Environmental software conference report

Environmental software conference report

Gwironmental PII:SO266-9838(96)00015-9 ELSEVIER S@ware, Vol. I I. No. 4. pp. 277-284, 1996 0 1997 Elsevier Science Ltd All rights reserved. Print...

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.Gwironmental

PII:SO266-9838(96)00015-9

ELSEVIER

S@ware,

Vol. I I. No. 4. pp. 277-284, 1996 0 1997 Elsevier Science Ltd All rights reserved. Printed in Great Britain 0266-9838/96/$15JXI + 0.00

Environmental Software Conference Report 4th Workshop on Harmonisation within Atmospheric Dispersion Modelling for Regulatory Purposes, Oostende, Belgium, 6-9 May 1996 Guido VITO,

Boeretang

(Received

24 June

Cosemans 200, B2400 Mol, Belgium

1996: accepted

12 July 1996)

Abstract In 1991, scientists and regulators in Europe started the Initiative for Harmonisation within Atmospheric Dispersion Modelling in Europe. One of the visible actions of this Initiative was the launch of a series of workshops, each one focusing on a particular step towards the achievement of better tools and data for model evaluation and towards an increasing awareness that models must be used in an appropriate way for decision making. In the 4th Workshop, an overview was given of relevant research co-ordinated at the European level, and a first bridge was established to the relevant European Agencies. 0 1997 Elsevier Science Ltd. All rights reserved. Keywords:

Harmonisation; atmospheric transport and dispersion models; model validation toolkit; model evaluation; sion; meteorological pre-processing; urban canopy; COST 6 15; COST 7 10; practical applications

model intercompar-

Environment. He said that progress in the validation and the intercomparison of operational models used for the assessment of air pollution is crucial within the current political process of harmonisation of environmental legislation and conditions of competition within Europe. He mentioned several important legislative measures upon which the EU Environment Ministers agreed recently: amendments to the Directive 85/337/EEC on Environmental Impact Assessment, obligations of the Member States with respect to projects likely to have important transboundary effects and new directives on ambient air quality assessment and management and integrated pollution prevention and control.

1. Introduction

The 4th Workshop on Harmonisation within Atmospheric Dispersion Modelling for Regulatory Purposes was held on 6-9 May, 1996 in Oostende, Belgium. The venue was the Thermae Palace Hotel, situated on the sea dike at the North Sea. The local organiser of this workshop was VITO, the Flemish Institute for Technological Research, Mol, Belgium. The workshop was attended by 180 participants from 30 different countries. The workshop was opened by Jan Peters, the Belgian State Secretary for Safety, Social Integration and 277

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2. The scientific programme A total of 78 oral presentations, eight demonstrations of modelling software on PC and 23 poster presentations were given during the workshop. This implied rather well-filled days from 9 a.m. until 6 p.m. The lengthy coffee and lunch breaks (2 x 40 min, lOO120 min, respectively) provided ample opportunity for contacts and informal information exchange. As one of the participants wrote on the evaluation form: ‘I am a newcomer in the field of air pollution modelling, and by the end of the workshop, I had made contact with the most important scientists in this field and have acquainted a good insight into the state-of-the-art and the current challenges in this discipline.’ The scientific programme was divided into six major parts: (1) Practical Use of Atmospheric Transport and Dispersion (ATD) Models for Real Life Environmental Impact Assessment (EIA) Problems; (2) Regulatory Modelling: Country Review; (3) Validation and Intercomparison of Operational Models; (4) Harmonisation in the Pre-processing of Meteorological Data for Dispersion Models; (5) Modelling in the Urban Canopy; and (6) A panel discussion with representatives from the European Environment Agency and members of the Steering Committee. Parts 1, 2 and 3 continue the work of previous workshops, part 4 presents preliminary results of a concerted European research programme that was defined during the first workshop, and part 5 deals with a problem area that is becoming more and more important.

