1 Summary

SATURN’s objective is to lead to a better understanding of urban air pollution as a prerequisite for finding effective solutions to air quality problems and for a sustainable development in the urban environment. The reporting period is the first year of the subproject’s Phase A which is mainly characterised by model development, the formulation of evaluation procedures, planning of experimental activities leading to data in support of model evaluation and first steps towards air quality management systems and integrated assessment methods.

Research activities in SATURN are organised into the four Main Groups each consisting of four individual tasks. In the reporting period substantial progress was achieved in most of these tasks. Although the level of co-operation effectively launched is still quite different within the task teams, the progress of most contributions is satisfactory and many informal co-operations have been established.

Proper quality assurance planning and implementation of quality control techniques are essential for the success of SATURN. In fact, the principal effort of contributors to SATURN is centred on model validation thus being directly related to model QA/QC. Moreover, quality of emission inventories and measured data is being evaluated in order to determine limitations and ensure their acceptance in accordance with project objectives.

As far as model development is concerned, the main advances in the reporting period refer to progress in formulating model hierarchy concepts, the identification of gaps in existing model architectures and the refinement of modules and schemes. Regarding model evaluation, SATURN progressed in clarifying the links between models and setting up methods to test their ‘fitness for purpose’. First model/data intercomparison exercises were launched and a harmonised methodology for urban emission inventories was developed.

Experimental activities in the reporting period include both comprehensive urban scale field campaigns and laboratory measurements. Collaborative work was in particular very successful in particle studies and local scale experiments. As an example for synergy between experimental groups and modellers, results of street level measurements and inverse modelling tools were used to estimate emissions from traffic under real driving conditions. Results of wind tunnel experiments were found to lead to useful conclusions with respect to model validation.

Work in SATURN appears to be reasonably distributed between basic and applied research. Some contributions aim at the development of Air Quality Management Systems thus being directly related to application. A first attempt to develop an application-oriented structure in the subproject revealed, however, that also most of the other contributions have application among their aims. In the next period structural contacts will be established between SATURN and urban authorities in order to ensure that SATURN’s ensemble of aims matches the demands of air quality management.
 
 

2 Aims of work in the reporting period

According to the SATURN description, the reporting period is the first part of the subproject’s Phase A [1]. The expected achievements in this phase of SATURN are as follows:

• Development of required model hierarchy and necessary components.
• Generation of evaluation procedures, specification of data needed to validate models.
• Identification of existing data sets qualifying to be used for model validation purposes.
• Planning of campaigns and performing early experiments.
• Set-up of the Framework Project.
• Development of concepts for integrated air quality management systems.

SATURN-MOD

1. Model hierarchy definition: Identification of: (i) the various types of models needed to study the various types of source receptor relationships and their essential characteristics, (ii) the existing models and model systems, and those in development and (iii) the possible and needed links between models.
2. Analysis of gaps: Identification of: (i) the models, modules, and parameterisations that do not exist and (ii) those that are missing in the SATURN models or model systems.
3. Model structure development: Analysis of (i) the existing methods to link modules within individual model systems, the data exchange methods and module interface 'standards' and (ii) of existing and possible methods to ensure data exchanges between model systems of different scales during co-operative exercises.
4. Model development: Improvement of existing sub-models, creation of new gap-filling sub-models and comparison of competitive sub-models or parameterisations or methods, in isolation.
5. Module development: Creation of individual and/or communal new modules, based on competitive or communal parameterisations, and co-operative exchange of existing or newly developed modules.

1. Development of formalised evaluation procedures: Definition of structured evaluation concepts for (i) obstacle resolving urban models and (ii) urban models which parameterise the urban canopy layer.
2. Collection and classification of existing data: Preparation of a database that can be used in the context of validating models for urban applications. These should not be just data but complete sets of quality data are needed (i.e. the quality of the data needs also be assured!).
3. Development of a www-databank: Work done in order to make the data generally available in convenient electronic form.
4. Specifications for various data relevant to model evaluation: Definition of data specifications from the viewpoint of model validation. Identification of gaps in present data base (e.g., which data are needed in order to test specific parameterisations used in urban models, etc.).
5. Generation of data sets: The data should be generated especially for the purpose of model validation, i.e., the data sets must be complete and quality assured.
6. Generation of emission inventories: Development of tools for emission inventorying, providing emission factors etc., quality control of emission data.
7. Model intercomparisons: Work done in preparation of model intercomparison studies. Development of strategies for such studies etc.

1. Set-up of experimental plans: Design and description of experiments prepared by the PIs for investigations of specific phenomena.
2. Field campaigns: (i) Initiation and completion of large field campaigns and (ii) dissemination of information about available data.
3. Individual experimental activities: (i) Initiation and completion of experimental activities under the individual PIs and (ii) dissemination of information about available data.
4. Wind tunnel experiments: 'Enhancement' of field data by means of wind tunnel experiments
5. Data analysis: Structuring and analysis of data in relation to the phenomena to be investigated. Preparation in appropriate formats and of aggregated data.
6. Preliminary evaluation: Analysis of correlations and other connections between air quality data results and between air quality data results and other parameters, e.g. meteorology, traffic etc. Adjustment of experimental set-up
7. Compilation of experimental data sets: Storage of data in databases.

1. Set-up of Framework Project: Description of the Framework Project. Acquisition of funds for Framework Project. Definition of information exchange between SATURN contributions. Establishment of contacts between SATURN and city authorities.
2. Specification of formats for deliverables: Collection of existing concepts and ideas for the structure of Air Quality Management Systems (AQMSs). Investigation of possibilities to develop a common structure, taking available data structures into account. Description of desired outputs of AQMSs. Same for AQ assessment methods integrating measurements and models.
3. Development of integrated systems: Development of AQMSs. Development of AQ assessment systems integrating monitor networks and models.

3 Activities in the reporting period

In order to meet the scientific aims of SATURN, individual tasks of manageable size are being addressed. Close co-operation within each task team will ensure a steady progress of the scientific research envisaged. At the same time, sufficient precautions are taken to avoid an independent evolution of work in individual task teams: Firstly, most PIs are involved in more than one tasks, thus providing clear links between the tasks. Secondly, regular concertation contacts take place, normally via e-mail. Finally, the "Framework Project", which corresponds to task INT1, represents an additional guarantee for coordinated work in the subproject (see sections 3.4 and 6).

3.1 Model development

Activities in Main Group SATURN-MOD are organized in 4 tasks: Local scale model development (MOD1), urban scale model development (MOD2), scale interactions in models (MOD3) and chemical modules with emphasis on heterogeneous chemistry (MOD4). In general, substantial and quite timely progress could be achieved in all four tasks. Although the level of co-operation effectively launched is still quite different within the four task teams, the progress of most individual contributions is impressive and many informal co-operations have been generated among model developers.

Local scale model development.

The main effort in the reporting period concerned the synergy in the development of computational fluid dynamic (CFD) models, operational street air quality models, and simulations within atmospheric wind tunnels - with use of the rare street-scale measurement data sets. The studies focused on:

• the dispersion of tracers within the street canyons, with a number of influencing factors such as street geometries, thermal convection due to wall heating, turbulence induced by the motion of the vehicles themselves,
• the emission of pollutants by the vehicles and their rapid transformations
• the momentum, heat and pollutant fluxes at the roof level and the relations between the urban canopy layer and the roughness sub-layer above the roofs.

Urban scale model system development.

Six model systems are being developed within the framework of SATURN to simulate the air quality and the pollutant source-receptor relationships at the scale of a complete city (mesoscale d). The main and common characteristic of these model systems is to take into account the presence of the urban canopy and of the canopy layer, either explicitely through the coupling with an obstacle-resolving model, or implicitely through a canopy model computing the soil/buildings-canopy-atmosphere exchanges of momentum, heat, and pollutants. Among the six groups four report sigificant progress in the reporting period.

A detailed questionnaire filled by participants during the year led to a very detailed model inventory reflecting the status of MOD2. The inventory is available to the participants on web pages and describes all important features of the models, their scientific and technical contents and their operational choices. Participants may thus easily compare their construction/development options. This inventory will be further developed and made accessible to all contributors to SATURN and other EUROTRAC-2 subprojects.

