Abstract: A simple approach for accurately estimating an urban concentration increment on top of the regional background for urban areas in Europe is presented. The method operates by establishing a functional relationship between the concentration increment and the local meteorological situation, the city characteristics, the urban emissions and the background concentrations. In the current study, the above method was applied for PM10 and NO2. Pollutant concentrations needed for the multiple regression process can be derived both from measurements and high resolution urban scale model results. The results demonstrate the capability of this simple approach to reproduce the urban increment with satisfactory accuracy, thus providing a tool for fast but still reliable quantitative assessments of urban air quality that can subsequently be used in calculations of exposure and health impact assessment. Moreover, scenario calculations for the urban increments can be based on scenario emissions and respective modelled regional background concentrations.
Abstract: Forum for Air Quality Modelling in Europe (FAIRMODE) sub–group 2 (SG2) on the 'Contribution of natural sources and source apportionment' has been formed in response to the need for a harmonised European approach in the use of models for source apportionment, addressing the requirements of the current Air Quality Directive 2008/50/EU. Within SG2, a review was performed on source apportionment modelling methods used by member states for the preparation of their extension reports regarding compliance with PM10 limit values. This review was extended to identify the modelling source apportionment methodologies used by member states for various pollutants. The extended study was performed by directly addressing a questionnaire to the national representatives of 38 countries of the European region and to 50 national experts. The responses revealed the widespread use of both receptor and dispersion models but also demonstrated a number of issues related to the validation of the source apportionment methodology applied.
Abstract: The recent air quality directive (2008/50/EC) encourages the introduction of modelling as a necessary tool for air quality assessment and management. Towards this aim, an air quality management system (AQMS) has been developed and installed in the Department of Labour Inspection (DLI) of the Republic of Cyprus. The AQMS comprises of two operational modules, providing hourly nowcasting and daily forecasting of the air quality status, implemented as an integrated model system that performs nested grid meteorological and photochemical simulations. A third operational module provides the capability of an interactive configuration of custom emission scenarios and corresponding model runs covering user-defined domains of interest. Statistical indicators are calculated at the end of each day for the measurement locations of DLI's air quality monitoring network. Besides, the system provides an advanced user interface, which is realised as a web-based application providing access to model results from any computer with an internet connection and a web browser.
Abstract: Systems of coupled prognostic mesoscale and microscale models have been suggested as a tool to accurately simulate flows around artificial structures and over densely built urban areas. Implementations of such two–way coupling are burdened by scale mismatches as well as the formidable computational cost of online microscale calculations. A simplifying approach is proposed, where microscale feedbacks are spatially and temporally upscaled and assimilated into the mesoscale calculation. A two–way coupled model system is developed, consisting of the mesoscale model MEMO and the microscale model MIMO, employing interpolating metamodels. As an illustrative application, multi–day simulations for Athens, Greece are presented.
Abstract: Air4EU is an FP6 European project with the major aim of providing recommendations on methodologies for the spatial assessment of air quality on local, urban and regional scales. The emphasis is on methodologies that combine monitoring and modelling and on spatial assessment for regulatory purposes, i.e., the EU daughter directives. The recommendations coming from Air4EU are intended as guidance for authorities involved in air quality assessment at the city, national and European levels as well as institutes involved in air quality research and application. This paper provides some highlights from the recommendations and case studies that emerged from the project.
Abstract: This paper aims at imprinting the urban air quality status and assessing the impact of various emission reduction scenarios on the photochemical and particulate matter air pollution levels in the Greater Thessaloniki Area, Greece. In particular, it is investigated under which conditions compliance with the EU air quality legislation can be achieved. For this purpose, the Ozone Fine Structure model is applied for a full calendar period (reference year 2002), as well as for specific scenarios, corresponding to predefined emission reductions for 2010. The model results for photochemical and particulate matter air pollution levels in 2002 agree fairly well with the observations. Predictions for 2010 indicate that significant improvement towards the EU legislation requirements can be achieved for certain emission reduction scenarios. However, an overall strategy will also have to include additional local scale measures.