3. Practical use of ATD models for real life EIA problems Frank de Leeuw (RIVM, Netherlands) opened this session with a review of requirements for models and model applications, work carried out for the sub-project MA3-1 of the 1994-1999 work programme of the European Environment Agency by the RIVM/NILU Topic Centre for Air Quality (TC-AQ). Project MA3 deals with harmonisation in the use of air quality models. Within MA3-1, the role of air quality models in the preparation of the report ‘Europe Environment; the DobrfS Assessment’ was analysed, the answers of a questionnaire sent to all 38 European countries were analysed, and the model requirements and needs from international organisations (EU directives and decisions, UN-ECE Convention on Long Range Transport of Air Pollution and Marine Conventions) were reviewed. Guido Cosemans (VITO, Belgium) presented an IFDM-modelling study for the optimal siting of ambient air quality monitors around five oil refineries. Given the relevant legislation, it was mandatory to look at the 98percentiles of the moving 24-h averages of

Software Conference Report the calculated ground-level concentrations. Calculations were done for 11 different years of meteorological data. Because different ‘optimal’ siting locations showed up for each year, a synthesis of the calculated groundlevel concentration fields was mandatory. Next, information from modelling was integrated with information from several measuring campaigns and existing monitoring networks, because emission inventories are not necessarily complete. E. Klimova (Greenwich University, UK) highlighted the long-range transport model UGEM (The University of Greenwich Evaluation Model): model description, validation and a local scale application for Thames Gateway, 1992 were discussed. M. V. Galperin (EMEPMSC-East, Russia) presented the results of the MSC_E model applied to sulphur deposition in the St Petersburg region. While regional calculations were done on a normal 39 x 37 EMEP grid with gridsize 150 km, the local calculations for subregion St Petersburg were done on a 18 x 18 grid with gridsize 25 km. As might be expected, this modelling indicated that there is a considerable non-uniformity of deposition within the 25 x 25 km* cells compared to the 150 x 150 km* cells. For the subregion, modelling indicated that about 40% of the emitted sulphur is deposited in it-a huge fraction, which may be due to local characteristics such as large areas of fresh water basins and prolonged periods of fog, rain and wet snow, leading to high-intensity scavenging. L. Andersen (Elkraft Power Company, Denmark) illustrated how model output and legislation were combined by a power plant in Denmark into an operational formula to decide on the allowable sulphur content of the coal used in the different units for different modes of operation. N. Moussiopoulos (Aristotle University, Thessaloniki, Greece) presented an analysis of the impact of the new Athens airport on urban air quality with contemporary air models such as MEMO (inert pollutant dispersion) and MARS (photochemical model), all constituents of the European Zooming Model (EZM). Several relevant meteorological situations were modelled, including those associated with the main synoptic classes during air pollution episodes in the Greater Athens Area and those for which data were available from a field campaign. Pollutants considered were CO, NO,, VOC, SO*, smoke (PMlO) and ozone. Emission estimates for three years were used (1993, 2002, 2012), the expected emissions for the year 2012 being the largest. E. Vrins (Bruro Blauw, Netherlands) described the combination of ambient dust measurements and the output of the Fugitive Dust Model to estimate the dust emissions from fugitive sources. Much attention was given to the statistical techniques used to obtain an optimal result.

