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1995 | Buch

The Air Pollution Problem Kapitel lesen Erstes Kapitel lesen

Computer Treatment of Large Air Pollution Models

verfasst von: Zahari Zlatev

Verlag: Springer Netherlands

Buchreihe : Environmental Science and Technology Library

Enthalten in: Professional Book Archive

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Über dieses Buch

"Models are often the only way of interpreting measurements to in­ vestigate long-range transport, and this is the reason for the emphasis on them in many research programs". B. E. A. Fisher: "A review of the processes and models of long-range transport of air pollutants", Atmospheric Environment, 17(1983), p. 1865. Mathematical models are (potentially, at least) powerful means in the efforts to study transboundary transport of air pollutants, source-receptor relationships and efficient ways of reducing the air pollution to acceptable levels. A mathematical model is a complicated matter, the development of which is based on the use of (i) various mechanisms describing mathematically the physical and chemical properties of the studied phenomena, (ii) different mathematical tools (first and foremost, partial differenti­ al equations), (iii) various numerical methods, (iv) computers (especially, high-speed computers), (v) statistical approaches, (vi) fast and efficient visualization and animation techniques, (vii) fast methods for manipulation with huge sets of data (input data, intermediate data and output data).

Inhaltsverzeichnis

Frontmatter
Chapter 1. The Air Pollution Problem
Abstract
The air pollution, and especially the reduction of the air pollution to an acceptable level,is an important environmental problem. The air pollution is not limited to regions where there are big emission sources. Air pollutants can be transported, mainly by advection due to the wind (but diffusion phenomena and chemical transformations under the transport also play an important role), to areas where there are no emission sources. Thus, the atmosphere is normally polluted not only in areas with emission sources, but also in the surrounding areas.Furthermore, air pollutants are deposited on the surface not only in areas where there are big emission sources, but also in the surrounding areas.
Zahari Zlatev
Chapter 2. Mathematical Models for Studying the Long-Range Transport of Air Pollutants
Abstract
The long-range transport of air pollutants, the LRTAP, is a very complicated physical phenomenon. Some air pollutants can be transported over long distances to remote areas that are far away from the big emission sources. Moreover, under certain circumstances the transported air pollutants may lead (directly or indirectly) to some damaging effects on plants,animals and humans. Therefore, it is important to be able to study the LRTAP carefully.Mathematical air pollution models are indispensable tools in the investigation of long-range transport phenomena. The analytical description of some types of such large models by systems of partial differential equations will be discussed in this chapter.
Zahari Zlatev
Chapter 3. Numerical Treatment of Large Air Pollution Models
Abstract
It has been shown in Chapter 2 that any LRTAP model (any long-range transport of air pollution model) can be described mathematically by a system of partial differential equations (PDE’s). The number of equations in this system is equal to the number of species which are to be studied by the model. Thus, including more species leads to an increase of the size of the problem. However, even more important is the fact that the system of PDE’s cannot be solved analytically (even if the number of species is small; say two) unless some very unrealistic assumptions are imposed. Therefore the systems of PDE’s, by which the large air pollution models are described mathematically, have to be treated numerically.
Zahari Zlatev
Chapter 4. Testing the Reliability of the Numerical Algorithms
Abstract
It is highly desirable to implement sufficiently accurate numerical algorithms in an LRTAP model. One of the main requirements is to obtain a model where the errors due to the use of numerical procedures are smaller than the error caused by other factors (as, for example, the uncertainties in the input data, the uncertainties of some of the physical parameters, the uncertainties of the implementation in the model of some physical processes, etc.). If this requirement is satisfied (i.e. if the numerical algorithms are sufficiently accurate), then the numerical errors have no influence on the results and, thus, one will be able to study successfully different problems connected with the physical nature of the model (sensitivity of the results to variations of different physical parameters, sensitivity of the results to variations of some of the emission sources in the space domain, sensitivity of the results to variation of some meteorological parameters, etc.).
Zahari Zlatev
Chapter 5. Need for Efficient Algorithms
Abstract
The discretization of the systems of PDE’s, by which the large LRTAP models are described mathematically, always leads to very big computational problems. Therefore it is crucial to perform efficiently the most time-consuming calculations during the numerical treatment of a large air pollution model. Efficiency can be achieved by selecting numerical algorithms which are both fast and accurate and by implementing correctly these algorithms in the codes by which the large air pollution models are treated numerically.
Zahari Zlatev
Chapter 6. Computations on High-Speed Computers
Abstract
The computational problems that are to be solved when large LRTAP1 models are treated numerically on computers are huge (this has been mentioned in several preceding chapters; see, for example, Section 5.1). Therefore it is critical to perform the whole computational work (or at least the most time-consuming parts of it) efficiently. In fact, in many cases the large air pollution models are not tractable at all unless the codes by which they are treated numerically are sufficiently fast. There are two ways to achieve the highly desired efficiency.
Zahari Zlatev
Chapter 7. Running Air Pollution Models on Vector Machines
Abstract
The long-range transport air pollution models (the LRTAP models) are, as shown in the preceding chapters, extremely complex and, therefore, a great amount of computing time is required to run them on computers. This (together with the fact that the big vector processors are still among the fastest computers that are available at the market) explains why large air pollution models are often run on big vector processors (as, for example, different types of CRAY computers).
Zahari Zlatev
Chapter 8. Running Models on Parallel Machines with Shared Memory
Abstract
Parallel computers with shared memory are rather popular. The main reason for this popularity is the fact that it is relatively easy to achieve high speeds of computations when such computers are used. Furthermore, and this is in many cases even more important, good performance could often be achieved with minimal efforts. Therefore one should consider the possibility of running large air pollution codes on parallel machines with shared memory. It must be emphasized here that many compan es that originally produced single vector processors are now producing parallel computers with shared memory. CRAY is a typical representative of this group of computer companies.
Zahari Zlatev
Chapter 9. Running Models on Massively Parallel Computers
Abstract
Massively parallel computers are gaining more and more terrain in the field of large-scale scientific computations, a development that is expected to continue in the future. Therefore it may be useful to test the performance of some large application codes on such computers.Of course, large air pollution models must also perform efficiently on massively parallel computers, especially if such computers are available at the particular site where the code is to be run.
Zahari Zlatev
Chapter 10. Numerical Experiments with the Danish Eulerian Model
Abstract
The Danish Eulerian Model has been mentioned many times in the previous chapters of this book. Many of the numerical methods described in the previous chapters are implemented in the modules of this model. The Danish Eulerian Model has been run on several high-speed computers. Since both the numerical treatment of the Danish Eulerian Model and its performance on several high speed computers have already been discussed in the previous chapters, only some experiments with the model (that have been carried out during the efforts to answer different questions concerning air pollution phenomena in Europe) will be discussed in this chapter.
Zahari Zlatev
Backmatter
Metadaten
Titel
Computer Treatment of Large Air Pollution Models
verfasst von
Zahari Zlatev
Copyright-Jahr
1995
Verlag
Springer Netherlands
Electronic ISBN
978-94-011-0311-4
Print ISBN
978-94-010-4137-9
DOI
https://doi.org/10.1007/978-94-011-0311-4