Boundary-Layer Meteorol (2010) 135:177–178 DOI 10.1007/s10546-009-9454-7 BOOK REVIEW

Cloud and Precipitation Microphysics by Jerry M. Straka Cambridge University Press, Cambridge, 2009 Andreas Bott

Published online: 2 December 2009 © Springer Science+Business Media B.V. 2009

Thermo-hydrodynamic processes in the atmosphere are largely controlled by the occurrence of clouds. Hence, numerical models of the atmosphere have to consider the influence of clouds on the time evolution of prognostic model variables. Usually, cloud microphysical processes take place on spatio-temporal scales that are distinctly smaller than the scales resolved by the numerical model. Therefore, in the model simulations clouds have to be treated as subgridscale processes, i.e. they have to be parameterized. The aim of these parameterizations is not to calculate the cloud processes themselves but rather their effects on the model variables. Most of the time, cloud processes are extremely complex, particularly when the ice phase is involved. Many important cloud processes, such as the formation of ice nuclei and the break-up of large hydrometeors, have not yet been completely understood. Moreover, it is often very difficult to obtain a detailed insight into the cloud microstructure by means of direct observations during field experiments. As a result of these problems, a large number of different cloud parameterization schemes has been developed in the last few decades. With his book, Jerry M. Straka attempts to give an overview of the immense number of parameterization schemes for cloud processes that has been published in the scientific literature. The book is written for advanced students and researchers who have already a broad and significant knowledge of cloud microphysics. It is also intended to be a reference for researchers and the operational community dealing with numerical simulations of cloud processes. In writing this type of book, a major problem consists in the selection of a manageable number of representative parameterization schemes that should be included and discussed in more detail. Among the large variety of different existing approaches the author has to choose only the most popular and long-lived methods. This is certainly a big challenge, particularly in view of the desired longevity of the book itself. Considering that research is a continuous, practically never ending process, one may argue that each choice of parameterization schemes will be insufficient. On the other hand, in the last few decades several parameterizations have emerged as so-called classical schemes that are often used as a basis

A. Bott (B) Meteorologisches Institut, Bonn Universität, Bonn, Germany e-mail: [email protected]

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for new algorithms. I believe that, in his book, Straka has included the most important and appreciable parameterization schemes of cloud microphysics. Most of the algorithms that are presented in more detail are widely used in numerical models and may be referred to as classical schemes. The book covers the main topics of cloud microphysics. After the introduction, giving a short overview of the different parameterization types as well as a categorization of the different hydrometeors, the second chapter deals with the foundations of microphysical parameterizations. This chapter clearly demonstrates the style in which the entire book has been written. Instead of presenting long derivations of equations or motivations for the use of certain experimental relations, most of the time the reader is directly confronted with the final results. Researchers with a well-founded background in cloud microphysics will, almost certainly, appreciate this condensed form of presentation. However, for readers without this profound knowledge, the book will most likely be very awkward to read. In Chaps. 3–12 the major topics of cloud microphysics are discussed. Starting with the nucleation of cloud particles, the diffusional growth of liquid water drops and ice particles are treated. In Chaps. 7 and 8 parameterizations for the collection growth of hydrometeors, as well as descriptions for the drop break-up, are presented. Autoconversion and conversion schemes for different hydrometeor types are presented in Chap. 9 while Chap. 10 is devoted to hail growth followed by Chap. 11 dealing with the melting of ice. Some known problems involving microphysical parameterizations are addressed in Chap. 12, and in Chap. 13 the governing equations of atmospheric dynamic models are summarized. In the preface the author mentions the problem that arises with the repeated use of the same symbols and letters for different physical quantities. This is indeed a problem that occasionally hampers the fluent reading of the book. Unfortunately, the author’s hope that the variables are defined in enough detail is not always fulfilled. Moreover, at several places typographical errors have crept in. Certainly, the reader with microphysical experience will immediately realize that, in some places, the drop diameter given in millimetres should be replaced by micrometres. However, the student without this experience might in the first instance be confused. All in all, in some cases the writing style appears a touch too sloppy. Finally, I was unsuccessful when trying to access the web page http://www.cambridge.org/ straka where model codes should be available online. In summary, with this book the author has tried to present the most important and popular parameterization schemes for cloud microphysical processes. The book is certainly helpful for readers who want a quick reference to cloud parameterizations widely used in atmospheric numerical modelling. However, for students who are interested in obtaining a deeper insight into the derivations of the governing equations of cloud parameterization schemes, I advise that they consult the original papers or study more comprehensive textbooks, such as the famous book Microphysics of Clouds and Precipitation by Pruppacher and Klett published in 1998.

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