Atmospheric Chemistry and Physics

Understanding emission fluxes from earth’s surface has considerable scientific importance because the variability of atmospheric composition is largely driven by emissions. Due to the rapid regional economic growth, emissions in East Asia have degraded regional air quality and visibility and damaged human health. East Asia emissions also contribute a large share of the global emissions and dominate the Asian continental outflow that travels across the Pacific. Hence they also have significant impacts on global air quality and climate and attract great attention of scientists and policy makers.

To date developing an understanding of emissions has largely relied on bottom-up approaches that aggregate fuel combustion data and emission factors. The large uncertainty in East Asia bottom-up inventories hampers interpretation of observation data, and has been recognized as the bottleneck in limiting the predictive performances of chemical transport models. The community has made considerable efforts to reduce uncertainties in emission inventories, e.g., development of improved emission models, application of inverse models with top-down constraints from in-situ and satellite observations. However, those different approaches are rarely compared and validated with each other. There are still large gaps among different top-down/bottom-up inventories.

Organized by the Global Emissions InitiAtive (GEIA) China Working Group, the East Asia Emissions Assessment (EA2) is designed to bridge these gaps through the integration of different approaches. The assessment includes inter-comparison of current bottom-up inventories in East Asia, development of novel emission inventory models, observation-based constraints on emissions, and evaluation and uncertainty analysis of different emission quantification approaches. The outputs from EA2 studies will not only help reduce uncertainties in East Asia inventories, but also provide improved emission quantification methodologies that can be applied to other world regions.

With the acute societal concerns about air quality, climate change and their effects on health and ecosystems, there is an increasing need for comprehensive, reliable and fast information services on the atmospheric environment. This is also of importance for a range of policy-relevant applications at different scales, from international treaty verification to urban planning for instance. Succeeding to GEMS (Global and regional Earth-system Monitoring using Space and in-situ data) and MACC (Monitoring Atmospheric Composition and Climate), MACC-II* (MACC- Interim Implementation) is the third in a series of projects funded since 2005 through the European Union's Seventh Framework programme to build up the atmospheric service component of the Global Monitoring for Environment and Security (GMES) / Copernicus European programme. MACC-II combines the expertise of its 36 partner institutes from 13 European countries to bridge the gap between the meteorological and environmental communities engaged in research and operational service provision. Using the extensive experience of both communities, MACC-II provides information on atmospheric composition using satellite observations, ground-based observations, and state-of-the-art numerical models (http://www.copernicus-atmosphere.eu). MACC-II not only monitors atmospheric composition over time, but also provides forecasts of air quality, dust storms, fire emissions and solar/UV radiation for a few days ahead both globally and in more detail for Europe. Furthermore, MACC-II supports studies of pollution events and possible responses to mitigate their effects, annual assessments of air quality, and the monitoring of greenhouse gases and their sources and sinks at the Earth's surface. This Special Issue focuses on the world-class research aspects that underpin the continuous development, evaluation and delivery of the GMES/Copernicus services for atmospheric composition.

*: The research leading to these results has received funding from the European Community's Seventh Framework Programme (FP7 THEME [SPA.2011.1.5-02]) under grant agreement n.283576.

In early 2011, a joint initiative was started under the auspices of SPARC, the International Ozone Commission (IO3C), the ozone focus area of the Integrated Global Atmospheric Chemistry Observations (IGACO-O3) programme, and the Network for Detection of Atmospheric Composition Change (NDACC). To aid digestion, an acronym of acronyms, SI2N, was adopted. Reports on the two workshops were published in SPARC Newsletters 37 and 39 (Harris et al., 2011, 2012 – http://www.sparc-climate.org/publications/). The main objective of SI2N is to assess and extend the current knowledge and understanding of measurements of the vertical distribution of ozone, with the aim of providing input to the next WMO/UNEP Scientific Assessment of Ozone Depletion anticipated for 2014. It is effectively a follow-up of the SPARC/IOC/GAW Ozone Profile Assessment (http://www.sparc-climate.org/publications/).

Guidelines for submissions:

• Anything which was or could have been considered for the last Ozone Assessment will not be included.
• Papers published prior to 2011 will be assessed using the following criteria.
• The content of the paper must still be valid and not superceded by more recent work.
• Datasets or technical advances (e.g. algorithm developments) will be looked on more favourably than interpretative papers such as trend analyses (since we assume they will updated if not by the same group.)
• Comparisons with model data or use in model runs can be included as long as they are using current datasets that will be used in SI2N.
• If a paper can be reasonably updated, then that is the preferable option.