G. Cosemans/Environmental 4. Regulatory modelling: country review The revision of the Dutch National Model was the subject of two presentations and one poster. The new model will be based on the model STACKS, a research model developed by Dr Hans Erbrink of the KEMA Research Institute (Netherlands). J. van Ham (TNO) presented some main modifications of the new regulatory model: dispersion parameters based on Taylor’s statistical theory; boundary-layer height for stable and neutral conditions by calibrated formulae, for unstable conditions by the growth model of Driedonks; plume rise: modified Briggs, partial penetration according to Briggs, deposition using the resistance method, NO, formation, and building wake effects. An empirical alternative to the E&man spiral, based on Van Ulden and Holtslag, is used. Ph. Cornille (SGS EcoCare, Belgium) presented experiences of users with the Belgian IFDM model. The work done by VITO with respect to model validation and the demonstration of the models’ applicability to atmospheric dispersion in various places in Belgium, was appreciated. Graphical output, or the possibility to export model results in a simple way to a GIS or other graphical tool is considered to be a very important feature of the model. J. Kukkonen (Meteorological Institute, Finland) discussed the wealth of dispersion models for regulatory modelling in Finland and their regulatory use. Most models are developed by the Finnish Meteorological Institute. They make use of a meteorological preprocessing model, based on Monin-Obukhov type boundary layer scaling, which estimates the relevant turbulence parameters from routine observations. In order to obtain model results that are independent of the meteorological conditions during any particular year, it has been shown that the use of three years of meteorological data is usually sufficient, and these are used in EIA. Models are: the Urban Dispersion Modelling System UDM-FMI, a multiple source Gaussian plume model (point, line, area, volume sources), giving time series of calculated hourly concentrations (Cray 94 computer); the Road Network Dispersion Model (CAR-FMI), a Gaussian finite-line source model with chemical transformations using the discrete parcel method of Benson (NO,, NO, NOz, 02, 03, no VOCs), available on PC; and two street canyon dispersion models, based on CPBM and OSPM. Real-time and forecasted air pollution information for dissemination to the public is available through the Air Pollution Information System (API-FMI). A dispersion model for odorous compounds (ODO-FMI), based on the work of Hanna, allows the spatial prediction of odour frequencies. Research needs and information required for successful application of the models are formulated. Some of these PC-based models were demonstrated. Two papers threw some light on the modelling situation in China. Xin Qiu (Ministry of Electricity

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Power, Nanjing) described some distinguishing features of four dispersion models: HPDM (USA); AMS (Canada); PPSP (Maryland, USA); and GB (Chinese National Standard Model), and comparisons of their output for a tall stack using one year of meteorological data. Zongkai Li (University of Nanjing) described the impact of different meteorological pre-processors (CRADM, HPDM, AMS) on the resulting frequency distributions of stable, unstable and neutral conditions and of mixing depth values. A comparison was also made of calculated ground-level concentrations, and a suggestion to improve the Briggs plume rise formulae by taking the influence of ambient turbulence on plume rise into account was presented. C. Borrego (University of Aveiro, Portugal) presented the POLARIS Model and compared the output of this model and two other models with groundlevel concentrations measured at four fixed monitoring sites. In the discussion after this presentation, the presented comparison of calculated and measured ground-level concentrations was one of the issues. Doing such a comparison using correlation or scatter diagrams is not very relevant. The real wind direction will almost certainly differ from the wind direction used in the model (frequency distributions are better). The model validation toolkit, which was developed at previous workshops, provides much better data and statistical tools for model evaluation and intercomparisons. V. Pocajt (University of Beograd, Yugoslavia) described a complex expert system for air pollutant modelling called ScalEx, which is still under development. M. C. Cirillo (ENEA, Italy) gave an overview of the current Italian debate on the role of regulatory models in the frame of the new European directives on air quality. Models are used for EIA in the context of EU Directive 85/337/EEC, for designing, evaluating and complementing air quality monitoring networks, areas (problem: emission especially in urban inventories), and for Regional Air Quality Management Plans (with emphasis on photochemical dispersion). Models have some difficulty, however, in being accepted, and several reasons for this were given and discussed. Better quality of model input data, harmonisation in model use and improvement in the quality of regulatory models used are important issues. Redundancy in measurements, that very often occurs in air quality networks, should be eliminated, and the resources thus saved could be used for building up a database for model evaluation. Well-tuned and properly used models may save a substantial amount of money by helping to identify the more cost-effective solutions to meet air quality goals.

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5. Validation and intercomparison models