Abstract: The spatial distribution of pollutant concentrations in street canyons can be described with the newly developed Semi-Empirical Parameterized Street Canyon Model (SEP-SCAM). The model calculates the two-dimensional horizontal pollutant concentration distribution at any height above street level. It makes use of a combination of a plume and a box model as well as of diagnostic equations based on empirically derived techniques previously used in the OSPM, CPB and STREET models. The novel elements in SEP-SCAM are the introduction of new empirical algorithms that refine the aforementioned models, as well as the use of a parameterized approach for the extraction of the horizontal distribution of concentrations. These modifications and approaches were deduced from extensive analysis of experimental data and tests with the three-dimensional microscale model MIMO.
The SEP-SCAM is applied to specific street canyons in three European cities, London, Stockholm and Berlin using data from monitoring stations located in the considered domains. The results from these simulations show a good agreement with measured concentrations.
Abstract: This paper gives an overview of the set up, methodology and the obtained results of the CityDelta (phase 1 and 2) project. In the context of the Clean Air For Europe programme of the European Commission, the CityDelta project was designed to evaluate the impact of emission-reduction strategies on air quality at the European continental scale and in European cities. Ozone and particulate matter (PM) are the main components that have been studied. To achieve this goal, a model intercomparison study was organized with the participation of more than 20 modelling groups with a large number of modelling configurations. Two following main topics can be identified in the project. First, in order to evaluate their strengths and weaknesses, the participating models were evaluated against observations in a control year (1999). An accompanying paper will discuss in detail this evaluation aspect for four European cities. The second topic is the actual evaluation of the impact of emission reductions on levels of ozone and PM, with particular attention to the differences between large-scale and fine-scale models. An accompanying paper will discuss this point in detail. In this overview paper the main input to the intercomparison is described as well as the use of the ensemble approach. Finally, attention is given to the policy relevant issue on how to implement the urban air quality signal into large-scale air quality models through the use of functional relationships.
Abstract: CityDelta is a model intercomparison exercise that assesses the performance of the participating models and compares them against observational data, allowing at the same time their validation and further development. In this framework, OFIS, an Eulerian photochemical dispersion model, was applied in several European cities, for both gaseous pollutants and particulate matter. The basic concept of OFIS is presented, along with the recent improvements that have been incorporated into the model. The results presented focus on the comparison, through several statistical indices, between the old version of the model, its improved version and the 3D photochemical dispersion model MUSE, revealing a considerable improvement in the performance of the new model version.
Abstract: The prognostic mesoscale meteorological model MEMO is applied to the Greater Marseille Area (GMA) and an extensive evaluation is carried out on the basis of the ESCOMPTE pre-campaign dataset. A series of tests are performed regarding the sensitivity of the model to grid resolution and the surface and soil parameters being used.
Abstract: Fossil fuels have been and still are the major energy source in cement production. However, the use of alternative fuels globally increases every year. This study aims to investigate the prospects for the partial replacement of conventional fossil fuel currently used in the TITAN cement factory in Thessaloniki, Greece, with alternative fuels, focusing on the impact of alternative fuels’ use on the emissions of air pollutants from co-incineration operations. Air emissions were estimated for the conventional fuel and for mixtures of conventional with alternative fuels, based on emission factors found in literature, but also using the measurements conducted by TITAN. Emission estimates indicate that legislative limit values for air pollutants are not exceeded when alternative fuels are used. Based on emission estimates and on measurements in the flue gas, the dispersion of the plume around the factory has been described with an appropriate numerical simulation model. Results suggest t hat the factory’s contribution to the air pollution levels in the surrounding area is very low.
