Initiative”. This activity observations (including Umkehr, li- sphere and mesosphere, which can focuses on comparing stratospheric dar, microwave and FTIR observa- lead to changes in stratospheric and and upper tropospheric/lower strat- tions). A final review meeting will tropospheric circulation. Over the ospheric satellite measurements be held in Helsinki, Finland, in Sep- past year global distributions, and of many important species, and is tember 2013. The activity will pre- seasonal and interannual variations carried out in close collaboration sent its final results through special of gravity wave momentum flux- with the satellite science teams. The issues of three journals (Atmospheric es in various global data sets and comparison entails determining a Chemistry and Physics, Atmospheric model estimates were analysed and zonal and monthly mean climatol- Measurement Techniques and Earth compared in a project supported ogy using all available overlap- System Science Data), which will by the International Space Science ping data, and then comparing the be published in time for the 2014 Institute (ISSI). Because gravity individual satellite records to this WMO/UNEP Ozone Assessment. waves are intermittent events, ac- climatology. This allows a charac- curately determining gravity wave terisation of measurements from Dian Seidel presented an update of momentum fluxes requires infor- individual instruments, while sta- the stratospheric temperature trends mation regarding both the ampli- tistical analyses of the differences activity. A NOAA team produced tude and frequency of occurrence also provide an overall assessment a new record of stratospheric tem- of wave events. Models that fully of the respective species. Michaela peratures derived from AMSU (Ad- resolve the middle atmosphere were presented the results of the water vanced Microwave Sounding Unit) found to have similar gravity wave vapour analysis and provided an and SSU (Stratospheric Sounding momentum fluxes, likely because overview of the status of the activ- Unit) instruments. These data show they require similar forces to obtain ity. The activity is hoping to finish remarkable differences compared realistic circulations. However, a its final report in late 2013. to an earlier analysis by the UK simple increase in horizontal reso- Met Office, particularly in terms of lution is insufficient to produce re- Johannes Staehelin presented the the evolution of stratospheric tem- alistic gravity wave fluxes. Other status of the SI2N initiative, which perature between 25-45km after factors such as dissipation, model focuses on understanding past the middle of the 1990s. The agree- numerics, and vertical resolution changes in the vertical distribution ment between stratospheric satellite also need to be improved. The of ozone. The activity is supported temperature records and chemistry analysis indicated that (1) observed by SPARC, the International Ozone climate models is also rather poor fluxes decrease more rapidly with

Commission (IO3C), Integrated for this period. A Nature article by height than parameterized fluxes; Global Atmospheric Chemistry Ob- Thompson et al.7 called into ques- (2) waves that can be observed have servations (IGACO-O3/UV), and tion our understanding of observed longer horizontal wavelengths and the Network for the Detection of stratospheric temperature trends, may dissipate lower in altitude; (3) Atmospheric Composition Change which are thought to be caused by the CAM5 global model’s strato- (NDACC). A challenge for this pro- changes in ozone, carbon dioxide, sphere acts as a “sponge” layer, and ject is to assess the consistency of and, at lower altitudes, also by water therefore dissipation is unrealistic; satellite measurements suitable for vapour. The activity encourages the and (4) even high resolution mod- deriving reliable information on publication of independent methods els still under-resolve important ozone profile changes. This is par- for merging SSU and AMSU data, orographic waves. The ISSI group ticularly difficult since chemical and will attempt to recover tapes of is preparing a new paper compar- ozone depletion reversed during the overlapping SSU observations from second part of the 1990s as a result the UK Met Office. They may also of the successful implementation link with work on stratospheric rea- of the Montreal Protocol. Research nalysis activities. 7Thompson et al., 2012: The mystery of is conducted by several working recent stratospheric temperature trends. Na- groups focusing on improving sat- Joan Alexander (SPARC co-chair, ture, 491, 692-6972

SPARC newsletter n° 41 - July 2013 5 ing intermittency in gravity waves ing stratospheric climate variability DA group will also produce a sum- in models and observations. In fu- on daily, interannual and decadal mary report on the representation ture, the activity will focus on grav- timescales was significantly better of the stratosphere in numerical ity wave forcing on circulation us- in the high-top ensemble. This is weather prediction models. ing global assimilation methods, particularly the case in regions and as well as regional foci on wave seasons during which wave-driven Emerging activities source regions, including high lati- stratospheric dynamical variability tude southern hemisphere winter is substantial. In addition, in the Markus Rex reported on the pro- waves and tropical waves. extra-tropical lower stratosphere, gress of the Stratospheric Sulfur and the region most critical for com- its Role in Climate (SSiRC) activity. Mark Baldwin began his presenta- municating stratospheric changes to Since the SSG meeting in Zürich, in tion on the DynVar (Dynamical Var- the troposphere, the mean climate which SSiRC was endorsed as an iability) activity, on behalf of Elisa was almost identical between low- emerging SPARC activity, a white Manzini, by asking several funda- and high-top ensembles. The Dyn- paper has been published, a kick-off mental questions related to dynami- Var activity held its 3rd workshop meeting took place, and an imple- cal coupling of the stratosphere and in Reading, UK, from 22-24 April mentation plan has been developed. troposphere: What is the role of dy- 2013 (see report, this issue). This activity will improve our un- namical and radiative coupling with derstanding of the processes that the stratosphere in extended-range David Jackson presented develop- sustain the stratospheric aerosol tropospheric weather forecasting ments in the SPARC Data Assimila- layer (largely made up of sulphur), and in determining long-term trends tion (DA) activity, out of which two as well as their variability and long- in tropospheric climate? By what new SPARC activities (SNAP and term changes. SSiRC will include mechanisms do the stratosphere and S-RIP, see below) are evolving. The the following major components: in troposphere act as a coupled sys- activity held a workshop in Socor- situ aircraft and balloon measure- tem? What will the role of the strat- ro, USA, in June 2012 (see the arti- ments, ground-based remote sens- osphere be as climate changes? In cle in SPARC newsletter No. 4010). ing, satellite remote sensing, mi- an attempt to answer some of these At the workshop, two new areas of crophysical lab studies, process and questions, DynVar has focused potential research were proposed: global modelling, and a database much attention on the analysis of the (1) an intercomparison of the miss- housing all related data. Results role of the stratosphere in CMIP5 ing body force due to sub-grid scale from new research examining how output. Key results from DynVar gravity wave drag (which may sulphur is transported into the strat- activities (described in Manzini et partly be dealt with by the Gravity osphere were presented. They indi- al., 20128, and Charlton-Perez et Wave activity, see above), and (2) a cate that one of the most efficient al., 20139) confirm previous pro- study of model vertical resolution, pathways for sulphur transport to jections, which indicate that by the although this would need to be fur- the stratosphere may be in the tropi- end of the 21st century, lower strat- ther refined to become realistic, for cal Western Pacific. In this region, ospheric polar winds will weaken example, by focusing on the impact extremely low ozone mixing ratios at high latitudes and strengthen at of vertical resolution on the QBO. low latitudes. Categorising models A study looking at the changes in as high- or low-top did not reveal surface ozone simulated by the significant differences in simulated GEOS-CHEM model when assimi- 8Manzini et al., 2012: Stratosphere-trop- polar winter stratospheric changes. lating MLS and TES satellite ozone osphere coupling at inter-decadal time Interestingly, the CMIP5 models observations was presented. Re- scales: Implications for the North Atlantic were found to be more usefully sults indicate that biases decrease Ocean. Geophys. Res. Letters, 39, DOI: subdivided according to projected by 5-15%, although more work is 10.1029/2011GL050771 winter polar stratospheric changes, required to understand what the 9Charlton-Perez et al., 2013: On the lack of since changes in the strength of the data assimilation can tell us about stratospheric dynamical variability in low- winter polar vortex can be an im- vertical mixing. At present, the in- top versions of the CMIP5 models. J. Geo- portant factor for the projection of teraction between the chemical data phys. Res., 118, DOI: 10.1002/jgrd.50125. surface changes. In terms of mean assimilation and satellite retrieval 10http://www.sparc-climate.org/filead- climate, the skill of high- and low- communities is still rather informal, min/customer/6_Publications/News- top model ensembles was found to but the activity is aiming to further letter_PDF/40_SPARCnewsletter_ be similar, but the skill in simulat- develop links between the two. The Jan2013_web.pdf.

6 SPARC newsletter n° 41 - July 2013 suggest very low OH levels (the so- mittee, held an initial workshop modelling the Quasi-Biennial Os- called “OH-hole”), a feature which from 24-26 April 2013 in Reading, cillation (QBO). The QBO is direct- is expected to slow the oxidation of UK (see article, this issue), and will ly linked to how well a model simu- key tropospheric species, includ- write a review paper on the role of lates circulation and transport of ing SO2 and its precursors, and thus the stratosphere in predictability. chemical species throughout much might provide a potentially efficient The planned stratospheric predict- of the atmosphere. QBO variability pathway for these species to enter ability modelling experiments are is a function of model discretisa- the stratosphere. Further measure- expected to start in June 2013. tion, diffusion, resolved waves, and ments and modelling studies are various parameterization schemes needed to confirm these results. The Continuing on, David discussed the (e.g. gravity waves, convection). SSiRC implementation plan was ex- plans of the SPARC-Reanalysis/ Very few models are able to pro- tensively discussed and SSiRC was Analysis Intercomparison Project duce internally-generated QBOs, approved as a new SPARC activity. (S-RIP), on behalf of Masatomo and there has been little recent pro- Fujiwara. Reanalyses contain key gress to improve this aspect. The David Jackson reported on the information on the time-evolving proposed plan included the design SNAP activity (Stratospheric Net- state of the atmosphere and are of a coordinated set of numeri- work on Assessment of Predict- widely used by a large community. cal experiments to systematically ability), on behalf of Andrew At present, several reanalysis prod- explore the effects of: (1) vertical Charlton-Perez. This activity aims ucts exist, and S-RIP is a coordi- resolution, (2) resolved waves, (3) to quantify: (1) current skill in ex- nated activity aimed at comparing parameterized small-scale (grav- tra-tropical stratospheric forecasts, these data sets for various “key” ity) waves, and (4) diffusion, on the (2) the extent to which accurate diagnostics. The activity aims to: morphology of the tropical QBO forecasts contribute to improved (1) understand the causes of differ- and projected changes thereof. tropospheric predictability, and (3) ences between reanalyses; (2) use Similar experiments with interme- the partitioning of any gains in pre- the results to provide guidance on diate complexity models, which dictability between improvements appropriate usage of various rea- can explore the parameter space in initial conditions and the forward nalysis products in scientific stud- more efficiently than GCMs, were forecast. Critical questions include: ies; (3) better coordinate with data also welcomed. The goal of the ac- Is it really stratospheric influence users, which hopefully will lead tivity would be to provide a better or other model changes that im- to improvements in the next gen- understanding of what is needed to prove tropospheric forecast skill? eration of reanalysis products; and produce a reliable QBO in climate Is the improvement due to improve- (4) establish a closer collaboration models, in terms of model details ments in the modelled stratosphere between the data users and rea- such as vertical resolution, wave or to the observations? Results are nalysis centres. Over the past year parameterizations, etc. The SSG likely model dependent, and there- S-RIP research activities have been strongly affirmed the importance fore prompts the question of how discussed at several meetings, in- of these goals. However, it was felt generic are improvements? Further cluding the 2012 DA workshop that any SPARC efforts focusing on questions include: Are stratosphere- (see above), and the activity held a the QBO had to be closely integrat- troposphere coupling effects impor- planning workshop from 29 April ed with DynVar, given the strong tant throughout the winter season to 1 May 2013 in Exeter, UK (see role of the QBO in many DynVar or only when major stratospheric report, this issue), where the final research topics, and the recom- dynamical events occur? How far S-RIP report structure, time sched- mendation was therefore made to in advance can major stratospheric ule, analysis guidelines, and chapter bring these issues to the attention dynamical events be predicted and lead authors were discussed. The fi- of DynVar at its workshop in April usefully add skill to tropospheric nal activity report is planned to be 2013, to help inform DynVar’s fu- forecasts? Which stratospheric finished by 2015. ture plans, rather than launching a processes, both resolved and unre- separate QBO initiative. solved, need to be simulated to gain Other Presentations optimal stratospheric predictabili- Ted also presented an update on the ty? To address these questions, mul- On behalf of Scott Osprey, Neal WCRP Polar Climate Predictability tiple model comparisons and case Butchart and Kevin Hamilton, Ted Initiative (PCPI). In polar regions studies will be needed. SNAP has Shepherd presented a proposal for the agreement between models and recently formed a Steering Com- a new SPARC activity focused on observations is generally poor, and

SPARC newsletter n° 41 - July 2013 7 some observations remain puzzling. eral support for work on improving monthly-average NASA observa- For example, in September 2012 a stratospheric physics and the un- tional data. In tandem with WGNE, record sea-ice minimum was ob- derstanding of errors in numerical the WGCM has put together a mod- served in the Arctic, while a record simulations. To this extent, WGNE el metrics panel to focus on model sea-ice maximum was observed could possibly verify S-RIP analy- performance metrics and to liaise simultaneously in the Antarctic. ses against their own analyses, with other WCRP groups. Brief The PCPI is aimed at understand- since these may be quite different results regarding the simulation ing such differences and whether from reanalysis data. This aspect of stratospheric ozone by CMIP5 sources of climate predictability on could become integrated into the models was also presented. In con- seasonal and decadal time scales S-RIP activity, or WGNE could trast to CMIP3, where half of par- exist in the polar regions, since initiate a complementary study. In ticipating models used a prescribed they are of importance to global terms of an investigation of mod- stratospheric ozone climatology, all climate. Although several inter- el vertical resolution, WGNE has CMIP5 models considered either national programmes focusing on some previous experience research- prescribed time-evolving ozone the polar regions already exist, the ing the effects of vertical resolution (i.e. past ozone depletion and fu- WCRP brings a global perspective in the Tropical Tropopause Layer ture ozone recovery), or simulated and adds significantly to the global and may be willing to refocus on ozone changes interactively, result- modelling capacity. PCPI will con- such a topic in response to SPARC ing in substantial improvements in stitute a major sub-initiative of the requests. WGNE also offered to simulated stratospheric ozone. This ‘Cryosphere in a Changing Climate’ help design numerical experiments progress led to a more realistic rep- GC (see above), and will work syn- looking into gravity waves. It was resentation of the effects of anthro- ergistically with the World Weather mentioned that WGNE focuses on pogenic forcings on stratospheric Research Programme’s Polar Pre- improving the understanding of the temperatures and subsequent im- diction Project, which is focused sources and physics of convective pacts on tropospheric climate. on polar predictability from hourly and shear-generated gravity waves, The representation of tropospheric to seasonal scales. To this end, they and it was suggested that a link chemistry in CMIP5 models was will share a common project office. could be made with Global Atmos- largely addressed by the Atmos- Key scientific questions include: pheric System Studies (GASS, part of pheric Chemistry-Climate Model How predictable is Arctic climate? GEWEX), which has a wide research Intercomparison Project (ACC- Why are the Arctic and Antarctic scope including a focus on convec- MIP), coordinated by Jean-François climates changing so differently tion, aerosols and gravity waves. Lamarque and Drew Shindell. from each other and from global climate? Why are climate models gen- Ted Shepherd made a presentation Standing in for Kaoru Sato, Greg erally unable to describe important on the Working Group on Coupled Bodeker presented the main aims observations in polar regions? What Modelling (WGCM) on behalf of and goals of the recently created are the implications of polar climate Veronika Eyring. The WGCM’s WCRP Data Advisory Council change for low latitudes? Is the sta- broad mandate covers reviewing (WDAC). WDAC will act as a fo- bility of the ice sheets changing? and fostering the development of cal point for all WCRP data and New measurements and modelling coupled climate and Earth System observation activities and will ad- capabilities in combination with Models, coordination of model ex- vise the JSC on all issues pertain- significant community interest will periments and intercomparisons ing to observations and climate hopefully help answer these ques- (e.g. CMIP5), as well as the promo- data. The council will also coordi- tions. A planning meeting was held tion and facilitation of model valida- nate high-level aspects across the in Toronto, Canada, in April 2012, tion. Experience from CMIP5 was WCRP, ensuring cooperation with and a draft implementation strategy briefly summarized. CMIP5 pro- the WCRP’s main partners, such as was published in November 2012. duced an extremely large volume the Global Climate Observing Sys- of data, which was managed and tem (GCOS), and other observing In his report on the Working Group made available through the Earth programmes. Furthermore, WDAC on Numerical Experimentation System Grid Federation (ESGF) will work together with WMAC (WGNE), David Jackson sum- architecture. In a parallel effort, the (see below) to promote effective marized WGNE feedback regard- obs4MIP database was created for use of observations for model coming requests from specific SPARC model comparison purposes. This parison and to address issues relat- activities. WGNE provides gen- database mainly contains gridded, ed to the coordinated development

8 SPARC newsletter n° 41 - July 2013 ly: WGNE is focused mainly on atmospheric modelling while WMAC addresses the Earth system as a whole; and (3) interactions with end users would generally be dealt with in the existing modelling groups, but if WMAC identifies gaps, it would advise the JSC on appropriate action. It was emphasized that the WMAC is primarily an advisory body and will not take on activities itself.

Shigeo Yoden presented results from a meeting on Sudden Strato- spheric Warmings (SSWs) that took place in Kyoto, Japan, in Febru- ary 2012. He also advertised: (1) Figure 1: Participants of the 20th SPARC Scientific Steering Group meeting, Buenos Aires, a WCRP Regional Workshop on Argentina. stratosphere-troposphere processes and their role in climate, which took place in Kyoto, Japan, from of data assimilation, reanalysis, ob- invited to present their approach to 1-3 April 2013; (2) the Asia Oce- serving system sensitivity experi- WDAC. WDAC’s 2nd meeting took ania Geosciences Society meeting, ments, and of paleoclimate data. place in Darmstadt, Germany, from held from 24-28 June 2013, which At the first WDAC meeting it was 4-5 March 2013. had a Middle Atmosphere Science concluded that (1) there is a sig- session; (3) a SSW symposium that nificant need for measurements of Ted Shepherd reported on the took place during the Davos Atmos- ocean biogenic trace gas and aero- WCRP Modelling Advisory Coun- phere and Cryosphere Assembly, sol emissions; (2) a more uniform cil (WMAC), who, in partnership held from 8-12 July 2013 in Davos, and formal approach needs to be with the WCRP core projects and Switzerland; and (4) a meeting during established for assessing the quality working groups, will serve as a fo- the International Association of Geo- of observational data sets used to cal point for WCRP modelling ac- magnetism and Aeronomy’s General validate models; (3) global environ- tivities and will advise the JSC and Assembly, to be held in Merida, Mex- mental change data sets, both from WCRP community on all issues ico, from 26-31 August 2013. models and observations, should be pertaining to modelling. It will reg- made available through the ESGF; ularly assess modelling capabilities Pablo Canziani advertised the (4) funding agencies need to en- within WCRP; identify gaps, over- WCRP Special Workshop on Cli- sure the long-term storage, man- laps, opportunities for synergy as matic Effects of Ozone Depletion in agement and preservation of col- well as provide advice on priorities the Southern Hemisphere: Assess- lected data; and (5) efforts need to for modelling across the WCRP. ing the evidence and identifying be made to improve the traceability WMAC aims to facilitate effective gaps in the current knowledge. The of data sets. There was also discus- communication on modelling issues workshop took place from 25 Feb- sion regarding the governance of both within the WCRP and with the ruary to 1 March 2013, in Buenos the ESGF, which is an open source broader community. In addition, it Aires, Argentina (see article this is- effort to provide a robust, data dis- will promote capacity development sue). tributed and computation platform in terms of model development, enabling world wide access to peta/ evaluation, and application. Out- SPARC items exa-scale scientific data. The need comes of the first WMAC meeting for a thorough assessment of rea- included: (1) WMAC will form a The SPARC Data Center was estab- nalysis water vapour data sets was task team with IGBP on prediction lished in 1999 and contains a num- endorsed. Furthermore, the ESA of the Earth system; (2) WMAC and ber of important SPARC data sets SPARC Initiative (SPIN) will be the WGNE will act complementari- (see http://www.sparc-climate.

