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The chemistry and deposition of nitrogen species in the troposphere
Book reviews dix. Full references to valuable papers and books over a wide range of subjects are given in 27 pages. This is a useful book; however, I consider that neither the author nor the publishers have given it the optimum title. M. .I. Rycroft International Space University
The Chemistry and Deposition of Nitrogen Species in the Troposphere, A. T. Cocks (Ed), 1993, x + 134 pp. Royal
Society of Chemistry, f35.00 hb, ISBN O-85186-355-8. This slim volume contains seven camera-ready papers presented at a one-day Symposium organised by the Royal Society of Chemistry in February 1992. It is especially important and useful since nitrogen species play a central role in tropospheric chemistry. Fossil fuel combustion leads to photochemical oxidants (particularly ozone) and to photochemical smog. Nitrogen oxides and ammonia, mainly arising from agricultural practices, lead to nitrogen deposition onto terrestrial ecosystems and adverse effects. Current knowledge, a.nd its uncertainties, are well covered. Emissions from power plants generating electricity cause plumes downwind which have been both measured and modelled. Similar studies have been performed in central London, and at urban and rural sites in relation to emissions from motor vehicles. The critical load concept is considered. Here, the sensitivity of the environment to pollutant loadings is derived and used to work back to estimate the amount of pollutants that can be emitted in the long term without causing environmental damage. The behaviour of p,articulates containing nitrogen, and their deposition, primarily wet rather than dry, is considered. The final paper, on the results of modelling nitrogen compound concentrations lover Europe, and a comparison with observations, is particularly valuable. M. J. Rycroft International Space University
Wave Packets and their Bifurcations in Geophysical Fluid Dynamics, Huijin Yang, 247 pp, 1991. Springer, New York
f31.00. The primary purpose of this monograph is presumably to present the author’s studies of wave-packet behaviour in the context of large-scale atmospheric or oceanic motion described by the quasigeostrophic equations. However, the account of these studies is preceded by an introduction to those aspects of the basic theory of wave propagation and of dynamical systems that are necessary to establish the author’s main results. In assessing this book, it is necessary, then, to consider both the plausibility of the central theme and whether or not the presentation of the introductory material is successful. The book has been typeset, presumably by the author himself, using LaTeX. It is perfectly legible, but there are a large number of minor typographical errors. In Chapter 1 the author gives a very brief introduction to the equations of motion and the common approximations that arise in considering geophysical flows. A reader who was starting from scmtch with no previous knowledge of geophysical fluid dyna.mics would almost certainly need to use other more basic textbooks that treat this material in much more detail. The substance of the book really begins with Chapter 2, which gives an introduction to the theory of
921
waves on a slowly-varying basic state. This is quite satisfactory, though the treatment seems a little laboured at times. Some of this chapter, e.g. that concerning wave-action conservation, is more a summary of the important results, rather than a step-by-step derivation and a reader who wished to verify the results for themself would probably have to consult one of the original references. The author chooses to give a detailed account of the Generalised Lagrangian Mean theory of Andrews and McIntyre. Although this is clear enough the detail seems misplaced in this case. After all, none of these results is used in the latter part of the book. It might have been better to make the general point that it is possible to derive wave-activity conservation theorems for finite-amplitude waves and leave it at that. It also seems fair criticism that the route chosen to deriving the wave action conservation results is not the most convenient to apply to Rossby waves which are the subject of the later part of the book. It is surely most straightforward to proceed straight from the quasi-geostrophic equations. Chapter 3 moves on to consider Rossby wave packets on barotropic basic states, starting with the shallow water equations. Various integral theorems for slowly varying wave packets are noted, though such theorems have analogues which are satisfied for general disturbances. The author introduces a definition of stability which is not standard and may cause serious confusion, particularly with regard to his Theorem I. (This definition allows him to pose the question ‘Is it necessary that a barotropically unstable wave packet always remains unstable?.) However the most substantial part of the chapter deals with the behaviour of wave packets in the presence of p (representing the planetary vorticity gradient), S (representing the variation in the planetary vorticity gradient) and topography. The author concentrates here, and later in the book, on the case where the spatial gradient of the dispersion relation is itself spatially independent. It follows that the differential equations predicting the time variation of the wavenumber components as a wave packet moves along a ray path have no explicit dependence on the position of the packet. This leads to some analytical simplification, but not, unfortunately, to notational simplification There is a tendency for the author to define large numbers of new constants and to repeat equations unnecessarily, all meaning that it is difficult to jump into a particular chapter and make sense of the results, without having plodded through previous chapters in detail first. The qualitative behaviour described in the latter part of Chapter 3 is familiar in many contexts of wave propagation on shear flows and it is difficult to see anything very new here, apart from an exhaustive exploration of parameter space. The wave packet theme is developed in Chapter 4, where it is noted that some basic states lead to vacillation in the spatial wavenumber of a packet. The author’s hypothesis (and this seems to be presented as the major idea in the monograph) is that the mechanism for this vacillatory behaviour, namely suitable variation of the wavenumber following the packet, as a result of variations in the basic state, may be an explanation for more general vacillatory behaviour observed in experiment (e.g. the classic baroclinic annulus experiments) or in atmospheric observations. In Chapter 5 the author moves on to consider in detail the bifurcation structure of the wave packet behaviour in wavenumber space (as the variations in the basic state change). The basic results of bifurcation theory are reviewed as preparation. Some of these results are useful in the subsequent development, but sometimes the treatment seems formal and disconnected. For