of operational

One of the results of the previous workshops is the Model Validation Kit, which currently contains three sets of experimental data: Kin&d, Copenhagen and Lillestrom, as well as software with relevant statistical tests for model evaluation and intercomparison. Martin Tasker of ICI Engineering Technology, UK, opened this session and explained that guidance and training are needed to facilitate good consistent application of the available air quality modelling tools. Using the best physics in the simulations means nothing if the users misapply the models. Nicolas Moussiopoulos then provided a summary of the strengths and weaknesses to be seen in the current state of air quality modelling. For all scales from local to global, there appears to be a need for well-packaged evaluation data sets, and for the urban scale there is a need to develop a community of researchers interested in collaborating in the evaluation of urban scale air quality models. To allow users to be better aware of the air quality modelling tools available, a web page is now being supported to provide easy access to an inventory of modelling methods and databases. The address is: http://www.dmu.dk/atmospheric environment/ default.html. Werner Klug of Technische Hochschule Darmstadt, Germany, provided a summary of the status of the European Tracer Experiment ETEX data set which will be well-suited for use in meso- and long-range transport and dispersion model evaluation studies. Results from the first 12-h release and 3-day sampling campaign are to be made available to the public in August 1996. The first release occurred on 23 October 1995 and samples were successfully collected at 141 sites (400-800 km downwind from the source) in 17 European countries. Results from the second release which occurred on 14 November 1995 are to be made available to the public by the end of 1997. An ETEX workshop is planned for early summer 1997. David Carruthers of Cambridge Environmental Research Consultants, UK, illustrated the use of threedimensional concentration results obtained using the RASCAL (Rapid Scanning LIDAR) and the DIAL (Differential Absorption LIDAR) for dispersion model evaluations. Unfortunately, the particular data sets described may not be available to the public. But hope was given that data from future planned studies can be made available. Peter de Haan (ETH, Zurich) used the Copenhagen evaluation data set. Better dispersion model results are obtained by explicitly accounting for the presence of an urban roughness sublayer. The height of the roughness sublayer was prescribed to be 2h, where h was the average building height (estimated to be 6 m). It was found that the sonic anemometer observation height was likely to be just below 2h, and hence provided

Software Conference Report measurements close to what would have been measured in the inertial surface layer above the roughness sublayer. Uhike Pechinger of the Central Institute for Meteorology in Austria used the Austrian Gaussian plume model and obtained favourable comparison results for Kincaid and Copenhagen, but found difficulties in replicating the Lillestrom observed concentration values. This is not surprising, as no model has been found so far that consistently performs well in simulating the Lillestrom tracer results involving dispersion at subzero temperatures during light-wind conditions over moderate snow cover in a suburban setting. R. Ries of Lahmeyer International, Frankfurt/Main, Germany, compared different Lagrangian Models (KLIMM-L, LASAT, STOER.LAG) using the Lillestrom data. The wind fields are calculated with the mesoscale model KLIMM-S (references to the subalgorithms in the paper). It was found that six out of the eight experiments were characterised by drainage flows. Not taken into account yet are microscale effects as local induced heat turbulence and dynamic effects due to buildings acting as flow obstacles. Robert Yamartino of Earth Tech, USA, evaluated the Kinematic Simulation Particle Model (KSP) with the Copenhagen and Lillestrom data. Dispersion characteristics were based on the Klug Stability scheme and the TA_Luft dispersion parameters. For each experiment, about 40 realisations were computed. E. Ferrer0 of the University of Alessandria, Italy, compared two Lagrangian Particle Models, based on the publications of Thomson in 1984 and 1987, with data from the water tank experiments by Willis and Deardorff and from the atmospheric dispersion data at Karlsruhe, 1983 (KATREX data). Two papers, presented by Kurt Petersen of Rise National Laboratories, Denmark, and A. Mercer, Health and Safety Laboratory, Sheffield, UK, gave an overview of the work of two workgroups established by the EC. The first one dealt with model quality and safety studies for potential industrial hazards, the second concentrated on heavy gas dispersion models. John Irwin of the US EPA reported on aspects relevant for the methodology to evaluate models against experimental data. The importance of natural variability (due to inherent uncertainty caused by the stochastic nature of atmosphere turbulence) is demonstrated using the Prairie Grass and Kincaid data. John further reported on the investigations on the sensitivity of different ensemble parameters for natural variability, and the consequences for establishing a model evaluation methodology. (An ensemble is a set of experiments corresponding to fixed external conditions.) C. Mensink of VITO, Belgium, presented results from a sensitivity study performed using a number of operational air quality models: NM, IFDM, AUSTAL86, OML, ADMS, STACKS, OPS and ISCST2. The result was that models which use mixing height