SPARC newsletter n° 41 - July 2013 9 org/). A mirror website and ftp da- the CCMI workshop (held in Boul- the discussion of suitable topics to tabase are maintained at Kyoto Uni- der, USA, from 14-17 May 2013). include new SSG members who versity, Japan, providing both an It was also suggested that SPARC will begin terms from January external backup and enhanced ac- may want to connect with Aero- 2014. Furthermore, after consider- cessibility. Marvin Geller recently Com activities, with mention of a able investigation, it was found that submitted a proposal to NASA for possible collaborative workshop. establishing a SPARC capacity de- three years of further funding for the In addition, SPARC may want to velopment fund at the ETH Zürich SPARC Data Center. The submitted consider greater focus on studies (the SPARC Office’s current host proposal will also serve to continue looking at transport and circulation institution) would not be feasible. research activities related to high changes that might lead to changes vertical resolution radiosonde meas- in precipitation patterns. Joan Alexander introduced a urements (archived at the SPARC joint SPARC-IGAC workshop on Data Center). A workshop regard- Carolin Arndt made a short pres- Atmospheric Chemistry and the ing the scientific analysis of these entation about SPARC communica- Asian monsoon. The Asian summer observations was held from 27-29 tion activities, including the SPARC monsoon plays a significant role May 2012 at Stony Brook Univer- website (http://www.sparc-cli- in chemistry-climate interaction, sity. Marvin also proposed a three- mate.org/), SPARC eNews and however experimental studies in year transitioning strategy, which the SPARC Newsletter. Website the region are extremely challeng- could be applied to migrate the data statistics show that from August to ing. The goal of the workshop is to from the SPARC Data Center to the November 2012 the SPARC web- improve collaborative efforts across British Atmospheric Data Centre to site was viewed over 9 500 times. the international community. This ensure the continuity of the provi- To avoid overloading the SPARC workshop took place in Kathmandu, sion of these data to the community. community with emails from the Nepal, from 9-12 June 2013. At the end of the three transition SPARC office, workshop and meet- years, all data storage would cease ing announcements are usually Carolin Arndt and Greg Bode- at Stony Brook University. advertised on the SPARC website ker discussed SPARC’s new name, and then included in the eNews bul- “Stratosphere-troposphere Pro- Joan Alexander discussed ideas for letin (sent out via email to about cesses And their Role in Climate”, a new SPARC implementation plan, 400 recipients approximately every which was selected after consulta- which needs to be prepared to ad- 2 months). To be sent out through tion with the SPARC community dress new science foci, the WCRP’s the eNews, announcements need to (the SPARC acronym will, howev- restructuring, including the Grand be sent to the SPARC Office a few er, remain unchanged). For the new Challenges, as well as SPARC’s weeks before the event takes place SPARC logo, a competition has been new mandate. This might imply (or the deadline for registration ex- run. Initially the SPARC community finding a new structure under which pires), so as to reach the SPARC was asked for contributions and then SPARC research activities may be community in a timely fashion. professional designers were asked to integrated (i.e. a replacement of the provide and adapt new versions. The themes in the present implementa- Carolin Arndt then continued by SPARC SSG and activity leaders tion plan). The implementation plan reporting on ideas for expanding were asked to vote on several options should envisage a time frame of ap- SPARC’s capacity development and the final version will be launched proximately 10 years. strategy. Several mechanisms were at the SPARC General Assembly in identified, such as mentoring and January 2014. The contribution of SPARC to visiting programmes for scientists aerosol-related research under the from developing countries and the Fiona Tummon presented the WCRP GCs was also discussed. establishment of a SPARC capac- progress of the implementation of There are different aspects regard- ity development fund. The possi- the SPARC community data base, ing the influence of aerosols on bility of networking with potential which is currently in the final stag- climate and climate change, one partners such as START, APN and es of development. The concept of being related to aerosol, cloud and the ICTP, amongst others, was also a new SPARC members’ database precipitation interactions. SPARC’s proposed. However, since no SSG was presented by Greg Bodeker at involvement in this aspect of the members are directly engaged in the 19th SPARC SSG meeting, held “Clouds, Circulation and Climate SPARC capacity development ac- in Zürich (see SPARC newsletter Sensitivity” GC was discussed at tivities it was decided to postpone No. 3911). Implementation of the

10 SPARC newsletter n° 41 - July 2013 database with an additional web- Zealand. The outline of the scien- proved of the new procedure. interface is planned for mid-2013. tific programme was also discussed The next SSG Meeting will take place with Veronika Eyring and Adam from 19-21 January 2014 in Queens- The SPARC Office team agreed to Scaife, co-chairs of the Scientific town, New Zealand, following the 5th produce the first SPARC annual re- Organising Committee. SPARC General Assembly. port using updated material from the activity leaders. The demand After a short discussion regarding for such a document and the time action items, Greg Bodeker asked required for its preparation will be the participants about their thoughts 11http://www.sparc-climate.org/filead- assessed. The annual report is now on the new format of the SPARC min/customer/6_Publications/Newslet- available online12. SSG meeting (i.e. a short descrip- ter_PDF/39_SPARCnewsletter_Jul2012_ tion of activities being provided be- web.pdf Greg Bodeker presented plans for fore the meeting, and then separa- 12http://www.sparc-climate.org/filead- the next SPARC General Assembly, tion of scientific presentations and min/customer/6_Publications/ProgPlan_ which will take place from 12-17 programmatic discussions during PDF/SPARC_Annual_Report_2012_ January 2014 in Queenstown, New the meeting). All participants ap- small.pdf

Report on the Regional WCRP/SPARC Workshop with focus on the Southern Hemisphere and South America

Carolina S. Vera1,3, Manuel Pulido2,3, and Andrea Carril1,3

1CIMA/University of Buenos Aires-CONICET, Argentina, [email protected], 2Department of Physics, FACENA, Universidad Nacional del Nordeste, Argentina, 3UMI-IFAECI/CNRS-CONICET-UBA, Argentina

From 26-27 November 2012 the issues is relatively small. The main models, but in other types of mod- Workshop on Southern Hemisphere goal of the Workshop was to gather els these biases have been reduced and South American Climate was local researchers interested in dif- through the application of gravity held in Buenos Aires, Argentina, ferent aspects of current and future wave drag parameterizations. One back-to-back with the SPARC SSG SPARC research together with par- of the key observational quantities Meeting, hosted by the “Centro de ticipants of the SPARC SSG meet- used to constrain gravity wave (GW) Investigaciones del Mar y la Atmós- ing to promote interaction among parameterizations is wave stress or fera” (CIMA). SPARC provides ex- researchers and to identify the main wave momentum flux (MF). Ale- pertise in several key areas related SPARC-related research topics of rel- jandro La Torre and Peter Alex- to climate variability and climate evance to the region. The Workshop ander identified and simulated GW change, such as dynamical variabil- included 22 oral talks and 5 posters, events above the southern Andes ity, ozone, stratosphere-troposphere with contributions from Argentina, and Antarctic Peninsula, with sig- dynamical coupling, gravity waves, Brazil, Uruguay, Bolivia, Colombia nificant MF occurring at low levels temperature trends, and data assimi- and Uruguay, combined with contri- and then decreasing with height. lation, amongst others. The southern butions from SPARC scientists. The Partial reflection, wave breaking and hemisphere (SH), and in particular Workshop agenda was broad, cover- absorption at critical layers seem to South America, are regions of the ing several different research topics. explain the momentum deposition world in which research of these key accompanying decreases in GW MF. themes is highly relevant, and needs Gravity Waves A prevailing negative zonal com- to be expanded and strengthened be- ponent of MF was observed almost cause the current South American re- Biases in SH middle atmosphere everywhere, in agreement with the search community addressing these winds still exist in many climate orographic source hypothesis.

SPARC newsletter n° 41 - July 2013 11 Joan Alexander discussed the chal- eration centre of GWD over the last particularly during summer. Obser- lenge of observing GWs globally be- 20 years was found in the MERRA vations highlight the role of the re- cause of the high spatial and tempo- reanalysis. sidual layer as a chemical reservoir ral resolution required to constrain for ozone and precursors during the their role in the momentum budget. Ozone night, which can then be transported A recent international intercom- and activated by the thermally driv- parison organized with the help of Elian Wolfram described the ozone en circulation during the day. Some SPARC and the International Space monitoring and research related to cases show evidence of stratospheric Science Institute, made significant ozone impacts that are currently intrusions, although the physical progress in constraining momentum being carried out in Argentina. Re- processes related to these events are fluxes using both global-scale meas- cently, the Ozone DIAL and SAOZ not yet clear. urements of GW momentum fluxes instruments of the Atmospheric in the SH, super-pressure balloon Observatory of Southern Patagonia Aerosols measurements in the SH high lati- (OAPA) radiometer joined NDACC tudes, and model simulations. She (Network for the Detection of At- Pablo Ristori described the new presented evidence that small islands mospheric Composition Change). multi-wavelength lidar network and in the Southern Ocean could contrib- Observations were used to analyse associated instruments currently be- ute significantly to the orographic extreme and persistent ozone holes ing installed at the main Patagonian gravity wave drag missing in the that develop over the southern tip of airports in Argentina. Their goal is to models around 60°S (see Figure 2). South America. Susana Díaz pre- monitor the presence of atmospheric sented an analysis of the monthly ash emitted by Andean volcanoes, Guillermo Scheffler and Manuel time series of total ozone column like the recent eruption of the Puye- Pulido used a variational data as- (TOC) at 20 stations in Antarctica hue Cordón Caulle volcano, whose similation technique to determine and South America from 1979-2011. aerosol plume reached as far as Bue- the middle atmospheric gravity wave She showed that events where TOC nos Aires city (see Figure 3). These drag (GWD) produced by unresolved remains below 220DU for several lidars are being developed by the Lidar GW in the MERRA reanalysis. The days occurred during September Division of CEILAP-Buenos Aires multiyear GWD evaluation shows and October at all stations analysed. and are going to be operated by the a characteristic latitudinal depend- Roberto Rondanelli presented re- National Weather Service. This new ence, with a strong deceleration cen- sults of a two-year effort to produce technology provides real time infor- tre at 60° in the winter hemisphere, ozone soundings in the Santiago area mation to airports, airlines, the Buenos and a weaker deceleration centre at in Chile, mostly to understand the Aires Volcanic Ash Advisory Centre 30° in the summer hemisphere. An diurnal cycle of urban photochem- and the research community. intensification of the summer decel- istry and transport in the region,

Figure 2: Left: Missing drag near 60°S due to lack of resolved topography is associated with zonal wind biases in models (figure from McLandress et al., 2012). Small Islands in Southern Oceans will provide some missing flux. Right: Orographic Waves over South Georgia Island observed as AIRS TB anomalies (figure from Alexander et al., 2009).

12 SPARC newsletter n° 41 - July 2013 Dynamics of Stratosphere- but improvements are still needed reiro showed that knowledge of the Troposphere Coupling so that the physical processes gov- state of the tropical oceans improves erning these systems are properly seasonal predictability of the South Carolina Vera presented recent evi- represented in these models. In ad- American Climate. dence that stratospheric dynamics dition, Carolina Vera showed that can alter tropospheric SH circula- the activity of the Southern Annular Climate Change tion, which in turn can impact South Mode has a large influence on south American climate. The coupling of eastern South American climate on Julie Arblaster and colleagues ex- stratosphere-troposphere dynam- intraseasonal, interannual and dec- amined shifts in the distribution of ics is, however, not yet well under- adal timescales. Such influence can ozone and winds in 46 CMIP5 mod- stood. Mark Baldwin showed that act synergistically or destructively els, separating between those with geopotential height might not be in combination with the influence prescribed ozone (NOCHEM) and the right variable to describe vor- of tropical Indian-Pacific convec- those with interactive or semi-offline tex dynamics, instead, he suggested tion variability. She also showed that chemistry (CHEM). They found considering a metric based on polar stratosphere-resolving models, such that in the high-mitigation RCP2.6 tropopause variability. Anomalous as those contributing to the WCRP/ scenario ozone recovery dominates upwelling/downwelling over the po- SHFP-CHFP (Stratospheric-Resolv- and the SH extra-tropical jet shifts lar cap can be thought of as a me- ing Historical Forecast Project-Cli- equatorward, although this change chanical “plunger effect”, with the mate-Systems Historical Forecast) was assessed as weak, as it is found anomalous upwelling/downwelling Project, can predict larger seasonal only in some models (see Figure that extends through the tropopause signals in the SH circulation than 4). In the business-as-usual RCP8.5 into the troposphere being driven by models with poor vertical resolution scenario the greenhouse gas (GHG) Rossby waves. in the stratosphere. Marcelo Bar- effect prevails and the SH extra-

Climate Variability in the SH

Mark also pointed out that the availability of analysis and tracking algo- rithms has improved our knowledge of cyclogenesis and cyclone trajectories over the SH and, in particular, over South America. Despite this, we still don’t fully understand all regional aspects of these systems. High-resolution regional models are useful tools for examining cyclones and cyclogenesis in specific regions,

Figure 3: Top: Volcanic aerosol plumes over Patagonia. Satellite image TERRA June 13, 2011 14.35 UTC, [http://rapidfire.sci.gsfc.nasa. gov/gallery/]. Bottom: Aerosol attenuated backscatter at 1064nm measured with a lidar system in Buenos Aires. Atmospheric boundary layer, volcanic ash layers and high level clouds can be observed (figure from Ristori et al., 2012).

SPARC newsletter n° 41 - July 2013 13 Figure 4: Long-term mean (thin black contour) and linear trend (color) of zonal mean DJF zonal winds for (a) ERA-Interim from 1979–2005; (b) CMIP5 (all models listed in Table 1 in Eyring et al., 2013, except those noted with #), and (c), (d), (e), (f): same as (b), but for the four RCPs over 2006-2050. Contour intervals of climatological wind are 10m/s starting from -20m/s. Trends which are statistically significant at the 5% level (95% confidence) are stippled (figure from Eyring et al., 2013).

mean circulation and resolved eddy fluxes helps identify the errors. A strong emphasis is needed on improving models and better understanding climate variability.

Final Remarks tropical jet shifts poleward, a result into question our understanding of assessed as robust across all mod- observed stratospheric temperature Large-scale variability and circula- els. In addition, differences between trends and our ability to test simu- tion change in the SH exhibit hemi- CHEM and NOCHEM models are lations of the stratospheric response spheric patterns that can impact the not large, and are clouded by other to emissions of GHGs and ozone- regional climate of South America, model characteristics. P. González depleting substances. Africa, Australia-Oceania, and Ant- presented an analysis of the posi- arctica, on time scales ranging from tive precipitation trends observed in Model Biases days to decades. It would be warmly south eastern South America during welcomed if SPARC could sup- the second part of the 20th century Ted Shepherd discussed the fact port future initiatives that provide a using different climate simulation that climate models generally do framework for research coordination experiments. She suggested that the not provide robust projections of of SH climate variability and pre- effect of ozone depletion might be as circulation-driven aspects of cli- dictability. or more important than that of GHGs mate change in the mid-latitudes. on the South America precipita- Mid-latitude circulation is subject to Many monitoring (ozone, UV, aero- tion trend. Dian Seidel presented a strong internal variability, leading to sols) activities are currently under- new data set of middle- and upper- non-robust decadal-timescale trends, way in southern South America, stratospheric temperatures based on an issue that needs to be taken into mainly to support meteorological a reprocessing of satellite radiances account in regional climate pro- services and environment agencies. from the Stratospheric Sounding jections. In addition, model errors There is a need to build partnerships Unit. The data set provides a view in both mean climate and climate between scientific and operational of stratospheric climate change dur- variability at mid-latitudes are most communities in order to accelerate ing the 1979–2005 period that is likely largely related to errors in pa- the development of climate infor- strikingly different from those of rameterized atmospheric processes. mation and tools relevant to societal earlier data sets. The new data call Breaking the feedback loop between needs (climate services).

14 SPARC newsletter n° 41 - July 2013 References changes and associated climate impacts in Ristori, P., et al., 2012: Development Of CMIP5 simulations. J. Geophys. Res., doi: An Argentinean Lidar Network To Monitor Alexander, M.J., S.D. Eckermann, D. Brout- 10.1002/jgrd.50316. The Volcanic Plume And Dust In Patagonia. man, and J. Ma, 2009: Momentum flux Reviewed and Revised Papers Presented at estimates for South Georgia Island moun- McLandress, C., T.G. Shepherd, S. Pola- the 26th International Laser Radar Confer- tain waves in the stratosphere observed varapu, and S.R. Beagley, 2012: Is Missing ence (ILRC 2012), Porto Heli, Greece, 25-29 via satellite. Geophys. Res. Lett., doi: Orographic Gravity Wave Drag near 60°S June 2012. Editors: A. Papayannis, D. Balis 10.1029/2009GL038587. the Cause of the Stratospheric Zonal Wind and V. Amiridis. Vol. I, 357 – 360. Biases in Chemistry–Climate Models? J. At- Eyring, V., et al., 2013: Long-term ozone mos. Sci., 69, 802–818.

The NASA Airborne Tropical TRopopause EXperiment (ATTREX)

Eric J. Jensen1, Leonhard Pfister1, David E. Jordan1, David W Fahey2,3, Paul A. Newman4, Troy Thornber- ry2,3, Andrew Rollins2,3, Glenn S. Diskin5, T. Paul Bui1, Matthew McGill4, Dennis Hlavka6, R. Paul Lawson7, Ru-Shan Gao2, Peter Pilewskie8, James Elkins2, Eric Hintsa2,3, Fred Moore2,3, Michael J. Mahoney9, Elliot Atlas10, Jochen Stutz11, Klaus Pfeilsticker12, Steven C. Wofsy13, Stephanie Evan2,3, Karen H. Rosenlof2

1NASA Ames Research Center, USA, [email protected], 2NOAA Earth Science Research Laboratory, USA, 3Cooperative Institute for Research in Environmental Science, University of Colorado, USA, 4NASA Goddard Space Flight Center, USA, 5NASA Langley Research Center, USA, 6Science Systems and Applications, USA, 7Spec, Inc., Stratton Park Engineering Company, USA, 8University of Colorado, USA, 9Jet Propulsion Laboratory, California Institute of Technology, USA, 10University of Miami, USA, 11University of California, Los Angeles, USA, 12Institut für Umweltphysik, Universität Heidelberg, Germany, 13Harvard University, USA

We report here on recent airborne Flight Research Center (DFRC). While the tropospheric water va- measurements in the tropical trop- ATTREX flights were conducted pour-climate feedback is well repre- opause layer (TTL, ~13-19km) from DFRC in southern California sented in global models, predictions provided by the NASA Airborne into the deep tropics during autumn of future changes in stratospheric Tropical TRopopause EXperiment 2011 (three flights) and late winter humidity are highly uncertain be- (ATTREX). ATTREX is a five-year 2013 (six flights). Planned flights cause of gaps in our understanding airborne science program focused from Guam in winter and early- of physical processes occurring in on the physical processes occurring summer 2014 will provide exten- the TTL. The composition and hu- in the TTL, which ultimately deter- sive measurements in the western midity of the TTL are controlled by mine the composition and humidity Pacific TTL. a complex interplay between slow, of air entering the stratosphere. The large-scale transport, rapid convec- long-range (16 000km), high-alti- Radiative transfer calculations show tive transport, atmospheric waves, tude (20km) Global Hawk (GH) un- that even small changes in strato- cloud processes, and radiative heat- manned aircraft system is equipped spheric humidity have climate im- ing (see Figure 5). High spatial-res- with twelve instruments measuring pacts that are significant compared olution measurements of TTL com- clouds, water vapour, meteorologi- to those of decadal increases in position are sparse in comparison to cal conditions, chemical tracers, greenhouse gases (Forster and other climatically important parts of chemical radicals, and radiation. Shine, 2002; Solomon et al., 2010). the atmosphere, partly because the The overall ATTREX project is Future changes in stratospheric high altitude of the TTL limits sam- managed by the NASA Ames Re- humidity and ozone concentration pling with aircraft. Furthermore, search Center, and the Global Hawk in response to changing climate the use of satellite measurements program is managed by Dryden are significant climate feedbacks. of TTL composition for assessing

SPARC newsletter n° 41 - July 2013 15 physical processes is complicated by the characteristically strong vertical gradients in this region.

The overarching goals of ATTREX are (1) to improve our understanding of how deep convection, slow large-scale ascent, waves, and cloud microphysics control the humidity and chemical composition of air entering the stratosphere, and (2) to improve global-model predictions of feedbacks associated with future changes in TTL cirrus, stratospheric humidity, and stratospheric ozone in a changing climate. ATTREX is providing an unprecedented dataset of high spatial-resolution measurements of TTL composition necessary to achieve these objectives. Figure 5: Schematic diagram showing TTL physical processes, including large-scale transport, detrainment from deep convection, gravity waves, thin cirrus, and radiative heating. Global Hawk Operations

The GH is nearly ideal for sam- the conditions being sampled, and the area, in precipitation, or with pling the TTL. The aircraft ceiling correct problems that arise. The re- standing water on the runway. As (ranging from about 54 000feet al-time data downloaded to the GH with other high altitude, long-wing (~16.5km) shortly after take-off to Operations Center is also extremely aircraft (such as the ER-2), flying 62 000feet (~18.9km) in the lat- useful for aircraft operations. While in convective regions is subject to ter part of the flight) permits sam- the aircraft was flying at cruise al- restrictions. The GH was also not pling through the depth of the TTL titude, the real time Cloud Physics designed for flying in the extremely and into the lower stratosphere. Lidar (nadir) and Microwave Tem- cold tropical tropopause air that is The range of the GH permits sam- perature Profiler measurements of critical for ATTREX science ob- pling large regions of the Pacific clouds and temperature below the jectives, necessitating mitigation TTL even with flights originating aircraft were used to decide when measures to ensure that critical air- in southern California (see Figures and where to execute vertical pro- craft components are not exposed to 6 and 7). As demonstrated on the files in order to sample the cloud the extreme outside temperatures. ATTREX flights, frequent vertical regions with particle and trace-gas The GH operation is also dependent profiling through the TTL can be instruments. Real-time data from on the functionality of multiple sat- conducted with the GH. The pay- the in situ instruments was also use- ellite communications systems that load capacity (~680kg) is adequate ful for determining the conditions are not necessarily required for op- for carrying remote-sensing and in the GH was sampling. The real- eration of manned aircraft. Despite situ instruments necessary to make time direction of the aircraft was these constraints, the GH has turned key TTL measurements (see pay- facilitated by support from the GH out to be an excellent platform for load section below). Inmarsat and pilots and mission manager who ac- achieving the ATTREX objectives. Iridium satellite-based communica- commodated numerous requests for tion systems are used for command flight plan changes from the scien- ATTREX Global Hawk Payload and control of the GH and its pay- tists. load. The GH also includes a Ku The ATTREX payload was designed satellite link for high-speed com- It should be noted that operation to address key uncertainties in our munication with the payload. Using of the GH presents certain chal- understanding of TTL composi- these communications systems, in- lenges. Take-offs and landings tion, transport, and cloud processes vestigators remotely monitor their are not possible with strong cross- affecting water vapour. Measure- instruments, optimize settings for runway winds, icing conditions in ments of water vapour, cloud prop-

16 SPARC newsletter n° 41 - July 2013 erties, numerous tracers, meteoro- ments have plagued past attempts to that unknown or underestimated sys- logical conditions, and radiative accurately quantify the humidity of tematic errors are associated with op- fluxes are included (see Table 1). the stratosphere and TTL (SPARC, eration of these instruments on mov- Instruments were chosen based on 2000; Peter et al., 2006; Weinstock ing platforms in the upper troposphere proven techniques and size/weight et al., 2009). In the very dry con- and lower stratosphere (UTLS). accommodation on the GH. ditions associated with the cold tropical tropopause, the discrepan- The ATTREX payload addresses The very dry conditions present in cies have been as large as a factor the concerns with water vapour ac- the tropical tropopause region (wa- of two in water vapour concentra- curacy and reliability by including ter vapour concentrations as low tion. A ground-based comparison two water vapour instruments, Di- as ~1ppmv) represent a significant of airborne instruments conducted ode Laser Hygrometer (DLH) and challenge for accurately measuring in 2008 showed much better agree- NOAA Water (NW), both of which water vapour. Discrepancies be- ment than had been seen in strato- have suitable sensitivity for wa- tween water vapour concentrations spheric measurements (Fahey et al., ter vapour values as low as 1ppm. measured with different instru- 2009). The resulting implication is The two hygrometers use very different methods and have particular strengths that complement each other. The NW instrument (added to the payload in 2013) provides a closed-cell tunable-diode laser (TDL) measurement that includes the in-flight calibration system used on the NOAA chemical ionization mass spectrometer (CIMS) instrument during MACPEX (Thornberry et al., 2013). Calibration in flight avoids the uncertainty associated with assuming that ground-based calibrations apply to in-flight conditions and that instrument performance is unaffected by the different pressure and temperature conditions in flight. The NW instrument Figure 6: Flight paths for 2011 ATTREX flights. also measures total water concentration using a forward-facing in- let that enhances ice concentration. The DLH instrument provides an open-path TDL measurement by fir- ing the laser from the fuselage to a reflector on the wing and measuring the return signal. The path length (12.2m) is long enough to provide a precise, fast measurement of water vapour. The precision is sufficient to permit detection of fine structure in the TTL water vapour field even at a data rate of 100Hz (corresponding to 1.7m horizontal resolution along the flight path for a typical GH speed of 172m/s). The preliminary NW and DLH data obtained in the Figure 7: Flight paths for 2013 ATTREX flights. Note the different latitude/longitude range 2013 flights suggest a high degree here than in Figure 6. of consistency and agreement for

SPARC newsletter n° 41 - July 2013 17 Table 1: Global Hawk Payload:

Instrument Investigator Institution Measurements REMOTE Cloud Physics Lidar (CPL) M. McGill NASA/GSFC Aerosol/cloud backscatter Microwave Temperature Profiler (MTP) M. Mahoney JPL/Caltech Temperature profile

Differential Optical Absorption Spectrometer (DOAS) J. Stutz, K. Pfeilsticker UCLA/Univ. Heidelberg O3, O4, BrO, NO2, OClO, IO

IN SITU

Global Hawk Whole Air Sampler (GWAS) E. Atlas Univ. of Miami CFCs, halons, HCFCs, N2O, CH4, HFCs, PFCs, hydrocarbons, etc.

