Man has been interested in clouds and precipitation as well as other phenomena in the sky since time immemorial. Looking at cloud formations, we may be fascinated by the variety of the shapes of the clouds, slowly drifting across the sky carried by the wind. A patient and perceptive observer, however, may additionally be able to notice also a change in the shape and size of the clouds, which occurs within a few minutes of observation. The appearance and development of the cloud formations make it possible even for an observer with elementary knowledge of meteorology to predict a radical change in the weather in the near future – thus a certain intuitive, very short-term weather forecast. A cloudy sky, heavy rain, hail or a number of rainy days can remind us whether and to what degree we know the rules of the game which nature plays with us when clouds, rain, snow, hail or tornado develop. These and similar questions are the subject of the discipline of meteorology called the physics of clouds and precipitation. It is precisely this book which attempts to answer a number of these questions or at least define our current knowledge.

The physics of clouds and precipitation has been a respected discipline which has been intensively developed since the end of the 1940s when the idea was expressed and experimentally verified that so-called cloud seeding is capable of producing or intensifying precipitation in a certain limited area and in other cases dispersing the cloud formations. The initial studies put the main emphasis on the research of microphysical cloud processes related to the conditions under which water droplets, ice crystals and other cloud and precipitation particles form, increase in size and interact with each other during their growth. Although these studies clarified many issues concerning cloud structure and the development of precipitation, it soon became apparent that microphysical processes are fundamentally affected also by macrophysical processes in a cloud and its surroundings. This by no means diminishes the importance of the microphysical processes themselves, which can retroactively affect also macroscopic dynamic and thermodynamic properties of clouds; however, we now view cloud and precipitation processes as a result of an intricate simultaneous action of dynamic, thermodynamic and microphysical processes of varying characteristic dimensions and durations.

The physics of clouds and precipitation has a very wide range of instruments at its disposal. Apart from visual observation, sampling of particles or detailed records on the course of cloud events, great emphasis at the beginnings of the cloud physics was put on laboratory experiments. In cloud chambers of various sizes and arrangements, a number of elaborate experiments attempting to simulate the course of some cloud processes both directly and employing the similarity theory were conducted. Nonetheless, the weather in its multiplicity is impossible to study in a laboratory.  The most emphasis has therefore always been placed on special experiments carried out in the field, which combine and take advantage of extensive measuring and observing techniques. Especially the measurements taken by especially equipped planes during their flight through clouds are of particular importance. In the last decades, so-called remote sensing has experienced massive development, and it can be said without exaggeration that the most important source of knowledge in the physics of clouds and precipitation are now mainly radar and satellite data, whose technologies are constantly being improved. Moreover, we are witnesses to the constant improvement of these technologies. The last method, which is of immense importance though, is the mathematical modelling of the processes occurring during the development of clouds and precipitation. The development in information technology as well as its accessibility have made it possible to conduct studies about which scientists several decades ago still could only dream, which makes all the more serious the fact that despite the increasing quality of all these technologies a large number of questions still remain to be answered. Another contributing factor is that our demands on the comprehension and usage of the knowledge which was still not accessible until recently have also risen. The well-known fact that real knowledge always leads to further questions is however also of great significance.

The book which has reached the hands of the reader focuses mainly on cloud and precipitation processes in middle geographic latitudes. Building on the laws of general physics of clouds and precipitation and meteorology, it thus attempts to describe the nature of the cloud processes which can be encountered in Central Europe as well. These can include not only relatively common processes, such as the formation of convective clouds and rain precipitation, but also less frequent phenomena, therefore surprising to a layman, for example heavy torrential precipitation, large hailstones or tornados.

Also the structure of the book, divided into fourteen chapters, corresponds to this purpose. In Chapter One, the reader is introduced to the world of various meteorological processes and their classification with the international classification of clouds being the second focus of this introductory chapter. The formation of clouds cannot be separated from the processes of synoptic dimensions, such as lows with their typical structure of cloud belts. To capture such processes, meteorology uses the methods which are summarised in Chapter Two. Chapter Three offers a synopsis of knowledge from the thermodynamics of the atmosphere, which is made use of in the following chapters. Chapter Four is devoted to the microphysics of clouds and provides a review of what is known in this area, which will make it possible for the reader to understand the formation of precipitation on the microphysical level. Chapter Five discusses general questions of atmospheric convection, which may lead to the formation of convective clouds. It attempts to describe the differences between the classic approach to dealing with atmospheric convection and more recent knowledge and methods of its study.

The next three chapters are very important, focusing on understanding the information on clouds and precipitation which is provided by remote meteorological measurements. For this reason, Chapter Six is devoted to the usage of meteorological radars while Chapter Seven elucidates and illustrates, using a number of examples, various types of information obtained from meteorological satellites. Chapter Eight complements this synopsis with a brief explanation of the detection and localisation of electric discharge.

The following chapters are arranged in such a way as to provide an overview of the elementary knowledge on various types of clouds. Chapter Nine deals with stratiform cloud formations and this summary is complemented by a brief description of the development of orographic clouds. Chapter Ten covers convective clouds and mainly the questions posed before us by such an impressive phenomenon as convection storms. Besides the description of the structure and properties of the basic types of convection storms, we have also paid attention to dangerous phenomena which may occur in the course of a storm, including the occurrence of torrential precipitation, large hailstones, squalls or tornados. In this chapter, we have also incorporated selected examples from the territory of the Czech Republic, which are a result of the work on our research projects. Chapter Eleven, which follows, deals with the basic physical properties of cirri, which form in the upper troposphere.