In MOD2 work has been conducted more in parallel than in an organized co-operation, although a large number of individual contacts and exchanges have been launched between the scientists.

Scale interactions in models and numerical simulations.

Main objective of this task is the development of scale exchange procedures. Work in the reporting period concentrated on formulating methods allowing to deduce from the local scale simulations the parameters needed to represent each city quarter in the simulations at the urban scale, in combination with specific urban mapping outputs, as e.g., terrain pre-processors, urban data base analysers, satellite image processors, or modules preparing boundary conditions. Individual activities aim at the assessment of the most proper methods of multi-domain simulation of the urban atmosphere with multiple nested grids or variable grids, the refinement of data assimilation techniques, and the development of proper meteo-processor modules.

Furthermore, it is attempted to represent adequately local (point or line) sources of reacting pollutants in grid simulations where the grid mesh size is much larger than the source, and to develop sub-grid scale chemical models.

Although the issues that were identified to constitute task MOD3 have been recognized of central interest by many of the modellers contributing to SATURN-MOD, it appeared that no effective co-operative work has been driven during the period. This is mainly due to organisational reasons and to the planning of development of the large urban scale model systems, although the work performed by MOD3 participants is excellent and should trigger new co-operations in the near future.

Chemical modules with emphasis on heterogeneous chemistry.

In the reporting period activities focused on

• the refinement and further assessment of the VOC chemical transformation schemes, especially the initial rapid ones taking place within the canopy,
• the quantitative description of aerosol early generation, resuspension and transformation processes, in connection with their dispersion within the canopy, and their further transformations as a function of background concentrations and
• the interactions of the locally-generated aerosols with the urban microclimatology and radiative transfer, especially during pollution episodes.

3.2 Model evaluation

SATURN-VAL focuses on the development and provision of a framework for validating urban scale models. This is being accomplished by the development of evaluation procedures (task VAL1), defining specifications for data relevant to model evaluation (task VAL2), the generation of emission inventories (task VAL3, in collaboration with GENEMIS), and hosting model validation exercises (task VAL4). The task contents were further specified August 1988 during the 2^nd SATURN Workshop in Hamburg.

Evaluation procedures.

Work progressed very satisfactorily with regard to the evaluation concept for obstacle resolving urban models. A formalised evaluation procedure was developed and its usefulness was exemplified at the example of a microscale prognostic model. Concerning mesoscale chemistry transport models, developments in line with the VAL1 objectives are ongoing in the frame of the German Tropospheric Research Programme.

Data relevant to model evaluation.

Activities in the reporting period concentrated on the preparation of a data base which can be used in the context of validating models for urban applications. Moreover, a www-databank was developed in order to make data generally available in convenient electronic form. Other ongoing activities refer to the generation of extensive data for validation purposes, including aerodynamic roughness and concentration flux data. Work has also been launched to extract useful data from satellite images.

Generation of emission inventories.

Consistency among emission inventories is a prerequisite for model validation and the intercomparison of results from various applications. Therefore, guidelines with minimum requirements are being designed within VAL3, in collaboration with the GENEMIS–2 working group "urban emission inventories". These guidelines contain requirements for methodologies and models (bottom–up, top–down), pollutants, resolution in time and space and emission factors including VOC and NO_x split. Work in this task includes also important elements related to QA/QC, such as the uncertainty estimation and validation of an emission inventory through comparison with the long-term evaluation of air quality and the validation of an emission inventory by comparison of results obtained from different methodologies.

Model intercomparisons.

As the main activity in the reporting period, the MESOCOM model intercomparison was initiated with the objective to compare results of several mesoscale models for an idealised situation and to determine the margin of their variability. For the first step it is suggested to compare only results of different models with each other assuming a simple set-up and prescribed initial and boundary conditions. Moreover, three roadside air quality models were intercompared in terms of CO, PM₁₀ and NO₂ predictions using measured air quality data from roadside sites and where possible, traffic and meteorology data.

3.3 Experiments

The Main Group SATURN-EXP was restructured in 1998 and consists now of local scale field experiments (task EXP1), urban scale field experiments (task EXP2), wind tunnel experiments (task EXP3), and urban aerosol experimental studies (task EXP4). In fact, all experimental groups are involved in measurements on local and urban scales as well as in particle experiments. It means that there are strong overlaps and coherence of the activities in the four tasks.

A data set inventory was carried out in March 1998. The information is available for all PIs and it is planned to integrate this inventory with the one on models carried out at the Hamburg University in order to be accessible through the Internet.

Local scale experiments.

The measurements at street sites in Helsinki and Copenhagen, especially designed for studies of atmospheric processes and validation of street pollution models, were continued and expanded. A street (and urban background) station was established in St. Petersburg using the DOAS technique. Tunnel experiments, mainly referring to VOCs, were started in Stockholm to be used for source fingerprint of the road traffic. In addition, many routine monitoring stations and urban scale measurement sites (EXP2) deliver data, which can be used for model validation and process studies in the local scale, e.g. London, Milan, Graz and Lisbon.

Urban scale experiments.

Urban scale measurements are often linked to local scale and urban plume experiments. Urban measurement campaigns were carried out in Graz, Austria with the aim to study dispersion of atmospheric trace elements in a poorly ventilated urban area in a valley. The measurement campaign took place during three days in January and was based on intensive measurements of meteorology and air pollutants.

In Milan the development and validation of models were based on routine monitoring data and the PIPAPO/LOOP urban plume experiment. The urban experiment in Lisbon was finalised in 1997 and no further large campaigns have been planned. The urban background (and local scale) measurements by DOAS were started by the end of 1998 in St. Petersburg. Studies of urban plume were carried out near London.

Wind tunnel experiments.

Experiments on dispersion of pollutants in urban areas, especially in and around streets, were carried out at the Hamburg University on a wind tunnel model of Hanover and recently preliminary experiments were carried out on another wind tunnel model of Copenhagen. The results were compared with model and monitoring data. Detailed wind tunnel measurements were also carried out on a model of buildings and streets to obtain data for validation of models in UK.

Aerosol experiments.

The work on particle measurements progresses very satisfactorily. Among the 6 PIs of this rather large task, some were also involved with modelling of particulates and this provided an opportunity to foster closer links with modellers. A key objective of the research activities was to conduct measurements sufficiently detailed to enable source apportionment studies and characterisation of the particles, including fine as well as ultra-fine particles.

Analysis of data from earlier campaigns in Helsinki was made in order to estimate the source-receptor relationship, gas-particle interactions and particle deposition. A new intensive campaign on particles was made at an urban site in Helsinki. The campaign included particle size fractions and gases. The activities in Budapest are a continuation of the analysis of data from the monitoring network and include mainly determination of source profiles based on elemental composition of aerosols. Similar analyses were also carried out in UK, but including size fractionated samples.

A field campaign was carried out in the Athens basin to investigate the physico-chemical transformation of aerosol. The measurements comprised ionic species in aerosols secondary pollutants. Size fractionated particle measurements were initiated in Copenhagen by an optical light scattering method and differential mobility analyser (DMA) in the range 10 nm to 29 m m to be related to traffic.

3.4 Integration

The contributions to this Main Group of activities explicitly address the needs of air pollution information by policy makers and other stakeholders involved in air quality management. Whereas the other Main Groups focus on the development of scientific methods, tools and insight, SATURN-INT has the application of the results of scientific developments in specialist fields as its primary goal.

In the activities of this Main Group, informatics and computer modelling are of major importance, because integration typically brings along the need to incorporate large amounts of data and other information on sources and processes that lead to air quality problems. Besides the software-related activities, however, the development of concepts, methods and structures is also essential in order to arrive at efficient methods to link the supply of data and tools to the demand of policy makers.

The most important activities in the reporting period were the establishment of a platform of PIs working on the field of SATURN-INT, discussion of common concepts and tools and identification of possibilities for a common approach.

Task INT1, the Framework Project, aims at bringing into a common framework all work conducted/systems developed under SATURN and communicating such an extensive range of knowledge to the wider user community. Developments over the past year in this area include a ‘Framework Questionnaire’ which was distributed to SATURN PIs to determine how they see their work linking in with other tasks and how their work could be applied or incorporated into systems for end users.