G. Cosemans/Environmental and/or boundary layer parametrisation are most sensitive to changes of the input parameters. J. Bartzis of NCSR ‘Demokritos’, Greece, presented the results of seven dispersion models for complex terrain applied to a set of six hypothetical sources (ambient temperature releases) situated at the foot of a mountain near Athens and for five different typical meteorological conditions. Important differences in calculated wind fields and maximum ground-level concentrations were predicted. Helge Olesen of NERI, Denmark, reported on further progress in the Model Validation Kit, its use and recent extensions. The new data sets are: Indianapolis, where SF6 was released from an 84 m power plant stack in an urban environment, and Bull Run, where a tracer gas was released from a 244 m stack located in moderately complex forested terrain in the Tennessee River Valley. Olesen showed preliminary results of the OML model on the Indianapolis data set. Steve Hanna of Earth Tech, USA, showed similar results for the HPDM model.

6. Harmonisation in the pre-processing of meteorological data for dispersion models The activity of inferring meteorological parameters needed for dispersion modelling using the available meteorological data, as well as the way in which time series of hourly data over long time periods are summarised into climatologies, is called pre-processing. This pre-processing is of comparable importance to the dispersion modelling itself. Within the EU, research on pre-processing is co-ordinated by COST Action 710. Topics of interest are: Surface Energy Balance; Boundary Layer Depth; Vertical Profiles of Wind; Temperature and Turbulence; Complex Terrain; and Climatologies. 6.1. Energy fluxes and mixing height There are several studies which evaluate models which describe surface fluxes of momentum, heat and energy, and related scaling parameters, using available experimental data. The impression is that there are 23 models which describe the real fluxes in a realistic way, and could be recommended for general use. There are continuous problems with the description and handling of the mixing height, to a large extent due to the lack of an instrument which determines the mixing height in a coherent and consistent way. It might be worthwhile to hold a 2-3 day workshop (about 20-30 participants) to discuss the mixing height problem. In discussions it was mentioned that the results presented in this section sometimes lacked the connection with applications, as for example in grid models, and that more attention should be given to uncertainty analyses of the results presented.

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6.2. Vertical projiles and complex terrain H. Erbrink (KEMA, Netherlands) gave an overview of the COST 710 activities in the pre-processing of vertical profiles with a review and preliminary recommendations for cr,, a, and TL, wind speed and direction. Finardi and Moselli (ENEL, CISE, Italy) presented papers on pre-processing wind and temperature in complex terrain. Erdun (Istambul University, Turkey) discussed grid transformations in mesoscale models. R. Salvador (CEAM, Spain) reported the special and interesting structure of the large-scale thermally driven cells over the Spanish peninsula. The observed thermal large-scale cells were well predicted by model simulations with RAMS. Deligiannis (NCSR, Greece) showed a comparison with Demokritos, measurements of model simulations of wind speed and wind direction during a sea breeze episode in the Athens basin. Detailed geographical information is taken into account in the interpolation procedure to determine the wind field. Kunz gave a presentation on the APSIS (Athenian Photosmog Simulation Intercomparison Study) exercise: predicted versus measured wind and temperature fields for two experiments in the Greater Athens Area for the mesoscale models GRAMM, KAMM, MAR, MEMO, MERCURE, PROMETE0 and TVM. 6.3. Pre-processing and climatologies Peter de Haan (ETH, Switzerland) elaborated ideas on the roughness sublayer and showed the importance of not regarding meteorological measurements at less than a few building heights as representative of the surface layer. Several papers discussed complete preprocessing systems: Karpinnen et al. presented the Finnish Meteorological Institute pre-processor and discussed the substantial differences between results from it and from the Berkowitz and Prahm heat flux scheme. Bolher (NILU, Norway) discussed the MEPDIIM preprocessor developed at NILU and difficulties experienced with it for inhomogeneous terrain, while Johanson (National Defence Research, Sweden) compared the FM1 and SMHI pre-processor for snow-covered surfaces. Scherer (Institut fur Meteorologie, Germany) discussed a pre-processor application from which the output was used to drive a Langrangian particle model. Two papers discussed climatological issues. Wichmann-Fiebig (North-Rhine-Westphalia State Environment Agency, Germany) showed that, for dispersion in complex terrain, the use of on-site wind statistics can give poorer results than the use of measurements from a well-exposed site some distance away, if the on-site wind is strongly influenced by local effects. Davies (UK Meteorological Office) discussed the general problem of climatologies for dispersion modelling and showed typical errors resulting from categorisation classes, and differences between modelling results

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obtained using climatologies for individual years compared to multi-year climatologies.

