‘Mesoscale Modelling for Meteorological and Air Pollution Applications’ combines the fundamental and practical aspects of mesoscale air pollution and meteorological modelling. Providing an overview of the fundamental concepts of air pollution and meteorological modelling, including parameterization of key atmospheric processes, the book also considers equally important aspects such as model integration, evaluation concepts, performance evaluation, policy relevance and user training.

Finishing this book is giving me a mixture of relief, satisfaction and frus tration. Relief, for the completion of a project that has taken too many of my evenings and weekends and that, in the last several months, has become almost an obsession. Satisfaction, for the optimistic feeling that this book, in spite of its many shortcomings and imbalances, will be of some help to the air pollution scientific community. Frustration, for the impossibility of incorporating newly available material that would require another major review of several key chap ters - an effort that is currently beyond my energies but not beyond my desires. The first canovaccio of this book came out in 1980 when I was invited by Computational Mechanics in the United Kingdom to give my first Air Pollution Modeling course. The course material, in the form of transparencies, expanded, year after year, thus providing a growing working basis. In 1985, the ECC Joint Research Center in Ispra, Italy, asked me to prepare a critical survey of mathe matical models of atmospheric pollution, transport and deposition. This support gave me the opportunity to prepare a sort of "first draft" of the book, which I expanded in the following years.

In 1949, when the North Atlantic Treaty was ratified, one of its articles explicitly noted '1hat member countries should contribute towards the further development of peaceful and friendly international relations." Specific problems related to the human environment were addressed by the Committee of Challenges of Modern Society (CCMS) of NATO, established in 1969. This provided a framework within which a series of International Technical Meetings (ITMs) on Air Pollution Modelling has been held. This volume documents the proceedings of the 18th meeting in this series. Science, like the arts and sports, provides an ideal vehicle for "developing peaceful and friendly international relations". National boundaries have never been barriers to the movement of air pollution, and fortunately this has also proved true of scientists studying the transport of air pollution. It is thus satisfying to record that since the mid-seventies it has been commonplace to find Eastern European scientists among attendees at the ITMs which have (in a very modest way) participated in a precursor to the process which has led to historical changes in Europe and which will undoubtedly lead to a tremendous increase in personal and intellectual exchange on a worldwide basis.

This unique volume introduces and discusses the methods of validating computer simulations in scientific research. The core concepts, strategies, and techniques of validation are explained by an international team of pre-eminent authorities, drawing on expertise from various fields ranging from engineering and the physical sciences to the social sciences and history. The work also offers new and original philosophical perspectives on the validation of simulations. Topics and features: introduces the fundamental concepts and principles related to the validation of computer simulations, and examines philosophical frameworks for thinking about validation; provides an overview of the various strategies and techniques available for validating simulations, as well as the preparatory steps that have to be taken prior to validation; describes commonly used reference points and mathematical frameworks applicable to simulation validation; reviews the legal prescriptions, and the administrative and procedural activities related to simulation validation; presents examples of best practice that demonstrate how methods of validation are applied in various disciplines and with different types of simulation models; covers important practical challenges faced by simulation scientists when applying validation methods and techniques; offers a selection of general philosophical reflections that explore the significance of validation from a broader perspective. This truly interdisciplinary handbook will appeal to a broad audience, from professional scientists spanning all natural and social sciences, to young scholars new to research with computer simulations. Philosophers of science, and methodologists seeking to increase their understanding of simulation validation, will also find much to benefit from in the text.

To effectively utilize mesoscale dynamical simulations of the atmosphere, it is necessary to have an understanding the basic physical and mathematical foundations of the models and to have an appreciation of how a particular atmospheric system works. Mesoscale Meteorological Modeling provides such an overview of mesoscale numerical modeling. Starting with fundamental concepts, this text can be used to evaluate the scientific basis of any simulation model that has been or will be developed. Basic material is provided for the beginner as well as more in-depth treatment for the specialist. This text is useful to both the practitioner and the researcher of the mesoscale phenomena.

The 20th International Technical Meeting on Air Pollution Modelling and Its Application was held in Valencia, Spain, during late 1993. At this conference, a new record of abstracts was submitted, a new record of scientists participated, and a new record of countries was represented. This clearly indicates society's continuous and growing interest in, as well as importance of, the complexities associated with the modelling of air pollution. The conference addressed the following main subjects: integrated regional modelling, global and long-range transport, new modelling developments, accidental releases, and model assess ment and verification. In addition, two project-oriented workshops were organized as part of the conference. The many contributing authors and scientists taking active part in the discussions following the papers, have made this proceeding a record of the current status in the field of air pollu tion modelling. We want to express our gratitude to their efforts. We also wish to extend our gratitude to the sponsors that made this conference possible. In addition to financial support from NATOjCCMS the conference received contributions from CEAM, the European Asso ciation for the Science of Air Pollution, Danish Center for Air Research, and Ris0 National Laboratory. A special grant was given by NATOjCCMS to facilitate attendance of scientists from Central and Eastern Europe. We also wish to express our gratitude to Rosa Salvador and Pilar Zamora of CEAM, who laboriously organized the conference pre-proceedings, and to Anne N0rregaard and Ulla Riis Christiansen of Ris0 National Laboratory, who seved as conference secretariat.

The interest in air pollution modelling has shown substantial growth over the last five years. This was particularly evident by the increasing number of participants attending the NATO/CCMS International Technical Meetings on Air Pollution modelling and its Application. At the last meeting 118 papers and posters were selected from an abundance of submitted abstracts divided over five modelling topics: (i) model assessment and verification, including policy applications, (ii) air pollution modelling in coastal areas with emphasis on the mediterranean region, (iii) accidental atmospheric releases, including warning systems and regulations, (iv) modelling of global and long-range transport and (v) new developments in turbulent diffusion. A round-table discussion chaired by John Irwin (USA) and Jan Kretzschmar (Belgium) on the harmonization of air pollution models was attended by more than 50 scientists and is reported in these proceedings. The opening paper addressed the main issue of this conference: modelling over complex terrain. Of particular interest were coastal areas where the surface inhomogeneities introduce small-scale circulation and varying atmospheric stability, often combined with a complex topography. As the conference was located on the beautiful island of Crete, problems faced by the host nation, particularly Athens and its environs were obvious examples for consideration. These together with other regions with similar geographical features were addressed. Heavily populated and industrialized as they often are, air quality is generally poor there and emission regulations are desired. Obviously, a major task of air pollution dispersion modelling is to assist policy makers in formulating sensible regulations.