The other tasks of SATURN-INT are closely connected. In order to appropriately distinguish them, it was decided in the 2^nd SATURN Hamburg August 1998 to re-define them as follows:

• INT2: Combinations of different components of an air quality management system (e.g. modelling and monitoring), but not a complete system.
• INT3: Air quality management systems (AQMS) and Decision Support Systems (DSS).
• INT4: This refers specifically to aspects of AQMS which calculate population exposure, health effects, economic impacts or cost benefits of various scenarios, however it does not include work specifically aimed at air quality as the end-point.

Most of the activities in tasks INT2-4 aimed at improving techniques and extending the fields covered by individual air quality assessment and management systems. In order to strengthen the interaction between the various PIs of INT ideas for co-operation were discussed and several of these were elaborated in descriptions of possible common projects.

It was decided to launch a web site for SATURN-INT (this has been realised in the beginning of 1999: http://www.cerc.co.uk/saturn/). As part of the dissemination of information to the wider community a demonstration of SATURN software will be held at the 3^rd SATURN workshop in Aveiro, Portugal (August 1999). The intention is to invite influential end users such as those responsible for environmental policy in major cities or representatives of Environmental Agencies.

3.5 QA/QC measures

Quality Assurance and Quality Control (QA/QC) plays an increasingly important role in environmental studies, especially when those studies are conducted to support decision in environmental problems. Hence, QA/QC is also an essential ingredient of SATURN. Proper quality assurance planning and implementation of quality control techniques provide compatibility of the project components, minimise procedural and technical errors, and guarantee the usefulness of final results.

Three principal components for QA/QC were distinguished in SATURN: models, emission inventories and measured data (see Fig. 1). A quality of each component is evaluated in order to determine limitations and ensure their acceptance in accordance with project objectives.

Models.

Model QA/QC includes: verification, validation, sensitivity test and uncertainty analysis.

• The verification of new modelling tools developed in SATURN is oriented to check if a technical model is a proper representation of the conceptual model. It also includes QC of the computer code.
• The principal objective of model validation is to ensure that the conceptual model and computer codes provide an adequate representation of the phenomena. To achieve this objective several measures are planned in SATURN.
• The sensitivity test permits to identify a model response to input parameters. This is of great importance to determine key parameters, which have the potential to significantly affect the output results. For such parameters quality requirements must be specified.
• Qualitative and quantitative uncertainty analysis is an important task in definition of model acceptability.

Emission inventories.

The quality assurance and quality control of emission inventories are designed to ensure that: (i) the appropriate methods and data are used; (ii) the errors in calculations or data transcriptions are minimised; and (iii) the documentation is adequate to reconstruct the estimates. Because of different emission estimating methods that can be used, an inventory quality program had to address both emission estimation methodology and data quality.

In conjunction with the development of a harmonised method for the compilation of urban emission inventories, the following QA/QC procedures are planned: completeness analysis, uncertainty estimation and validation of inventories.

Measured data.

QA/QC procedures for measured data refer to data acquisition (requirements to data collection, handling, analysis of samples), and data validation (data review, validation, verification). It is anticipated that SATURN experiments will include laboratory intercomparison, ring test, parallel measurements with independent method, parallel sampling at same site and also split analysis by different laboratories. For wind tunnel experiments, specific criteria will have to be followed in order to assure the quality and usefulness of the generated data (among other, through dimensional analysis and comparison of velocity profiles and turbulence spectra with atmospheric measurements).

Quality Assurance Plan.

Success of QA/QC implementation in SATURN will be assured by preparing a Quality Assurance Plan. This document will include description of

• Quality Objectives for each task;
• Quality Indicators used to provide an assessment of how these objectives are met;
• Quality Control procedures to be apply to project components.

4 Principal results

4.1 Model development

Local scale models.

Hirsch et al’s numerical studies focus on modelling traffic induced flow field and turbulence, traffic emissions and turbulent dispersion in a canyon street and in a tunnel, with a single pollutant source in the street, with different geometry of the buildings and roofs, compared with experimental data obtained in the wind tunnel of the Karlsruhe University. Vehicles are considered as sources of additional momentum and turbulent kinetic energy, which are parameterised through the average vehicle speed and through geometrical parameters describing the traffic (i.e. average vehicle height and average distance between consecutive vehicles). Pollution induced by the traffic is taken into account by considering surface or volume sources of heat, momentum, and mass on the road: the strength of these sources is determined by a global mass, momentum, and heat balance.

Jicha et al’s study also concern traffic induced pollutant production and dispersion. An Euler-Lagrangian method has been developed based on CFD calculations using Eulerian approach to the continuous phase (air) and Lagrangian approach to the discrete phase of moving objects (vehicles). As a basis for the tests, a road tunnel was chosen to assess influence of tunnel length, traffic rate and vehicle speed. Three different formulas for the additional generation of kinetic energy were tested . The same method was further applied to a street canyon, with different aspect ratios of the canyon, and different traffic situations comprising traffic rate, speed and one- or multi-lane traffic.

Mestayer et al’s contribution to MOD1 also concerns CFD simulations of flow and pollutant concentrations in one street-canyon within heuristic studies. The relative influence of the following factors is studied: street geometry, partial heating of the walls by solar radiation (generating thermal convection), turbulence induced by vehicle motions. The study is run in close co-operation with SATURN and TRAPOS participants running wind tunnel simulations in similar configurations.

Moussiopoulos et al. are also developing models and individual modules for the adequate description of microscale phenomena, i.e. those occurring at the scale of one street or a small set of blocks. Local scale studies involve the description of vehicle-induced turbulence, fast chemical transformations and buoyant effects due to the differential heating of the street canyon walls. Where essential, the multiscale character of the governing processes is properly accounted for.

Schlünzen et al’s contribution is done in the frame of the development of the microscale model MITRAS. This development is a co-operation of four German research groups. MITRAS will resolve obstacles with a horizontal resolution of some metres in an area of some hundreds to some thousands of metres. A forcing utility will be implemented in MITRAS so that it can be nested into models of the urban area scale, which have a coarser horizontal resolution and don't resolve the obstacles. It will include passive tracer transport as well as chemical reactions by directly solving the gas phase chemical reactions important close to traffic sources. Soot is transported as aerosol with its deposition dependent on size and is treated as a sink for VOC compounds. During the year different turbulence schemes based on prognostic equations for turbulent kinetic energy and the energy dissipation rate have been tested by comparing model results with wind tunnel observations. A test version of MITRAS which includes a Prandtl-Kolmogorov turbulence closure, a new numerical solver with on-line calculation of photolysis rates is available now and being tested.

Urban scale model systems.

Calpini et al. re-analysed the existing set of turbulence measurements in urban areas performed in collaboration with M. Rotach (ETH Zurich), stressing that the complex town morphology strongly modifies the flow and the turbulence structure of the atmosphere. The urban surface layer has to be split up into two parts, the Roughness Sublayer with a vertical extension of several tens of meters and where the turbulence is fully three dimensional and explicitly depends on the properties of the roughness elements, and the Inertial Sublayer, above, where the Monin Obukov similarity theory may apply. They also note that, to simulate pollution transport-transformation processes, it is needed that 4-5 computational grid levels, or even more, are included in the Roughness Sublayer (80-100 m depth).

This year, a series of 2D tests were made to investigate the reaction of the flow to a change in surface roughness and surface heating with the mesoscale turbulence parameterisations of Therry and Lacarrere (level 1.5) for the transition layer and Louis for the surface layer. An analysis of the vertical profiles of Reynolds stress and turbulent kinetic energy computed by the model show that this traditional approach fails in the representation of the roughness sublayer turbulence structure. Furthermore, the modifications in the mesoscale pressure distribution, induced by the presence of rough and warm region, are not able to explain the behaviour of the Reynolds stress vertical profiles in the roughness sublayer.

An approach based on the introduction of a drag force to represent the presence of buildings in the first layers of the model is being tested and the results obtained so for are very promising.

Mestayer et al.’s contribution concerns the development of the French communal model system SUBMESO. The version 2.0 has been achieved, with full compatibility of dynamics, chemistry and microphysics modules, and full portability on workstations and supercomputers. In particular, this year novel turbulence closure models for the stable atmospheric boundary layer with active turbulence have been developed and extensively tested on experimental results where the classical mesoscale closures fail, such as the Boulder storm.