Compared to other European regions, the metropolitan area of Barcelona sees relatively high particulate matter due to high anthropogenic emissions, a dry and warm Mediterranean climate and low dispersive conditions due to a unique topographical situation. During the autumn of 2010, the SAPUSS experiment took place, involving measurements of aerosols with multiple techniques occurring simultaneously in order to deduce point source characteristics and to understand the atmospheric processes responsible for their modifications. The unique approach is the large variety of instrumentations deployed simultaneously in a number of monitoring sites used including: a main traffic road, two urban background sites, a regional background site and two towers within the city (150 m and 545 m above sea level, 150 m and 80 m above ground, respectively). The purpose of this issue is to contribute to the advancement of our understanding of the sources and the evolution of aerosols in the atmosphere. This integrated study would also be of interest for other similar sites worldwide.

The Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP) is primarily designed to characterize radiative forcings in the Climate Model Intercomparison Project phase 5 (CMIP5) historical and future climate simulations, and to provide diagnostics to facilitate understanding of differences in those forcings between models. Most of the participating ACCMIP models were also used in CMIP5 simulations. The primary emphasis is on tropospheric ozone and aerosols, both of which have substantial climate forcing that varies widely in space and time. ACCMIP includes extensive evaluations of the models against observations. Papers cover a wide variety of analyses, including studies of ozone, methane, hydroxyl radical, and multiple aerosol types, their role in issues from climate change to air quality in the past and future, and evaluation against remote sensing data, in situ observations, and ice cores.

The joint ACP/AMT special issue on "Observations and modeling of aerosol and clouds properties for climate studies" brings together publications on characterization of aerosol and cloud properties and their impact on climate.

This special issue is motivated by presentations and discussions happened during the Workshop on "Observations and modeling of aerosol and clouds properties for climate studies" held in Paris, Université Pierre et Marie Curie, 12-14 September 2011 (http://www-loa.univ-lille1.fr/workshop). The Workshop gathered more than 130 scientists already involved in decades of collaboration, and generated a number of insightful discussions on the community accomplishments and outlined the most appealing dynamics for near future remote sensing activities. The advances and challenges of accessing aerosol and cloud effects on climate dynamics were discussed. It also included coordination between the international space-based observations of the atmosphere activities and evaluation of satellite products with the help of modelers, ground-based remote sensing and in situ measurement scientists.

We encourage submissions describing the studies presented at the workshop and also coming from relevant broader community.

Main topics are:

• Achievements in characterization of aerosols, clouds and Earth's atmosphere.
• Inversions, new ideas and algorithms to derive detailed aerosol and cloud properties: passive and active remote sensing, characterization from satellite, ground-based, airborne and in situ.
• Modeling of aerosols, clouds and their climate effects.
• Progress expected from future satellite missions.

Developing Arctic Modelling and Observing Capabilities for Long-term Environmental Studies (DAMOCLES) was the flagship EU project for the IPY. It concerned 47 partners from about 10 European Countries and triggered an active international scientific cooperation with Russia, China, Japan and the USA. At the time the DAMOCLES contract ended about one year ago, more than 150 scientific papers appeared in peer-reviewed publications under DAMOCLES. There are more publications to come as evidenced during the final General Assembly of Damocles in Tromsø, Norway in May 2010. During this final GA it was agreed and decided that DAMOCLES should find an appropriate scientific journal to release an important set of publications based on 6 synthetic papers and up to 30 topical papers. After some investigation it was decided to contact the European Geosciences Union Copernicus Publications to check the adequacy for submitting Damocles results dedicated to Ocean, Atmosphere and Sea Ice sciences in three Copernicus relevant journals: Atmospheric Chemistry and Physics (ACP), The Cryosphere (TC) and Ocean Science (OS).

The special issue publishes results from the BORTAS aircraft campaign in summer 2011 and related ground-based and space-borne measurement studies in 2010 and 2011. The overarching goal of BORTAS is to investigate the connection between the composition and the distribution of boreal biomass burning outflow, ozone production and loss within the outflow, and the resulting perturbation to oxidant chemistry in the troposphere. In July 2011, the FAAM146 research aircraft was used to sample the outflow from boreal fires over the Western boundary of the North Atlantic. These aircraft-based measurements were complemented by satellite data and a range of ground-based measurements.