UAS Chromatograph for Tracers (UCATS) J. Elkins NOAA/GMD N2O, SF6, CH4, H2, CO, O3, H2O

NOAA Ozone R.-S. Gao NOAA/CSD O3

Harvard University Picarro Cavity Ringdown Spectrometer (HUPCRS) S. Wofsy Harvard University CO2, CO, CH4

NOAA Water (NW) T. Thornberry, A. Rollins NOAA/Cires H2O (vapor and total)

Diode Laser Hygrometer (DLH) G. Diskin NASA/LaRC H2O vapor Hawkeye P. Lawson Spec, Inc. Ice crystal size distributions, habits Solar and infrared radiometers P. Pilewskie Univ. of Colorado Zenith and nadir radiative fluxes Meteorological Measurement System (MMS) P. Bui NASA/ARC Temperature, pressure, and winds

Table 2: ATTREX Global Hawk flights:

Flight Date in 2011 Flight time (hours) Tropical sampling region (south of 20 N) Notes RF01 28 29 October 21.4 6.3 20°N, 113 120°W Eastern Pacific TTL profiling RF02 5 6 November 16.5 6.5 20°N, 119 127°W TTL cirrus sampled RF03 9 10 November 23.4 12 20°N, 114 134°W TTL cirrus and convective detrainment sampled

Flight Date in 2013 Flight time (hours) Tropical sampling region (south of 20 N) Notes RF01 5 6 February 24.5 11.3 20°N, 142 151°W Central Pacific TTL profiling RF02 9 10 February 24.3 10.1S 20°N, 143 150°W Meridional TTL cross section RF03 14 15 February 24.5 6.8 20°N, 141 172§W Central Pacific TTL profiling RF04 21 22 February 24.6 12.3S 20°N, 100 114°W Eastern Pacific meridional cross section RF05 26 27 February 24.4 6.5 20°N, 147 174°W Central Pacific cold TTL cirrus profiling RF06 1 2 March 24.1 0.2 20°N, 93 111°W Eastern Pacific cold TTL cirrus profiling

TTL values less than 10ppm. The and 2013 flights. The FCDP is sim- High temporal and spatial resolu- UCATS instrument also contains a ilar to the FSSP in that it measures tion measurements of basic tracers

TDL water sensor; although its pre- the scattering from individual cloud are also included. The NOAA O3 cision is only +/-1ppmv, it provides particles. The FCDP was designed instrument is a dual-beam UV ab- useful information and calibration for measuring water droplets, and sorption photometer that provides checks for water vapour >10ppmv. the uncertainty associated with siz- 2Hz ozone measurements. The ing non-spherical ice crystals is Harvard University Picarro Cavity The ATTREX plan calls for use of not well quantified. However, the Ringdown System (HUPCRS) pro- the Hawkeye instrument for cloud instrument provides accurate meas- vides precise, stable measurements

measurements. Hawkeye is a com- urements of ice concentration in of CO2 and CH4. The HUPCRS also bination of two imaging instruments cirrus clouds. The cloud measure- includes a CO channel that should (equivalent to the two-dimensional ments, along with the water vapour provide useful data with some av- Stereo (2D-S) and Cloud Particle and temperature measurements, eraging. The UAS Chromatograph Imager (CPI)) and a spectrometer will be used to test our theoretical for Atmospheric Trace Species (equivalent to the Forward Scatter- understanding of ice crystal nuclea- (UCATS) provides measurements

ing Spectrometer Probe (FSSP)), tion, depositional growth, and ag- of N2O, SF6, H2, CO (tropospher-

all of which have been used in the gregation. These processes control ic), and CH4, as well as additional past for airborne cloud measure- TTL cirrus formation and dehydra- measurements of ozone and water ments. Since engineering work for tion of air entering the stratosphere. vapour. the Hawkeye wing mount on the The ATTREX payload provides Global Hawk was not completed in a number of tracer measurements The Global Hawk Whole Air Sam- time, the Fast Cloud Droplet Probe that can be used to quantify TTL pler (GWAS) provides 90 gas canis- (FCDP) was flown during the 2011 transport pathways and time scales. ter samples that are spaced through-

18 SPARC newsletter n° 41 - July 2013 out each flight. The times for the in October and November 2011. Al- cirrus were apparent: (1) vertically GWAS samples are determined on though the focus of the 2011 flight extensive cirrus with low ice num- a real-time basis depending on the series was evaluating aircraft and ber concentrations, low extinctions, flight-plan. Post-flight, gas chroma- instrument performance under the and large supersaturations (up to tographic analysis provides a pleth- extreme tropical tropopause condi- approx. 70%) with respect to ice; ora of trace gases with sources from tions, useful science-quality meas- and (2) vertically thin cirrus lay- industrial mid-latitude emissions, urements in the TTL were obtained. ers with much higher ice concen- biomass burning, and the marine Three long flights into the tropics, trations that effectively deplete the boundary layer, with certain com- with durations ranging from 15 to vapour in excess of saturation. The pounds (e.g. organic nitrates) that 24 hours, were conducted (see Ta- low-concentration clouds are likely have a unique source in the equa- ble 2 and Figure 6). These flights formed on a background population torial surface ocean. GWAS also targeted cold tropical tropopause of insoluble particles with low con- measures a full suite of halocarbons regions where in situ cirrus occur- centrations, whereas the high ice that provide information on the role rence was likely, regions down- concentration layers (with concen- of short-lived halocarbons in the stream of deep convection detrain- trations up to 10cm−3) can only be tropical UTLS region, on halogen ing into the TTL, and regions with produced by homogeneous freezing budgets in the UTLS region, and on strong tracer gradients. Each of of an abundant population of aque- trends of HCFCs, CFCs, and halo- the flights included multiple verti- ous aerosols. These measurements, genated solvents. cal profiles in the tropics (seeTable along with past high-altitude air- 2), typically extending from cruise craft measurements, indicate that The ATTREX payload also includes altitude (54,000-60,000ft) down to the low-concentration cirrus occur radiation measurements, which will 45,000ft (~13.7km). As discussed frequently in the tropical tropopause be used to quantify the impacts of above, real-time lidar data indicat- region, whereas the high-concentra- clouds and water vapour variability ing the altitudes and structures of tion cirrus occur infrequently. The on TTL radiative fluxes and heat- clouds below the aircraft were used predominance of the low-concen- ing rates. The spectral solar flux to decide when and where to exe- tration clouds means cirrus near the measurements additionally provide cute vertical profiles. tropical tropopause may typically be information about cirrus micro- less effective at dehydrating air enter- physical properties. Lastly, the Dif- As a result of instrument developing the stratosphere than is typically ferential Optical Absorption Spec- ment and integration delays the parameterized in climate models. trometer (mini-DOAS) instrument HUPCRS and Hawkeye instru- In February through early March provides slant-path measurements ments were not on board during the 2013, six ATTREX flights were of BrO, NO2, O3, IO, O4 absorp- 2011 flights. Furthermore, integra- conducted from DFRC into the deep tion, and cloud/aerosol extinction tion and centre of gravity issues tropics (see Figure 7 and Table at various elevation angles near the prevented inclusion of GWAS and 2). Again, the flights targeted cold limb. These measurements can be CPL in the first 2011 tropical sci- tropopause regions where TTL cir- converted to vertical trace gas con- ence flight (28−29 October). The rus were likely (typically southwest centration profiles from 1km above FCDP was flown to provide basic of Hawaii or in the extreme tropical to 5km below flight altitude using information about the concentration eastern Pacific), and regions with radiative transfer calculations and and size of TTL cirrus ice crystals. convective transport into the upper optimal estimation techniques. The The NOAA water vapour instru- TTL. Flights RF02 and RF04 pro- combination of the mini-DOAS BrO ment was not included until the vided surveys of TTL composition (and IO) measurements, along with 2013 flights. The ATTREX instru- versus latitude. GWAS measurements of major hal- ments that were flown performed ogenated hydrocarbons will provide remarkably well, particularly given Figure 8 shows an example of the constraints on the TTL and lower that several of them were on the GH TTL sampling strategy used on stratospheric Bry and Iy budgets. for the first time. these flights. An even greater emphasis was placed on vertical profil- 2011 and 2013 Flights The 2011 ATTREX measurements ing through the TTL than in the 2011 provided unique information about flights. The number of TTL profiles The first ATTREX Global Hawk TTL cirrus microphysical proper- per flight ranged from 16 to 24. As flights from the Dryden Flight Re- ties and ice supersaturation (Jensen a result of a required reduction of search Center (DFRC) were made et al., 2013). Two classes of TTL the payload power draw when the

SPARC newsletter n° 41 - July 2013 19 Figure 8: Example of TTL sampling strategy used for the ATTREX flights. Top: time series of height and temperature showing numerous vertical profiles. Bottom left: flight path. Bottom right; Vertical profiles of temperature and water vapour from an ascent just south of the equator. Blue circles on all plots indicate the times/locations of GWAS samples.

engine power is reduced during de- and tropical Kelvin waves. Figure poleward motion resulted in sink- scents, the GWAS instrument only 9 depicts the SSW and QBO ef- ing in the polar region that rapidly took samples on ascents. The engi- fects using Modern-Era Retrospec- warmed the stratosphere north of neering for the Hawkeye wing mount tive analysis for Research and Ap- about 45°N (hence the expression was still not complete in time for the plications (MERRA) analysis data “stratospheric sudden warming”). 2013 flights, and the FCDP was again from 20 December 2012 through 20 The poleward motion (B in Fig- flown as a substitute. January 2013 (before and after the ure 9) caused a tropical ascent (at SSW). A large planetary wave de- C) that balanced the polar descent. The tropical tropopause in January veloped in the northern hemisphere This tropical rising motion (C) led 2013 was anomalously cold (zonal and propagated vertically into the to a ~2K cooling just above the mean tropical (15°S–15°N) cold stratosphere (indicated by the green tropical tropopause. In January- point temperatures as low as about lines in Figure 9, which show the February 2013, the QBO was in 187K) and elevated (~82.5hPa). Eliassen-Palm flux vectors). The its easterly phase (westward blow- The cold, high tropical tropopause planetary-scale wave deposited ing winds), which also induced an was likely the result of multiple easterly momentum in the middle effect on temperature, causing ap- processes, including a strong strato- stratosphere, which then caused proximately 1-2K colder tempera- spheric sudden warming (SSW), the “poleward” motion in the middle tures (thick blue) at altitudes below quasi-biennial oscillation (QBO), stratosphere (B in Figure 9). The the QBO wind minimum (thick or-

20 SPARC newsletter n° 41 - July 2013 ange). It is important to note that the tropopause temperature in the ATTREX sampling region (Figure 7) was affected by a number of factors, including the QBO, the SSW, Kelvin waves, and other intraseasonal variations.

Dry air in the tropopause region associated with the anomalously cold January 2013 tropical tropopause was sampled on multiple ATTREX flights, with water vapour concentrations as low as about 1.5ppmv indicated by both the NOAA and DLH hygrometers. As in past high-altitude aircraft tropical campaigns, in situ TTL cirrus Figure 9: The blue/red colour scale and magenta contours show the zonal mean temperature were generally encountered when change between 20 December 2012 and 20 January 2013. The black streamlines show the the aircraft was directed into cold time-averaged residual circulation (20 Dec. 2012 to 20 Jan. 2013). The green lines show tropical tropopause regions. The the average Eliassen- Palm flux vectors, and the thick grey line shows the average tropo- last flight in 2013 (RF06) provided pause (20 Dec. 2012 to 20 Jan. 2013). The thick orange line shows the 21-31 January 2013 extensive TTL cirrus sampling in 5m/s zonal wind contour, and the thick blue line shows the 21-31 January 2013 2K zonal an eastern Pacific tropopause cold temperature contour after subtracting the 1979-2012 climatology. See text for discussion. pool with minimum temperatures below 185K. Figure 10 shows temperature, water vapour, relative in situ TTL cirrus formation (Pfister enough such that relatively large humidity, and cirrus ice concentra- et al., 2001). Flight RF05 provided water vapour concentrations were tion measurements from an ascent a case study of cirrus driven by this left behind after ice sublimation. through a cirrus layer at the tropo- flow pattern (see Figure 11). As This pool of moist, low-ozone air pause. Within the cloud layer be- the GH approached the cold tropo- was then transported around the an- tween 17.5-17.6km where the ice pause region at the western end of ticyclone into the cold tropopause concentration is several hundred the flight track, a layer between region southwest of Hawaii, result- particles per litre, the relative hu- about 16-17.5km was encountered ing in the TTL cirrus sampled by midity was near 100% (within the with low ozone (~25−40ppbv) and the GH. This transport/cloud forma- 15% combined water vapour and a cloud with relatively high ice wa- tion mechanism may be typical for temperature uncertainty), and the ter content. The NOAA total wa- TTL cirrus that occur frequently in water vapour was depleted down to ter measurement indicated up to the western Pacific. about 1.8ppmv. This case is con- ~20ppmv condensed mass, which is sistent with the cloud and water va- considerably higher than the back- The ATTREX measurements pro- pour measurements from the 2011 ground water vapour concentration. vide additional evidence for the flight series. No convection in the immediate preponderance of small-scale, vicinity of the flight track was pre- wave-driven temperature fluc- Two flights (RF03 and RF05) ex- sent with cloud tops above about tuations in the tropopause region. tended as far into the western Pacific 15km. However, the low ozone and Typical small-scale (a few km) cold pool as possible given the GH considerable condensed mass sug- variations along the flight track range. These flights nearly reached gest recent convective detrainment were about 1K peak-to-peak. As the international dateline (180°E). near the tropopause. We hypoth- expected for a red spectrum, vari- Previous measurements have esize that convective transport of ations were larger at larger scales. shown that flow around the western moist, low ozone air to the tropo- Over a few 100km, wavelike varia- Pacific anticyclone that brings air pause must have occurred upstream tions were as large as 4-5K. Though south into the cold tropical region of the observed cloud in a location these scales are greater than the grid in the vicinity of Hawaii can drive where the tropopause was warm size of large-scale models, many of

SPARC newsletter n° 41 - July 2013 21 gion to sample for understanding TTL processes. The lowest temperatures and largest radiative heating rates occur in the western Pacific, and this region is where models predict that parcels frequently experience their final dehydration before entering the stratosphere (Schoeberl and Dessler, 2011). The next ATTREX flights will be based from Guam (13.5°N, 144.8°E), with flights in January-February for winter season data collection and then additional flights in early summer (May-June). Figure 13 shows an example of possible GH flight plans from Guam. The transit from DFRC (orange dotted line in Figure 13) will provide an opportunity to fly a long, constant-latitude transect for analysis of tropical waves with scales intermediate between those that can be measured with shorter- range conventional aircraft and those that can be measured with satellite instruments. The western Pa- Figure 10: Vertical profile of temperature (black), water vapour (green), relative humidity cific cold pool is essentially directly with respect to ice (blue) and FCDP ice concentration (red dots). The data shown here are overhead at Guam, therefore the preliminary and may well change with further analysis. Within the high ice concentration full 24-hour GH flight time will be layer at about 17.5-17.6km, both the DLH and NOAA water instruments indicate relative sampling the region of interest for humidities of about 100%, as expected. Above and below this layer, substantial ice super- ATTREX (in contrast to the flights saturation is present. The two preliminary water vapour measurements differ by no more from DFRC that required a 6-8 hour than a few tenths of a ppmv. transit to reach the tropics). La- grangian flights along streamlines through the western Pacific cold these fluctuations were not captured tracer measurements will be useful pool will be used to investigate the by the meteorological analyses. AT- for evaluating pathways and time full lifecycle of TTL cirrus forma- TREX provided the opportunity to scales for transport into and through tion and its impact on the vertical make multiple samples of the same the TTL. Figure 12 shows a sam- profile of water vapour. location. In one case, these samples pling of preliminary GWAS meas- showed changes of 4-5K in just 3 urements from the 2013 flights. The fact that the ATTREX mis- hours, with changes of nearly 2K in As expected, the vertical gradient sion was awarded in 2010 with the 1 hour. These fluctuations created of tracer concentration depends on intent from the outset to have GH challenges for flight operations of a the lifetime of each species. Pre- flights from Guam in 2014 has per-

temperature sensitive aircraft; precise measurements of CO2 from the mitted the inception, planning, and vious history of sampling a given HUPCRS instrument and SF6 from approval of two additional aircraft region was not always a reliable the UCATS instrument can also be campaigns that will be coordinated guide for resampling the same re- used for quantifying TTL transport with ATTREX. The UK Co-ordinat- gion, even over short time intervals. times (e.g., Park et al., 2010). ed Airborne Studies of the Tropics The small-scale temperature fluctu- (CAST) programme will bring the ations are also critical for cloud for- Outlook FAAM BAe-146 aircraft to Guam, mation and dehydration processes. with a payload focused on measure- As discussed above, ATTREX The western Pacific is a critical re- ments of tracers and halocarbons.

22 SPARC newsletter n° 41 - July 2013 Figure 11: Top: RF05 (26-27 March 2013) flight path extending into cold air in the central-western Pacific. Bottom: ozone and total water concentrations are plotted versus distance along the flight track for the out- bound and return section of the flight path shown in magenta in the top panel. As the aircraft approached the cold tropopause region at the far western end of the track, a layer at about 16-17.5km was sampled with relatively low ozone and high ice water content, both of which suggest recent convective injection to near the tropopause.

Figure 12 (below): Vertical profiles of a few of the numerous species measured by GWAS (preliminary data). Species shown here have lifetimes ranging from 0.1-0.5 years. The dependence of concentration gradient in the TTL on lifetime is evident.

SPARC newsletter n° 41 - July 2013 23 Jensen, E. J., et al., 2013: Ice nucleation and dehydration in the tropical tropopause layer. Proc. Nat. Acad. Sci., doi:10.1073/ pnas.1217104110.

Kley, D., et al., 2000: SPARC Assessment of Upper Tropospheric and Stratospheric Water Vapour. http://www.sparc-climate. org/fileadmin/customer/6_Publica- tions/SPARC_reports_PDF/2_WAVAS_ SPARCreportNo2_Dec2000.pdf.