The main effort this year concerns the construction of a urban canopy layer model, by "urbanising" the submeso soil model SM2. Based on simplified computations of heat and water transfer within the soil and vegetation, it allows to compute the interactions between the ground and the lowest atmosphere, and to define the boundary conditions at the lower boundary of the computation domain. In urban areas the canopy layer appears as a buffer layer between the real surface and the apparent surface at roof level. The rationale adopted here is to transform the original "force-restore" soil model into an urban canopy layer model. In a first stage the model is equipped with urban surface parameterisations, but it still considers a flat interface. In a second stage the model will take into account the horizontal and vertical transfer processes through the canopy air layer: complex radiative transfer, mixed convection, fast chemistry.

For the first stage, a series of new semi-empirical equations for the water/moisture circulation and for the radiative heat transfer have been created to simulate the partial coverage of ground by artificial materials (tar or concrete) and by building roofs, such as tiles, slates, or concrete (Guilloteau et al., 1998).

The second stage is prepared by three types of process studies driven in parallel with specific numerical models: roughness modelling and mapping, canopy ventilation and transfer to the atmosphere, radiative transfer. The model parameterisations of the roughness parameters as a function of building heights and arrangements have been partially validated by the site measurements of Grimmond and Oke (1999); numerical experiments are run with the small-scale model CHENSI where the flow is simulated, with 0.5 m resolution, within the streets of an idealised uniform quarter and in the constant flux internal boundary layer that develops over it. In parallel, a mapping software has been developed. The canopy layer ventilation and transfer study is developed in MOD1. Radiative transfer simulations (Peneau et al.’s contribution to VAL) are also analysed to derive new parameterisations of the radiative and heat budgets within the canopy.

Moussiopoulos et al’s contribution concern the development of the model system ZEUS (Zooming model for European Urban air pollution Studies). This year a new efficient scheme was developed for the calculation of microphysical processes in the atmosphere and the radiative transfer through cloudy air. The efficiency of the scheme is based on the possibility to describe the influence of clouds on the atmospheric flow without considering droplet spectra. Thus, the scheme is suitable for three-dimensional mesoscale models. The conservation equations for water vapour, cloud water and rain water are coupled by the source-sink terms that describe the interactions between the three quantities with Kessler’s parameterisation schemes.

Wind flow depends strongly on the temperature distribution, which is highly influenced by the radiative transfer. The presence of pollutants and clouds affects atmospheric radiation. An efficient radiation scheme is embedded in MEMO providing atmospheric heating/cooling rates and radiative fluxes at ground for both clear and polluted air (Moussiopoulos, 1987). The parameterisation of longwave radiation is based on an enhanced emissivity method, whereas shortwave radiation is calculated considering multiple reflexions between single clouds. In earlier versions of the radiation scheme clouds were prescribed diagnostically in individual model layers. The new version of the scheme benefits from the prognostic calculation of clouds within the model domain: Based on the obtained liquid water content, the liquid water path can be integrated over the height and may be used to calculate the optical depth of the cloud. The latter quantity is relevant for calculating the radiative quantities of the cloud.

Scale interactions in models and numerical simulations.

ApSimon et al’s contribution concerns the source apportionment project. It includes an initial case study in modelling the relative contributions to concentrations of primary PM10 at an urban location from sources over different distance scales. Initial progress towards nested modelling has concentrated on implementation of MIMO as a local scale model, with application to exploratory 2D studies. Preliminary consideration has been given to the production and use of source-receptor matrices in exploring abatement strategies to improve urban air quality. Initial data has been obtained from the Silwood Park Atmospheric Research Station, SPARS, to the West of London, and looks very promising for studying pollutant fluxes entering and leaving London. Emissions of primary particulate over Europe were based on the PM10 inventory compiled by TNO, subdivided into 3 size categories, and European scale transport was modelled with a simple Lagrangian trajectory model. The contribution from London emissions was calculated using the URBPM model (similar to the URBNOX model of O'Keeffe) to simulate dispersion and concentration profiles above the city.

Coppalle et al’s contribution concern the simulation of pollutant dispersion and chemical transformation in the immediate vicinity of emission sources (streets, roads, highway, stacks etc.). The accuracy of the concentration calculation in the far field depends on the initial values estimated close to the source due to the Lagrangian aspect of the wind transport. A particular phenomenon exists in the case of reacting pollutants, a mutual influence of the dispersion and chemistry processes.

A novel model has been developed to handle the coupled near source processes. It assumes that the spatial distribution of the reactive species concentrations (presently limited to NO-NO₂-O₃) can be represented by generalised Gaussian profiles. Extended Gaussian formulae for reactive plumes are used with generalised dispersion parameters. The model has been applied to the stack emission case. Comparison between the results of this model and calculations involving the complete partial differential equations solved on a refined mesh show excellent agreement. It appears that the non linear effects and the perturbation provided by the chemistry on the pollutant concentration profiles in the plume are more important for O₃ than for NO.

Chemical modules with emphasis on heterogeneous chemistry.

Andersson-Skoeld et al. used empirical data to simulate the urban heterogeneous formation of HONO and HNO₃. The IVL photochemical trajectory model has been used for a preliminary investigation of deposition and some heterogeneous reactions. Simulations have been conducted for the London plume and the concentrations of ozone and NO_y species have been calculated. As the main result it was found that among the heterogeneous reaction studied only the formation of HNO₃ from water and N₂O₅ has any significant influence on the ozone concentration.

Perego et al’s contribution deals with the simulation of summer smog. Since high pollutant impacts mostly occur in clear sky conditions, most air pollution models neglect the influence of clouds and of aerosols. lt has become clear in the past years, however, that aerosols are important constituents of summer smog. Like clouds, they have an important influence on the radiation balance in the polluted atmosphere. By modifying the radiation balance, aerosols, therefore, can influence meteorological parameters and local climate. Their ability to change the properties of clouds is another interesting impact. Only a fully coupled meteorology/atmospheric chemistry model is able to simulate these coupling effects. To do this, a model must include a radiation module which is able to consider multi-scattering effects, as well as aerosol and cloud modules and all the necessary links. From a literature survey it appeared that, while radiation effects and aerosols were judged to be very important, aqueous chemistry seemed to be of less importance.

For the radiation module the TUV-program of Madronich was chosen. To achieve higher performance, the code was optimized and the effect of surface slope was introduced (the original version is not able to account for inclined terrain). For the aerosols ISORROPIA-Code by Nenes et al., a thermodynamic equilibrium aerosol model, was chosen, in combination with a code from Spyros Pandis (Carnegie Mellon University) and Staphan Musarra (Sonoma Technology Inc) to calculate the number and size distribution of the aerosols. The whole aerosol module is currently being coupled to an up-to-date atmospheric chemistry module in order to perform the first calculations.

Kukkonen et al. developed a modelling system for evaluating the traffic volumes, emissions from stationary and vehicular sources, and atmospheric dispersion of pollution in an urban area containing the UDM-FMI and CAR-FMI models. The modelling system was refined to allow for the chemical interaction of pollutants, originating from a large number of urban sources. The predicted NOx and NO₂ concentrations were compared with the results of the urban air quality monitoring network of YTV. The agreement of predicted and measured NO₂ concentrations was good at all the stations considered (Karppinen et al., 1998).

They have also developed models in order to evaluate the exposure of population to air pollution, particularly for nitrogen oxides, combining emission inventories collected previously, and the above mentioned atmospheric dispersion modelling system. While regulatory modelling systems commonly assume for simplicity that the urban background O₃ concentration is equal to the regional O₃ background concentration, they have thus developed a modelling system which allows for the chemical interdependence of the NOx concentrations originating from various sources and the O₃ concentrations.

4.2 Model evaluation

General remarks.

As the most important result from this Main Group of activities, in the reporting period it was decided which general model evaluation framework will be followed in the subproject.

The development of urban-scale meteorological models has progressed in recent years. Some of them are already commercially available. Without much hesitation, consulting engineers apply them to complex real world problems. This provokes a few critical questions: Are these models already matured enough to be applied outside of the (mostly academic) world in which they were developed? Is their application by third persons reasonably fool-proof? Are these models sufficiently fit to fulfill their purpose? Since there are large differences from model to model and from user to user, precise answers to these questions could only be given on an individual basis (Schatzmann et al., 1999).