Abstract: The radiative effects of atmospheric aerosols have been recognised as the main modes of interaction, coupling
meteorological phenomena and atmospheric pollution. Aerosol radiative forcings on the surface radiation budget
include the combined effect of scattering and absorption of solar radiation and have a profound impact on the total
amount of absorbed radiation as well as in the increase of low-level static stability. In recent years, two-way coupling
of mesoscale and urban-scale numerical weather prediction and chemical transport models has been an area
of active research, aiming to an improved description of aerosol-induced feedbacks in these scales. In an online
coupled mesoscale model system, the interaction between pollutant fields and the meteorology is usually implemented
through the use of specialised submodules that aim to account for the contribution of aerosol feedbacks on
the main radiative processes. In the present work, a coupled model system consisting of the mesoscale Eulerian
meteorological model MEMO and the chemical transport model MARS-aero is applied to the study of impact
of the aerosol direct effect on the urban meteorology and the evolution of air pollution in an urban area. During
the coupled model’s operation, the aerosol concentration fields calculated by the dispersion model are introduced
back as input in the enhanced radiation module of a three-dimensional non-hydrostatic mesoscale meteorological
model by means of the OPAC (Optical Properties of Aerosols and Clouds) software library. For the assessment
of the system’s performance, simulations of meteorological fields and dispersion of atmospheric pollutants were
performed for the Paris metropolitan area during the MEGAPOLI study period of summer 2005. The performance
of the new formulation was assessed by evaluating the response of the primary meteorological variables governing
the transport and dispersion of pollutants, as well as trends in particulate matter concentrations. The introduction
of the direct effect leads to a consistent reduction of calculated mean wind speeds over most of the domain, while
a notable decrease of the turbulent kinetic energy production at the first layer of the model is also evident, indicating
a significant reduction of thermal forcings on the surface. At the same time, PM10 concentration fields
calculated by the coupled model system reveal a significant increase over almost the entire domain covering the
Paris metropolitan area, compared to the stand-alone calculations, as well as higher pollution loads in the southern
part of the computational domain which can be attributed to the prevailing wind flows during the simulation period.
Further evaluation of the coupled model’s predictive skill was performed by comparing calculated PM10 concentrations
with time series of measurements at several AIRPARIF stations, which indicated an improved ability of
the coupled system in reproducing the evolution of particulate concentrations throughout the area of study.
Abstract: The radiative effects of atmospheric aerosols have been recognised as one of the main modes of interaction between meteorological phenomena and atmospheric pollution. Aerosol radiative forcings on the surface radiation budget include the combined effect of scattering and absorption of solar radiation and have a profound impact on the total amount of absorbed radiation, as well as low-level atmospheric stability. Nowadays, two-way coupling of numerical weather prediction and chemical transport mesoscale and urban-scale models has been an area of active research. In an online coupled mesoscale model system, the interaction between pollutant fields and meteorology is usually implemented through the use of specialised submodules that aim to account for the contribution of aerosol feedbacks on the main radiative processes. In the present work, a coupled model system consisting of the mesoscale Eulerian meteorological model MEMO and the chemical transport model MARS-aero is applied to study the impact of the aerosol direct effect on the urban meteorology and the variation of urban air pollution. During the coupled model’s operation, the aerosol concentration fields calculated by the dispersion model are introduced back as input in the enhanced radiation module of a three-dimensional non-hydrostatic mesoscale meteorological model by means of the OPAC (Optical Properties of Aerosols and Clouds) software library. For the assessment of the system’s performance, simulations of meteorological fields and dispersion of atmospheric pollutants were performed for the Paris metropolitan area during the MEGAPOLI study period of summer 2005. The performance of the new formulation was assessed by evaluating the response of the primary meteorological variables governing the transport and dispersion of pollutants, as well as trends in particulate matter concentrations. The introduction of the direct effect leads to a consistent reduction of calculated mean wind speeds over most of the domain, while a notable decrease of the turbulent kinetic energy production at the first layer of the model is also evident. At the same time, PM10 concentration fields calculated by the coupled model system show a significant increase over almost the entire computational domain, compared to the stand-alone calculations, as well as higher loads in the southern part of the domain. Further evaluation of the coupled model’s predictive skill was performed by comparing calculated PM10 concentrations with timeseries of measurements at several AIRPARIF stations, which indicated an improved ability of the coupled system in reproducing the variation of particulate concentrations throughout the area of study.