Park, S., et al., 2010: Vertical transport rates and concentrations of OH and Cl radicals in the Tropical Tropopause Layer

from observations of CO2 and halocarbons: Figure 13: Hypothetical tracks of 2014 ATTREX Global Hawk flights from Guam. implications for distributions of long- and short-lived chemical species. Atmos. Chem. Phys., 10, 6669-6684. The BAe-146 flights will be pri- ATTREX dataset will be used by marily used to survey the chemi- many groups for evaluating and Peter, T., et al., 2006: When dry air is too hu- cal composition of the boundary improving representations of TTL mid. Science, doi:10.1126/science.1135199. layer and lower free troposphere composition and physical processes south of Guam down to the ITCZ. in global models. Pfister, L., et al. (2001) Aircraft observa- The National Science Foundation tions of thin cirrus clouds near the tropical (NSF) Convective Transport of Ac- Acknowledgments tropopause. J. Geophys. Res., 106, 9765- tive Species in the Tropics (CON- 9786. TRAST) program will bring the We acknowledge the support of the DFRC NSF GV aircraft to Guam. The GV GH crew, pilots, mission managers, project Schoeberl, M. R., and A. E. Dessler, 2011: payload includes instruments meas- managers, and all others who contributed Dehydration of the stratosphere. Atmos. uring a number of the same tracers to the project. ATTREX is supported by Chem. Phys., 11, 8433-8446. measured by CAST and ATTREX the NASA Earth Ventures program, with instruments. The GV sampling will Dr. Ken Jucks as the NASA Headquarters Solomon, S., et al., 2010: Contributions of focus on characterizing the chemi- Program Officer. NOAA water and ozone stratospheric water vapor changes to decad- cal composition and ozone pho- instruments have additional support from the al variations in the rate of global warming. tochemical budget in the primary NASA Upper Atmosphere Research Program Science, doi:10.1126/science.1182488. deep convection detrainment alti- and the NOAA Climate Program Office. tude range (about 10km up to the Thornberry, T. D., et al., 2013: Measure- GV ceiling of about 15km). Stacked ment of low-ppm mixing ratios of water flights with the three aircraft will References vapor in the upper troposphere and lower provide measurements from the stratosphere using chemical ionization mass surface to the lower stratosphere. Fahey, D. W., R.-S. Gao, and O. Möhler, spectrometry. Atmospheric Measurement 2009: Summary of the AquaVIT Water Techniques, doi:10.5194/amtd-6-381-2013. As with all NASA science mis- Vapor Intercomparison: Static Experi- sions, the final archived data from ments. https://aquavit.icg.kfa-juelich. Weinstock, E. M. et al., 2009: Valida- ATTREX (due 21 months after de/WhitePaper/AquaVITWhitePaper_ tion of the Harvard Lyman-a in situ wa- each flight series) becomes public Final_23Oct2009_6MB.pdf. ter vapor instrument: Implications for immediately. Data from the 2011 the mechanisms that control stratospher- ATTREX flight series is publicly Forster, P. M. F., and K. P. Shine, 2002: As- ic water vapor. J. Geophys. Res., 114, available on the Earth Science Pro- sessing the climate impact of trends in strat- doi:10.1029/2009JD012427. ject Office archive (espoarchive. ospheric water vapor. Geophys. Res. Lett., nasa.gov). We are hopeful that the 29, 10-1/4.

24 SPARC newsletter n° 41 - July 2013 Combined SPARC Data Requirements/ SPIN Mid-Term Review Workshop 20-22 February 2013, ESA/ESRIN, Frascati, Italy

Susann Tegtmeier1

1GEOMAR Helmholtz Centre for Ocean Research Kiel, [email protected]

As a scientific user of observa- party mission satellite data sets by focused on various SPARC and tional data, SPARC has been go- ESA. The outcome of the workshop ESA ozone initiatives. The session ing through a process of assessing will help SPARC to synthesize the was opened by Susann Tegtmeier, and summarizing its measurement activity-level measurement require- who presented ozone evaluations needs and priorities. Information on ments developed to date into an from 18 limb-viewing satellite in- the kind and quality of observations integrated document. Such a docu- struments within the SPARC Data needed to support the individual ment will provide coordinated input Initiative. The comprehensive in- SPARC activities has been collect- to international bodies such as GCOS tercomparisons provide an estimate ed and summarized in measurement (Global Climate Observing System) of the uncertainty in the measured requirement reports. These activi- and CEOS (Committee on Earth Ob- field, which is found to be largest ty-level reports aim to ensure that servation Satellites), help to respond in the tropical lower stratosphere future observational data sets meet to requests from funding entities, and and at high latitudes. The initiative specific scientific needs. In paral- stimulate greater use and improve- on “Past Changes in the Vertical lel with this process, SPARC has ment of observational products by Distribution of Ozone” was intro- been engaged in an European Space SPARC activities. duced by Johannes Staehlin who Agency (ESA)-funded project to de- outlined the scientific challenges velop long-term climate data records The meeting was opened by the when determining long-term ozone of stratospheric temperature, water va- meeting organisers, Greg Bodeker, profile changes based on differ- pour, ozone, and aerosols, as well as Theodore Shepherd, and Michael ent observational data sets. In par- climatologies of short-lived species – Van Roozendael, outlining the ra- ticular, measurements from a net- the ESA SPARC Initiative (SPIN). tionale and goals of the workshop. work of ground-based instruments The first day of the workshop in- were presented and suggested to A combined SPARC data require- cluded sessions on ozone, water va- be a critical independent meas- ments/SPIN mid-term review pour and aerosols, while the second ure of ozone trends. Michael Van workshop was held at ESA/ESRIN, day was focused on temperature and Roozendael talked about the Ozone Frascati, Italy from 20-22 Febru- other trace gases. Each session was project of the ESA Climate Change ary 2013. During the workshop the followed by a discussion of future Initiative (CCI) programme. The activity-level measurement require- measurement needs for the particu- project aims to generate improved ments were presented and related lar species. The workshop ended series of ozone column and profile topics such as the scientific motiva- with a session on other SPARC ac- data derived from multiple satellite tions for present and future meas- tivities and a final discussion on the sensors, with a particular emphasis urements, estimated uncertainties, priorities of SPARC measurement on European and ESA Third Party and measurement network design requirements. All sessions included Mission instruments. were discussed. In combination presentations of the results of the with the presentations focused on various SPIN activities and presen- Vitali Fioletov shifted the focus the data requirements of the SPARC tations on other related activities, to total ozone variations estimated activities, results from various SPIN both within and outside SPARC. from satellite and ground-based work packages were shown. This instruments. He pointed out that provided a review of phase 1 of the Ozone long-term drifts in individual data SPIN project on the detailed analy- sets are comparable to the expected sis and maturation of ESA and third The first part of the ozone session ozone trends and that even a small

SPARC newsletter n° 41 - July 2013 25 observational bias can impact the his talk on a water vapour Essential for merging and trend studies. Ac- interpretation of ozone changes Climate Variable (ECV) review. tivities of the ESA Aerosol_CCI (see Figure 14). The two following project were presented by Chris- presentations from Erkki Kyrölä Aerosol tine Bingen. The talk included in- focused on ozone measurements formation on a new improved GO- from the stellar occultation in- During the first part of the aerosol MOS aerosol retrieval algorithm strument GOMOS. First, the GO- session, current SPARC and ESA and recent progress in data merging MOS bright limb retrieval method aerosol initiatives were introduced. activities. In the following presen- (SPIN-Work Package (WP) 17), Michaela Hegglin showed results tation given by Michaela Hegglin including a comparison of day- from the SPARC Data Initiative (standing in for Larry Thomason) and night-time ozone profiles, was aerosol comparisons including a requirements of in situ and remote presented. Second, a new merged new approach based on scaled aero- aerosol data sets from ground- SAGE II-GOMOS ozone data set sol anomalies and a discussion of based, aircraft, balloon and satellite covering the years 1984-2011 was the value of the different data sets platforms were defined based on the introduced. Jessica Neu gave the last presentation of the ozone session on satellite measurements of the Upper Troposphere and Lower Stratosphere (UTLS) region including an intercomparison of existing observations and a discussion of availability and analysis of future observations.

Water vapour

Gabriele Stiller opened the water vapour session with an overview of currently available satellite measurements and their intercomparisons carried out within the SPARC Water Vapour Assessment II (WA- VAS II). The presentation illustrated the difficulties in developing a consistent, multi-instrument, long-term data set. Water vapour comparisons within the SPARC Data Initiative were presented by Michaela Hegg- lin, including key results on the evaluation of the water vapour tape recorder, polar vortex dehydration, interannual variability, and seasonal cycles (see Figure 15). The SCIA- MACHY limb scattering water vapour product and its validation by comparisons with occultation data from SCIAMACHY, other satellite data and frost point hygrometer data was introduced by Alexei Ro- Figure 14: Tropical ozone deviations and trends based on the total ozone zonal mean data zanov (SPIN-WP13). Greg Bode- sets used in the Ozone Assessment 2010 (Figure 2-2). Shown are deseasonalized, area- ker pointed out the need for a meas- weighted total ozone deviations adjusted for solar, volcanic, and QBO effects and smoothed urement requirements analysis of by 12-month running mean (left panel), and corresponding sliding 12-year linear trends [% stratospheric water vapour during per decade] (right panel) for 10°S-10°N. Figure courtesy: Vitali Fioletov.

26 SPARC newsletter n° 41 - July 2013 scientific and programmatic goals Presentations on SPIN temperature from those measurements. In a sec- of the new SPARC activity SSiRC activities (WP18 and WP14) com- ond presentation he talked about (Stratospheric Sulfur and its Role in pleted the session. Ted Shepherd short-lived species observed by Climate). applied the SSU weighting func- Odin and the methods applied to tions to temperature climatologies correct for their LST dependence The aerosol session was continued from ESA instruments to identify (SPIN-WP16). Nathaniel Livesey with two SPIN-WP12 contribu- data sets suitable for extending the presented an overview of two pro- tions. Alexei Rozanov presented historical SSU temperature record jects producing long-term records the maturation of the SCIAMA- beyond 2006. Greg Bodeker pre- based on observations from multi- CHY aerosol product, achieved us- sented a temperature ECV review ple satellite instruments. While the ing an optimized phase function, including a quantitative assessment Global Ozone Chemistry and Re- and it’s validation with co-located of measurement requirements based lated Datasets (GOZCARDS) pro- SAGE II measurements. The devel- on how uncertainty in monthly ject focuses on stratospheric spe- opment of the new OSIRIS aerosol mean temperatures is determined cies relevant to ozone decline and product (Version 6.00) based on the by the sampling frequency and ran- recovery, the Mesosphere and Up- incorporation of new particle size dom errors. per Stratosphere Temperature and information was the focus of the Related Data (MUSTARD) project talk given by Landon Rieger. Other trace gases aims to produce a unified temperature record. Temperature Presentations on other trace gases started with a contribution from the Other SPARC activities Bill Randel talked about data re- SPARC Data Initiative (see online quirements of the SPARC tempera- supplementary material for a com- Measurement requirements for oth- ture trends activity. He pointed out plete table of species this initative er SPARC activities were discussed that substantial uncertainties exist covers). Susann Tegtmeier gave in the next session, starting with a when combining different data sets an overview of the comparisons presentation from Ted Shepherd from the NOAA operational satellite of the various nitrogen species and on the SPARC Chemistry-Climate instruments, especially for the mid- explained the difficulties arising Modelling Initiative (CCMI). He and upper stratosphere. An overview when comparing short-lived gases talked about planned and existing of temperature measurements in measured at different local solar efforts to improve the comparabil- the UTLS by the radio occultation times (LSTs). Jo Urban reported ity between models and observa- (RO) technique from the CHAMP, on trace gas measurements from tions. An extension of the CCM GRACE, and TerraSAR-X missions the Odin satellite and the data re- Validation Diagnostic (CCMVal- was given by Torsten Schmidt. cords and climatologies derived Diag) tool, an open source pack-

Figure 15: Summary of the water vapor annual zonal mean state for 2001-2008 based on the annual zonal mean cross-sections of the multi- instrument mean (MIM) (left panel), and relative standard deviations with respect to the MIM (right panel). Black contour lines in the right panel repeat the MIM distribution. Instruments included in the MIM are SAGE II, SAGE III, HALOE, POAM III, ACE-FTS, Aura-MLS, MIPAS, SAGE III, SMR, and SCIAMACHY. Figure courtesy: Michaela Hegglin.

SPARC newsletter n° 41 - July 2013 27 age that facilitates the evaluation NOx measurements in the polar factors for short-lived species, the of global models, was introduced winter. An overview of the Equato- value of UTLS constraints on sur- by Irene Cionni. Updates of the rial Atmosphere Radar (EAR) Data face source inversion, the need for CCMVal-Diag package are planned Facilities at Kototabang, Indonesia, high-resolution measurements in to include new analysis of the rep- was given by Eddy Hermawan, the UTLS, and the impact of sam- resentation of tropospheric chemi- who pointed out the potential use pling biases and vertical resolution cal processes, chemistry-aerosol in- of the EAR for SPARC activities were identified. teractions and the impact of climate with a focus on the UTLS. The fi- change. Data requirements of the nal presentation by Peter Preusse The importance of ground-based SPARC Dynamical Variability ac- identified data requirements of and balloon sampling networks and tivity (DynVar) focus on measures the SPARC gravity wave activ- their need for further support was of variability at all scales, their con- ity such as super-pressure balloon highlighted. During the following nection to tropospheric sources and campaigns, new radars, and world- discussion the significance of an derived diagnostics of the Brewer- wide, high-resolution radiosondes. optimally designed ozone network, Dobson circulation as explained by the need for balloon measurements Elisa Manzini. Final discussion of stratospheric aerosol, and the value of the combined balloon- A combined presentation on data It was noted that the “golden age” hygrometer data set produced in requirements for stratospheric of measurements will continue to WAVAS II were identified. Further chemistry Data Assimilation (DA), be a key reference period for model data needs include, amongst others, and the SPARC DA working group, and reanalysis validation and that a estimates of the Brewer Dobson cir- was given by Quentin Errera. He clear statement of the value of ex- culation, additional SSU retrievals, pointed out the importance of con- isting data is needed. One important gravity wave parameters, strato-

tinuous trace gas profile and wind need mentioned in various presen- spheric winds, and NOx measure- observations and the visibility tations and discussions is for future ments in the mesosphere and lower limits impeding gravity wave ob- follow-on satellite missions target- thermosphere. The general part servations. Bernd Funke presenting global and vertically resolved of the discussion concluded that a ed open science questions in the trace gas and temperature obser- systematic characterization of all SOLARIS+HEPPA (SOLAR Influ- vations. Additionally, opportunity sources of error for single measure- ences for SPARC + High Energy missions of short duration and herit- ments is needed. Furthermore the Particle Precipitation in the Atmos- age instrumentation have been sug- need for measurements and models phere) activity and resulting data gested as low-cost gap-fillers. Dur- to “meet in the middle” and for an requirements including, amongst ing the discussion of satellite trace expansion of Obs4MIP efforts were others, continuous long-term moni- gas observations, the importance identified. toring of UV radiances and future of the accuracy of diurnal scaling

SPARC Office Imprint

Director: Contact Editing J. Staehelin SPARC Office D. Pendlebury, F. Tummon Project Scientists: c/o ETH Zurich D. Pendlebury Institute for Atmospheric and Design/layout F. Tummon Climate Science (IAC) C. Arndt Communication Manager: Universitaetsstrasse 16 C. Arndt CH-8092 Zurich Print & distribution Office Manager: Switzerland ETH Zurich A. Witten [email protected] ISSN 1245-4680

28 SPARC newsletter n° 41 - July 2013 WCRP Special Workshop on Climatic Effects of Ozone Depletion in the Southern Hemisphere: Assessing the evidence and identifying gaps in the current knowledge 25 February - 1 March, 2013, Buenos Aires, Argentina

Pablo O. Canziani1, Alan O´Neill2, Robyn Schofield3, Marilyn Raphael4, Gareth Marshall5, Gianluca Re- daelli6, and Daniel Mitchell7

1Pontificia Universidad Católica Argentina and CONICET, Argentina, [email protected], 2National Centre for Earth Observations, UK, 3School of Earth Sciences, The University of Melbourne, Australia, 4Department of Geography, UCLA, USA, 5British Antarctic Sur- vey, UK, 6CETEMPS/Department of Physical and Chemical Sciences, University of L’Aquila, Italy, 7Clarendon Laboratory, University of Oxford, UK

A WCRP Special Workshop on the 1. There is new and stronger evi- Workshop aims ‘Climatic Effects of Ozone Deple- dence for radiative and dynami- tion in the Southern Hemisphere: cal links between stratospheric There was overall consensus in the Assessing the evidence and iden- change and specific surface cli- stratospheric and climate commu- tifying gaps in the current knowl- mate changes. nities that the current state of our edge’, was convened at the Pontifi- 2. Changes in stratospheric ozone, understanding of Southern Hemi- cia Universidad Católica Argentina, water vapour and aerosols all sphere ozone had to be thoroughly Buenos Aires, Argentina, from 25 radiatively affect surface tem- evaluated and discussed in order February to 1 March, 2013. perature. to consolidate our views on the is- 3. Observations and model simu- sues at hand. This was necessary to The workshop aims were to discuss lations show that the Antarctic identify future research needs, both our current understanding of South- ozone hole caused much of the in light of the expected ozone layer ern Hemisphere ozone depletion, in observed southward shift of recovery over the coming decades particular high latitude ozone deple- the Southern Hemisphere mid- and ongoing climate changes be- tion, its impacts on hemispheric cli- latitude tropospheric jet during ing driven by sustained increases in mate and relative role with respect summer since 1980. GHGs and other environmental pro- to greenhouse gas (GHG) induced 4. This southward shift has been cesses, such as deforestation, deser- climate changes. Discussions were linked to a range of observed tification and land-use changes that initiated from results published in climate trends in the Southern impact climate. Furthermore, differ- the 2010 UNEP/WMO Scientific Hemisphere mid- and high lati- ent WCRP core projects also agreed Assessment of Ozone Depletion tudes during summer. that given the scope of issues, the and research published since. The 5. The influence of stratospheric discussion had to be interdiscipli- workshop was supported by WCRP, changes on climate will contin- nary, bringing together the SPARC, the Agencia Nacional de Promoción ue even after ozone is no longer CLIVAR and CliC communities. Científica y Técnica (Argentina), the affected by emissions of ozone National Science Foundation (USA), depleting substances. The driving questions of the work- NASA (USA) and the Pontificia 6. Future recovery of the Antarc- shop were: Universidad Católica Argentina. tic ozone hole and increases in GHGs are expected to have op- 1. How well do we understand the The main conclusions from the last posing effects on the Southern mechanisms relating Antarc- Ozone Assessment, relevant to the Hemisphere mid-latitude jet. tic ozone loss to tropospheric workshop topics, can be summa- climate in the Southern Hemi- rized as follows: sphere?

SPARC newsletter n° 41 - July 2013 29 2. How will GHG increases and sia, United Kingdom, Japan and Ar- State of Knowledge ozone depletion/recovery inter- gentina attended the workshop. The act in future, and what will their keynote speakers were: Ozone observations and modelling: impacts be on the polar vortex • Severe ozone depletion has oc- and on tropospheric climate? Session I: Sophie Godin, Darryn curred in the Antarctic spring 3. What don’t we know, and what Waugh, Steve Rintoul (rapporteur: stratosphere caused by anthro- observing or research programs Peter Braesicke) pogenic ozone depleting sub- need to be undertaken? Session II: Edwin Gerber, Ryan Fogt stances (ODSs) – the Antarctic (rapporteur: Ulrike Langematz) ozone hole. In order to foster an environment Session III: Marilyn Raphael, Ga- • The Montreal Protocol has for the much required exchange of reth Marshall, Wenju Cai (rappor- been successful in reducing ideas and interdisciplinary interac- teur: Darryn Waugh) the amount of ODSs in the at- tion, the scientific organizing com- Session IV: Michael Sigmond, Nathan mosphere, but the return to mittee (Gareth Marshall, Thando Gillett (rapporteur: James Renwick) pre-1980 levels will take dec- Ndarana, Paul Newman, Manuel ades. The Antarctic ozone hole Pulido, Marilyn Raphael, Gianluca Research presentations were facili- should return to 1980 levels in Redaelli, James Renwick, Robyn tated through poster sessions, held the 2050-2070 period. Schofield, David Thompson, Anne in an adjoining room, where coffee • By 2100, models predict an Thompson, Darryn Waugh, Shigeo breaks and food were served for ozone “super-recovery” in the Yoden, with Alan O´Neill and Pa- extended viewing. Over 30 posters SH mid-latitudes as a result of blo Canziani co-chairs) determined were presented and displayed for an increase in the strength of the that the workshop dynamics should the duration of the workshop. PDF Brewer-Dobson Circulation, return to the historical roots of sci- versions of the posters presented and a decrease in ozone loss entific meetings, following the con- are available at: http://www.uca. rates in the upper stratosphere cept of the famed early 20th Century edu.ar/index.php/site/index/es/ due to stratospheric cooling. Solvay Conferences. A strong em- uca/investigacion-viejo/pepacg/ Both of these effects are driven phasis was thus placed on rigorous wcrp-special-workshop/poster/ by increasing levels of GHGs. discussion after each invited keynote presentation. The oral sessions were Furthermore, a special session, SH climate organized around specific topics: chaired by early career scientists • There have been large changes and PhD students, was held before in the SH summer climate over I Stratospheric ozone variability the concluding session. During this the last thirty years, from the and impact on climate session they presented and dis- surface all the way through to II Processes I: tropospheric climate cussed early career perspectives on the stratosphere, and from polar and weather events the topics discussed, as well as the regions to the subtropics. III Processes II: cryosphere, ocean future of the field. These perspec- • Many of the recent SH climate circulation and carbon uptake tives are also reported below. changes have been attributed IV Modelling and predictions to the ozone hole causing an During the final session the rap- increasingly positive trend in For each topic, two or three keynote porteurs presented summaries of the Southern Annular Mode speakers were invited to deliver a each session. The final conclusions (SAM), or a poleward shift in review talk, followed by an extend- of the workshop were also actively the jet during austral summer ed period of discussion and debate. discussed during this final plenary and autumn. In practice, the exchange of views session, providing further interest- • Other important changes in cli- tended to start within the keynote ing insights by allowing all differ- mate, which appear to be ozone speaker presentations, leading to ent aspects to be viewed together. driven, have been noted, in par- excellent results. The session chairs ticular (1) a winter reversal of did a wonderful job of conducting Main Workshop Conclusions the jet in the stratosphere has the debates, while session rappor- been delayed from late spring teurs took note of all proceedings. Session I: Stratospheric ozone vari- to summer, (2) through impacts Over 50 participants from Aus- ability and impact on climate on the SAM, the jet changes tralia, New Zealand, South Africa, have affected Antarctic surface USA, France, Germany, Italy, Rus- temperatures, with a warming