Instead of restricting its scope to individual models or even specific users, SATURN intends to provide support to model developers and the public by issuing statements on how the quality of numerical models can be assured. In particular, within SATURN-VAL the concept was adopted which was originally developed by CEC’s Model Evaluation Group (MEG 1994). Following this concept, the evaluation of a numerical model comprises 5 steps:

• The model description provides a brief identification of the model to the interested party, either a user or a referee. It contains details of the model as, e.g., its name, version number and release date, the model type, its area of application, the name and the affiliations of the model developer, hardware and software requirements, the efforts taken to assure the quality of the model and a list of references to relevant publications.
• The data base description identifies the data sets employed during the development of parameterisations contained in the model, and which were used during the process of model validation. It contains statements on the appropriateness of the data and the features and parameters covered by the data sets.
• The scientific assessment comprises a detailed description of the physics and chemistry contained in the model; an assessment of the appropriateness of the scientific content; the limits of applicability of the model and any special features.
• The user oriented assessment provides information on the availability of the model, computational costs, the associated documentation, the installation procedures, a description of the user interface, explanations concerning the output, etc.
• The QA/QC techniques (see section 3.5) are used to define limitations and acceptance of models.

It should be noted that certain strategies for evaluating the quality of a model can, in general, only be based on scientific principles such as the principle of falsification. Which particular tests and which particular model/dataset comparison should be made for a given model type can ultimately be based only on a consensus. Such a consensus needs to be built up for individual groups of models within and by the scientific and operational community, which develops and uses those models. Consequently, it is a major objective of SATURN-VAL to use its ‘grass root’ capabilities and to launch such a consensus building process within the ‘urban air pollution community’.

Evaluation procedures.

Schlünzen and Panskus developed a formalized evaluation procedure for obstacle resolving models and exemplified its usefulness at the example of the micro-scale prognostic model MITRAS.

With respect to mesoscale chemical transport models, a structured evaluation procedure was developed and applied within the German Tropospheric Research Programme (under strong participation of the Hamburg University). The leader of this project (Schaller, Cottbus) gave an invited lecture at the 2^nd SATURN Workshop in Hamburg. The project is still ongoing, but it appears that the concept is well thought-over and in line with the SATURN-VAL objectives.

A plan for a concerted action in the field of quality assurance of models has been worked out by a group of SATURN Steering Group members and suggested to the European Commission. This was done in order to find acceptance for our quality assurance ideas not only inside SATURN and EUROTRAC-2 but in the whole European scientific community.

Finally, Borrego provided a first approach on quality assurance/quality control within SATURN (section 3.5 of this document). The paper is of direct relevance to task VAL1 and puts the evaluation work into a wider perspective. The draft was presented and discussed during the 2^nd SATURN Workshop in Hamburg.

Data relevant to model evaluation.

Under active participation of SATURN Steering Group members (Bozo, Britter, Larssen, Mestayer, Moussiopoulos, Palmgren, Schatzmann), an extensive inventory of data sets has already been produced by COST 615 and made public in the world wide web (http://www.mi.uni-hamburg.de/cost/index.html). The data were categorised into

• data arising from air pollution monitoring networks,
• data arising from specific air pollution monitoring campaigns,
• data arising from field experiments involving controlled releases, and
• data arising from laboratory experiments.

• obstacle resolving microscale models,
• mesoscale chemistry transport models models,
• the interaction between both types of models,
• specific modules of the models,
• full operational air quality models.

A new www-databank was developed by Schatzmann for the wind tunnel data newly generated in the Hamburg University boundary layer wind tunnel (http://ww.mi.uni-hamburg.de/cedval). When producing these data, most up to date instrumentation was used. It is believed that the new data are as complete as presently possible. They are meant to test obstacle resolving microscale models and specific modules (e.g. turbulence parameterisations) included in such models. The data sets comprise 3-dimensional mean and turbulent velocity fields around single or groups of simply shaped obstacles, complete approach flow profiles, turbulent fluxes, spectra etc. The data are freely available and are already used by several SATURN-MOD groups. Further wind tunnel data are being produced in the Czech Republic and UK, first results are presented in the contributions by Colvile and Janour.

Generation of emission inventories.

In future studies real world situations will have to be taken into account which include also traffic emissions. In preparation of this work, significant effort is spent to generate reliable emission inventories for single streets or whole cities. Coordinated by the Technical University of Graz, this work is carried out in co-operation with GENEMIS-2. Guidelines were worked out containing requirements for methodologies and models (bottom–up, top–down), pollutants, resolution in time and space, emission factors including VOC and NO_x split, and, last but not least, a chapter about quality assurance.

Taking the emission inventory for the city of Graz as an example, Sturm shows the importance of having the best and most accurate activity and emission data available. Especially when using statistical data, this data has to be adjusted to the local situation instead of using national statistics.

Borrego et al. based the generation of an emission inventory for Lisbon on two different approaches: a top-down approach for disaggregation of CORINAIR inventory, and a bottom-up estimation considering emission factors and a local data set. These methodologies were applied to road traffic emissions (Borrego et al., 1998). For data validation the emissions inventories obtained by two different approaches were compared. This comparison was performed separately outside Lisbon City and for some areas inside the city. It was concluded that with the increase of spatial resolution of the national inventory the error also increases as a result of the spatial disaggregation process. Comparison of data obtained by different methodologies is an important task for understanding the magnitude of uncertainties associated with an emission inventory to be used for atmospheric modelling purposes. Crucial issues for the development of these methodologies are the availability of detailed base data for performing the bottom-up approach, and the development and testing of different criteria used for the top-down approach.

A preprocessor model for emission input data has been designed and applied to Lombardia Region by Finzi et al.. The model can provide both emission inventory and alternative scenario estimations by means of a mixed approach. Taking into account recent EU guidelines on traffic emission scenarios scheduled for 2005, the corresponding emission fields have been estimated for the studied area in order to perform simulations of the consequent urban air quality impact.

Baldasano et al. developed air pollutants emission inventories that will later be used as input for dispersion and photochemical models to be applied to the Barcelona-Catalonia area. The work developed during this project is directed towards the establishment of a general methodology for the elaboration of emission inventory models. Later this method should be applied to a region or area under consideration. That is why special emphasis is given to the mathematical model formulation.

Model intercomparisons.

Another important task of VAL is the organisation of model intercomparison studies. Graziani started with the development of a strategy for such a study. Presently, the work focuses on meso-scale models only. For the first step it is suggested to compare only results of different models with each other. A simple set-up was chosen for which all initial and boundary conditions are provided.

4.3 Experiments

In particular, it is recognised that work on local scale measurements has made good progress. Although the PIs are liaising well, a new collaborative project on field measurements of fine particulates is proposed. Four partners of EXP1 have shown interest in becoming involved in this project, and other research groups are encouraged to participate. This will enable closer-working links not only between the individual partners of EXP1 but also between the individual EXP tasks. In addition, this will provide a more effective way of creating data sets for local and urban scales. EXP1 has a particular relationship with the TMR programme TRAPOS dealing with street level air pollution (see section 3.1) and further collaboration, also involving new groups, is strongly encouraged.

Many of the experimental results are still under analysis or are included in integrated project including model development and validation. However, many experimental data are available within SATURN and are listed in the inventory.

Local scale experiments.

The experimental data from the street Jagtvej in Copenhagen have been used to estimate the emissions of NO_x, CO and benzene from the actual car fleet under real driving conditions. The method is based on inverse model calculations using the Danish street pollution model, OSPM. Palmgren et al. demonstrated that the method is useful for separating meteorological influences when documenting how air concentrations are influenced by measures taken to reduce the emissions from cars, e.g. catalytic converters and fuel composition (Palmgren et al., 1998). Preliminary results show that the directly emitted ultra-fine particles from vehicles do not coagulate to fine particles in the street. The same method will be used in St. Petersburg in a collaboration with Genikhovich.