The last chapters focus on some techniques building on the knowledge of the physics of clouds and precipitation. Chapter Twelve summarises the current methods of long-range precipitation detection based on radar and satellite observations of cloud and precipitation fields. From there, it is already only one step to the attempts to proceed from the detection of precipitation and clouds to the forecast of their further development or movement in the nearest hours, which is the content of Chapter Thirteen. Finally, the last Chapter Fourteen discusses the possibilities of artificial interventions into the development of clouds. It undertakes to explain the principles of these methods and cover the degree of their physical justifiability and uncertainty as well as the risks related to their use.

A part of the publication is the accompanying DVD. It contains some of the graphic supplements of the publication at their original full resolution for easier viewing on a large monitor. The reader will also be able to find some materials here which cannot be presented in a printed form, for instance various animations, or those for which the publication simply had no space left.

Already by its name, the book emphasises its drawing on the monograph Fysika oblaků a srážek (Podzimek, 1959; /The Physics of Clouds and Precipitation/), which was published in Czechoslovakia almost half a century ago and provided a valuable synopsis of the contemporary knowledge supported by an extensive list of the cited literature. If we have managed to capture the immense increase in the knowledge on clouds and precipitation in comparison with 1959, to outline the development of observation methods and at the same time to maintain a similar professional level, we have hopefully fulfilled our intention well. In many directions, we have naturally drawn on the structure as well as knowledge of a number of monographs on similar issues which have been published in the last two decades abroad. We have further used several high-quality Czech books which deal with the elementary questions of the physics of clouds and precipitation on the level of university textbooks. We have had to seek more recent knowledge, which has not been covered in monographs yet, in specialised journals, conference proceedings or search for some information on the Internet.

The book is intended for a wide circle of those interested in meteorology. We have compiled it keeping in mind meteorologists and climatologists specialised in different areas who need a comprehensive collection of knowledge on cloud and precipitation processes for their work. We attach the same importance also to the needs of specialists from other fields whose work touches upon questions related to the formation of clouds and precipitation. However, when writing the individual chapters, we also bore in mind all other people interested in these issues, which attract perceptive and enthusiastic sky observers, many of whom have been trying to understand more profoundly the processes taking place in the sky in front of their eyes, and we would be glad if precisely they found the presented book useful.

The book is being presented by the authors from the Institute of Atmospheric Physics of the Academy of Sciences of the Czech Republic (IAP ASCR) and from the Czech Hydrometeorological Institute (CHMI). Although the text as a whole is a result of close cooperation of a team of authors, different chapters were authored by individual co-authors based on their narrower meteorological specialisation. Marek Kašpar is the author of Chapter Two. Chapters Six and Thirteen are the work of Petr Novák while the author of Chapter Seven is Martin Setvák. Chapter Ten was compiled by Daniela Řezáčová and Martin Setvák. The cooperation of Petr Novák and Martin Setvák has yielded Chapters Eight and Twelve. The other chapters were prepared by Daniela Řezáčová.

At the end of the preface, the authors would like to express their thanks for multilateral and manifold support and assistance. The book would not have been possible without the support of the Czech Science Foundation (grant No. 205/05/0458) and substantial financial and technical support from the CHMI and IAP ASCR.

In the final stage of assembling the text and revising it, we were readily assisted by our colleagues (in alphabetical order) Mgr. Alžbeta Demeterová, RNDr. Jan Kráčmar, RNDr. Vilibald Kakos, Mgr. Hanka Kyznarová, Mgr. Miloslav Müller, Mgr. Martina Lacinová, RNDr. Petr Pešice, PhD. and Mgr. Petr Zacharov. We are greatly obliged to them for the help rendered. The managements of both the institutions also deserve to be thanked, who made it possible for the authors to concentrate on the preparation of the book. Special thanks are owed to RNDr. Radim Tolasz, deputy director for meteorology and climatology of the CHMI, for the interest he has shown in the publication being presented. We would naturally like to thank also all other colleagues who have supported us morally in our work.

An important part of the information presented in our publication is the result of research projects supported by the Czech Science Foundation which were implemented in the first years of the 21st century (grant Nos. 205/00/1451 and 205/04/0114) and significantly altered and augmented our knowledge pertaining to the structure and manifestation of heavy convection storms on the territory of the Czech Republic. It is therefore fitting to thank also all co-researchers in these projects and numerous meteorologists as well as laymen who have provided various complementary information or materials on the heavy storms examined. It is impossible to name them all here. Neither is it possible to list all the foreign colleagues who have helped us by providing advice, materials or simply by showing their interest in the research of heavy storms on the territory of the Czech Republic. Neither should the acknowledgement of the three foreign and two Czech anonymous reviewers of the book proposal be omitted.

The preparation of such a book always significantly insinuates itself also into personal leisure time and requires the patience and graciousness of the authors’ family members. Last but NOT least, the authors would therefore like to thank profusely their families and especially their wives or husbands.

We are aware that the book being presented is far from being perfect and already today we could have written something better or differently. Nevertheless, we believe that for many readers with a predilection for natural science, the book will be a useful and interesting source of knowledge and will contribute to a better understanding of such “mundane” processes like the behaviour of clouds in the sky and their “falling” to the Earth’s surface in the form of precipitation.