Atmospheric Environment (v.43, #33)

FOREWORD by José Manuel Silva Rodríguez (5135).

Editorial by Sandro Fuzzi; Michela Maione (5136-5137).

Atmospheric composition change: Climate–Chemistry interactions by I.S.A. Isaksen; C. Granier; G. Myhre; T.K. Berntsen; S.B. Dalsøren; M. Gauss; Z. Klimont; R. Benestad; P. Bousquet; W. Collins; T. Cox; V. Eyring; D. Fowler; S. Fuzzi; P. Jöckel; P. Laj; U. Lohmann; M. Maione; P. Monks; A.S.H. Prevot; F. Raes; A. Richter; B. Rognerud; M. Schulz; D. Shindell; D.S. Stevenson; T. Storelvmo; W.-C. Wang; M. van Weele; M. Wild; D. Wuebbles (5138-5192).
Chemically active climate compounds are either primary compounds like methane (CH4), removed by oxidation in the atmosphere, or secondary compounds like ozone (O3), sulfate and organic aerosols, both formed and removed in the atmosphere. Man-induced climate–chemistry interaction is a two-way process: Emissions of pollutants change the atmospheric composition contributing to climate change through the aforementioned climate components, and climate change, through changes in temperature, dynamics, the hydrological cycle, atmospheric stability, and biosphere-atmosphere interactions, affects the atmospheric composition and oxidation processes in the troposphere. Here we present progress in our understanding of processes of importance for climate–chemistry interactions, and their contributions to changes in atmospheric composition and climate forcing. A key factor is the oxidation potential involving compounds like O3 and the hydroxyl radical (OH). Reported studies represent both current and future changes. Reported results include new estimates of radiative forcing based on extensive model studies of chemically active climate compounds like O3, and of particles inducing both direct and indirect effects. Through EU projects like ACCENT, QUANTIFY, and the AeroCom project, extensive studies on regional and sector-wise differences in the impact on atmospheric distribution are performed. Studies have shown that land-based emissions have a different effect on climate than ship and aircraft emissions, and different measures are needed to reduce the climate impact. Several areas where climate change can affect the tropospheric oxidation process and the chemical composition are identified. This can take place through enhanced stratospheric–tropospheric exchange of ozone, more frequent periods with stable conditions favoring pollution build up over industrial areas, enhanced temperature induced biogenic emissions, methane releases from permafrost thawing, and enhanced concentration through reduced biospheric uptake. During the last 5–10 years, new observational data have been made available and used for model validation and the study of atmospheric processes. Although there are significant uncertainties in the modeling of composition changes, access to new observational data has improved modeling capability. Emission scenarios for the coming decades have a large uncertainty range, in particular with respect to regional trends, leading to a significant uncertainty range in estimated regional composition changes and climate impact.
Keywords: Atmosphere climate chemistry; Feedbacks modelling;