Abstract: Inhomogeneous, time-dependent coastal flows, as a result of the juxtaposition of contrasting thermal environments, are characteristic mesoscale features the importance of which has been highlighted in numerous studies. There are a number of factors with a strong impact on local circulation phenomena, such as sea surface temperature (SST), coastline configuration, topography and landuse. SST can have an important influence on the behavior of the overlying atmosphere, such as the forcing of convection which leads to showers and the formation of sea and land breeze. The coastal marine atmospheric boundary layer appears to be far from horizontally homogeneous and isotropic; it does not have a distinct diurnal pattern, but can be stable or unstable depending on the air type which is advected, relative to the sea surface temperature. Therefore, the use of accurate sea surface temperature fields in weather forecast models can be important. Τhe objective of the present study falls within the above mentioned framework. The Princeton Oceanic Model (POM) was applied to the coastal area of Athens and as a result, hourly base SST data were derived. Thereinafter, mathematical simulations with the non-hydrostatic mesoscale model MEMO were performed to analyse and evaluate changes induced by the spatial and diurnal variation of SST on local circulation phenomena, along the Attica peninsula. In this study, two multi-day periods, characterised by stagnant meteorological conditions were selected. Satellite data of land and sea surface temperature, orography and landuse were used in order to achieve more accurate simulations. The results demonstrated successful multi-day simulations, as well as the importance of including spatial and temporal high-resolution sea surface temperature data in model simulations for studying local circulation phenomena.
Abstract: In this paper, two mesoscale meteorological models, MM5 and MEMO, were applied over the Greater Area of Athens, Greece, during the period between the 16-19 of July 2002, using the model simulations as a tool for understanding the characteristics of the Urban Heat Island. Both models can capture fairly well the diurnal variations of the observed wind speed, direction and temperature during the simulation period, recognising the weak summer urban heat island. The intercomparison between the two models also revealed that in most cases they generated very similar predictions. However, MM5 significantly overestimates the cloud cover during the last few days resulting in the underestimation of temperature values.
Abstract: The MERLIN project aims at the development and application of methodologies and tools for the multi-pollutant, multi-effect assessment of European air pollution control strategies. Within this framework, an approach has been formulated to assess in how far cost-effective regional air pollution abatement strategies may be sufficient to improve urban air quality in order to achieve compliance with legislation currently in force and with future limit values. By taking into account all relevant air pollutants and their impact, costs and benefits could be assessed in an integrated way. Furthermore, benefits (i.e. avoided damage costs) were calculated, by implementing air pollution control measures, first in a physical way and in a second step, as far as possible, in monetary terms. Thus, costs and benefits of different bundles of measures were estimated, while macroeconomic effects and distributional impacts of pollution control strategies could be determined. For the purposes of urban air quality assessment, 20 European cities were modelled using the OFIS model, taking advantage the low computational cost of the model. Three different emission abatement scenarios were applied for the year 2010. The results obtained from the application of the models in very diverse meteorological conditions such as those found in the 20 cities under examination reveal an adequate description of the urban background levels for the base year 2000 and provide valuable insight regarding the correlation of regional and urban background pollutant levels. At the same time, a major contribution of urban emissions to urban scale pollution is confirmed, a phenomenon typical for pollutants such as PM10, which are principally emitted by road transport. These results set the ground for the assessment of the effects of regional emission control strategies to the urban scale environment, which are examined here through a number of different emission scenarios. The study of the scenarios using concentration deltas, calculated for nine locations throughout the greater area of each city, reveals that the largest reductions in annual mean NO2 concentrations occur in the city centre. For mean annual O3 levels, deltas are positive in the city centre, while small decreases are expected in the peripheral locations. A similar behaviour is also exhibited for the exceedance days for O3, where larger decreases are expected at the suburbs. Regarding PM10, significantly lower concentration levels are calculated in the city centre which is evident from reductions of both the mean annual concentration and the number of exceedance days, a fact which is caused by a considerable decrease of road traffic emissions.
Abstract: The objective of this paper is to assess the impact of various emission reduction scenarios on the photochemical air pollution levels in the Greater Athens Area. In particular, it is investigated under which conditions compliance with the EU air quality legislation can be achieved within the given deadlines. For this purpose, the OFIS model is applied for a full calendar reference year period (2002) as well as for specific scenarios, corresponding to predefined emission reductions in 2010. The predicted photochemical air pollution levels for 2002 agree fairly well with the observed behaviour. Model results for 2000 indicate that a significant improvement towards the EU legislation requirements can be achieved for certain emission reduction scenarios. However, an overall strategy will also have to include additional local scale measures.
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