30 SPARC newsletter n° 41 - July 2013 over the Antarctic Peninsula ture trends are consistent from ucts? How should we tackle and a cooling in East Antarc- 1960-2007). The position of variability and trend studies tica, especially in austral sum- the tropospheric jet is a signifi- with reanalysis? mer, (3) in conjunction with cant driver of oceanic changes GHG increases, the jet changes in response to the ozone losses Session II: Processes I: tropos- have likely induced changes to of the past decades, through pheric climate and weather events the pattern of regional mid-lat- the ocean’s thermal response to itude drying and mid- to high- the position of the atmospheric State of Knowledge latitude moistening observed in jet, and the ocean’s dynamical the Southern Hemisphere, and response to changes in tropo- • West Antarctic temperatures (4) changes in the Hadley and spheric temperature. have risen, and these tem- Ferrel cells´ circulation patterns • How these two ocean response peratures are sensitive to the have been observed. processes are represented with- strength and position of the • Models (ranging from idealized in models explains, to a large Amundsen-Bellingshausen atmospheric models to climate extent, the spread among cur- Seas Low (ABSL). A minority models with interactive chemis- rent climate models. of climate models suggest that try) indicate that the ozone hole • There are different potential ozone depletion has contributed is the primary cause of the ob- mechanisms driving these pro- to the deepening of the ABSL. served changes, which lie out- cesses, but these are not yet • Although the SAM is a hemi- side the range of natural vari- understood. A key necessity for spheric-scale mode of variabil- ability of the SH extra-tropical reducing uncertainty is to im- ity, its impact varies significant- summer climate. prove our understanding of the ly at the regional level. • The cause of the recent positive tropospheric variability within • Predominant spatial patterns trend in the SAM during austral models for a given stratospheric in the relationship between the autumn is not currently under- ozone perturbation. SAM and elements of the SH stood and may simply be the surface climate exist, but can result of natural climate vari- Future Research Questions reverse sign on decadal time ability. scales. Such sign changes ap- • Ozone loss and GHG increases • Can we prioritize observations? pear to be due to internal cli- have both driven the recent pos- At what sampling rates do we mate variability, which in par- itive trend in the SAM during need the different observations: ticular could be related to the austral summer. Ozone recov- sub-daily, daily, weekly, month- phase and amplitude of plan- ery over the next decades will ly? Do we need more ocean etary wave-3 over the Southern impose a negative forcing on measurements? Ocean. the SAM, thus dampening the • Are there coherent changes in • This has implications for identi- positive influence of a continu- all quantities in the Earth sys- fying a robust methodology using rise in GHG concentrations. tem? ing the Antarctic ice core record Therefore, while increasing • Is ozone behaving like we think to generate a proxy of the SAM, GHGs are expected to cause an it is supposed to? What is the ef- and on the level of certainty overall warming of the Southern fective equivalent stratospheric with which we can ascribe fu- Hemisphere, SAM-related past chlorine doing? Are chlorine ture projections of Antarctic cli- trends in summer climate will and bromine declining as we mate and related predictions of likely weaken, and maybe even think they should do? sea level rise. reverse, contingent on the extent • What will the relative roles of • In future, there are likely to be of changes in GHG forcing. ozone and GHGs be in future? opposite SAM trends in austral • Linearity of the response to summer (negative) compared Impacts on the SH Ocean GHG and ODS changes: how to other seasons (positive). This • The wind stress curl is chang- linear/non-linear and uncorrelat- may lead to increased summer ing, with the zero line shifting ed/synergistic is the atmospheric melting for regions with a pre- poleward, which induces an in- response to their changes? dominant negative SAM tem- tensification of the super gyre. • How do we define the Hadley perature relationship (East Ant- • Observations support this in- Cell? arctica), while over the Antarctic tensification (ocean tempera- • Can we trust reanalysis prod- Peninsula there is likely to be

SPARC newsletter n° 41 - July 2013 31 greater winter accumulation. driven a hemispheric total sea when compared to reanalysis ice extent decrease. data. The bias in jet latitude ap- Future Research Questions • Observed changes in the South- pears to be positively correlated ern Ocean have been linked to with the size of the simulated • What is the natural variability changes in near surface winds. jet shift in response to ozone of SAM? What are the causes These changes include the sub- and GHG depletion. The future of the SAM trends in austral au- tropical super gyre, the meridi- evolution of jet trends remains tumn? onal overturning circulation, unclear, and depends on the • What causes the variability/ and the ocean becoming a less relative role of ozone vs GHG

deepening trend of the ABSL? effective sink of CO2. forcing. Is there a possible contribution • Links to SAM: the mixed lay- • A well-resolved stratosphere of asymmetric modes of vari- er depth response to the SAM and a high upper boundary are ability? shows zonal asymmetry. required to simulate a proper • How do zonal mean ozone tropospheric response. The re- asymmetries affect climate? Future Research Questions sponse to prescribed ozone de- • There is a need for further stud- pletion is significantly larger in ies investigating the regional • What is the cause of the dis- models with high vertical reso- variability and trends to better crepancy in sea-ice trends be- lution in the lower stratosphere assess the climate response to tween observations and models compared to models with low- ozone forcing. over the 20th century? Are dif- top and low vertical resolution ferences due to model deficien- in the stratosphere. This may Session III: Processes II: cies or unknown processes af- be related to a lack of momen- cryosphere, ocean circulation, and fecting sea ice variability? tum conservation at the top of carbon uptake • What is the intrinsic model the model, leading to an unre- variability of ice and ice core alistic dynamical response in State of Knowledge properties? What are the impli- the stratosphere. Many CMIP5 cations when this variability is models probably have high • On average, observed sea-ice simulated? enough stratospheric resolution extent around Antarctica has • How will the ocean circulation to resolve this response. been increasing. This increase and carbon uptake evolve as • Zonal mean ozone is usually has not been uniform - there are ozone recovers? prescribed in models, but ozone large regions of significant in- • Where is the heat derived to exhibits zonal asymmetry in crease and significant decrease. support ocean heat content spring when the ozone hole is The causes of the changes in sea changes associated with ocean often centred off the pole. The ice extent are not fully under- circulation changes induced by use of zonal mean ozone dis- stood, however, they appear to wind stress? tributions underestimates the be mediated by changes in sur- • How will the ocean circulation climatic response, leading to a face wind speed and direction, and wind changes affect carbon weaker and warmer vortex in as well as ocean currents. The uptake? austral spring, an overall re- changes in winds may be asso- duction in the stratospheric re- ciated with the strength of the Session IV: Modelling and sponse, and an underestimation ABSL, as well as the strength predictions of the SAM changes. At present, and polarity of the SAM. most CMIP5 models likely un- • Although observations of sea- State of Knowledge derestimate the tropospheric ice indicate that Antarctic sea impacts of ozone changes. ice extent has been increasing, • Models show that the rela- • The stratospheric temperature all available model studies of tive role of ozone and GHGs response varies by a factor of 20th century climate simulate a in forcing past climate trends, two or more over the pole for a decrease. This includes models particularly of the SAM, varies given ozone forcing, adding to that explicitly simulate strato- seasonally, while being compa- the spread of model responses spheric ozone depletion, which rable in the annual mean. in the troposphere. also indicate that stratospheric • A bias remains in the simulation • Climate models consistently ozone depletion should have of the mid-latitude jet position fail to reproduce Antarctic

32 SPARC newsletter n° 41 - July 2013 sea-ice trends. This is prob- for future GCM experiments Particular care should be taken re- ably caused by the insufficient without coupled chemistry to garding the timescales on which representation of processes re- account for the effects of the these observations are made, for lated to sea-ice formation and zonal asymmetry of ozone? instance, surface wind observations ocean-atmosphere interactions. • What are the heat sources caus- over the ocean do not capture many Furthermore, the contribution ing the surface warming pattern high frequency variations - ideally of Antarctic ozone depletion and do models capture them? these observations need to be made to the recent Antarctic sea ice • Models disagree with sea-ice on sub-daily timescales. They also trends is unclear, even if sever- observations. Why has total noted that more reanalysis data sets al recent model studies regard- Antarctic sea-ice extent in- could be output at higher frequency, ing ocean-atmosphere coupling creased and why don’t current and more intercomparison of such seem to indicate that this may models capture this? What reanalyses could be implemented not be the case. should we do to solve this ma- so that issues such as trends in rea- jor issue? For example, does nalyses can be better constrained. Future Research Questions freshwater input play a major role? How important is strato- There was a general consensus that • How important is the representa- spheric resolution and ocean- a reduction in the observational tion of natural variability in mod- atmosphere coupling for sea-ice uncertainty associated with ozone els? How do we improve tropo- modelling? measurements is needed, and that spheric variability in models? • How important is stratospheric this would lead to a better and more • What are the mechanisms for resolution for sea-ice modelling? consistent implementation of ozone stratosphere-troposphere cou- • The coupling between the fields in model comparison pro- pling? Which mechanisms need important Earth systems (at- jects. Specifically, the use of a zon- to be included in models? mosphere, ocean, land and ally symmetric stratospheric ozone • What is the cause of the bias in cryosphere) remains a major data set may not be sufficient for the mid-latitude jet latitude? modelling challenge. detection and attribution of surface • How important is simulated climate change and variability. natural variability and what is Early Career Scientists and PhD its contribution compared to Students Special Session Physical Understanding ozone and GHG forcing? Do we need to better differentiate The young scientists attending the It was recognized that there was long-term trends from seasonal workshop met to discuss what, in a need to revisit the fundamental to interannual variability when their view, were the most relevant dynamics of some models (i.e. the analysing model outputs? topics driving research develop- dynamical cores) instead of con- • How well do the models repre- ment. Their foremost concern was tinuously adding and expanding on sent the change in the Hadley how they, as early career scientists, current models. This may allow for Cell? Why, while reanalyses could progress their careers while less ‘tuning’, and a better under- suggest the trend in the Hadley continuing interesting and relevant standing of currently parameterized Cell extension is larger in aus- science. Major concerns in this area processes. tral summer than in austral au- were model and instrument devel- tumn, do models fail to repro- opment, and the lack of high-impact As a community, the early career duce this seasonality? publications that come with this scientists felt that to further re- • Do current GCMs underesti- area of research. The broad issues search on ozone-related topics, a mate the tropospheric response raised by the early career scientists zonally asymmetric view must be to ozone due to a lack of ver- were as follows: adopted, both in terms of the evo- tical resolution or momentum lution of stratospheric ozone and conservation? Do they overesti- Observations the corresponding surface response. mate the tropospheric response This may involve employing new to ozone due to the jet bias? They recognized the need for a ro- (or less frequently used) diagnos- • How important a shortcoming bust global observational network, tics other than the SAM. They also is the use of zonal mean ozone which has research-relevant meas- noted that the use of the SAM can for the interpretation of CMIP5 urements (not only ozone, but also be misleading, both in terms of its results? What is the best design precipitation and other variables). trend and variability. The need to

SPARC newsletter n° 41 - July 2013 33 focus on the seasonal response is Concluding Remarks related atmospheric processes on of particular importance, especially ocean circulation and, in particular, over the March-May period. This workshop provided a space for carbon uptake. solid scientific discussion and ex- Finally, the issue of coupling in change of ideas. It permitted a thor- Given the climate system’s intrinsic models was raised. They noted that ough analysis of our current under- variability, the workshop empha- testing coupling mechanisms at all standing of the coupling between sized that using models to establish scales, from the large-scale, such as ozone depletion and SH surface cli- causal links between stratospheric between the stratosphere and tropo- mate. The discussions resulted in a ozone changes and tropospheric cli- sphere, down to the small-scale, is large number of issues that need to mate changes (e.g. trends) must be important. They concluded by not- be addressed, both from the analy- based on the use of ensemble simu- ing that the co-variability between sis of observations and from model- lations. Though such an approach different climate systems is key to ling, preferably in a joint approach. is now standard practice, there is understanding the tropospheric cir- The issues at hand require strong further scope for work with larger culation response to stratospheric interdisciplinary interaction to pro- numbers of ensemble members, as ozone changes. vide appropriate answers. well as multi-model ensembles, to ensure that results are indeed robust. On Communication and One issue that came up frequently Interdisciplinary Research refers to reanalyses - their quality The workshop structure, by return- and applicability to climate studies. ing to the roots of scientific debate The importance of framing relevant The community is concerned about and discussion following the con- scientific issues was raised, not just their use, given the differences ob- cept of the original Solvay Confer- to policy makers, but also to us as an served between the various ver- ences, provided an optimal envi- atmospheric community. This will sions, which can lead to widely dif- ronment for the exchange of views help focus research, as well as im- ferent results depending on the aim and debate about future research prove chances of obtaining funding. of the study. This is a particularly directions. Furthermore, the active crucial issue that needs to be dis- participation of early career scien- Of particular importance was the cussed beyond the sphere of issue- tists and PhD students - thanks to the necessity of networking, in terms oriented workshops. support received from the WCRP, of developing cross-disciplinary NSF and NASA - provided new per- research (i.e. oceanographers talk- Regarding models, there was an spectives, views, and concerns to ing with atmospheric scientists, or overall view that much work needs this debate. In addition, the poster modellers talking with observation- to be carried out to improve mod- session provided both an opportu- al scientists). This will also help els, including the coupling between nity for the presentation of current make the community aware of older sub-models that represent the vari- research and an informal atmosphere or less well-known studies, and ous Earth sub-systems involved. for sustained exchanges during cof- prevent unnecessary duplication of This is crucial to improving the re- fee, lunch breaks, and even at the such studies. They also mentioned lationship between model outputs end of the day - exchanges that made it may also help to have a central and observations so that we can an essential contribution to the aims, location with relevant links to dif- better understand the coupling and spirit and outcomes of the workshop. ferent observational or reanalysis physics involved, for example, in data sets. understanding the effect of ozone-

34 SPARC newsletter n° 41 - July 2013 Report on the WCRP Regional Workshop on Stratosphere-Troposphere Processes And their Role in Climate 1-3 April 2013, Kyoto, Japan

Shigeo Yoden1, Masato Shiotani2, Negar Banan3, Subrata Kumar Das4, Young-Ha Kim5, and Vinay Kumar6

1Kyoto University, Japan, [email protected], 2Kyoto University, Japan, 3University Kebangsaan Malaysia, Malaysia, 4Indian Institute of Tropical Meteorology, India, 5Yonsei University, Korea, 6University of Delhi, India

A three-day World Climate Re- was to enrich the exchange of in- Global observations and search Programme (WCRP) re- formation between communities modelling of the stratosphere gional workshop on stratosphere- involved in scientific research of and troposphere troposphere processes and their role stratosphere-troposphere interac- in climate was held from 1-3 April tions and related processes using The workshop was opened by Ma- 2013 at the Maskawa Hall of Kyo- observations, data analysis, mod- sato Shiotani, who provided an to University, Japan. There were elling and numerical studies, and overview of the WCRP and SPARC, 80 participants, including 24 from theoretical studies. The workshop including their current activities, abroad (Figure 16). The “regional” program consisted of three sessions and presented the main aims of the workshop successfully promoted of invited talks and two poster ses- workshop. The first session was the participation of early career sci- sions on the first two days, and then composed of five oral presentations entists and PhD students from Asian a special fourth session open to that highlighted research cover- countries, including China, India, wider research communities and the ing stratospheric and tropospheric Indonesia, Iran, Japan, Korea, Ma- public on the third day. The invited chemical and dynamical process- laysia, Pakistan, and Taiwan. Travel talks and poster sessions focused on es on a global scale. John Gille support grants from the WCRP were the principal scientific findings and used high-resolution data from the awarded to four participants who con- uncertainties in the current knowl- HIRDLS (High Resolution Dynam- tributed to this report as co-authors. edge of the indicated subjects. ics Limb Sounder) instrument to The program and other relevant information can be found on the workshop homepage: http://www-mete.kugi. kyoto-u.ac.jp/Kyoto2013/.

This WCRP/SPARC sponsored regional workshop addressed the following topics: 1. Global observations and modelling of the stratosphere and troposphere 2. Tropical and extra-tropical upper troposphere/lower stratosphere processes 3. Trends and variability in the stratosphere and troposphere 4. Special session: Climate research in service to society.

The main purpose of the workshop Figure 16: Group photo of the participants at the WCRP Regional Workshop held in Kyoto.

SPARC newsletter n° 41 - July 2013 35 examine how the Brewer-Dobson Kalman-Filter technique. He also cal upwelling is the predominant Circulation (BDC) affects the me- discussed future possible efforts to cause of the observed cycle. In ad- ridional distribution of ozone in improve the estimation by intro- dition, WACCM (Whole Atmos- the stratosphere, and controls its ducing additional constraints from phere Community Climate Model) seasonal variation through interac- other chemically-related species. simulations were used to quantify tions between the BDC overturning Kengo Sudo discussed the role of the contribution of eddy forcing. motion and isentropic mixing in the climate change and stratospheric These simulations also showed that lower and lowermost stratosphere ozone in tropospheric chemistry in-mixing processes resulting from

(330-450K). Seasonal variation of involving O3 and CH4, based on the Asian summer monsoon circu- the transport and mixing processes his simulations with the CHASER lation is also an important factor in was discussed, and a comparison coupled chemistry-climate model the upper tropospheric annual cycle, between HIRDLS and OMI (Ozone from 1970-2009 with the EDGAR- as suggested by previous model- Monitoring Instrument) ozone ob- HYDE emission data. He performed ling studies. Masatomo Fujiwara servations was also shown. Shi- several sets of sensitivity simula- presented results from SOWER geyuki Ishidoya reported on the tions to isolate impacts of emission (Soundings of Ozone and Water in gravitational separation of minor change, climate change, and strato- the Equatorial Region) campaigns, atmospheric constituents in the spheric ozone depletion on tropo- in which balloon-borne observa- stratosphere using high-precision spheric ozone evolution over the tions were made at various sites in measurements of the isotopic ratios 40-year period. He found that long- the tropical Pacific. Most recently, 15 18 of N2, O2, and Ar (δ N of N2, δ O term climate change (warming) and they matched observed air parcels 40 of O2, and δ Ar) and the concentra- short-term variability (e.g., ENSO, between the observation sites using

tion of Ar (δ(Ar/N2)) from air sam- the Arctic Oscillation, and the Pa- isentropic trajectories calculated ples collected over Japan on 4 June cific North American pattern) play with reanalysis data to measure the 2007. He suggested the possibility an important role in the trend and difference in water vapour concen- of using gravitational separation variability of tropospheric ozone. trations between the matched sites. as a new indicator of changes in His simulations also showed that This provided direct evidence of stratospheric circulation. Takatoshi both the warming trend and strato- dehydration in the tropical tropo- Sakazaki focused on the diurnal spheric ozone depletion reduce the pause layer (TTL) resulting from

variation of ozone in the strato- increasing CH4 trend. horizontal advection. In addition, sphere as observed by the SMILES a summary of the development and (Superconducting Submillimeter- Tropical and extra-tropical validation of various balloon-borne Wave Limb-Emission Sounder) in- upper troposphere/lower instruments focused on TTL pro- strument, attached to the Japanese stratosphere processes cesses was presented. Experiment Module (JEM) on- board the International Space Sta- Upper Troposphere/Lower Strato- Andrew Gettelman reviewed trop- tion. He explored the role of dynam- sphere (UTLS) processes in the ical and extra-tropical UTLS pro- ics and photochemistry in the global tropics and extra-tropics modulate cesses, including their impacts on structure and the seasonal variability climate forcing and impact not only climate and climate trends seen in of the diurnal variations of dynami- the stratosphere but also the tropo- the UTLS region (Figure 17). For cal fields (i.e., tides) and ozone fields sphere. William Randel presented example, water vapour changes by analysing datasets from satellite the annual cycle of lower strato- in the TTL affect radiative forc- observations, global reanalyses and spheric ozone and other tracers in ing in the UTLS and therefore the chemical transport models. the tropics, and quantified the mech- tropopause temperature and height. anisms controlling its variability. Also, cooling resulting from ozone Kazuyuki Miyazaki assimilated Lower stratospheric ozone varies by depletion in the stratosphere ac- multi-satellite data into the global up to a factor of two near 17.5km, celerates the stratospheric jets by chemical transport model CHASER with the variability being in phase satisfying the thermal wind rela- (CHemical AGCM (Atmospheric (out of phase) with temperature tionship. This jet acceleration then Global Circulation Model) for Stud- (carbon monoxide). He estimated alters planetary wave propagation ies of atmospheric Environment ozone tendencies in the frame of the and momentum deposition in the and Radiative forcing) for chemical transformed-Eulerian mean (TEM) lower stratosphere, which ultimate- composition in the troposphere and equation using observational data, ly strengthens the BDC. Results stratosphere based on an ensemble and showed that transport by tropi- from large-scale modelling studies

36 SPARC newsletter n° 41 - July 2013 indicate that the UTLS changes in change. This session was started by also provided a discussion on a pos- temperature and stability caused by a talk by Karen Rosenlof, detail- sible change of the vertical gradi- ozone and other greenhouse gases ing what observations can be used ent of CO2 in the mid-stratosphere. even affect tropospheric circulation to infer variations in the strength of Seok-Woo Son reported that the by shifting the subtropical jets pole- the BDC, and its subsequent impact Antarctic ozone hole has affected ward. Shigenori Otsuka presented on stratospheric water vapour and not only the long-term trend, but results from numerical simulations ozone distributions. The distribu- also the intra-seasonal variability of the formation of the tropopause tion of water vapour is impacted by of Southern Hemisphere (SH) sur- inversion layer (TIL) associated changes in meridional circulation, face climate. He showed a negative with an extra-tropical “bomb” cy- and can in turn alter the radiative correlation between the September clone. In the life-cycle simulation, budget and surface climate. A cost- ozone concentration and October a negative correlation between the effective trace gas measurement Southern Annular Mode index, strength of the TIL and relative program using AirCore to monitor and with systematic variations in vorticity at the tropopause is clear changes in strength of the BDC was precipitation and surface tempera- during the developing and mature introduced, as well as the Airborne ture throughout the SH. This talk stages of the cyclone. The three- Tropical Tropopause Experiment provided an overview of ozone re- dimensional structure of the TIL (ATTREX, see the article in this is- covery that started around the year shows an arc-shaped wave packet sue) using the Global Hawk, which 2000. of inertia-gravity waves propagat- is focused on water, aerosol and ing up- and northward from the jet clouds in the TTL. Satoshi Suga- Kaoru Sato presented the three- streak associated with the cyclone, wara reported on their high-pre- dimensional structure of the mid- implying that gravity waves may cision analysis of various gas con- dle atmosphere circulation based on play an important role in producing centrations, such as CO2, CH4, N2O, data from a high-resolution middle the negative correlation. SF6, and their isotopes, in strato- atmosphere GCM without gravity spheric air samples collected sys- wave parameterizations. A new for- Trends and variability in the tematically over Japan since 1985. mulation of the unified three-dimen- stratosphere and troposphere The estimated increasing trend in sional wave activity flux of inertia-