Atmospheric composition change: Ecosystems–Atmosphere interactions by D. Fowler; K. Pilegaard; M.A. Sutton; P. Ambus; M. Raivonen; J. Duyzer; D. Simpson; H. Fagerli; S. Fuzzi; J.K. Schjoerring; C. Granier; A. Neftel; I.S.A. Isaksen; P. Laj; M. Maione; P.S. Monks; J. Burkhardt; U. Daemmgen; J. Neirynck; E. Personne; R. Wichink-Kruit; K. Butterbach-Bahl; C. Flechard; J.P. Tuovinen; M. Coyle; G. Gerosa; B. Loubet; N. Altimir; L. Gruenhage; C. Ammann; S. Cieslik; E. Paoletti; T.N. Mikkelsen; H. Ro-Poulsen; P. Cellier; J.N. Cape; L. Horváth; F. Loreto; Ü. Niinemets; P.I. Palmer; J. Rinne; P. Misztal; E. Nemitz; D. Nilsson; S. Pryor; M.W. Gallagher; T. Vesala; U. Skiba; N. Brüggemann; S. Zechmeister-Boltenstern; J. Williams; C. O'Dowd; M.C. Facchini; G. de Leeuw; A. Flossman; N. Chaumerliac; J.W. Erisman (5193-5267).
Ecosystems and the atmosphere: This review describes the state of understanding the processes involved in the exchange of trace gases and aerosols between the earth's surface and the atmosphere. The gases covered include NO, NO2, HONO, HNO3, NH3, SO2, DMS, Biogenic VOC, O3, CH4, N2O and particles in the size range 1 nm–10 μm including organic and inorganic chemical species. The main focus of the review is on the exchange between terrestrial ecosystems, both managed and natural and the atmosphere, although some new developments in ocean–atmosphere exchange are included. The material presented is biased towards the last decade, but includes earlier work, where more recent developments are limited or absent.New methodologies and instrumentation have enabled, if not driven technical advances in measurement. These developments have advanced the process understanding and upscaling of fluxes, especially for particles, VOC and NH3. Examples of these applications include mass spectrometric methods, such as Aerosol Mass Spectrometry (AMS) adapted for field measurement of atmosphere–surface fluxes using micrometeorological methods for chemically resolved aerosols. Also briefly described are some advances in theory and techniques in micrometeorology.For some of the compounds there have been paradigm shifts in approach and application of both techniques and assessment. These include flux measurements over marine surfaces and urban areas using micrometeorological methods and the up-scaling of flux measurements using aircraft and satellite remote sensing. The application of a flux-based approach in assessment of O3 effects on vegetation at regional scales is an important policy linked development secured through improved quantification of fluxes. The coupling of monitoring, modelling and intensive flux measurement at a continental scale within the NitroEurope network represents a quantum development in the application of research teams to address the underpinning science of reactive nitrogen in the cycling between ecosystems and the atmosphere in Europe.Some important developments of the science have been applied to assist in addressing policy questions, which have been the main driver of the research agenda, while other developments in understanding have not been applied to their wider field especially in chemistry-transport models through deficiencies in obtaining appropriate data to enable application or inertia within the modelling community. The paper identifies applications, gaps and research questions that have remained intractable at least since 2000 within the specialized sections of the paper, and where possible these have been focussed on research questions for the coming decade.
Keywords: Dry deposition; Trace gas fluxes; Resuspension; Biogenic emissions; Compensation points;

Atmospheric composition change – global and regional air quality by P.S. Monks; C. Granier; S. Fuzzi; A. Stohl; M.L. Williams; H. Akimoto; M. Amann; A. Baklanov; U. Baltensperger; I. Bey; N. Blake; R.S. Blake; K. Carslaw; O.R. Cooper; F. Dentener; D. Fowler; E. Fragkou; G.J. Frost; S. Generoso; P. Ginoux; V. Grewe; A. Guenther; H.C. Hansson; S. Henne; J. Hjorth; A. Hofzumahaus; H. Huntrieser; I.S.A. Isaksen; M.E. Jenkin; J. Kaiser; M. Kanakidou; Z. Klimont; M. Kulmala; P. Laj; M.G. Lawrence; J.D. Lee; C. Liousse; M. Maione; G. McFiggans; A. Metzger; A. Mieville; N. Moussiopoulos; J.J. Orlando; C.D. O'Dowd; P.I. Palmer; D.D. Parrish; A. Petzold; U. Platt; U. Pöschl; A.S.H. Prévôt; C.E. Reeves; S. Reimann; Y. Rudich; K. Sellegri; R. Steinbrecher; D. Simpson; H. ten Brink; J. Theloke; G.R. van der Werf; R. Vautard; V. Vestreng; Ch. Vlachokostas; R. von Glasow (5268-5350).
Air quality transcends all scales with in the atmosphere from the local to the global with handovers and feedbacks at each scale interaction. Air quality has manifold effects on health, ecosystems, heritage and climate. In this review the state of scientific understanding in relation to global and regional air quality is outlined. The review discusses air quality, in terms of emissions, processing and transport of trace gases and aerosols. New insights into the characterization of both natural and anthropogenic emissions are reviewed looking at both natural (e.g. dust and lightning) as well as plant emissions. Trends in anthropogenic emissions both by region and globally are discussed as well as biomass burning emissions. In terms of chemical processing the major air quality elements of ozone, non-methane hydrocarbons, nitrogen oxides and aerosols are covered. A number of topics are presented as a way of integrating the process view into the atmospheric context; these include the atmospheric oxidation efficiency, halogen and HOx chemistry, nighttime chemistry, tropical chemistry, heat waves, megacities, biomass burning and the regional hot spot of the Mediterranean. New findings with respect to the transport of pollutants across the scales are discussed, in particular the move to quantify the impact of long-range transport on regional air quality. Gaps and research questions that remain intractable are identified. The review concludes with a focus of research and policy questions for the coming decade. In particular, the policy challenges for concerted air quality and climate change policy (co-benefit) are discussed.
Keywords: Atmosphere; Troposphere; Air quality; Emissions; Climate; Co-benefit; Oxidation chemistry; Aerosols; Transport of pollutants; Ozone;