Software Conference Report discussed. Moreover, it follows that the model results substantially depend on the turbulence model applied. 7.2. Buildings

7. Modelling in the urban canopy 7.1. Street canyon and tunnel exits Rudwin Berkowitz (NERI, Denmark) opened this session with: ‘Modelling street canyon dispersion: model requirements and expectations’. The various basic approaches to street canyon dispersion models are recalled, limitations are mentioned, and applications of models are given. A combination of modelling and measurements is most effective for understanding air pollution. H. Kono (Environment and Public Health Bureau, Osaka) presented past modelling results for NO, over the larger Osaka region. D. Y. C. Leung (Hong Kong) described modelling techniques used in Hong Kong to predict peak CO concentrations. R. Sokhi, University of Hertfordshire, UK, described capabilities and limitations of three models to predict NO, concentrations (CAR, CALINE4, DMRB (Design Manual for Roads and Bridges)), and compared some of the predicted concentration parameters with those of the measured values. J. Eichhorn (Gutenberg University, Mainz, Germany) presented the three-dimensional numerical model MISCAM (Micro Scale Air Pollution Model) for wind flow and pollutant dispersal in densely built-up areas: theory, simulation of wind tunnel data, simulation of traffic induced pollution. The model can be used operationally. The next public version will include heat and radiation budgets. C. A. McHugh (CERC, UK) reported on recent extensions of the ADMS model such as a street canyon model (based on the Danish Operational Street Pollution Model), chemistry (GRS of CSIRO) and input from a map (GIS). The resulting model is called ADMS-Urban. G. Schadler (Ingenieurbiiro Dr. A. Lohmeyer, Karlsruhe) compared six microscale models with wind tunnel data. For idealised urban structures, the MISCAM model gave the best performance. For field data (yearly average, 98-percentile of pollutant (benzene, NO,, CO) concentration measured in the Gottinger Strasse, Hannover, 1994), the non-dimensional concentrations given by ASMUS and MISCAM could be transformed to give a minimal error between calculated and observed time series. R. Ries used MISCAM to model CO, NO, and ozone near a tunnel exit and compared model output with measurements. Good agreement was found. M. Jicha (University of Brno, Czech Republic) and D. Delaunay (CSTB, Names) both reported on modelled pollutant distributions at road tunnel outlets. An important result is the confirmation of the importance of properly describing air flow in the tunnel. The dependence of the latter on several parameters was