CO2 is 1.55±0.03ppmv/year in the gravity waves and Rossby waves Trends and variability of tempera- mid-stratosphere. He also discussed was also introduced to diagnose the ture, water vapour, and ozone in that stratospheric age-of-air can be three dimensional structure. The the stratosphere and troposphere estimated from the phase shift of in- role of sudden stratospheric warm- are important components of global terannual CO2 variations. This talk ing (SSW) events in dynamical coupling between the stratosphere and troposphere was also discussed in this session. Hitoshi Mukouga- wa examined the predictability of stratosphere-troposphere dynamical coupling using the Japan Meteoro- logical Agency (JMA) operational one-month ensemble forecast data set and a series of hindcast experiments from the JMA/MRI (Meteor- ological Research Institute) AGCM. He showed prolonged predictability of an SSW event and its relation to the persistence of a blocking event over the Atlantic. He also described downward propagation of stratospheric planetary waves and blocking formation over the North Figure 17: Schematic snapshot of dominant processes in the upper troposphere and lower Pacific during several SSW events. stratosphere region using data from a Northern Hemisphere section along 60°W on Febru- Masakazu Taguchi investigated ary 15, 2006 (Gettelman et al., 2011). the ENSO-induced changes in the

SPARC newsletter n° 41 - July 2013 37 Northern winter stratosphere using Tetsuzo Yasunari, new director of mate research and its near-future di- the JRA-25/JCDAS reanalysis and the Kyoto-based Research Institute rections. A USTREAM webcast of JMA hindcast datasets. He showed for Humanity and Nature, talked the whole special session is avail- that the frequent occurrence of dis- mainly about the “Future Earth” Pro- able at http://www.ustream.tv/ turbed vortex conditions during cold gram (Figure 18). Future Earth is a channel/wcrp-sparcwskyoto2013. ENSO years was mainly the result new 10-year international research of a couple of SSWs (e.g., those in initiative aimed at developing the Poster sessions the 1984/85 and 2005/06 winters). knowledge needed to effectively re- These SSWs occurred with moder- spond to the risks and opportunities Takuki Sano and Koji Imai report- ate upward and marked poleward of global environmental change, ed on the product improvements and propagation of wave activity under and to support transformation to- validation, respectively, of the new- easterly QBO conditions. wards global sustainability over the est version of JEM/SMILES prod- coming decades. Future Earth will ucts. These products provide global Special session: Climate research mobilise thousands of scientists measurements of trace gases in the in service to society while strengthening partnerships middle atmosphere from October with policy-makers and other stake- 2009 to April 2010. Makoto Suzu- The special session, open to the wider holders, so as to provide options ki presented JEM/SMILES obser-

research communities and the public, and solutions for sustainability in vations of O3, ClO, HO2, HOCl and was intended to provide a unique op- the wake of Rio+20. Future Earth BrO, and their photochemical diur- portunity to discuss the roles of cli- aims to integrate four international nal variations. CloudSat-CALIPSO mate research in service to society. global environmental change pro- data were used to investigate cloud grammes (GECs), including WCRP, properties over five different sum- Guy Brasseur, director of the Ger- to facilitate collaboration and trans- mer monsoon regions (Subrata Ku- man Climate Service Centre, could disciplinary research through co- mar Das), and for the study of the not attend the workshop but sent designing and co-producing scien- simultaneous occurrence of polar his video message and recorded tific programs with stakeholders to stratospheric clouds and upper trop- slide show. He opened the presenta- promote protection of global and ospheric clouds caused by blocking tion by stating that we are entering regional environments, and to help anticyclones in the SH (Masashi a new period of geological history construct a sustainable society. Kohma). Gwenael Berthet intro- dominated by human impacts on duced a new LOAC (light optical the Earth system, called the Anthro- After a break, Matthew Hitchman, aerosol counter), capable of char- pocene. He highlighted four grand Hiroshi Kanzawa, and Karen acterising particles for tropospheric challenges that have been posed to Rosenlof commented on the two and stratospheric aerosol measure- the scientific community in the last keynote lectures from the viewpoint ments, and Fabrice Jegou reported century: (1) numerical weather pre- of a university professor in the US, on Arctic stratospheric aerosol ob- diction, (2) understanding the role Japan, and as a researcher of a gov- servations made using the LOAC of chemical species, (3) projecting ernmental research institute, respec- and other instruments during the climate change, (4) understanding tively. Tetsuzo Yasunari joined 2009 summer in the framework of the Earth as a complex non-linear these panellists for discussion on the International Polar Year. Sev- interactive system, and a new grand multi-disciplinary aspects of cli- eral presentations related to obser- challenge (5) responding to global change, i.e. planetary stewardship. He concluded that planetary stewardship requires new interdisciplinary approaches, two-way communication between scientists and Figure 18: Schematic of stakeholders, and that science will the conceptual framework play a fundamental role in address- for Future Earth. Available ing these issues. Also, that tradi- at http://www.icsu.org/ tional climate and environmental future-earth/whats-new/ research must be complemented by relevant_publications/ a well-designed approach to adapta- future-earth-research- tion to planetary changes. framework

38 SPARC newsletter n° 41 - July 2013 vational studies on ozone and other the vertical and zonal propagation ated with equatorial waves over the trace gases in Asia were also made: of stratospheric planetary waves on tropical Indian Ocean in November multi-year ozonesonde observa- tropospheric blocking after SSW 2011 during the CINDY2011/DY- tions in Hanoi (Shin-Ya Ogino); events (Kunihiko Kodera); and NAMO campaign (Junko Suzuki). Car-MAX-DOAS observations dynamical-core model experiments Further posters using model simula- along a national highway in Pakistan looking at the role of tropospheric tions were focused on: the roles of (Fahim Khokhar); and diurnal and synoptic eddies in stratosphere- parameterized convective gravity seasonal variations of surface ozone troposphere coupling during SSW waves in tropical stratospheric vari- over nine years in three cities in Ma- events (Daniela Domeisen). Ryo ability (QBO and SAO) in a climate laysia (Negar Banan). Mizuta reported on the projected model (Young-Ha Kim), and the change in extra-tropical cyclones climatology, seasonality, and intra- Several numerical modelling stud- in CMIP5 models associated with seasonal to interannual variability ies focused on chemical processes: changes in the UTLS region. Chika- of the TTL temperature in CMIP5 a meso-scale air quality study of ra Tsuchiya investigated the clima- models (Joowan Kim). Ryosuke climate change scenarios in Tai- tology and trend of fronts as a grav- Shibuya presented a poster about wan (Jiun-Horng Tsai); a global ity wave source in reanalysis data. the latitudinal dependence of iner- chemistry-transport model simu- tial oscillation in the atmospheric lation of greenhouse gases and Several posters were presented in boundary layer revealed by large ozone depleting substances from relation to tropics-extra-tropical eddy simulations. 1980-present (Prabir Patra); an interactions, with emphasis on the idealized model study of the role role of the stratosphere: ENSO in- Acknowledgments of well-mixed greenhouse gases fluence of tropical convection on the in stratospheric cooling (Shinji SH high latitudes during the win- The workshop conveners (Masato Shiotani Goto); and comprehensive chem- ter to spring transition (Matthew and Shigeo Yoden) would like to thank the istry-climate model simulations of Hitchman); downward coupling generous sponsors of the meeting: WCRP, the SH stationary wave response processes through the TTL during SPARC, Kyoto University Global COE and seasonal dependence of future an SSW event (Nawo Eguchi); and Program on Sustainability/Survivability stratospheric temperature trends on intraseasonal to seasonal variability Science for a Resilient Society Adaptable to ozone and greenhouse gas changes of tropical upwelling in the BDC in- Extreme Weather Conditions (KU GCOE- (Lei Wang). Using reanalysis data fluenced by high-latitude planetary ARS), Kyoto University Inter-Graduate sets, Tetsu Nakamura analysed waves (Rei Ueyama). Some posters School Program for Sustainable Develop- the long-term Boreal summer trend focused on the vertical dynamical ment and Survivable Societies (KU GSS), during the ozone-depletion period, coupling in the tropics using obser- the Grants-in-Aid for Scientific Research and Masatomo Fujiwara studied vational data: influence of the QBO of the Japan Society for the the global temperature responses to on the interannual variability of Promotion of Science (JSPS), and the Japan the El Chichón and Pinatubo vol- tropopause temperature and height Aerospace Exploration Agency (JAXA). canic eruptions. using COSMIC/FORMOSAT-3 Thanks also to local logistical support from data (Vinay Kumar); distinct the Integrated Earth Science Hub staff of A small number of poster presenta- stronger warming in the TTL as- Kyoto University (Fumiko Furutani and tions focused on the dynamics of sociated with minor volcanic erup- Yoko Uemoto). We also thank invited mesospheric circulation during po- tions during the 2000s as revealed speakers and all attendees who participated tential vorticity increasing events by GPS radio occultations (San- for making it a most successful workshop. (Akihiro Masuda) and SSW events jay Kumar Mehta); variability in (Toshihiko Hirooka). Several post- the temperature structure around ers presented new research related the TTL and its relationship with Reference to stratosphere-troposphere interac- convective activity analysed with tions: winter predictability in JMA reanalysis and OLR datasets (Eriko Gettelman, A., P. Hoor, L. L. Pan, W. J. Ran- one-month ensemble predictions Nishimoto); upper tropospheric del, M. I. Hegglin, and T. Birner, 2011: The (Shunsuke Noguchi); intensifica- cloud top height over the tropical extratropical upper troposphere and lower tion of planetary wave activity in Pacific observed with geostationary stratosphere. Rev. Geophys., 49, RG3003, the troposphere prior to SSW events satellites (Noriyuki Nishi); and the doi:10.1029/2011RG000355. (Patrick Martineau); influence of occurrence of cirrus clouds associ-

SPARC newsletter n° 41 - July 2013 39 Report on the 3rd SPARC DynVar Workshop on Modelling the Dynamics and Variability of the Stratosphere-Troposphere System

Elisa Manzini1, Andrew Charlton-Perez2, Edwin Gerber3, Thomas Birner4, Amy Butler5, Steven Hardiman6, Alexey Karpechko7, François Lott8, Amanda Maycock9, Scott Osprey10, Om P. Tripathi11, Tiffany Shaw12, Michael Sigmond13

1MPI-M, Hamburg, Germany, [email protected], 2University of Reading, Reading, UK, 3Courant Institute, New York University, USA 4Colorado State University, Fort Collins, CO, USA, 5NOAA/NCEP/Climate Prediction Center, Maryland, USA, 6Met Office Hadley Center, Exeter, UK, 7Finnish Meteorological Institute, Helsinki, Finland, 8LMD/ENS, Paris, France, 9University of Cambridge, UK, 10De- partment of Physics, University of Oxford, UK, 11University of Reading, Reading, UK, 12Columbia University, New York, USA, 13CCCMA, Toronto, Canada

The third Workshop of SPARC’s that the CMIP5 archive presented to tematically. Ted also pointed out (Stratosphere-troposphere Process- assess the stratosphere and its im- that while there is strong consen- es and their Role in Climate) Dyn- pacts on the climate system, which sus among climate models on the Var activity took place in Reading DynVar decided it would focus on energetics of climate change, there from 22-24 April 2013, jointly with during its second workshop held in is less consensus on the dynami- the first SPARC SNAP Activity 2010 (Gerber et al., 2012; Manzini cal aspects of climate change, and workshop, held from 24-26 April et al., 2010, 2011; Charlton-Perez et that simulations suggest consider- 2013. Both workshops were kindly al., 2013). Discussions in Reading able multi-decadal variability in hosted by the Department of Me- demonstrated that the stratosphere- the stratosphere, whose origin still teorology, University of Reading. troposphere dynamical coupling needs to be identified. Improving We would like to acknowledge the community was highly interested in climate models by incorporating great hospitality of the University being informed and participating in realistic stratosphere-troposphere of Reading and the excellent or- the broader activities of the World coupling, might reduce uncertainty ganization by the local committee. Climate Research Programme related to atmospheric circulation Synergy between the DynVar and (WCRP), specifically in the devel- variability and change, with impli- SNAP themes provided a vibrant opment of the next phase of the cations for regional climate change. environment for the whole week. A Coupled Model Intercomparison Ted also called for a systematic as- total of ~100 participants from 16 Project Phase 6 (CMIP6). sessment of model sensitivity and countries attended both workshops. biases arising from gravity wave In his keynote presentation, Ted parameterizations, the topic of the The DynVar workshop was struc- Shepherd focused on the challeng- keynote presentation by Joan Al- tured around the DynVar Research es of understanding and modelling exander. In her presentation, Joan Topics (http://www.sparcdynvar. the mechanisms of stratosphere- emphasized the importance of the org/research-topics-groups-folder/), troposphere coupling on various indirect role that gravity waves play with invited oral and contributed timescales. On long time scales, in shaping the mean stratospheric poster presentations spread over the the causes, extent and magnitude flow, and consequently in affecting week (see report this issue) and two of a strengthened Brewer-Dobson the behaviour of planetary and syn- keynote presentations by Ted Shep- Circulation (BDC) in response to optic waves, both crucial elements herd (22 April) and Joan Alexan- climate change are current topics of stratosphere-troposphere cou- der (23 April). Results from many of investigation: Which dynamical pling. She questioned the current CMIP5 analyses were discussed in processes (wave breaking, criti- use of gravity wave parameteriza- the nine invited oral and 24 contrib- cal layer filtering, dissipation) and tions and their limitations in correct- uted poster presentations of the first which spatial and temporal scales ing model biases. Future directions two days. This outcome is a rec- are dominant? Proposed mecha- in gravity wave parameterization ognition of the unique opportunity nisms need to be examined sys- development, such as climate sen-

40 SPARC newsletter n° 41 - July 2013 sitive gravity wave sources and lat- events in high-top CMIP5 models ics: (1) QBO, (2) circulation and eral propagation, are underway and generate anomalous signals in the climate change, and (3) mecha- may provide the needed realism and polar stratosphere in the Northern nisms of stratosphere-troposphere coupling between the lower and up- Hemisphere, while low-top models coupling. This discussion time was per atmosphere, although their ben- do not show such a coherent signal. the first step toward the construc- efits still need to be demonstrated. A negative Arctic Oscillation-like tion of a new DynVar implementa- pattern in sea level pressure and tion plan. A second discussion ses- A common theme of the DynVar surface temperature is stronger in sion is planned as a side event at presentations was the need for a re- the high-top than low-top models the SPARC General Assembly, to newed appreciation of the definition (Natalie Calvo, Margaret Hur- be held from 12-17 January 2014 of a “well-resolved” stratosphere. witz); (3) upper troposphere-lower in Queenstown, New Zealand. In There is a clear tendency to raise stratosphere water vapour: clear Reading, the goal of the discus- the lid of climate models - almost differences between high- and low- sions focused on how DynVar can all CMIP5 models have tops at top models arise only in the repre- best participate and take advantage pressures <10hPa, and a substantial sentation of the water vapour tape of the next phase of climate model fraction of the CMIP5 models have recorder (Chiara Cagnazzo); and inter-comparisons (CMIP6), ex- tops at pressures <1hPa. However, (4) planetary wave coupling: most pected to start in 2015. One impor- drawing from our expertise in con- low-top models underestimate tant common outcome of the three structing and analysing models, it negative and extreme positive heat discussion sessions was the need to is clear that raising a model’s lid to flux events. The bias in the nega- provide justification for diagnostics include the stratosphere in a climate tive events has implications for the focused on stratospheric dynamics, model domain is a necessary but downward dynamical coupling dur- such as Transformed Eulerian Mean not a sufficient condition for a fully ing strong vortex events, manifested (TEM) variables, gravity wave pa- satisfactory representation of strato- by low pressure and eastward near- rameterization tendencies, as well spheric dynamical processes, such as surface winds in the North Atlantic as all physical tendencies to assess the Quasi-Biennial Oscillation (QBO), basin, impacts consistent with the the momentum and heat budgets. stratospheric sudden warming events, positive phase of the North Atlantic extreme wave events, variations in the Oscillation (Tiffany Shaw). Quasi-biennial oscillation wave forcing of the BDC, tropopause variability, water vapour variability, The high-/low-top distinction was Simulation of the QBO in climate and vortex variability and change. not found to be a predictor for the models remains challenging, with climate change signal in the strato- only a small minority of CMIP5 Nevertheless, the high-/low-top sphere in CMIP5 models (Alexey models reporting successful simula- subdivision (top pressure <1hPa Karperchko), a sign that other tion of the QBO (Thomas Krismer for high-top models) grouping of model features other than strato- and Scott Osprey). New develop- the CMIP5 model set has proven spheric variability, such as param- ments based on stochastic and/or to be useful in demonstrating that eterized gravity wave processes, or convection-driven gravity wave stratospheric variability at all scales tropospheric and ocean responses to sources (François Lott) have the is better represented in the high- climate change, play a more domi- potential to increase the number top models (Andrew Charlton- nant role in shaping the simulated of climate models with a QBO in Perez). Further insights of high-/ response of the stratospheric circu- the next phase of CMIP. However, low-top differences emerged in lation to climate change. A similar given the competition of resources presentations reporting inter-com- difficulty is found in identifying a in climate modelling centres, it is parisons of: (1) tropopause charac- signature of the high-/low-top model expected that there will be the need teristics: the CCMVal2 models with distinction in simulating the connec- to justify the application of atmos- anomalously cold tropopause cold tion between the stratosphere and the pheric model components with points tend to be anomalously cold North Atlantic Ocean, in spite of a proper resolution and parameteri- throughout the stratosphere, but this stronger air-sea coupling in the high- zations to be able to simulate the behaviour is not exactly true for all top model set (Thomas Reichler). QBO. We assessed several robust CMIP5 models, due to high-/low- reasons why the QBO is impor- top differences in mean temperature The regular program of the work- tant: the QBO is a dominant mode (Thomas Birner); (2) ENSO tele- shop was followed by discussion of stratospheric inter-annual vari- connections: Eastern Pacific ENSO sections focused on three main top- ability; the QBO and solar cycle

SPARC newsletter n° 41 - July 2013 41 variability interact in their modu- at all levels. The extraction of more the tropospheric circulation and lation of the propagation of plan- diagnostics may possibly be restrict- depend on the response of gravity etary waves in the stratosphere; ed to dedicated experiments, such wave parameterizations, sources of the residual circulation driven by as AMIP-type runs. Note, however, large uncertainty in stratospheric the QBO affects the BDC; and the that ocean coupling may degenerate modelling. QBO affects tropopause tempera- the QBO performance. We agreed ture in the tropics, and hence water that the QBO initiative presented For CMIP6, questions were posed vapour in the stratosphere. Tropo- by Osprey et al., aimed at designing about the availability of raw data spheric QBO impacts such as the a set of experiments to address the versus more derived quantities effects on the Monsoon, Madden limitation of current models in sim- (e.g., EP flux divergence), the pos- Julian Oscillation, NAO and ENSO ulating the QBO, could possibly be sibility of having more levels near are much less robust and are just initiated by involving a core group the tropopause, all physical tenden- starting to be investigated. In addi- of modelling centres and by report- cies from parameterisations to close tion, the impact of the QBO on the ing what progress has been made in momentum and thermodynamical mid-latitude stratosphere, through modelling the QBO so far. budgets, more flexibility in getting the Holton and Tan effect, needs the model outputs, and observa- to be re-assessed since this effect Circulation and climate change tion datasets prepared for straight- does not appear much in the CMIP5 forward comparison with models. models (Bo Christiansen), with To reduce the uncertainty in cli- Concerning the availability of de- consequences on the representation mate projections of atmospheric rived quantities, the question of of the QBO-NAO relationship. An circulation and its implications for developing a DynVar data archive open question is whether improve- surface and regional climate, the was posed. Regarding the CMIP6 ments in the simulation of precipi- assessment of tropospheric and experiments, we felt that for char- tation variability may facilitate the stratospheric dynamical processes acterizing the relative role of inter- simulation of the QBO, given that in climate models is crucial. Fun- annual versus inter-model variance, convection generates the tropical damental questions that need to be fewer scenarios and more ensemble waves (at planetary and gravity addressed are: members would be a valuable op- scales) that drive the QBO. Specific • What are the causes of tropo- tion, and that we might wish to fo- issues to be addressed are: spheric and stratospheric circu- cus on more idealized experiments • What makes equatorial waves lation changes? (e.g., AMIP4K) or reduced com- dissipate so fast in the lower • What are the impacts of tropo- plexity models, including experi- stratosphere? spheric changes on the strato- ments with dynamical cores. How- • Lower level penetration of the sphere, and vice versa? For ever, concrete plans still need to be QBO is underestimated in cur- which changes do we under- made, calling for a dedicated small rent models, why? This affects stand the mechanisms? workshop, as concluded during dis- water vapour entry and strato- • Which atmospheric circulation cussions about the following topics. sphere-troposphere coupling. changes are robust across models? • Radiative ozone feedback. • What are the dominant sources Mechanisms of stratosphere- of uncertainty in projections of troposphere coupling Recommendations for further anal- atmospheric circulation changes? ysis of the CMIP5 runs include: A number of mechanisms have been • Equatorial waves and QBO Robust changes include a poleward proposed: downward control; hy- structure (Lott et al., in prepa- shift of the subtropical jets, BDC drostatic and geostrophic (fast and ration) strengthening, tropopause rise, slow) adjustments, as for instance • Relations with tropical tropo- and Antarctic vortex change (this inferred by PV inversion; eddy spheric variability latter also driven by ozone deple- feedbacks (baroclinic, planetary, • The QBO-NAO relationship tion). Less robust are shifts of the etc.); wave coupling; resonance; (Hardiman et al., in planning; Arctic polar vortex and northern and linear versus non-linear (index Christiansen, in preparation). mid-latitude tropospheric jet, and of refraction). There are questions the QBO response. The Arctic vor- about how independent the mecha- To progress further, more data will tex and QBO response to climate nisms are? How can we create tests be need to be output in CMIP6, in- change may be critical because that can falsify some mechanisms? cluding tendencies from the physics both involve indirect responses of Whether different mechanisms mat-