A measurement campaign was conducted in a street canyon in Helsinki as a cooperation of Kukkonen et al. and Palmgren et al. The hourly concentrations of CO, NO_x, NO₂ and O₃ were measured on the street and roof levels, together with meteorological measurements and electronic traffic counts. The experimental results were used in order to validate the OSPM model (Operational Street Pollution Model). The agreement of measured and predicted values was analysed in terms of the wind direction; the model reproduces the observed behaviour qualitatively very well. The database, which contains all measured and predicted data, will soon be available for a testing of other street canyon dispersion models.

Like the Helsinki data, also the experimental data collected in the UK by Sokhi et al. have been used for model evaluation and validation.

Urban scale experiments.

Very comprehensive urban scale field campaigns have been carried out and experimental data are included in numerous tasks of model developments and validations.

The contribution of Almbauer et al. refers to the DATE Graz project (Dispersion of Atmospheric Trace Elements in an urban area - taking the City of Graz as an example). The aim of the project is the investigation of the dispersion and conversion of atmospheric pollutants in a poorly ventilated urban area under anticydonic weather conditions, the Austrian city of Graz, located in the pre-alpine region south-east of the Alp, in a basin surrounded by hills of 100 - 400 where the orography is dominated by the valley of the river Mur and mountains of more than 1500 m.The work of this year essentially concerned the initial analysis of this very successful experiment. The results of the winter campaign are available in a data bank using the netCDF-format.

Calpini et al. applied LIDAR measurement techniques in the plume of Milan and obtained results, which were found to be in good agreement with those from a traditional method. In addition, resolved OH spectra were analysed in the laboratory. The method will be used to study the OH reactivity in urban plumes.

Borrego et al’ finally report on the successful completion of the LisbEx97 campaign. The campaing was structered in order to integrate all monitoring stations located on the study domain and mobile monitoring stations. Beside that ground-based information, radiosondes and tether-balloon sounding have been done. The vertical structure of the atmospheric boundary layer was also studied with aircraft measurements.

Wind tunnel experiments.

The unique potential of boundary layer wind tunnels in the micro-scale was further exploited by Schatzmann. Here, the field data from a street canyon monitoring station were enhanced through wind tunnel modelling. The field and wind tunnel data were compared with each other, the importance of certain geometrical details on model results was investigated, and the statistical significance of mean concentration values from field measurements was quantified. Apart from conclusions drawn with respect to model validation, it is shown that the established system is useful for detailed studies of the wind flow in streets under controlled conditions.

Colvile et al.’s detailed wind tunnel measurements on a block of four cuboid-shaped buildings separated by two perpendicular roads, carried out in conjunction with numerical simulations demonstrated the high sensitivity of the flow to small changes in building geometry, specifically departures from the base case of a regular, symmetrical arrangement perpendicular to the incident flow.

Aerosol experiments.

Several studies of the composition and origin of PM₁₀ /PM _2.5 were carried out under SATURN. In Budapest source apportionment analyses by Bozo lead to quantification of contributions from incineration and traffic. The particle size fractionated particles collected by Sokhi in Hatfield were used to characterise the aerosol. The principal results obtained in UK contributed a case study on the relative contributions to primary PM₁₀ concentrations from local roads, other sources across the London area, and longer range contributions in air imported into London. The data were compared with results from CALINE 4, a local scale model, and more complex CFD modelling of street canyons, but with some deviations.

Colbeck et al’s contribution concern aerosol concentrations measured at two sites in the Athens basin, one upwind and one downwind of the city. The preliminary results of ionic species in particles and secondary gases from this campaign demonstrate the land-sea-breeze circulation. The results of this investigation are being used for a detailed evaluation of the processes governing formation and transport of secondary pollutants arising from emissions within the Metropolitan area.

Pakkanen shows that the PM_2.5 concentration at an urban site in Helsinki was mainly caused by local traffic and was found to be an important source for black carbon, organic carbon, road dust and nitrate. The most important contributors to PM_2.5 were sulphate (20%), black carbon (19%), organic carbon (an estimation of 19%), nitrate (14%), ammonium (9%), crustal material originating mostly from road dust (8%) and sea-salt (3%). Moreover, results from detailed measurements of black carbon were shown which revealed that this fraction consisted of mainly the very fine particles, i.e. those smaller than 2.5 microns

4.4 Integration

The main results of the Framework Project (task INT1) are presented in section 6.

Of the three other tasks INT2-4, most activity over the last year has been in INT3 where the seven contributions covering a range of developments of air quality management systems are all proceeding well. These projects cover integration of a wide range of models and data acquisition systems. Such systems were developed for particular areas, e.g. the project, or consist of flexible software designed to be used for a range of cities (ADMS-Urban, AIRQUIS, URBIS). A further activity in this area has been a discussion aimed at developing a generic and widely acceptable description for the structure of an air quality management system or decision support system. On the basis of this discussion the structure given in Fig.2 was drawn up.

Compared with the aims of SATURN-INT as a whole, it has to be noted that most contributions have their own time schedule, which means in practice that several elements that are planned in SATURN for future years are already addressed now. The existing ambition to develop a common description of the desired outputs of AQMSs and integrated AQ assessment methods was discussed, and it was considered necessary to have a common funded project to accomplish this complicated task.

In the individual contributions much progress was accomplished. Examples from the contributions of the PIs in SATURN-INT are the following:

Larssen et al. developed their AQMS (AirQUIS) further and conducted tests, including an evaluation of NO₂ calculations in Oslo. A module for calculating population exposure was added to include exposure as a pollution indicator.

Carruthers extended his AQMS (ADMS-Urban) considerably. Significant additions included improved flexibility of input/output, direct input of traffic flow prediction data and links with meteorological forecast for real time air quality prediction. Comparisons of model output were undertaken in many UK cities.

Van den Hout et al. developed methods to make the existing municipal data usable as input to AQMS. In their AQMS (URBIS) much emphasis is given to the generation of high resolution maps and overviews.

Colvile et al. started the development of methods to add to AQMS the capability of estimating personal exposure to aerosols along commuting routes. This work complements microscale model development using both wind tunnel and Computational Fluid Dynamics models.

Papalexiou et al. worked on the development of an Integrated AQMS. They demonstrated its use to assess the impact of traffic scenarios in Athens. Furthermore, the OFIS model was developed as an efficient tool for calculating statistics of urban ozone levels.

San Jose et al. installed and applied their air pollution forecast system OPANA in Madrid. A web site shows the predicted 24-48 ambient air concentrations real-time. A new version is developed which included zooming capabilities.

The contribution of Borrego et al. encompassed tasks in all Main Groups. In relation to INT a linkage between a Gaussian plume model and a photochemical model with the Carbon Bond Mechanism IV was made.

The experimental and modelling work on photochemical pollution in the Po Valley and its control, by Finzi et al., focused in 1998 on activities in the other main tasks.

Herbarth et al. studied data series of ozone concentration and meteorological parameters for Budapest in order to develop and test a time series model for smog warning. In another part of their contribution they analysed the correlation between health and concentrations to demonstrate the impact of SO2 on health.

A preliminary population exposure model was developed by Kukkonen. The computed results illustrated the temporal and spatial variation of population exposure to NO₂.

5 Main conclusions

The results presented in the preceding section show that scientific work in SATURN is progressing satisfactorily in all four Main Groups of activities. Work appears to be reasonably distributed between basic research and application-oriented activities. Intense co-operation between individual research groups was established in several subproject tasks. On the other hand, collaborative work across the borders of the Main Groups has been rather rare in the reporting period. There is, however, an obvious intention towards a gradual increase of the emphasis put on integration which, combined with the successful launching of the Framework Project (see section 6), is expected to accelerate the synthesis of modelling and experimental work to result in various policy relevant results.

The development of Air Quality Management Systems proceeds satisfactorily and a first conceptual structure for such systems has been drawn up. Although a broad range of types of systems is encompassed, the level of co-operation between individual PIs is still rather limited. More parallel actions are needed to explore the possibilities of detailed common input-output structures of modules. In a few contributions monitoring data are linked to models, but more needs to be done on this. Some work has started on methods to calculate population exposure, but the methods are still very simple.

With regard to model and module development, the most important results are the timely advancement of the overall model formulations, progress in constructing model hierarchy concepts, the identification of gaps in model architectures, and the launch of effective and close co-operations in local scale model validation and further development. Several new modules have been developed for later implementation in urban scale model systems: microphysical adjustments in connection with the radiation schemes that are prerequisites for photochemical simulations, the soil-canopy-atmosphere exchange models, and refined schemes to describe urban scale chemical reactions.

