The author has sought to incorporate in the book some of the fundamental concepts and principles of the physics and dynamics of the atmosphere, a knowledge and understanding of which should help an average student of science to comprehend some of the great complexities of the earth-atmosphere system, in which a three-way interaction between the atmosphere, the land and the ocean tends to maintain an overall mass and energy balance in the system through physical and dynamical processes.

The book, divided into two parts and consisting of 19 chapters, introduces only those aspects of the subject that, according to the author, are deemed essential to meet the objective in view. The emphasis is more on clarity and understanding of physical and dynamical principles than on details of complex theories and mathematics. Attempt is made to treat each subject from first principles and trace its development to present state, as far as possible. However, a knowledge of basic calculus and differential equations is sine qua non especially for some of the chapters which appear later in the book.

In Part-I (the physics part), Chap. 1, after introductory remarks about the place of the earth in the solar system, stresses the importance of solar radiation and gravitation in atmospheric physics and dynamics. Chap. 2 describes the origin, composition, structure and properties of the atmosphere. Heat and thermodynamics of a dry and moist atmosphere and the physics of formation of cloud and rain are discussed in Chaps. 3-5. Laws of radiation in general are reviewed in Chap. 6. A brief account is given of our current knowledge of the sun as a source of radiation in Chap. 7. Chapter 8 describes the passage of solar radiation through the different layers of the earth's atmosphere and the thermodynamical effects it produces in each layer. Physical processes leading to the warming of the earth's surface by the incoming shortwave solar radiation and its subsequent emission of longwave radiation to produce greenhouse effect, the heat balance of the earth-atmosphere system and formation of heat sources and sinks in the earth-atmosphere system are discussed in Chaps. 9 and 10.

In Part-II (the dynamics part), the first two chapters are devoted to derivation of the fundamental equations of atmospheric motion in different co-ordinate systems and their simplification in order to derive some types of balanced winds. Some essential properties of air flow, such as divergence, vorticity, vertical motion and circulation, involved in the formation of weather and climate, are discussed in Chap. 13. Effects of friction on flow in the boundary layers of the atmosphere and the ocean are discussed in Chap. 14. Chapters 15 and 16 discuss waves and oscillations that are excited in the atmosphere by fluctuations in atmospheric pressure, temperature and wind, including those at or near the equator. Some aspects of dynamical weather prediction by numerical methods and dynamical instability of the atmospheric flows are discussed in Chaps. 17 and 18. The concluding chapter summarizes our current knowledge of the general circulation of the atmosphere derived from observations as well as results of laboratory experiments and numerical simulation studies.

The book is primarily aimed at meeting the needs of students at undergraduate level pursuing courses in earth and atmospheric sciences, but could be used as a reference book by graduate students as well as scientists working in other fields of science, desirous of learning more about the earth-atmosphere system. Inspite of the care taken in the preparation of the book, it is likely that there have been errors and omissions. The author will be thankful if cases of such lapses are brought to his notice.

The author is extremely grateful to his family, especially his daughters, Manjushri and Suranjana, who supported this work from the very beginning. Manjushri helped actively during preparation of the draft manuscript with library and referencing work. Suranjana along with her husband, Professor Dr. Huug van den Dool, provided all the logistic support and helped the author in completing all the technical aspects of the book. Suranjana handled all the diagrams and helped with their insertion in the book. Huug's comments on the draft chapters were immensely helpful in improving the manuscript. Without their help, it would have been well-nigh impossible to complete the work. He also received encouragement from his eldest daughter Jayshri while writing this book. His special thanks are due to the National Centers for Environmental Prediction (NCEP) of the National Weather Service (NWS) of the United States of America for several of their analysis products incorporated in the book. He expresses his indebtedness to the numerous authors, publishers and learned Societies who permitted him to reproduce diagrams and excerpts from their published work.

University Park, U.S.A. January 11,2008

Kshudiram Saha

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