Measuring atmospheric composition change by P. Laj; J. Klausen; M. Bilde; C. Plaß-Duelmer; G. Pappalardo; C. Clerbaux; U. Baltensperger; J. Hjorth; D. Simpson; S. Reimann; P.-F. Coheur; A. Richter; M. De Mazière; Y. Rudich; G. McFiggans; K. Torseth; A. Wiedensohler; S. Morin; M. Schulz; J.D. Allan; J.-L. Attié; I. Barnes; W. Birmili; J.P. Cammas; J. Dommen; H.-P. Dorn; D. Fowler; S. Fuzzi; M. Glasius; C. Granier; M. Hermann; I.S.A. Isaksen; S. Kinne; I. Koren; F. Madonna; M. Maione; A. Massling; O. Moehler; L. Mona; P.S. Monks; D. Müller; T. Müller; J. Orphal; V.-H. Peuch; F. Stratmann; D. Tanré; G. Tyndall; A. Abo Riziq; M. Van Roozendael; P. Villani; B. Wehner; H. Wex; A.A. Zardini (5351-5414).
Scientific findings from the last decades have clearly highlighted the need for a more comprehensive approach to atmospheric change processes. In fact, observation of atmospheric composition variables has been an important activity of atmospheric research that has developed instrumental tools (advanced analytical techniques) and platforms (instrumented passenger aircrafts, ground-based in situ and remote sensing stations, earth observation satellite instruments) providing essential information on the composition of the atmosphere. The variability of the atmospheric system and the extreme complexity of the atmospheric cycles for short-lived gaseous and aerosol species have led to the development of complex models to interpret observations, test our theoretical understanding of atmospheric chemistry and predict future atmospheric composition. The validation of numerical models requires accurate information concerning the variability of atmospheric composition for targeted species via comparison with observations and measurements.In this paper, we provide an overview of recent advances in instrumentation and methodologies for measuring atmospheric composition changes from space, aircraft and the surface as well as recent improvements in laboratory techniques that permitted scientific advance in the field of atmospheric chemistry. Emphasis is given to the most promising and innovative technologies that will become operational in the near future to improve knowledge of atmospheric composition. Our current observation capacity, however, is not satisfactory to understand and predict future atmospheric composition changes, in relation to predicted climate warming. Based on the limitation of the current European observing system, we address the major gaps in a second part of the paper to explain why further developments in current observation strategies are still needed to strengthen and optimise an observing system not only capable of responding to the requirements of atmospheric services but also to newly open scientific questions.
Keywords: Atmosphere; Instrumentation; Observation; Air quality; Climate;

Educating the next generation of atmospheric scientists within a European Network of Excellence by E. Schuepbach; E. Uherek; A. Ladstätter-Weissenmayer; M.J. Jacob (5415-5422).
Keywords: European Network of Excellence; Atmospheric composition change; Integrated Learning Environment; Next generation; Early-career scientists; Schools; Science workshops; Transferrable skills; E-learning;

Atmospheric composition change research: Time to go post-normal? by Ângela Guimarães Pereira; Frank Raes; Tiago De Sousa Pedrosa; Paulo Rosa; Søsser Brodersen; Michael Søgaard Jørgensen; Francisco Ferreira; Xavier Querol; John Rea (5423-5432).
For more than two decades a number of frameworks for scientific knowledge production are being proposed by science and technology researchers. They all advocate an extended involvement of non-specialists, in particular when it comes to knowledge production applicable to practical societal problems. We look to what extent these new frameworks have taken ground within a particular research community: the ACCENT Network of Excellence which coordinates European atmospheric chemistry and physics research applicable to air pollution and climate change. We did so by stimulating a debate through a “blog”, a survey and in-depth interviews with ACCENT scientists about the interaction between science, policy making and civil society, to which a great deal of ACCENT member contributed in writing or verbally. Most of them had interactions with policy makers and/or the general public, and they generally believe that interactions with spheres other than the scientific are needed. While such interactions give personal insight and satisfaction, they seem to have little impact on the goals and the practice of the scientific work itself. Extended frameworks of science production that go beyond the disciplinary mode seem to emerge at the level of individual scientists, yet they still need to find their way to the level of scientific project management. In this paper we discuss the justifications and barriers to implement a higher degree of extended knowledge integration in applied science projects such as ACCENT. It is felt that the community of atmospheric chemists and physicists is mature for such an implementation and recommendations are given to help and make this happen.
Keywords: Atmospheric science; Science communication; Policy formulation; Post-normal science; Accent community;