The Chemistry and Deposition of Nitrogen Species in the Troposphere, A. T. Cocks (Ed), 1993, x + 134 pp. Royal
Society of Chemistry, f35.00 hb, ISBN O-85186-355-8. This slim volume contains seven camera-ready papers presented at a one-day Symposium organised by the Royal Society of Chemistry in February 1992. It is especially important and useful since nitrogen species play a central role in tropospheric chemistry. Fossil fuel combustion leads to photochemical oxidants (particularly ozone) and to photochemical smog. Nitrogen oxides and ammonia, mainly arising from agricultural practices, lead to nitrogen deposition onto terrestrial ecosystems and adverse effects. Current knowledge, a.nd its uncertainties, are well covered. Emissions from power plants generating electricity cause plumes downwind which have been both measured and modelled. Similar studies have been performed in central London, and at urban and rural sites in relation to emissions from motor vehicles. The critical load concept is considered. Here, the sensitivity of the environment to pollutant loadings is derived and used to work back to estimate the amount of pollutants that can be emitted in the long term without causing environmental damage. The behaviour of p,articulates containing nitrogen, and their deposition, primarily wet rather than dry, is considered. The final paper, on the results of modelling nitrogen compound concentrations lover Europe, and a comparison with observations, is particularly valuable. M. J. Rycroft International Space University
Wave Packets and their Bifurcations in Geophysical Fluid Dynamics, Huijin Yang, 247 pp, 1991. Springer, New York
f31.00. The primary purpose of this monograph is presumably to present the author’s studies of wave-packet behaviour in the context of large-scale atmospheric or oceanic motion described by the quasigeostrophic equations. However, the account of these studies is preceded by an introduction to those aspects of the basic theory of wave propagation and of dynamical systems that are necessary to establish the author’s main results. In assessing this book, it is necessary, then, to consider both the plausibility of the central theme and whether or not the presentation of the introductory material is successful. The book has been typeset, presumably by the author himself, using LaTeX. It is perfectly legible, but there are a large number of minor typographical errors. In Chapter 1 the author gives a very brief introduction to the equations of motion and the common approximations that arise in considering geophysical flows. A reader who was starting from scmtch with no previous knowledge of geophysical fluid dyna.mics would almost certainly need to use other more basic textbooks that treat this material in much more detail. The substance of the book really begins with Chapter 2, which gives an introduction to the theory of
921
waves on a slowly-varying basic state. This is quite satisfactory, though the treatment seems a little laboured at times. Some of this chapter, e.g. that concerning wave-action conservation, is more a summary of the important results, rather than a step-by-step derivation and a reader who wished to verify the results for themself would probably have to consult one of the original references. The author chooses to give a detailed account of the Generalised Lagrangian Mean theory of Andrews and McIntyre. Although this is clear enough the detail seems misplaced in this case. After all, none of these results is used in the latter part of the book. It might have been better to make the general point that it is possible to derive wave-activity conservation theorems for finite-amplitude waves and leave it at that. It also seems fair criticism that the route chosen to deriving the wave action conservation results is not the most convenient to apply to Rossby waves which are the subject of the later part of the book. It is surely most straightforward to proceed straight from the quasi-geostrophic equations. Chapter 3 moves on to consider Rossby wave packets on barotropic basic states, starting with the shallow water equations. Various integral theorems for slowly varying wave packets are noted, though such theorems have analogues which are satisfied for general disturbances. The author introduces a definition of stability which is not standard and may cause serious confusion, particularly with regard to his Theorem I. (This definition allows him to pose the question ‘Is it necessary that a barotropically unstable wave packet always remains unstable?.) However the most substantial part of the chapter deals with the behaviour of wave packets in the presence of p (representing the planetary vorticity gradient), S (representing the variation in the planetary vorticity gradient) and topography. The author concentrates here, and later in the book, on the case where the spatial gradient of the dispersion relation is itself spatially independent. It follows that the differential equations predicting the time variation of the wavenumber components as a wave packet moves along a ray path have no explicit dependence on the position of the packet. This leads to some analytical simplification, but not, unfortunately, to notational simplification There is a tendency for the author to define large numbers of new constants and to repeat equations unnecessarily, all meaning that it is difficult to jump into a particular chapter and make sense of the results, without having plodded through previous chapters in detail first. The qualitative behaviour described in the latter part of Chapter 3 is familiar in many contexts of wave propagation on shear flows and it is difficult to see anything very new here, apart from an exhaustive exploration of parameter space. The wave packet theme is developed in Chapter 4, where it is noted that some basic states lead to vacillation in the spatial wavenumber of a packet. The author’s hypothesis (and this seems to be presented as the major idea in the monograph) is that the mechanism for this vacillatory behaviour, namely suitable variation of the wavenumber following the packet, as a result of variations in the basic state, may be an explanation for more general vacillatory behaviour observed in experiment (e.g. the classic baroclinic annulus experiments) or in atmospheric observations. In Chapter 5 the author moves on to consider in detail the bifurcation structure of the wave packet behaviour in wavenumber space (as the variations in the basic state change). The basic results of bifurcation theory are reviewed as preparation. Some of these results are useful in the subsequent development, but sometimes the treatment seems formal and disconnected. For