Analysis and comparison of trends in concentrations and emissions of VOC and CO and VOC:CO ratios in urban European cities

Since 2007, more than half of the world's population live in urban areas. Megacities, urban agglomerations with more than 10 million inhabitants, are rapidly increasing in number: in 1950 there were only two, New York and Tokyo with ~12 million, while by 2005 there were already 20, with Tokyo ranging the 35 millions. The urban atmospheres of these megacities are dominated by pollutants associated with vehicular emissions, as well as the formation of secondary pollutants responsible for photochemical smog. A comparative assessment of emissions and concentrations of volatile organic compounds (VOC) and carbon monoxide (CO) ratios in London (L) and Paris (P) is hereby presented. The work is based on three recent studies by Baker et al. (2008), Parrish et al. (2009) and von Schneidemesser et al. (in press) where concentrations of these compounds were analyzed for 28 US cities in the former and some global megacities in the second and third studies. Considering the fact that VOC provide information on the main emissions sources of cities, these studies found that even though concentrations of VOC varied greatly among cities, the ratio with the combustion tracer CO remained rather constant and was very useful for city comparison, as well as a good indicator of traffic emissions. VOC patterns in ambient air concentrations were observed to be similar in most cities, being able to consider that deviations from those patterns could be the result of measurement problems. Nevertheless, the representation of these emissions in global inventories has large uncertainties. The goal of our study is to compare and contrast emission inventory estimates with measured ambient concentrations of non-methane hydrocarbons (NMHC) and CO, as well as NMHC:CO ratios. Within the European CityZen project we have built an updated global emissions inventory with the best available datasets of anthropogenic, biomass burning and natural sources. As part of this research we will follow the same approach to compare emissions ratios between NMHC and CO for the megacities region of Paris and London and to compare these trends with measured ambient concentrations from three monitoring sites: Eltham (L) suburban station, Marylebone Road (L) kerbside station and Les Halles (P) urban station for the period 1997-2006

The impact of anthropogenic VOC speciation on SOUTH AMERICAN MEGACITIES’ URBAN ATMOSPHERES

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Evaluation of chemistry transport model simulations in the MACC project: comparison with satellite and in-situ data

The distribution and variability of tropospheric ozone and precursors are being assessed within the European project MACC using the MOZART chemistry transport model coupled with the ECMWF integrated forecasting system (IFS). Reanalysis simulations were performed for the 2003-2008 period providing information on global tropospheric composition and regional air quality. With the aim to improve forecasting system of the tropospheric ozone and precursors, several validation exercises of model results were performed using independent in-situ and satellite data. Model simulations were compared with surface data from NOAA-GMD, EMEP and other surface networks as well as with tropospheric NO2 and CO retrievals from SCIAMACHY and MOPITT instruments. This provides an evaluation of the model performance regarding long-range transport of pollutants and air quality over polluted regions such as Asia, Siberia, Europe and North America. Simulations were also performed with assimilation of satellite data from different sensors and without coupling with ECMWF IFS. Model results are improved when ECMF IFS assimilation modules were used to constrain the tropospheric CO by satellite measure- ments. Uncertainties in satellite retrieval techniques could explain some biases found in model results compared to measurements. Indeed, changes in MOPITT retrieval algorithm resulted in important changes in CO observations leading also to strong impact on modeled CO in runs using assimilation. Assimilation of surface and airborne mea- surements could reduce the discrepancy between the model and some surface measurements in particular over the northern latitudes, although uncertainties in anthropogenic and biomass burning emissions inventories may explain a part of the discrepancy. Comparisons with MOZART simulations performed within the CityZen project will also be discussed particularly in order to assess sensitivity of model results to emissions

Access to Emissions Distributions and Related Ancillary Data through the ECCAD database