The data obtained in the BORTAS campaign are used to:

• describe observed chemistry within plumes, with particular attention to the NOy and organic chemistry;
• derive a reduced chemical mechanism from the Master Chemical Mechanism (MCM), informed by the measurements, suitable for use in a global chemical transport model to reproduce observed chemistry within the plumes;
• quantify the impact of boreal forest fires on oxidant chemistry over the temperate and subtropical Atlantic using a nested 3-D chemistry transport model, driven by assimilated field measurements and the reduced chemical mechanism; and
• detect, validate and quantify the impact of boreal biomass burning on global tropospheric composition using data from space-borne sensors.

The Pan European Gas AeroSOls-climate interaction Study (PEGASOS) European large scale integrating project brings together most of the leading European research groups, with state of the art observational and modeling facilities to:

1. Quantify the magnitude of regional to global feedbacks between atmospheric chemistry and a changing climate and to reduce the corresponding uncertainty of the major ones.
2. Identify mitigation strategies and policies to improve air quality while limiting their impact on climate change.

The project will combine development of anthropogenic and biogenic emission inventories, laboratory studies in some of the premier European smog chamber facilities, field measurements over Europe using a Zeppelin combined with mobile and fixed ground platforms, air quality and climate models, and policy analysis to achieve its objectives.

The SI will include papers on the experimental, theoretical and modelling results related to the CERN CLOUD experiment. The scientific focus of the experiment is to make fundamental measurements of aerosol nucleation under highly controlled laboratory conditions, including the effects of natural and synthetic cosmic rays. There were two campaigns of a month long: the first (2010) focused on inorganic aerosols and cosmic ray influences (NH3/H2SO4). The second campaign (June 2011) focuses on organic impacts on nucleation. There are also detailed modelling studies, plus papers on parameterisation development and global model applications.

The special issue aims at collecting research papers from the WAVACS final workshop and, more in general, from the broader community involved in the action.

Main topics are:

• Water vapor time series and trends;
• Cirrus inhomogeneities and relationship to the environmental water vapor field and radiative transfer Submissions of papers dealing with broader WAVACS objectives are also encouraged:
  • Accuracy of atmospheric water vapor observations and harmonization;
  • Results from specific field campaign;
  • Process related to water vapor isotopes;
  • Regional/Global modelling and data assimilation.

The Earth system is undergoing extensive change, with important implications for human health, resource management, ecosystem services and the environment. The ability to predict these changes and their impacts on time scales of months to a decade is becoming increasingly important. Key to improving the predictability of Earth system behavior over these time scales is an improved understanding of the coupling between water, energy and biogeochemical cycles in a multi-scale modeling framework. Robust predictions at these time scales require coordinated modeling, observations and process studies that explicitly address the coupled water, energy and biogeochemical cycles at multiple temporal and spatial scales. The BEACHON (Biosphere-atmosphere-hydrosphere-interactions of Energy, Aerosols, Carbon, Organics, and Nitrogen) project initiated two complementary field studies in a ponderosa pine woodland to enhance understanding of the roles of biogenic volatile organic compounds (BVOC), aerosols, nitrogen trace gases and oxidants in linking and regulating the carbon and water cycles. The BEACHON-ROCS (Rocky mountain Organic Carbon Study) was conducted in summer 2010 and was focused on understanding BVOC oxidation and the impact on atmospheric oxidants. The BEACHON-RoMBAS (Rocky Mountain Biogenic Aerosol Study) will be conducted in summer 2011 and will be focused on understanding the formation, growth and properties of biogenic organic aerosol. This special issue will highlight field and modeling investigations associated with the BEACHON ROCS and ROMBAS studies.

iLEAPS is the land-atmosphere core project of the International Geosphere-Biosphere Programme (IGBP). The scientific goal of iLEAPS is to provide understanding how interacting physical, chemical and biological processes transport and transform energy and matter through the land-atmosphere interface. Atmospheric Chemistry and Physics (ACP) and Biogeosciences (BG) have opened a joint special issue on iLEAPS-related science, and you are welcome to contribute by sending manuscripts on land-atmosphere interactions to this joint issue via either ACP or BG.

