AND CONCLUSIONS OF THE WARSAW II MEETING ON ATMOSPHERIC COMPUTATIONS TO ASSESS ACIDIFICATION IN EUROPE JOSEPH ALCAMO and JERZY BARTNICKI International Institute for Applied Systems Analysis Schlossplatz 1, A-2361 Laxenburg, Austria (Received June 1, 1988; revised June 20, 1988) Abstract. Three topics are discussed in this report: sensitivity/uncertainty analysis of long range transport models, the interface between atmospheric models of different scales, and linkage between atmospheric and ecological models. In separate analyses oflong range transport models, it was found that uncertainty of annual S deposition was mostly affected by uncertainty of wind velocity, mixing height and wet deposition parameterization. Uncertain parameters collectively caused S deposition errors of around 10-25% (coefficient of variation) in the models examined. The effect of interannual meteorological variability on computed annual S deposition was relatively small. Different methods were presented for combining models of regional and interregional scale. It was found to be more important to include interregional information in regional-scale models for annual computations compared to episodic computations. A variety of linkage problems were noted between atmospheric and ecological models. The vertical distribution of pollutants and 'forest fittering' of pollutant deposition were found to be important in ecological impact calculations but lacking in the output of most interregional atmospheric models.

Sensitive receptors such as soil and fresh bodies of water are at the end of a long chain of events in the process of regional acidification. This chain begins thousands of kilometers upwind at the emitters of acidifying pollutants. The topics covered in this book are important in the study of regional acidification for two reasons. First, it is important to assess the sensitivity of terrestrial and aquatic ecosystems to the deposition of acidifying pollutants. If the sensitivity of an ecosystem is known, then international control strategies can be developed to reduce deposition in the receptor areas of greatest importance. This is an impor tant factor in designing the most effective strategies because of the very high costs of reducing emissions of acidifying pollutants. Second, it is important to be able to predict changes in ecosystems for decades into the future, whether it be an improvement owing to decreases in aci difying emissions or, alas, a further deterioration because control strategies are nonexistent or inadequate. In either event, it is important to be able to judge the results of our actions. Decision makers tend to be mistrustful of models unless they can judge their reliability. The application and testing of the models in Part III of this book cover, therefore, an important facet of model building.

The development of European policies on air pollution prevention is currently in an intensive phase. The European Commission Clean Air for Europe (CAFE) programme is preparing an air pollution strategy and the Convention on Long-range Air Pollution may start a review of the Gothenburg Protocol during 2005. On the 25th-27th of October 2004 a workshop on review and assessment of the scientific basis and tools employed in this policy work was held to provide guidance to the policy development. Future needs of scientific support in a longer perspective were also discussed. A large part of the workshop was focussed on the role of airborne particles. Human health effects caused by exposure to airborne particles have received increasing attention in recent years and concerns of health effects are today the main driving force for air pollution prevention and research. In addition to this, new concepts for describing effects of acidification and ozone are being introduced, providing more accurate and relevant descriptions of ecosystem effects to changes in air pollution levels. The needs for considering air pollution on a hemispheric scale were also highlighted. This workshop was organised by the ASTA programme, the Swedish research programme on air pollution, in co-operation with the Nordic Council of Ministers, the EU CAFE programme and CLRTAP.