During the past few years, the ECCAD (Emissions of atmospheric Compounds & Compilation of Ancillary Data) database was developed in order to provide a user-friendly access to surface emissions and ancillary data, i.e. data on land use, active fires, burned areas, population, etc. This database and the emissions portal of the GEIA (Global Emissions InitiAtive) project have been merged. ECCAD is a sub-project of the ETHER French Atmospheric Chemistry Data Centre (CNES and CNRS, http://www.pole-ether.fr). The ECCAD database includes currently a large diversity of datasets, which provide global and regional surface emissions for a large set of chemical compounds. All the data are provided at a 0.5x0.5 or 1x1 degree resolution. ECCAD provides detailed metadata on each of the datasets, including information on complete references and methodology, and links to the original inventories. Several tools are provided for the visualization of the data, for computing global and regional totals and for an interactive spatial and temporal analysis. The data can be downloaded as interoperable NetCDF CF-compliant files, i.e. the data are compatible with many other client interfaces and can be downloaded through requests as geographical coverage or geo-referenced maps. ECCAD has currently more than 700 users originating from more than 30 countries. ECCAD benefits from this large international community of users to expand the number of emission datasets made available. The ECCAD database and the web interface are in continuous development: new tools are being built to improve the analysis and comparison of emissions and ancillary data. These new tools include a regridding tool, arithmetic expressions to combine different maps, interactive selection of scale values, and new tools for temporal profiles analysis. Comparisons of data at different scales is also in development. An online module to calculate biomass burning emissions is being improved, and will also be extended to anthropogenic emissions. The presentation will provide information on all the datasets available within ECCAD, as well as examples of the analysis work that can be done online from the database. All the datasets, associated metadata, tools and download can be achieved from the ECCAD website: http://eccad.pole-ether.f

Evolution of the distribution of tropospheric ozone and its precursores during the 1997-2030 period

As part of the CityZen (Megacity - Zoom for the Environment) European project, global and regional European chemistry transport models were used to simulate the past evolution of the composition of the troposphere during the 1997-2008 period, as well as its future evolution up to 2030. The simulations were performed using a consistent dataset for surface emissions. European emissions for the past period were provided by the European Monitoring and Evaluation Programme (EMEP) and processed by INERIS. The global emissions are given by the MACCity emissions dataset, derived from the ACCMIP (Emissions for Atmospheric Chemistry and Climate Model Intercomparison Project) dataset. We will discuss the consistency between global and regional emissions dataset, focusing on a few regions, and more particularly on Europe, the United States and China. The future emissions are based on the GEA (Global Energy Assessment) scenarios developed by IIASA. Two scenarios will be considered in this study: the first scenario assumes a full implementation of all current and planned air pollution legislation world-wide until 2030. The second scenario assumes, in addition to air quality legislation, implementation of a stringent climate policy corresponding to a 2 degree global temperature target including a moderate energy access policy corresponding to microfinance as well as fuel subsidy. We will discuss the results obtained by the simulations for the full period considered, with a focus on NOx, CO, OH and ozone. We will also discuss comparisons of the simulations provided by the reanalysis of the atmospheric composition from the MACC European project. Comparisons with surface observations of CO and ozone at selected sites located at different latitudes for the 1998-2008 period will be presented. The results of the simulations for the future will also be compared with simulations performed for different scenarios, such as the one provided by the RCPs (Representative Concentration Pathways)

Evolution of the distribution of tropospheric chemical species during the past decade

Megacities, with a population exceeding ten million inhabitants, represent hot spots of emissions that need to be correctly quantified in order to evaluate their effects at the local, regional and global scale. Within the 7th Framework European project CityZen (Megacity - Zoom for the Environment), the impact of changes in emissions on the global distributions of chemical compounds is being assessed, with a focus on the impact of megacities in Europe, Northern Africa and China. The goal of the project is to comprehend the feedbacks between climate change and air quality from the largest world cities at the global and regional scales. In order to simulate the changes in the distribution of gaseous compounds as well as aerosols we have used the MOZART (Model for OZone And Related chemical Tracers) global chemistry transport model. This model is driven by offline meteorological fields: for the present study we have used the meteorological fields provided by the National Center for Environmental Prediction (NCEP). The focus of the study is the 1996-2007 period, during which the changes in the distribution of the chemical compounds related to changes in emissions during that period will be discussed. The global emissions used in the present study are derived from the new dataset developed in support of the next IPCC (Intergovernmental Panel on Climate Change) AR5 report under discussion. We will discuss the methodology we have used to update the IPCC anthropogenic emissions up to year 2007. The new emissions inventory for Europe developed within CityZen for the 1996-2007 period will be discussed and compared with the emissions provided by other inventories. Furthermore, we will discuss the biomass burning inventory used in this work, which provides monthly averaged emissions for the full period of the study. Emissions of biogenic volatile organic compounds are derived from the most recent version of the MEGAN (Model of Emissions of Gases and Aerosols from Nature) model. Simulations covering the considered period will be performed using different combinations of the emissions of the datasets being performed. We will discuss the results of the simulations, focusing more particularly on the simulations using either IPCC dataset or a combined IPCC / European emissions dataset, or different Biogenic Volatile Organic Compounds emissions. We will discuss the changes in the distribution of tropospheric chemical species from the different simulations, considering both gaseous compounds and different types of aerosols

Monitoring the changes in the tropospheric composition over the past two decades using Satellite observations and CTM

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