The HUMPPA-COPEC 2010 intensive field measurement campaign was conducted at the Boreal forest research station SMEAR II (Station for Measuring Ecosystem-Atmosphere Relation) in Hyytiälä, Finland from 12th July-12th August 2010. This campaign was focused on characterizing the summertime chemistry and physics over the Boreal forest when emission fluxes of volatile organic compounds (VOC), OH initiated photochemistry, and particle growth rates reach their seasonal maximum. An international consortium co-ordinated by the Max Planck Institute for Chemistry, Germany and the University of Helsinki, Finland was assembled to quantity a comprehensive suite of gas and particle phase species. The natural biogenic emissions from the surrounding coniferous forest were characterized under the long summer daylight and warm temperature conditions. Furthermore the campaign sought to capture and characterize influences from biomass burning, urban anthropogenic pollution and nearby sawmills at the site.

The MEGAPOLI PARIS campaigns in summer 2009 and in winter 2010 aimed at better quantifying sources of primary and secondary aerosol in and around a large agglomeration and to document their evolution in the megacity plume. A focus was put on carbonaceous aerosol, where uncertainties are major. As related issues, also gas phase photochemistry and the evolution of dynamical conditions during the campaign were addressed. Analysis of experimental data and modelling studies are solicited. Papers on timescales beyond the campaign, but dealing with this target region, are also welcome.

The atmospheric composition of the past is stored in the bubbles of polar ice sheets and glaciers. This archive now reaches back to 800,000 years before present. The last several decades of the atmospheric composition history is not yet occluded in the ice but can be found in the open porous layer at the surface of the ice sheet at high resolution. In this layer a large amount of gas is available which allows for analyses not (yet) possible from the bubble section, and in many cases recovery of atmospheric histories of compounds for which there were no direct measurements in the atmosphere. Within the NEEM deep drilling project in Greenland air was collected from the firn during two very comprehensive field sampling seasons and several surface drillings. Laboratories from Europe, Australia, the US and Japan have measured this air for a suite of components in what is the most extensive set of firn air measurements yet made. In addition, as part of this project an extensive modeling effort is being conducted to better understand the translation from the composition found in the firn to the atmospheric history. The purpose of this issue is to bundle all information from the NEEM measuring campaign and the corresponding modeling attempt at one place. However, we do not want to limit the issue to the NEEM project. We welcome contributions from other ongoing and previous firn air campaigns, and hope that the special issue will provide a comprehensive state-of-the-art view of firn air science.

From 09 – 24 October 2009 the IFM-GEOMAR (Kiel, Germany) conducted a cruise with RV Sonne in the tropical western Pacific to investigate trace gas emissions on a transit between Tomakomai (Japan) and Townsville (Australia) in different biogeochemical regimes and their stratospheric contribution.

The project aims to reduce uncertainties in stratospheric halogen loading and ozone depletion resulting from oceanic emissions and atmospheric transport of ozone depleting substances. The tropical oceans are a known source of reactive bromine and iodine to the atmosphere in the form of short-lived brominated and iodinated methanes as e.g. bromoform (CHBr3), dibromomethane (CH2Br2) and methyl iodide (CH3I). Elevated atmospheric concentrations above the oceans are related to oceanic supersaturations of the compounds and to natural photochemical and biological production. Increasing scientific evidence suggests that there could be significant contributions from the ocean derived, halogen-containing short lived substances to stratospheric ozone depletion, which is addressed in the scientific program of the Sonne ship cruise. This cruise is part of the national research project "TransBrom"(www.ifm-geomar.de/~transbrom). The tropical western Pacific is a largely uncharacterized region for the oceanic compounds and a projected hot spot for their emissions and transport pathways into the stratosphere.

Of particular relevance during the cruise was the characterization of the climate-sensitive oceanic emission strengths of a suite of halogenated gases in various biogeochemical regimes and the investigation of the real contribution of these emissions to stratospheric bromine with a new transport model. This was validated by the atmospheric structure determination through intense radio, ozone and water vapor sounding during the cruise. We further investigated more marine trace gases as nitrous oxide (N2O), dimethylsulfide (DMS), oxygen (O2) and carbon dioxide (CO2), and possible relationships between these compounds. Satellite measurements of phytoplankton groups, obtained by special retrieval methods from the SCIAMACHY and GOME-2 instruments give further information about biogeochemical conditions during the cruise. The total atmospheric column concentrations and atmospheric concentration profiles of several other long-lived trace gases were also determined. These measurements allow studying the transport of tropospheric trace gases through the tropopause, in this way yielding information on the entry of natural and anthropogenic tropospheric trace gases into the stratosphere.

