Air quality model intercomparisons: an overview of the City- and Euro-delta exercises

CityDelta and Eurodelta are two projects currently carried out at the Joint Research Centre (European Commission), of Ispra, Italy to explore air quality changes (Ozone and PM) as a response to different emission scenarios in 2010. While the first of these exercises focuses on the city-scale air quality, the second one investigates the regional European scale. These two projects have as a common purpose to give support to the Clean Air for Europe Programme of the DG Environment of the European Commission. In this presentation, an overview of these two European model intercomparison exercises will be given.

CITYDELTA

CityDelta (Feb 2001 – Oct 2004) co-organised by IIASA (Vienna, Austria), EMEP/MSC-W (Oslo, Norway), TNO-MEP (Apeldoorn, The Netherlands), CONCAWE (Brussels, Belgium) and JRC-IES (Ispra, Italy) is a policy-underpinning model-intercomparison activity to explore the changes in urban air-quality predicted by different atmospheric chemistry-transport-dispersion models in response to changes in urban emissions.

CityDelta aimed at the study of ambient levels of Ozone and Particulate Matter and had for specific objectives 1) to assess the performance of the participating models and compare them against available observational data; 2) to identify the range of responses of models towards emission reductions; 3) to provide information on the effectiveness of Europe-wide emission controls compared to local measures; 4) to provide quantitative information in relation to legal obligations, e.g. whether a certain trend in emissions will comply with air-quality limit values; 5) to provide guidance on how urban air-quality could be included in a European-wide evaluation of the cost-effectiveness of emission control strategies.

Approximately 20 modelling groups (from all over Europe) participated to this project with a total of 40 different model configurations and delivered 6-months scenario simulations for O3 and yearly simulations for PM for a series of 2010 emission projections. CityDelta provided information concerning the impact of various emission-reduction strategies on Ozone and Particulate Matter in 6 different cities in Europe (Berlin, Katowice, London, Milan, Paris, Prague).

An interactive graphical interpretation tool has been built-up during this exercise and made available to all project participants. Based on an “Ensemble approach” (defined as an average of the participating models), functional relationships of emissions versus concentrations were derived for PM for implementation of the urban signal into the regional EMEP air quality model, and subsequently in the IIASA-RAINS model for cost-effectiveness analysis.

A summary of the main findings of this project will be presented.

EURODELTA

EURODELTA is a regional model intercomparison exercise initiated by the Task Force on Measurements and Monitoring (UNECE_TFMM) and the Task Force on Integrated Assessment Modelling (UNECE_TFIAM) and coordinated jointly by IIASA, EMEP, CONCAWE and JRC-IES. It currently includes the participation of 6 models (EMEP, REM (D), LOTOS (NL), CHIMERE (F), MATCH (S) and TM5 (JRC)). Similarly to Citydelta, this activity focuses on gas and aerosol phase coumpounds concentrations both in 1999 and 2001 for a total of 28 different emission scenarios. These scenarios investigate emission reductions not only in specific countries (Italy, Germany, France) but also over sea areas over the whole of Europe. The purpose of this regional model inter-comparison is threefold: 1) evaluate the performance of different regional models against an identified set of observations and quantify their performance in terms of agreed quality criteria. 2) gain insight into the ability of regional atmospheric dispersion models to reproduce chemical nonlinearities in response to emission changes. The response to emission changes (the s/r relationships) is indeed an important output from the chemical transport models used in integrated assessment modelling for policy applications. 3) to establish the performance of the UNIFIED EMEP model with respect to other state-of art regional scale models and objective criteria and determine the range of confidence of modelled responses to emission changes at the regional scale. The model inter-comparison is carried out among models operating with long-term chemical transport simulations in regional scale (with a horizontal scale of ~50x50 km2).

An overview of the main results from this program will be presented in this presentation.