Furthermore, the identification of gaps in the present models or schemes for simulating the urban atmosphere led to new model developments. Examples are traffic induced turbulence within streets, turbulence closures in the lower atmosphere, diffusion of reactive compounds in the immediate vicinity of sources, and particle-radiation-thermodynamics interactions.

The amount and quality of work related to model evaluation is reassuring. The subproject is under way to clarify the links between the models, their purposes, the methods to test their ‘fitness for purpose‘ and the tools (data sets including emission inventories) necessary to accomplish this task. The next step should be the development of general model evaluation protocols for all types of models and submodels which are relevant for SATURN. In addition it seems to be necessary to organise model/data intercomparison exercises not only for mesoscale but also for microscale, obstacle accommodating models. Data from a street canyon monitoring station in Germany will be used as the basis for a ‘blind test’ with the participation of several SATURN PIs. Successfully passed blind tests are probably the best method to convince the authorities and the general public on the quality of such models.

During 1998 many of the experimental activities have been carried out in accordance with the workplan of the subproject, e.g. design of experiments for process studies in the laboratory and the field, publication of data, data analysis in relation to models, wind tunnel experiments, emission estimates etc. Very fruitful collaboration has been established between experimental groups, as for instance the co-operation on particle studies and the local scale experiments in Helsinki, St. Petersburg and Copenhagen. Among other important achievements in the reporting period it was demonstrated that field data might be substantially enhanced by the aid of wind tunnel measurements.

Finally it should be noted that many PIs performing experiments have activities also related to model development and model validation. This underlines the large potential for co-operation between the various disciplines in SATURN.

6 Policy-relevant results

6.1 Introduction

The aims of EUROTRAC-2 are not restricted to the scientific realm; practical application is also a primary goal. Because of this, the structure of SATURN has not been defined from a scientific viewpoint alone: two important elements support its orientation to application (see Fig. 3). In the first place the Main Group of activities SATURN-INT (INT2-4) clusters all activities that have their main focus on application to air pollution management. The second element is the Framework project (INT1), encompassing all SATURN contributions.

6.2 The Framework Project

A work programme for the Framework Project was proposed in close co-operation with EUROCITIES, the representative of the large EU cities in Brussels. It comprises the following elements:

• Organising and managing information exchange and feedback between science and air quality management;
• Developing a framework for application inside SATURN;
• Developing the Quality Assurance Plan for application inside SATURN (see section 3.5);

• Summarising and reporting the work in SATURN to city authorities.

Recently Shell Research Limited provided funding for the Framework Project in the form of a grant for 1999.

6.3 SATURN’s contributions in relation to the application chain

In 1998 a first attempt to develop an application-oriented structure of SATURN was undertaken and a survey of how the individual contributions contributed to the elements of this structure was conducted. The application chain given in Figure 2, based on Fig. 4, shows how results of studies at a more basic level are needed to improve decision making on urban air quality, which can be regarded as the ultimate application of the scientific work in SATURN. It is important to stress that results from all elements in the chain are needed to arrive at rational decision making. So, the science-oriented elements in the upper part of the chain are not less important for application than elements that are linked more directly to policy making, provided that they aim downstream in the chain.

6.4 First inventory of SATURN’s application structure

Fig. 5 summarises results of a first inventory of the aims of the various contributions in which all PIs were asked to indicate their direct aim(s) [3]. Not surprisingly, many contributions have more than one aim. All aims are addressed, and also for more detailed sub-aims distinguished in the inventory (not shown here) this conclusion could be drawn. A large majority of the contributions have elements 1 and 2 of the chain (improving insight, models, techniques) among their direct aims, which illustrates the scientific orientation of the SATURN work. Fig. 5 also displays the distribution of the direct aim with the highest number (the "farthest" aim) indicating how directly the contributions are linked to decision making. Many contributions are found to have direct aims beyond the first ones.

Other conclusions from the inventory are that SATURN extensively addresses the microscale (streets, buildings) as well as the city as a whole. Regarding the pollutants investigated, much emphasis is on both primary and photochemical pollutants; particulate matter is, however, studied in only 15% of the contributions, which seems rather low in view of the current interest of air quality management.

The inventory describes the supply side of scientific information. Whether the supply is well distributed over the chain obviously depends on the demand side, i.e. the needs of AQ management, and also on which results are needed to maintain the chain. SATURN’s research should primarily aim at the weak areas in the structure, which are not necessarily evenly distributed over the application chain. In the next year the Framework Project intends to develop an overview of the demands on the basis of structural contacts with urban air quality managers.

An important question for SATURN is whether its contributions together can be viewed as one application chain, i.e. whether the contributions aim at applications within other SATURN contributions "downstream" in the chain. About 30% of the contributions reported to have planned its application in another scientific project, among which about 10% are in another SATURN contribution. This low percentage is explained by the way in which SATURN was initiated: in its initial stage SATURN is more a platform of independent studies than a set of linked studies. (This should not be confused with scientific interaction, in which data, knowledge etc. are usually shared within one element of the application chain.)

6.5 Concluding remarks

The overview of SATURN emerging from a first attempt to develop an application-oriented structure shows that most contributions have application among their direct aims. The various fields of work seem to be well covered, though aerosols could deserve more emphasis; how well SATURN’s ensemble of aims really matches the demands of air quality management should become clearer in the next period.

7 Aims for the coming year

The most important aim for SATURN in the coming year will be the successful completion of the subproject’s Phase A. Taking into account any recommendations to be formulated in the course of the planned review procedure (see SATURN description), the Steering Group will proceed to Phase B which will be characterised by a gradual increase in the collaboration among the Main Groups of activities.

In particular, it is expected that in the coming year the required model hierarchy and necessary components will be fully developed. Coupling of different models in co-operative simulations will be facilitated by the harmonisation of the data exchange procedures. It is planned to conduct a study of the model hierarchies needed in numerical modelling exercises over urban areas, as concerns constraints, availability, and guidelines.

At the same time, adequate evaluation procedures will be formulated for both obstacle resolving microscale models and mesoscale chemistry transport models. This will allow launching model validation activities which in the coming year will have to be based on existing data sets. The farther the progress of experimental activities in SATURN, but also in EUROTRAC-2 as a whole, the more these validation activities will rely on new quality assured data sets.

In the coming year it is anticipated that several field and laboratory experimental studies will be executed to facilitate launching the appropriate interpretation activities which will lead to establishing new experimental data sets. In this context it should be noted that experimental data suitable for the evaluation of multiscale model cascades are expected to result from the international co-operative programme URBCAP (Mestayer, 1998).

With regard to integration, it is expected that the concepts for integrated air quality management systems will be further developed, taking advantage from advances in computer technology and telematics. During the next year emphasis will be put on demonstrating newly developed integrated systems.

Finally, the Framework Project is expected to progress considerably in the coming year by establishing structural contacts between SATURN and urban authorities. It is anticipated to provide information to urban authorities using various forms of presentation including the internet. The results will be further monitored in terms of deliverables and improvement of input/output structure along the application chain. Gaps in information or tools will be identified and new projects will be stimulated to fill these gaps.

8 Acknowledgements

On behalf of all scientists contributing to SATURN, the authors gratefully acknowledge the support of national funding agencies for the research work constituting the subproject. The funding of national projects formed the basis for all achievements obtained during the reporting period. The Framework Project is financially supported by Shell Research Ltd.

9 References

6 Main Group Leaders

MOD     Patrice Mestayer

VAL     Michael Schatzmann

EXP     Finn Palmgren

INT K. Dick van den Hout

7 Task Leaders

III Publications

1 Refereed literature

2. Contributions to the EUROTRAC Symposium ‘98T

 

Almbauer R. A., D. Öttl, Ch. Sudy and P. J. Sturm: DATE Graz: Dispersion of Atmospheric Trace Elements using the City of Graz as an Example.

Borrego, C.; Barros, N.; Lopes, M.; Conceição, M.; Valinhas, M. J.; Tchepel, O.; Coutinho, M. and Lemos, S. (1998): Emission inventory for simulation and validation of mesoscale models.