42 SPARC newsletter n° 41 - July 2013 ter on different time scales? Wheth- Summary and future plans Initiative (Bitz and Shepherd, leads). er the mechanism can accurately capture the region where impacts The DynVar workshop was a suc- Given the common scientific in- are observed (e.g., Pacific versus cessful event thanks to the dedi- terest of stratosphere-troposphere Atlantic)? What signal would we cated participation of all attendees, coupling (although different time expect at the surface? And, under to whom we would like to express scales are addressed) and that a what conditions do events couple our gratitude. The current focus of joint DynVar and SNAP workshop to the troposphere? Given the rapid the DynVar Activity is on exploit- has proven very successful, we are growth of literature on stratosphere- ing the unique opportunity offered evaluating the possibility of recon- troposphere coupling mechanisms, by the CMIP5 and SHFP (Strato- vening with a second joint DynVar- it would be timely to write a review sphere-resolving Historical Fore- SNAP workshop to be held in early paper, and two such efforts are cur- cast Project) archives. In terms of 2015. rently underway (Kidston et al., its future scientific direction, the in preparation; Baldwin et al., in emerging vision is to embrace the planning). Note also that previous “one-atmosphere” concept, and ad- References comprehensive reviews happened dress tropospheric dynamical issues eight or more years ago (Haynes, as well. This is a natural evolution Charlton-Perez, A. J., et al., 2013: On the 2005; Shepherd, 2002; Holton et of DynVar since stratosphere-trop- lack of stratospheric dynamical variability al., 1995). osphere dynamical coupling is an in low-top versions of the CMIP5 models. essential process in extra-tropical J. Geophys. Res., 118, 2494-2505. Independently from these efforts, climate variability and change, and and based on our developing ex- is consistent across timescales. A Gerber, E. P., et al., 2012: Assessing and perience in analysing CMIP5 runs, further important emerging item of understanding the impact of stratospheric a proposal was made to write a discussion is what research opportu- dynamics and variability. Bull. Am. new position paper to help focus nities the WCRP Grand Challenges Meteorol. Soc., 93, 845-859. and clarify a set of diagnostic and (GC) (http://www.wcrp-climate. possibly idealized experiments for org/index.php/grand-challenges) Haynes, P. H., 2005: Stratospheric CMIP6 (timeframe: one year from may open to DynVar, and how we dynamics. Annu. Rev. Fluid Mech., 37, 263- now). A major question emerged can best contribute to them. Dyn- 293. regarding which model experi- Var appears to be well positioned ments should be designed to test to contribute to GC1 on Regional Holton, J. R., et al., 1995: Stratosphere- stratosphere-troposphere coupling Climate information (given that the Troposphere exchange. Rev. Geophys., 33, mechanisms: Are there differences atmospheric circulation is a major 403-439. in how stratosphere-troposphere source of uncertainty in regional dynamical coupling operates if the climate) and GC5 on Cloud, Cir- Manzini, E., et al., 2011: Stratosphere- coupling originates in the strato- culation and Climate Sensitivity resolving models in CMIP5. Exchanges: sphere from radiative perturbations (through the “changing patterns” CLIVAR Newsletter, 56, 29-31. (water vapour, ozone, solar, GHG) initiative lead by Sobel and Shep- or via a dynamical source in the herd). The ideas regarding the fu- Manzini, E., et al., 2011: Report on the troposphere (e.g., acting as a strat- ture scientific direction of the ac- SPARC DynVar Workshop 2 on Modelling ospheric pathway in tropospheric tivity, its contribution to the GCs, the Dynamics and Variability of the Strato- teleconnections)? Further questions and participation in CMIP6 will be sphere-Troposphere System. SPARC News- are: What are the implications of the subject of discussion at a Dyn- letter, 36, 19-22. distinguishing types of coupling? Var side event planned during the Could DynVar propose an ideal- SPARC General Assembly. Revi- Shepherd, T. G., 2002: Issues in strato- ized experiment to be carried out sion of the DynVar Research Top- sphere-troposphere coupling. J. Meteorol. in models of varying complexities? ics and Groups will follow, as well Soc. Japan, 80, 769-792. These questions would need careful as the activity implementation plan thought about goals and suitable ap- requested by SPARC. DynVar will Tripathi et al., 2013: Report on the first proaches, and could be addressed in also maintain links with the seasonal SPARC Stratospheric Network for the As- a dedicated small workshop. forecasting community, the SHFP sessment of Predictability (SNAP). SPARC project (Butler and Scaife, leads), Newsletter, 41, this issue. and the Polar Climate Predictability

SPARC newsletter n° 41 - July 2013 43 Report on the 1st SPARC Stratospheric Network for the Assessment of Predictability (SNAP) 24-26 April 2013, Reading, UK

Om P. Tripathi1, Andrew Charlton-Perez1, Edwin Gerber2, Elisa Manzini3, Mark Baldwin4, Martin Char- ron5, David Jackson6, Yuhji Kuroda7, and Greg Roff8

1Department of Meteorology, University of Reading, UK, [email protected], 2New York University, USA, 3MPI-M, Hamburg, Germany, 4University of Exeter, UK, 5Environmental Canada, Canada, 6Met Office, UK, 7Meteorological Research Institute, Japan, 8Bureau of Meteorology, Australia.

The first SPARC Stratospheric Net- 26 April an extensive discussion was His case study experiments used a work for the Assessment of Pre- held, focusing on future plans for different but related technique, at- dictability (SNAP) workshop was SNAP, including an experimental tempting to quantify the role the organized at the Department of protocol for the SNAP predictabili- stratosphere played in recent cold Meteorology, University of Read- ty experiment, which will take place winters by damping the strato- ing, UK, from 24-26 April 2013. during 2013 and 2014, and links to spheric state toward a reanalysis. In This was a joint workshop with other related activities including the these experiments, small reductions the 3rd SPARC Dynamical Vari- seasonal to sub-seasonal prediction in tropospheric forecast error were ability (SPARC-DynVar) work- initiative (S2S, http://www.wmo. found in the stratospheric damping shop held from 22-24 April, with int/pages/prog/arep/wwrp/new/ experiments. He also emphasized 24 April as a joint day (see report S2S_project_main_page.html). the potential tropical source of this issue). The joint workshop stratospheric variability by showing was well attended and had around Thomas Jung gave the keynote that, in some cases, reduction in ex- 100 participants (http://www. talk, presenting a detailed overview tra-tropical forecast error is similar met.reading.ac.uk/~pn904784/ of the role of the stratosphere in for cases when either stratospheric DynVar_SNAP_Workshop/par- extended range weather forecast- damping or an equivalent tropical ticipant.html) from 16 countries ing, with case studies including tropospheric damping is used. in Europe, Asia, Africa, Australia, the stratospheric sudden warming North America, and South America. (SSW) of 2009 and the extremely Martin Charron gave an introduc- cold European winters of 2005/06 tion to the Canadian Global Weather The SNAP workshop was formally and 2009/10. His studies used the Forecasting System that includes opened by Simon Chandler-Wide, ECMWF Integrated Forecast Sys- the stratosphere, and discussed the Head of the School of Mathemati- tem (IFS). He described a study of additional skill in surface weather cal and Physical Sciences, Univer- the generic tropospheric circulation forecasting gained from raising the sity of Reading. Simon gave a short response to an optimized strato- model lid. The new Environment speech about the history of the Uni- spheric forcing that changes the Canada NWP (numerical weather versity and Department of Meteor- strength of the wintertime North- prediction) global model has a lid ology, and formally welcomed the ern Hemisphere stratospheric polar at 0.1hPa and 80 vertical levels. The participants. The welcome address vortex. Results of the experiment model includes a non-orographic was followed by an introduction to showed that the response of the wave drag scheme, methane oxida- SNAP by Andrew Charlton-Perez tropospheric circulation to strato- tion scheme, and a new ozone cli- (see also Charlton-Perez and Jack- spheric forcing was significant, and matology. In addition to comparing son, 2012). During the workshop, had the expected strong projection the forecast skill of the old and new participants presented their work, onto the surface Northern Annular models, he also showed results from underlining current understanding Mode (NAM). The response was a comprehensive set of experiments of stratospheric dynamical variabil- found to be linear with respect to that attempted to systematically ity, its predictability, and its impact the forcing and delayed by around identify the source of the forecast on surface weather and climate. On 10 days from forcing onset. skill improvements in the new mod-

44 SPARC newsletter n° 41 - July 2013 el. One interesting result was that promote its uptake by operational Stratospheric variability and additional tropospheric forecast centres (Table 3), and exploita- predictability skill was obtained without any ex- tion by the applications commu- tra observations in the stratosphere, nity. The project is designed to An invited talk on the predictabil- suggesting that improvements in pay specific attention to the risk of ity of the stratosphere and associ- the estimation of the initial state extreme weather, including tropi- ated teleconnections was given by due to reduced stratospheric bias cal cyclones, droughts, floods, heat Adam Scaife. He presented a series were important. waves, and the waxing and wan- of monthly forecasts of the January ing of monsoon precipitation. S2S 2013 SSW. These forecasts showed Greg Roff presented results from is in the process of establishing an that a SSW signal started appearing extended range forecasts using the extensive database of sub-seasonal on 21 December 2013 in the opera- Australian Community Climate and to seasonal (up to 60 days) forecasts tional forecast model, and that Met Earth System Simulator (ACCESS). and re-forecasts. The database will, Office forecasts were modified to ACCESS runs a global and regional in part, be modelled on the THOR- include the potential effects of this short-range ensemble prediction PEX Interactive Grand Global En- event. This was an example of the system (AGREPS) in pre-opera- semble (TIGGE) database for medi- importance of what Adam called tional research mode. He found that um range forecasts (up to 15 days). ‘actionable information’ for fore- the AGREPS system performs com- The impact of stratospheric variabil- casters, which SNAP should bear in parably, to the operational ECM- ity on surface weather and climate mind when considering the impact WF-EPS system, as shown for the will be a key topic of the S2S project. of stratospheric variability on sur- forecasts of the Queensland, Aus- tralia, flooding of 27 January 2013 (Figure 19). He also presented an important challenge to SNAP, that is, to clearly identify where operational forecasting centres might see benefit in forecast skill from better representing stratospheric dynamical processes.

An introduction to the WCRP- WWRP S2S project was given by the S2S co-chair Frédéric Vitart. S2S is a new WWRP/THORPEX- WCRP joint research project whose main goal is to improve forecast skill and understanding on the sub- seasonal to seasonal timescale, Figure 19: The flooding of Queensland, Australia as simulated by AGREPS and ECMWF-EPS.

Table 3: Major operational forecasting systems and their configuration for the S2S initiative:

Time Range Resol. Ens. Size Freq. Hcsts Hcst Length Hcst FreqHcst Size ECMWF D 0-‐32 T639/319L62 51 2/week On the ﬂyPast 18y weekly 5 UKMO D 0-‐60 N96L85 4 daily On the ﬂy 1989-‐2003 4/month3 NCEP D 0-‐60 N126L64 16 daily Fix 1999-‐2010 daily4 EC D 0-‐35 0.6x0.6L40 21 weekly On the Fly Past 15y weekly 4 CAWCR D 0-‐120 T47L17 33 weekly Fix 1989-‐2010 3/month 33 JMA D 0-‐34 T159L60 50 weekly Fix 1979-‐2009 3/month 5 KMA D 0-‐30 T106L21 20 3/month Fix 1979-‐2010 3/month10 CMA D 0-‐45 T63L16 40 6/month Fix 1982-‐now monthly48 Met. Fr. D 0-‐60 T127L31 41 monthly Fix 1981-‐2010 monthly11 SAWS D 0-‐60 T42L19 6 monthly Fix 1981-‐2001 monthly6 HMCR D 0-‐60 1.1x1.4L28 20 weekly Fix 1981-‐2010 weekly 10

SPARC newsletter n° 41 - July 2013 45 face weather. Adam also discussed Model. He showed the enhanced one-month ensemble hindcast (HC) a number of case studies of recent potential predictability that can experiment data using the Japan cold winter events and discussed be achieved in sea level pressure, Meteorological Agency (JMA) nu- experiments that highlighted the surface temperature, and precipita- merical weather prediction model. role of stratospheric variability in tion for forecasts initialized during The HC data exhibits a large spread the predictability of these events. SSWs. This was contrasted with and low skill when the polar night He estimated that the mean time on the lower levels of model skill for jet is in a weakening phase. The which the current version of the Met forecasts initialized during periods spread and skill are found to be cor- Office model could predict SSW in which the stratospheric state was related, as expected (large spread events was around 12 days. He also close to the climatology. As a way corresponds to low skill), but their showed experiments highlighting of exploiting the additional skill, distributions are also characterized the role of drivers of variability in he suggested that forecasting cen- by outliers, which have markedly the extra-tropical stratosphere in- tres run additional, special seasonal low skill for a given spread. cluding ENSO, the QBO, and the forecasts once an SSW appears in solar cycle. Finally, he presented re- observations. Stratosphere-troposphere cou- sults from the most recent version of pling, stratospheric warmings the Met Office seasonal forecasting Daniella Domeisen gave a presen- and surface weather model, GloSea5. Excitingly, these tation about the ability of the MPI- results show much greater skill than ESM seasonal prediction system to The tropopause connects the strato- previous models in predicting the reproduce stratospheric variability sphere and troposphere and plays a wintertime NAO, with a correlation and predictability. The mean state very important role in stratosphere- between DJF mean NAO and No- of the stratosphere was shown to troposphere coupling. Mark Bald- vember forecasts of around 0.6 over be well reproduced, but the model win highlighted the role of the a series of hindcasts. Alberto Ar- still struggles in the tropical upper tropopause and suggested that the ribas discussed this result in further stratosphere, where there appears understanding of the variation of detail, highlighting some of the im- to be a large positive bias in zonal tropopause height may hold the provements made to the Met Office mean zonal wind. In a composite key to understanding the strato- systems, including enhancements of 67 SSWs the model appears to spheric impact on surface weather. of both vertical and horizontal reso- successfully reproduce downward He described the large variability lution, which led to this step change coupling. of tropopause height (upwelling/ in forecast skill. downwelling) at the polar cap as a Masakazu Taguchi investigated mechanical plunger, influencing the The role of SSWs in producing skil- basic characteristics of stratospher- entire troposphere. Because of the ful seasonal forecasts was also dis- ic predictability for the NH winter large signal to noise ratio in tropo- cussed by Michael Sigmond, using stratosphere by comparing the JRA- pause height, he suggested using the Canadian Middle Atmosphere 25/JCDAS reanalysis data with new metrics for stratosphere-troposphere coupling, such as the variance of tropopause height and the e-folding timescale of tropopause height (Figure 20).

Shigeo Yoden introduced a five-year Japanese research project looking at extreme weather variability in the coupled stratosphere-troposphere system. This project is a collaboration between groups working on data analysis, mechanistic circulation modelling, general circulation modelling, NWP modelling studies, and JMA/Meteorological Re- search Institute climate modelling Figure 20: Large variation in PV anomaly at the tropopause. studies. The project aims to per-

46 SPARC newsletter n° 41 - July 2013 form comprehensive studies of ex- that distinguished between the im- variability. He also showed that the treme weather events in the coupled pact of vortex displacement and Holton-Tan (HT) relationship is stratosphere-troposphere system, vortex splitting during SSWs on the significantly weaker in models than understanding their dynamical pro- surface weather using reanalysis in the reanalysis (Figure 21). cesses with a hierarchy of numeri- data. He found that vortex splitting cal models, and future projections events are more strongly correlated Peter Watson gave a presentation with a state-of-art climate model. with surface weather and lead to considering the effect of the QBO on This research project may also con- positive temperature anomalies of the stratospheric polar vortex. Using tribute towards the promotion of in- more than 1.5K over eastern North dynamical system theory, he argued ternational research collaboration, America, and negative anomalies of that composite pictures of the vor- including WCRP/SPARC activities. up to -3K over Eurasia. The signals tex evolution during different QBO from vortex displacement events phases could be misleading, and in- Miriam D’Errico presented the ef- were found to be weaker and gen- stead advocated a detailed study of fects of stratosphere-troposphere erally associated with cold-air out- the transient response of the vortex coupling on decadal predictability of breaks over North America. to QBO forcing. Using results from the climate system using a coupled the HadGEM2 model, he described ocean-atmosphere model. She showed Toshihiko Hirooka presented a how transient experiments of this results from climate projections using study of mesopause circulation type favour the standard HT mecha- both the high- and low-top versions of changes during SSWs. He found nism over other explanations for the the CMCC climate model. that mesospheric easterlies do not QBO-vortex link. always appear before SSW easter- The tropical stratospheric response lies in the upper stratosphere. He Another presentation on the HT to SSW events was presented by also discussed dynamical reasons mechanism was made by Hua Lu, Miguel Gomez-Escolar. He found for the difficulty that models have in who discussed changes in the HT that the upper and middle tropical reproducing the mesopause changes effect on decadal time scales. Us- stratosphere is significantly coupled associated with SSW events. ing ERA-40 and ERA-Interim rea- to the evolution of the polar cap. nalysis data she showed that more He discussed new ways of extract- Quasi-biennial oscillation planetary waves break in the up- ing composite temperature anoma- per stratosphere in winter when lies during SSW events, avoiding Bo Christiansen made a presenta- the previous QBO phase transition contamination from QBO-induced tion about the QBO influence on occurred during NH winter, caus- temperature changes. He showed variability of the stratospheric win- ing stronger meridional circulation that lower stratospheric responses ter vortex in CMIP5 and CCMVal2 and a warmer, more disturbed polar to SSW events are only present dur- models. He showed that while mod- vortex. She also showed that from ing easterly QBO phases and are els show significant bimodality in 1977-1997 the HT effect was weak related to changes in sub-tropical the tropical stratosphere associated due to more frequent winter transi- wave breaking. with the QBO, there is little bimo- tions of the QBO phase during that dality in the polar vortex region de- period. Beatriz Funatsu investigated the spite models having realistic vortex impact of SSWs on changes in the occurrence of tropical convection following two SSWs that occurred in January 2009 and January 2010, Figure 21: Correlations using satellite observations from between winter mean the Advanced Microwave Sound- vortex and QBO. The ing Unit. She found that follow- colours indicate the rep- ing the onset of a SSW there was resentation of the QBO a subsequent overall increase in in the models: No QBO the occurrence of deep convection (red), Prescribed QBO over South America, Africa, and the (blue), Spontaneous Maritime Continent. QBO (green), and NCEP (black). Daniel Mitchell presented work

SPARC newsletter n° 41 - July 2013 47 Manfred Ern studied observed osphere dynamical coupling. He cursors. Splitting SSWs tend to be QBO forcing with ECMWF and showed that the high-top models preceded by eastern Pacific blocks satellite temperature data, using represent stratospheric zonal wind during La Niña, but by reduced east- longitude-time 2D spectral analy- anomalies better, however, little ern Pacific blocking activity and sis. The Kelvin wave contribution distinction was found in the mag- enhanced western Atlantic blocking to momentum forcing of the QBO nitude and structure of zonal wind frequency during El Niño. during the 2002-2006 period was anomalies at tropospheric levels. found to be only 30% of the total. James Anstey used the CMIP5 A study of the relationship between dataset in combination with CMAM Annular modes, ENSO ENSO, blocking, and stratospheric runs to assess the blocking-SSW and blockings sudden warmings was presented by relationship. He showed that there David Barriopedro using reanaly- was little observable difference in Torben Kunz presented a study of sis data for the 1958-2010 period. blocking between high- and low- the effect of stratospheric variabil- Results reveal that SSWs character- top models, but that models with ity on the NAM surface signal. He ized by splits of the stratospheric higher vertical resolution in the up- quantified the relative role of the polar vortex exhibit different re- per troposphere and lower strato- downward effect of the zonal mean gional blocking precursors, asso- sphere tend to show reduced block- secondary circulation induced by ciated wave numbers, and vortex ing biases (Figure 23). quasi-geostrophic (QG) adjustment structure depending on the ENSO to stratospheric wave drag and ra- phase. This indicates some ENSO External Forcings diative damping, and of wave drag influence on the determination of local to the troposphere. The role of different tropospheric SSW pre- Edwin Gerber explored the im- both contributions appeared to be quantitatively similar but differed qualitatively. QG adjustment was found to be responsible for the ini- tiation of the surface NAM signal, while the wave drag maintains the persistence of the signal for several weeks.

The effect of SSWs on the predictability of the tropospheric NAM over nine winters from 2001/2002 to 2009/2010 was presented by Yuhji Kuroda, using the MRI climate model. Results showed that the stratosphere plays an important role for better medium-range prediction of the tropospheric NAM when stratospheric variability is very large during a SSW (as in 2004 and 2006). The predictability of the tropospheric NAM reaches a few months, as shown in Figure 22.

Robert Black presented a performance assessment of the CMIP5 model representation of the primary modes of boreal extra-tropical low- frequency variability, the vertical and temporal behaviour of the annular modes, and stratosphere-trop- Figure 22: The effect of SSWs on the predictability of tropospheric NAM.