Ian Cowan (University of Surrey, UK) compared wind tunnel data with k-epsilon CFD (Computational Fluid Dynamics) packages for workstations in order to evaluate CFD uncertainty. He compared four models on the same test cases (L-shaped buildings). His conclusion: even for the simplest test cases, solutions are still grid-dependent. Alan Robins (University of Surrey, UK) described a model based on Hunt’s rational method of splitting the flow into a series of recognised regions around a building. This simplifies the dispersion in each region but procedures for the transfers from one region to the neighbouring one have not yet been perfected. Eugene Genikovich (MGO, St Petersburg, Russia) gave an account of the development of the OND-86 model based on flow splitting in several regions and nonsuperposition of two (recirculating and recirculating) concentration fields. Jorg Getting (University of Karlsruhe, Germany) presented predictions of dispersion over U-shaped buildings calculated with the MIMO (Eulerian kepsilon) model, which is based on MEMO. Comparison of computed concentrations with wind tunnel data are satisfactory when performed with a grid of 48 x 48 x 28 mesh cells covering a domain of 400 x 400 x 150 m. For the most simple U-shaped building, computation times varied from 5 min (wind direction 0’) to 15 min (135”) on a vector computer SNI S600/20. P. Kastner Klein (University of Karlsruhe) presented wind tunnel data for diffusion behind buildings and in a series of parallel street canyons and a cross-roads, and compares some data with the outcome of the models MISCAM (prognostic model) and ABC (diagnostic model). Spyros Rafailidis (University of Hamburg, Germany) worked on concentration and flow measurements in parallel streets with and without cross-roads, in a wind tunnel. His conclusions: generation of three-dimensional flow deflection and transverse vortices in twodimensional canyons, large effects of roof shape and height; cross-roads can induce concentration transport two streets upwind of sources. M. Wichmann-Fiebig (Northrhine-Westphalia State Environment Agency, Germany) investigated the dispersion of traffic pollution (CO, NO,) at complex crossroads. Real world measurements (one-year period) were compared with results from wind tunnel and numerical simulations. Jari H&k&en (FMI, Finland) compared NO,, NO* and O3 measured in the vicinity of a road at three heights with CAR-FM1 output. He used a ‘simpler model’ for background concentrations. Models underestimate measurements by only lO-20%. His con-

G. Cosemans/Environmental elusions point towards nocturnal concentration of O3 (null in model since solar radiation is zero) as a potential source of error. Questions were posed about the validity of measurements because of the experimental set-up (van very close to mast and as high as the first measurement level). 7.3. Regional modelling K. Lagouvardos (University of Athens, Greece) described the modelling of a peak NO, pollution day in Athens with the RAMS and HYPACT models, with particular emphasis on the effect of different initialisations of the RAMS model. Modelling of an ozone episode in Madrid with a set of models requiring supercomputers was described by R. San Jose, University of Madrid, Spain. N. Moussiopoulos (Aristotle University, Thessaloniki, Greece) reported on the numerical simulations of wind and ozone during the Heilbronn (Germany) experiment using the EZM model, which is based on the wind flow model MEMO and the three-dimensional Eulerian model photochemical model MARS. Intermediate model results at different spatial scales were discussed. The beneficial effect of local emission reduction was seen only at larger distances. P. Mestayer (Ecole Centrale de Names, France) presented work in progress on the SUBMESO model, a large communal modelling system that is being developed in France by 11 research groups. Presented were: urban aerodynamic roughness modelling, atmospheric flows over strongly heterogeneous grounds and the interactive mapping of city quarters.

8. The panel discussion The workshop ended with a panel discussion. On the panel were: Roe1 van Aalst and Frank De Leeuw for the European Environment Agency, Nicolas Moussiopoulos for TC-AQ and COST 615, Bernard Fisher for COST 710, Helge Olesen for the Initiative on Harmonisation and Jan Kretzschmar as moderator. The main task of the European Environment Agency (EEA) is to provide reliable, objective and comparable information in support of the environmental policy at the European level and to provide information for the public. The principal goal of the European Topic Centre on Air Quality (ETC-AQ) is to support EEA in all aspects where air quality information is needed. Relating air quality to emissions and to effects is an important part of this work, and consequently air pollution models are of great interest to the ETC-AQ. In this and other aspects, the EEA and its topic centre can be one of the interfaces between the scientific communities and the users of environmental information. For atmospheric transport and dispersion modelling,