Borrego, C.; Barros, N.; Lopes, M.; Conceição, M.; Valinhas, M. J.; Tchepel, O.; Coutinho, M. and Lemos, S. (1998): Data collection for mesoscale models validation: experimental field campaign.

Bozó L., Labancz K., Pinto J., Baranka Gy. and Kelecsényi S. (1999): Source-Receptor Relationships of Trace Elements in Budapest.

Catenacci G., M. Riva, M. Volta, G. Finzi; A Model for Emission Scenario Processing in Northern Italy.

Karppinen, A., Kukkonen, J., Konttinen and Koskentalo, T., 1998. Verification of a Modelling System for Predicting Urban NO2 and NOx Concentrations.

Pirovano G., G. Bruasca, G. Calori, F. Desiato, S. Finardi, F. Lena, A. Longhetto, M.G. Morselli; Meteorological input for photochemical models in Milano region.

S. Anquetin, J. P. Chollet, A. Coppalle, P. Mestayer & J. F. Sini (1999) The Urban Atmosphere Model SUBMESO.

Sturm P., P. Blank, T. Bohler, M. Lopes, C. Mensink, M. Volta, W. Winiwarter; Harmonised method for the compilation of urban emission inventories for urban air modelling.

Mensink C., J. Van Rensbergen, P. Viaene, I. De Vlieger and F. Beirens; Temporal and spatial emission modelling for urban environments using emission measurement data.

Moussiopoulos N. (1999), Urban air pollution: Current knowledge and future research.

Moussiopoulos N. and Sahm P. (1999), The OFIS model: An efficient tool for assessing ozone exposure and evaluating air pollution abatement strategies.

Moussiopoulos N., Theodoridis G. and Assimakopoulos V. (1999), The influence of fast chemistry on the composition of NOx in the emission input to atmospheric dispersion models.

Moussiopoulos N., Samaras Z., Papagrigoriou S. and Tourlou P.M. (1999), Projection of future air quality in Athens.

Pakkanen T.A., C.H. Ojanen, V.-M. Kerminen, R.E. Hillamo, J. Meriläinen, P. Aarnio, T.Koskentalo and K. Hämekoski (1999) Effect of nitrate evaporation on the determination of PM2.5 by virtual impactor.

Kovar, A., Leitl,B., Liedtke. J.,and Schatzmann, M.(1998) Physical Modelling of Vehicle Emissions in Respect of Car Induced Turbulence.

Schatzmann, M., Liedtke,J., Leitl, B., and Kovar,A. (1998) Modelling and Validation in an Urban Environment.

Liedtke,J., Leitl, B. and Schatzmann, M. (1998) Dispersion in a Street-Canyon: Comparison of Wind Tunnel Experiments with Field Measurements.

SCAPERDAS A, R N COLVILE A G ROBINS, 1999. Understanding flow patterns at street canyon intersections using wind tunnel and CFD simulations.

Sturm P.J., Sudy Ch., Almbauer R.A., Meinhart J., 1998; Updated urban emission inventory with a high resolution in time and space for the City of Graz

3. Theses

Ch. Hirsch, N. Hakimi, P.E. Bournet
Turbulent flow simulations in urban configurations

M. Jicha, J. Katolicky, J. Pospisil
Air quality in urban areas: Traffic induced pollutants concentration and dispersion

N. Moussiopoulos, W. Bickmeier, P. Sahm
Microphysical processes and radiative transfer in ZEUS

P.G. Mestayer, J.F. Sini, J.P. Chollet
Pollutant transfers within streets - model development for SUBMESO

B. Calpini, A. Clappier, A. Martilli
Air quality in urban areas: modelling with variable grids

A. Coppalle, L. Delamare
Subgrid-scale dispersion and chemical processes in the vicinity of Nox emission sources

Y. Andersson-Sköld
Development of chemical transformation mechanisms to be used in models of urban areas and urban plumes

S. Perego, M. Junier
The influence of heterogeneous processes onto the urban atmosphere

K. Heinke Schlünzen, H. Panskus
An evaluation concept for microscale numerical models of the obstacle laye

G. Smiatek, W. Xiaoling
Mapping roughness length in urban and suburban areas using ERS interferometric SAR data

J.P. Peneau, M.J. Antoine, D. Groleau, L. Tiraoui
Radiative modelling in urban canopy

P.J. Sturm
Harmonised method for the compilation of urban emission inventories for urban air modelling

J.M. Baldasano, C. Soriano, I. Toll
Development of an upgrade urban source emission model for atmospheric pollutants

C. Borrego, O. Tchepel, N. Barros, M. Lopes, M. Conceição, M.J. Valinhas, A.I. Miranda, S. Lemos
Generation and validation of emission inventory for Lisbon region

C. Mensink, I.D. Vlieger
Development of an urban emission inventory for the Antwerp area

P. J. Sturm, Ch. Sudy, R. A. Almbauer, J. Meinhart
Update of an emission inventory for urban air quality modeling purposes with a high resolution in time and space for the city of Graz

G. Graziani, P. Thunis, S. Galmarini, C. Cuvelier
MESOCOM: An inter-comparison exercise of flow models used for urban air quality simulations

R. S. Sokhi, S. Bualert, A. Lester, B. Fisher I. McRae (task summery)
Evaluation of roadside air quality models

R. S. Sokhi A. Tremper, L. Luhana A. Burton
Measurement of fine particulates in an urban location

F. Palmgren, R. Berkowicz, O. Hertel, E. Vignati
Car fleet emissions estimated from urban air quality measurements and street pollution models

J. Kukkonen, A. Karppinen, P. Aarnio, J. Walden
Studying atmospheric pollution in urban areas by mathematical modelling and measurements

R. A. Almbauer, P. J. Sturm, L. Windholz, M. Piringer, R. Lazar, E. Putz
DATE Graz, dispersion of atmospheric trace elements in an urban area – taking the city of Graz as an example

E. Genikhovich, I. Gracheva, A. Ziv, E. Iakovleva, E. Filatova
Study of air pollution in St. Petersburg area

C. Johansson, U.Wideqvist, V. Veseley, R. Westerholm, E.Swietlicki
Carcinogenic substances: Importance of different sources for the distribution and for man’s exposure

M. Schatzmann, B. Leitl, J. Liedtke
Wind tunnel modelling in support of model validation

R. Colvile, A. Scaperdas, A. Robins
Microscale urban dispersion: wind tunnel measurements

Z. Janour
Urban microscale dispersion data development - wind tunnel experiment

L. Bozó, J. M. Pinto, K. Labancz
Chemical composition and source origin of fine aerosol particles in Budapest, Hungary

I. Colbeck, M.Chen Chung
Aerosol transport in urban areas

T. Pakkanen, C. Ojanen, R. Hillamo, P. Aarnio, T. Koskentalo, W. Maenhaut
Atmospheric particulate matter in urban environments

H. ApSimon, V. Asimakopoulos, A. Mediavilla , G. Martinez-Villa, K. Clemitshaw, R. Colvile
Source apportionment project, SAP

K. Karatzas, N. Moussiopoulos, S.Papalexiou, G. Theodoridis, P.M. Tourlou, T. Nitis
Development and application of tools for smog episode forecasting and for management decision support in urban areas

U. Schlink, O. Herbarth, L. Bozo
Time series analysis of ozone air pollution in Budapest, Hungary

D. J. Carruthers
Development of an air quality management system

D. v. d. Hout, P. Zandveld
SURFIS - Studying the URban FIne Structure

S. Larssen, T.Bøhler, S. E. Walker
Development of an air quality information system (the AirQUIS System), including an urban scale model evaluation/validation exercise

G. Finzi, G. Brusasca, P. Buttini, G. Calori, G. Catenacci, C. Cavicchioli, F. Desiato, F. Lena, A. Longhetto, A. Marzorati, U. Pellegrini, G. Pirovano, M. Riva, C. Silibello, M. Volta
A comprehensive modelling system for photochemical pollution control in metro-politan areas

R. San José, M.A. Rodriguez, I. Salas, R.M. González
Integrated and operational environmental forecasting model in metropolitan areas: OPANA

O. Herbarth, U. Schlink, M. Richter, U. Müller, G. Fritz
Analysis of environmental impact on health status data