48 SPARC newsletter n° 41 - July 2013 pact of anthropogenic forcing on EOS MLS ozone profile is superior to changes in stratospheric ozone the austral jet stream in CCMVal2, to that of the control, tropospheric and greenhouse gases, finding that CMIP3, and CMIP5 models, focus- errors in the medium- to extended- variability in the final warming ing on summer, the period of the range forecasts are dominated by date on timescales associated with year when stratospheric ozone loss the spread of ensemble members, changes in stratospheric ozone con- and recovery has been shown to im- and hence he found no significant centrations was only significant in pact the troposphere. He found that reduction of root mean square er- the high-top ensemble. the multi-model mean response of rors due to an improved representa- the jet stream to greenhouse gases tion of ozone. Encarna Serrano evaluated the and ozone is fairly comparable, ability of the Whole-Atmosphere suggested that ozone changes have Laura Wilcox quantified the effect Community Climate Model (WAC- dominated the jet position in the of external forcings on the Southern CM) to reproduce tracer transport recent past, and that the effects of Hemisphere final warming date, and processes through the tropical trop- ozone and greenhouse gases will the sensitivity of projected changes opause. Model results showed that largely offset each other in future. to model representation of the strat- the main features of vertical struc- osphere using high- and low-top ture and seasonality of tempera- The impact and the potential ben- CMIP5 model ensembles. The final ture, ozone and CO near the tropi- efits of using ozone data from the warming date in the models was cal tropopause in WACCM are very Earth Observing System Micro- found to be generally too late in similar to satellite observations, and wave Limb Sounder (EOS MLS) in comparison with those from reanal- that WACCM is a valuable tool for medium- to extended-range tropo- yses - around two weeks too late in evaluating ozone and CO transport spheric forecasts in a current NWP the low-top ensemble, and around near the tropical tropopause, al- system was examined by Jacob one week too late in the high-top though the cold point tropopause is Cheung. In the extreme case (Arctic ensemble (Figure 24). She also ex- slightly higher (~1km) in the model ozone hole, March 2011) where the amined this behaviour in response than in observations (Figure 25).

Figure 23: Effect of model resolution on blocking trends. Top Row: high-top vs. low- top models; Middle Row: fine vs. coarse vertical resolution model versions; Bottom Row: fine vs. coarse horizontal resolution model versions.

SPARC newsletter n° 41 - July 2013 49 A model study of the tropospheric decrease in solar activity over the ing. The discussion focused on the circulation changes in response to coming century would enhance the future plans for the SNAP experi- zonally asymmetric ozone anoma- stratospheric cooling in response to ment and modifications of the origi-

lies was presented by Dieter Pe- increasing CO2 concentrations. The nally planned activities in lieu of re- ters. He found significant changes cooling would weaken the stratospher- cent findings about the performance in intra-seasonal and interannual ic polar jet and consequently result in of low- and high-top operational variability in the stratosphere when an equatorward movement of the mid- models. Ideas presented by the par- comparing model runs with sym- latitude jet, thus affecting the regional ticipants will be used to draft an metric and asymmetric ozone dis- climate over Western Europe. experiment protocol for the project, tributions. These changes also have which will later be agreed upon by links to tropospheric circulation. Summary and future plan the project steering committee. A possible impact of a future grand Next actions for SNAP are to com- solar minimum on surface climate The first SNAP workshop conclud- plete the SNAP predictability ex- was presented by Amanda May- ed with an extensive and fruitful periment, which is to be carried out cock, who indicated that a large discussion session on Friday morn- in two phases. Phase I will focus

Figure 24: Mean final Southern Hemisphere warming dates for CMIP5 model for (a) 1870–1900 (left bars) and 2070–2098 (right bars) in RCP4.5, (b) 1870–1900 (left bars) and 2070–2098 (right bars) in RCP8.5, (d) 1979–2005. Whiskers show +/-2 standard errors. High-top models are indicated by hatching. In Figure 4d, the horizontal solid lines show the mean final warming date from ERA-Interim (black) and CFSR (blue), with dashed lines indicating ˙2 standard errors in each case. (c) The relationship between 1870–1900 and 2070–2098 final warming date is shown for RCP4.5 (squares) RCP8.5 (stars). Figure source: Wilcox and Charlton-Perez, 2013.

50 SPARC newsletter n° 41 - July 2013 Figure 25: Top panel: Ver- tical structure of time mean (2004-2009) temperature (a), ozone (b), and CO (c) averaged over 18°S-18°N for WACCM and observations. The error bars represent the vertical thickness of the layers where MLS measures ozone and CO. The horizontal lines in panel (a) indicate the location of the annual mean cold point tropopause. The black dots in panel (c) indicate the WACCM values when using MLS averag- ing kernels for CO. Bottom panel: As in top panel but for the vertical structure of the annual cycle in temperature and tracers. The amplitude for the tracers is shown relative to the annual mean concentration. (Source: Abalos et al., 2012).

on forecasts of two very recent test A key part of the forecast protocol Acknowledgments events, the NH January 2013 SSW, will be to specify, in detail, which and the late SH final warming of stratospheric fields can be collected The authors are grateful to the Natural En- October 2012. Once this test phase from the modelling centres to pro- vironment Research Council and WCR- has been completed, the project will vide a detailed understanding of the SPARC for their financial support. work to define additional dates for dynamical background of strato- forecast comparisons to be added to spheric predictability. the SNAP forecast archive. In ad- Reference dition, SNAP will begin to collect SNAP furthermore agreed to play a a set of operational forecasts from role in the upcoming S2S project. Abalos, M., Randel, W. J. and Serrano, E., each of the modelling centres in- SNAP will seek to encourage mem- 2012: Variability in upwelling across the volved, to facilitate the comparison bers of the network to make use of tropical tropopause and correlations with of forecast performance during pe- S2S to examine stratosphere-trop- tracers in the lower stratosphere. Atmos. riods in which extreme stratospher- osphere predictability on the sub- Chem. And Phys., 12, 11505–11517 ic events are not occurring. seasonal time range, using the large archive of data that S2S will collect.

SPARC newsletter n° 41 - July 2013 51 SPARC Reanalysis Intercomparison Project (S-RIP) Planning Meeting 29 April – 1 May, 2013, Exeter, UK

Masatomo Fujiwara1, and David Jackson2

1Hokkaido University, Japan, [email protected], 2Met Office, UK

The SPARC community has been 39 participants, 20 oral presenta- (USLM), and Gravity Waves. Prior using reanalysis datasets to under- tions, and 21 poster presentations. to the meeting two co-leads were stand atmospheric processes and confirmed for most of the chapters. variability, and to validate chem- Meeting outline At the meeting, all chapters, except istry-climate models. Currently, for the introduction, were given there are eight global atmospheric The purposes of the meeting were one hour for a presentation by the reanalysis datasets available and to finalize the report outline, to co-leads and discussion with the four more will be available soon determine the diagnostics list and participants. The Brewer-Dobson (Table 4). The SPARC Reanalysis observational data required for vali- Circulation session included short Intercomparison Project (S-RIP) is dation for each chapter, to agree on invited talks by some of the main an emerging SPARC activity that the general guidelines and proto- contributors to the chapter (Hella was proposed last year (Fujiwara et cols, and to define the project time- Garny, Gabriele Stiller, Bernard al., 2012). The goals of S-RIP are table. Based on past SPARC activi- Legras, and Howard Roscoe). For to create a communication platform ties (e.g., SPARC CCMVal, 2010), each chapter, the co-leads and two between the SPARC community the WG initially proposed 11 chap- rapporteurs prepared a one-page and reanalysis centres, to under- ters. The first four “basic” chapters summary slide for the wrap-up on stand current reanalysis products, are the Introduction, Description the final day. The finalized chap- and to contribute to future reanaly- of the Reanalysis Systems, Clima- ter list with the co-leads’ names is sis improvements. By August 2012, tology and Interannual Variability shown in Table 5. We decided to di- the working group (WG) with 11 of Dynamical Variables, and Cli- vide the UTLS chapter in two, one members had been formed, and the matology and Interannual Vari- focusing on the extra-tropical UTLS reanalysis centre contacts for the ability of Ozone and Water Vapour. (ExUTLS) and the other on the project had been confirmed. The The following, “advanced” chap- Tropical Tropopause Layer (TTL), WG discussed chapter titles, co- ters were initially proposed to be: with a section in the ExUTLS chap- leads, and initial contributors to the The Brewer-Dobson Circulation, ter summarizing overlapping issues final SPARC report and planned a Stratosphere-Troposphere Cou- between the two chapters. Also, is- kick-off meeting. This article sum- pling, The Upper Troposphere and sues related to transport processes marizes the discussions held during Lower Stratosphere (UTLS), Polar and gravity waves will be distribut- the S-RIP Planning Meeting hosted Processes, The Quasi-Biennial Os- ed to various chapters (Simon Cha- at the Met Office, Exeter, UK, from cillation (QBO), The Upper Strat- brillat and Nedjeljka Žagar led 29 April-1 May 2013. There were osphere and Lower Mesosphere the discussion on these issues at the meeting). There were also a large number of poster presentations that stimulated discussion. Table 4: Available global atmospheric reanalysis datasets: At the meeting it was also decided Reanalysis Centre Name of the Reanalysis Product that the project would focus solely ECMWF ERA-40, ERA-Interim, [ERA-20C], [ERA-SAT] on reanalyses (although some chap- NOAA/NCEP NCEP/NCAR (R-1), NCEP/DOE (R-2), NCEP-CFSR ters may include diagnostics from JMA JRA-25/JCDAS, [JRA-55] operational analyses). Therefore, NASA MERRA, [MERRA-2] we decided to slightly rename the NOAA – CIRES 20CR 52 SPARC newsletter n° 41 - July 2013 project to the SPARC Reanalysis In- presented NOAA’s activities (R- of the newer reanalyses for the pe- tercomparison Project, (i.e., “analy- 1, R-2, CFSR, and 20CR), while riod 1979-2012 (1979-2001, allow- sis” has been dropped from the Paul Berrisford presented routine ing comparison with ERA-40, in the name suggested in the original pro- diagnostics activities for various appendix) will be created on both posal). For most of the chapters, we reanalyses carried out at ECMWF. standard pressure levels and poten- will compare newer reanalyses, i.e., Steven Pawson presented NASA’s tial temperature levels. Various key MERRA, ERA-Interim, JRA-25/ activities (MERRA and MERRA-2) plots of the ensemble climatologi- JCDAS, NCEP-CFSR, and 20CR. remotely. Adrian Simmons dis- cal means and individual reanalysis We also aim to include JRA-55, cussed detailed comparisons of anomalies from these means will be ERA-20C, ERA-SAT, MERRA-2, MERRA and ERA-Interim temper- created and presented in an online etc., when available. Some chapters atures and assimilated observations. atlas. Inter-reanalysis variations may include older reanalyses such will be quantified. Observations as R-1, R-2, and ERA-40, because S-RIP Report outline for validation include radiosondes, they have been heavily used in the lidars, rocketsondes and various past and are still being used for cer- The chief outcome of the meeting satellites, whose data were not as- tain studies, and to gain insight into was the drafting of plans for Chap- similated in the reanalyses. potential shortcomings of past re- ters 2-11 of the S-RIP final report. search results. At the beginning of These plans are briefly summarized Chapter 4. Climatology and each chapter an explanation will be as follows: interannual variability of ozone given as to why specific reanalyses and water vapour were included/excluded. The inter- Chapter 2. Description of the comparison period is 1979-2012, reanalysis systems This chapter will include a detailed i.e., “the satellite era,” but some evaluation of ozone and water va- chapters will also consider the pre- This chapter shall include a detailed pour in the reanalyses using a range satellite era before 1978. description of the forecast model, of observations obtained from assimilation scheme and observa- sonde, aircraft, and satellite instru- On the first day of the meeting, be- tional data assimilated for each rea- ments. The diagnostics considered fore starting the chapter discussion, nalysis, together with information will include climatological evalua- there were seven presentations by on each reanalysis “stream” and on tions, seasonal cycles, interannual reanalysis centres. David Tan pre- what data are archived. variability, and trends. Other, more sented introductory comments on event-based diagnostics such as reanalyses and then talked about Chapter 3. Climatology and the tape recorder, QBO, and polar both the JMA’s activities (JRA-25/ interannual variability of dehydration will be used to under- JCDAS and JRA-55), on behalf of dynamical variables stand differences in the climato- Yayoi Harada, and the ECMWF’s logical evaluations, while detailed activities (ERA-Interim, ERA- A climatology of major dynamical analysis of these processes will be 20C, ERA-SAT, etc.). Craig Long variables, created from an ensemble covered in the “advanced” chapters.

Table 5: List of chapters and names of co-leads:

Title Co-leads 1 Introduction Masatomo Fujiwara, David Jackson 2 Description of the Reanalysis System Masatomo Fujiwara, David Tan, Craig Long 3 Climatology and Interannual Variability of Dynamical Variables Craig Long, Masatomo Fujiwara 4 Climatology and Interannual Variability of Ozone and Water Vapour Michaela Hegglin, Sean Davis 5 Brewer-Dobson Circulation Thomas Birner, Beatriz Monge-Sanz 6 Stratosphere-Troposphere Coupling Edwin Gerber, Yulia Zyulyaeva 7 ExUTLS Cameron Homeyer, Gloria Manney 8 TTL Susann Tegtmeier, Kristin Krüger 9 QBO and Tropical Variability James Anstey, Lesley Gray 10 Polar Processes Monica Santee, Alyn Lambert 11 USLM Diane Pendlebury, Lynn Harvey 12 Synthesis Summary Masatomo Fujiwara , David Jackson SPARC newsletter n° 41 - July 2013 53 In addition, relevant information on ing impact on diagnostics of strato- Chapter 10. Polar processes the assimilated ozone and water va- sphere-troposphere coupling will be pour, and the prognostic representa- explored. This chapter will cover the formation of these fields in the reanalyses tion of polar stratospheric clouds, will be summarized. Chapter 7. Extra-tropical UTLS chlorine activation, denitrification and dehydration, and (possibly) Chapter 5. Brewer-Dobson The diagnostics to be produced will chemical ozone loss in the lower circulation include various tropopause identi- stratospheric winter polar vortices. fication methods, multiple tropo- Focus will be on process-oriented This chapter will evaluate strato- pauses, the tropopause inversion and case studies. The chapter will spheric circulation using diagnos- layer, UTLS jet characterization, also include a review of previous tics such as the age-of-air (mean estimates of horizontal boundaries works showing significant biases age and spectrum), metrics for the between the ExUTLS and TTL, tra- in lower stratospheric temperature, strength of mixing barriers, and re- jectories, and Rossby wave break- winds, or vortex strength/structure/ sidual circulation quantities. Ten- ing. This chapter will also have a evolution rendering some reanaly- dencies for heat and momentum section that reviews common diag- ses (e.g., R-1, R-2, and ERA-40) as well as analysis increments will nostics for the ExUTLS and TTL. unsuitable for polar process studies. be considered. Eulerian chemistry transport models and trajectory Chapter 8. TTL Chapter 11. USLM calculations will be used. Results will be validated against satellite, The diagnostics shall include the This chapter will look at diagnostics ground-based, balloon, and aircraft general TTL structure (cold point including the Semi-Annual Oscilla-

observations of SF6, CO2, and NO2, and lapse rate tropopause, etc.), tion, climatology of the winter po- including the recent MIPAS data clouds and convection (cloud frac- lar vortex, SSWs focusing on stra- sets. Both climatological results tion profiles, OLR, etc.), diabatic topause evolution and mesospheric and trends in the main diagnostics heat budget, transport (Lagrangian cooling, various waves (tides, two- will be examined. cold point, residence time based on day wave, and normal modes), iner- vertical winds and heating rates, etc.), tial instability of the tropical strato- Chapter 6. Stratosphere- wave activity, and long-term changes pause, and Hadley circulation of the troposphere coupling (e.g., tropical belt widening). stratopause region. Observations including SABER, MLS, the NDACC This chapter covers two-way cou- Chapter 9. QBO and tropical database, and CMAM20 (a model pling between the troposphere and variability nudged to reanalysis), will be used stratosphere, focusing in particu- for validation purposes and to ex- lar on extra-tropical coupling on Diagnostics for this chapter will in- tend our knowledge of the state of daily to intraseasonal time scales, clude analysis of the tropical QBO, the middle atmosphere. NOGAPS– and how this shorter-term vari- its extra-tropical teleconnections (as ALPHA may also be considered for ability is modulated on interannual well as other relevant teleconnec- case studies. time scales (e.g., by ENSO). The tions such as with ENSO and the chapter will synthesize and com- solar cycle), its zonal momentum Overview of the project schedule pare established approaches with budget, and spectral characteristics more recent metrics to characterize of tropical waves including modal We shall finalize the “basic” chap- planetary wave coupling and block- analysis and equatorial wave en- ters (i.e., Chapters 1-4) within 2 ing, coupling of the zonal mean ergetics. Observations for valida- years. The “advanced” chapters flow (e.g. the annular modes), and tion include operational and cam- (5-12) will evolve slightly more the mechanism(s) connecting the paign radiosondes, rocketsondes, slowly, with an interim report every stratosphere and troposphere (e.g., and satellites such as HIRDLS and year. We will have dedicated S-RIP changes in tropopause height). SABER. Information regarding non- meetings every year and side-meet- There has been recent discussion orographic gravity wave parameteri- ings at various occasions. on how to best characterize Strato- zation (if present) and analysis in- spheric Sudden Warmings (SSWs). crements may also be utilized. We welcome your contributions to The established and alternative this project. Please contact the au- definitions of SSWs and the result- thors of this article and/or the co-

54 SPARC newsletter n° 41 - July 2013 leads of the relevant chapters directly. vided by WCRP/SPARC and the Met Office. SPARC CCMVal, 2010: SPARC Report Up-to-date information will be made on the Evaluation of Chemistry-Climate available through the S-RIP website Models. V. Eyring, T. G. Shepherd, D. (temporally at http://wwwoa.ees. References W. Waugh (Eds.). SPARC Report No. 5, hokudai.ac.jp/~fuji/s-rip/). WCRP-132, WMO/TD-No. 1526. Fujiwara, M., S. Polavarapu, and D. Jack- Acknowledgments son, 2012: A proposal of the SPARC Rea- nalysis/Analysis Intercomparison Project. Financial support for the meeting was pro- SPARC Newsletter, 38, 14-17.

dynamical change during the period when The brave and unambiguous link of ozone the Antarctic spring ozone values were de- depletion to CFCs made in that paper could clining so rapidly. Chemistry had to be the only be proposed because all other options cause – and yet it surely couldn’t be! Their had been considered and rejected. careful analysis of the measurements was soon confirmed and within a remarkably After Joe retired from BAS in 1990, he short period the main chemical processes joined us in the European Ozone Research had been elucidated by the international Coordinating Unit. For the following 23 community. years he came in nearly every day, following the development of polar ozone loss in Joe’s career seems very unorthodox from each Arctic and Antarctic winter. He made Joe Farman a modern perspective. Prior to the Nature important contributions to the European † 11 May 2013 paper, Joe had been working quietly with Arctic Stratospheric Ozone Experiment and just two scientific publications in the 29 subsequent pan-European field campaigns Joe Farman, the leader of the team which years since he had joined BAS, having been exploring ozone loss. He also provided sage first reported the existence of the Antarctic lured from de Havilland Propellors (where advice on all aspects of the stratospheric Ozone Hole, passed away on Saturday 11th he worked on missile guidance systems) by ozone research programme in Europe, May 2013. The publication of this finding the prospect of Antarctica. After the Nature which was often a valuable counterpoint in Nature was a truly seminal moment in paper, he immediately moved into a very when dealing with the European Commis- atmospheric science, by the then almost prominent position, both scientifically and sion and various national interests. unknown team of Joe, Brian Gardiner, and publically. His character did not change – Jonathan Shanklin at the British Antarctic working with Joe was always both reward- A service to mark Joe’s passing was held in Survey (BAS). The immediate reaction of ing and frustrating – but, for a private man, the chapel of his much-loved Corpus Christi most active researchers was disbelief – even he showed a remarkable facility for dealing College, Cambridge, where he studied as an if the observations were right, the proposed with the press, the political world and the undergraduate and was later a Fellow and link to the degradation products of chloro- public. His impact here was based on his Honorary Fellow. He is survived by his wife fluorocarbons (CFCs) seemed unlikely, to scientific integrity. He did not like anyone Paula, whom he met in 1959. He will be put it mildly. However, what was not im- making claims they could not back up. That greatly missed by those who knew him, and mediately realised was the level of care that included himself – while he was an excel- his life will be honoured and remembered had been put into ensuring that the ozone lent critic, he often struggled to come up by many for years to come. measurements were correct, or that the si- with suggestions that he was happy with. multaneous meteorological measurements Presumably this was one of the reasons that By Neil Harris and John Pyle (also started in 1957) showed no major the Nature paper took a while to emerge.

SPARC newsletter n° 41 - July 2013 55 SPARC meetings SPARC-related meetings

18-20 September 2013 26-27 July 2013 8-20 September 2013 Ozone Profile Trends (Si2N) Re- ACCESS XII - Twelfth Atmos- NCAS Climate Modelling Summer view Meeting, Helsinki, Finland pheric Chemistry Colloquium for School 2013, Oxford, UK Emerging Senior Scientists, Upton, 26-27 September 2013 NY, USA 9-13 September 2013 Stratospheric Temperature Trends, ESA Living Planet Symposium Reading, UK 28 July - 2 August 2013 2013, Edinburgh, UK Gordon Research Conference for 28-30 October 2013 Atmospheric Chemistry, West Do- 4-7 November 2013 Stratospheric Sulfur and it’s role in ver, VT, USA International Conference on Re- Climate (SSiRC), Atlanta, Georgia, gional Climate - CORDEX 2013, USA 25-30 August 2013 Brussels, Belgium Goldschmidt 2013, Florence, Italy 12-17 January 2014 11-15 November 2013 5th SPARC General Assembly, 26-31 August 2013 First COSPAR Symposium, Bang- Queenstown, New Zealand IAGA 2013 Scientific Assembly, kok, Thailand Mérida, Mexico 19-21 January 2014 9-13 December 2013 SPARC Scientific Steering Group 26-30 August 2013 AGU Fall Meeting 2013, San Fran- meeting, Queenstown, New Zealand International Technical Meeting cisco, CA, USA (ITM) on Air Pollution Modelling and its Application, Miami, USA www.sparc-climate.org/meetings/

SPARC General Assembly 2014

12-17 January 2014 Queenstown, New Zealand

www.sparc2014.org

Important Dates

Registration opens: 1 July 2013 Early-bird registration closes: 1 October 2013 Standard registration close: 8 December 2013

56 SPARC newsletter n° 41 - July 2013