This might have been the first oceanic study, we are aware of, where the transport of oceanic emission of halogenated trace gases from the surface into the stratosphere was investigated. The impact of the natural ozone depleting substances will be highly sensitive to climate change in terms of their emissions to the atmosphere, their transport, and their chemical processing. Future changes in the mechanisms, that regulate these processes, are largely unknown. Therefore the oceanic emissions have the potential to cause surprises in the future evolution of the ozone layer in the changing climate, unless they are better understood. The measurements are thus needed to improve the understanding of future stratospheric halogen loading and therewith ozone depletion.

Eastern Asia has a large number of megacities including many regions of ongoing rapid urbanization with the potential to produce new megacities in the coming decades. Recent field experiments and associated modeling studies in eastern China, Korea and Japan have demonstrated that human activities in Eastern Asia megacities have had dramatic impacts on atmospheric chemistry and physics in this region which have important implications for air quality and climate. These studies are characterizing emission and ambient distributions, atmospheric chemical processing, aerosol and oxidant production and growth, urban/rural interactions, and long range transport. It is widely recognized that individual megacities can influence other regions and effective air pollution control strategies in any of these locations requires a better understanding of emissions, chemical processing and interactions within the entire region. This special issue will highlight recent field studies and associated modeling investigations that address scientific questions associated with the impact of Eastern Asia megacities on atmospheric chemistry and physics. Papers submitted to this special issue will focus on Eastern Asia megacity studies of chemical emission and deposition, atmospheric chemical composition and processing, impacts on weather and climate, regional transport and related topics. This will include investigations conducted within specific megacities of Korea, Japan and Eastern China as well as larger scale studies linking individual Eastern Asia megacities to the regional and global environment.

Clouds constitute one of the major uncertainties in understanding the climate system and changes in the clouds as a consequence of global climate change is not well constrained by observations. This is particularly true in the Arctic, where clouds constitute the larges single factor affecting the surface energy balance, and therefore on melting and freezing of sea ice.

ASCOS is a highly interdisciplinary project with a major field experiment in the central Arctic Ocean during August/September 2008, approximately at 87N and 7W, deployed on the Swedish icebreaker Oden as a part of the International Polar Year (IPY). The ASCOS main target is to study the formation and life cycle of Arctic summer low-level clouds. To achieve this we deployed instruments for process level observations in a column from 0.5 km in to the ocean, through the ocean/ice surface up through the atmospheric boundary layer, and to the top of the troposphere (also see http://www.ascos.se). ASCOS measurements range from in-situ observations, to surface-based remote sensing, to airborne observations. The most intense observations were during a 3-week ice drift, starting with typical Arctic summer melt conditions and ending with the initial freeze-up of autumn. ASCOS was also coordinated with the Arctic Mechanisms of Interaction between the Surface and Atmosphere (AMISA) project, providing airborne measurements from the NASA DC8 research aircraft in the vicinity of the ASCOS column, flying in from Kiruna, Sweden.

The science team on Oden consisted of 33 researchers from 14 institutes in 11 different countries; many more are involved in analysis and associated modelling studies. This, and the experimental set-up, makes ASCOS the most extensive atmosphere-oriented experiment in the central Arctic for the entire IPY. ASCOS science cuts across several disciplines, with links to microbial life in ocean and ice, atmospheric chemistr

The VAMOS Ocean-Cloud-Atmosphere-Land Study (VOCALS) is an international CLIVAR/VAMOS program designed to develop and promote scientific activities leading to improved understanding, model simulations, and predictions of the southeastern Pacific (SEP) coupled ocean-atmosphere-land system, on diurnal to interannual timescales. The major components of VOCALS are a modeling program with a model hierarchy ranging from the local to global scales, a major international field program (The VOCALS Regional Experiment, VOCALS-REx), and a suite of extended observations from regular research cruises, instrumented moorings, and satellites. The combination of intensive field measurements, long-term observations, and modeling will provide important insights that will directly benefit climate modeling. Some 200 scientists from 40 institutions in 8 nations are currently participating in VOCALS. Details of the three main components of VOCALS are given below.

The SEP climate is a tightly coupled system involving poorly understood interactions between clouds, aerosols, marine boundary layer (MBL) processes, upper ocean dynamics and thermodynamics, coastal currents and upwelling, large-scale subsidence, and regional diurnal circulations, to the west of the Andes mountain range.

Further information on VOCALS can be found on the program website http://www.eol.ucar.edu/projects/vocals