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the ETC-AQ has already carried out a review of the requirements for air quality models and model applications (project MA3-l), and developed a report on the state-of-the-art of air pollution models, needs and trends (project MA3-2). Both these reports were presented at the workshop. The need for more experimental data for supporting model evaluation was expressed in these reports. In the future, guidance reports will be provided on the documentation, selection and application of air pollution models, and an information system on available models and their documentation, will be accessible via the Internet. The ETC will carry on in collaboration with the ad hoc initiative in this field. COST 615 should serve as the scientific basis for activities of the European Topic Centre of Air Quality of the EEA. As such, it has already performed the task of compiling an inventory of dispersion models which are being used in Europe. In the future, COST 615 can provide services by supporting ETC’s activities towards guiding model use for practical applications. The Workshop has encouraged research and development of methods for pre-processing meteorological data for dispersion models, the subject of the COST 710 programme, and 17 papers on this subject were presented at the meeting. Dispersion models should not be discussed in isolation from the factors required to run the models. Four areas have been covered: the surface energy balance, the mixing layer depth, profiles and complex terrain. Conclusions emerging were that: to estimate surface energy balances one needs to determine if local factors are important, a consistent definition of mixing depth is required, profiles in the upper part of the mixing layer are not accurate and the user needs to know when to apply complex terrain models. There is much more work that could be done. It is hoped that work will continue under a new meteorological COST programme on the meteorology of urban pollution episodes. As for the future activities in the context of the initiative on ‘Harmonisation within Atmospheric Dispersion Modelling for Regulatory Purposes’: a 5th international meeting, continuing the series of workshops, is being planned to take place in Rhodes in May 1998. In parallel, it is the intention to continue activities on model evaluation etc. in a number of smaller workshops with a few dozen participants. During the 4th Workshop the idea of a World Wide Web based catalogue of atmospheric dispersion models was discussed; it is likely that the TC-AQ in co-operation with the ‘Harmonisation’ initiative will organise a workshop to discuss experiences with such a catalogue. As plans for smaller workshops develop, information will become available on the WWW home page of the Initiative (http://www.dmu.dk/AtmosphericEnvironment/ harmonihtm). H. Olesen also mentioned that work with the Model Validation Kit is continuing. At present, two packages

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are available: (1) the ‘old’ Model Validation Kit used in the workshops in Manno, Mol and Oostende, and (2) a pilot version of an extension to the kit. Olesen referred to the WWW for details. Several interesting questions and suggestions emerged during the discussions. Training sessions for modellers (or administrative staff) where recent model app1ication.s from different states are critically evaluated could serve as an effective way of information exchange and lead to an improvement of the modelling culture. From an engineering point of view, for how many different kinds of problems (source configurations, simple/coastal/complex/urban-rural terrain) do we use models? For how many of these combinations are there experimental data in the Model Validation Kit? What additional research and/or money is needed to include the next 20% of typical cases?

9. Conclusions The 4th Workshop on harmonisation within atmospheric dispersion modelling was very well attended. The successive workshops have grown out to a meeting place for those who are directly involved in using and/or developing atmospheric transport and dispersion models for practical applications. A bridge has been established between the workers in the field and the appropriate agencies of the European Union. The proceedings of these workshops reflect the current state of the art in today’s modelling skill for ‘routine’ applications, and are a mirror of important questions that are being tackled by current research co-ordinated at the European level. With respect to the model

Software Conference Report validation kit, continuing progress is being made based on voluntary work since the first workshop in 1992. Acknowledgements This conference report was compiled using information given to me by the chairmen of the sessions (John Irwin, John Bartzis, Rex Britter, Peter Builtjes, Mario Cirillo, Sven-Erik Gryning, Nicolas Moussiopoulos, David Thomson, Patrice Mestayer, Andreas Skouloudis, Werner Klug and Jan Kretzschmar) and by the panelists. I have mixed their information with my own notes during the workshop and with my reading of the papers as submitted for the preprints of the proceedings. The 4th Workshop was sponsored by ERCOFTAC, the European Research Community on Flow, Turbulence and Combustion; COST 710, the European Concerted Research Action on Harmonisation in the Preprocessing of Meteorological Data for Dispersion Models; COST 615, on Database, Monitoring and Modelling of Urban Air Pollution; ETC AQ, the European Topic Centre on Air Quality NILU/RIVM; EURASAP, the European Association for the Science of Air Pollution; NFWO, the Nationaal Fonds voor Wetenschappelijk Onderzoek, Belgium: APWB, the Administratie voor de Programmatie van het Wetenschappelijk Onderzoek, Flanders and SABENA. Several of the sponsors provided valuable contributions to the scientific programme of the workshop. For more information about the 5th Workshop, Greece, May 1998, please contact John Bartzis, NCSR ‘Demokritos’, AG. Paraskevi, GR-15310 Attiki, Greece.