WEATHER ELEMENTS A. Text in Elementary Meteorology by THOMAS A. BLAIR Senior MefcoroloRi f, U. . S. Weather Bitrcar Associate Prof f m of Meteorology University of Nebraska REVISED EDITION NEW YORK PRENTICE-HALL, INC. 1946 Preface to the Revised Edition THE science of meteorology has made continuous prog ress since this book was first published, five years ago. In the present limited revision the newer ideas and practices are introduced by numerous revisions in the text modifying many paragraphs and sections but without changing the general manner and order of treatment. Some of the newer subjects discussed are latent instability, isentropic analysis, conditions necessary for copious rain fall, snow crystals in connection with the electrical charge in cumulonimbus clouds, and frontal activity in tropical cyclones. There are new drawings and a new discussion of the development of a traveling wave depression, and a new description of air masses embodying present-day classifica tion and classification symbols. There are six new con secutive daily weather maps. Several other drawings have been revised and many minor changes made in the text. The discussion of the organization and procedure of the United States Weather Bureau is brought up to date. T. A. BLAIR Preface to First Edition THIS book aims to present, concisely and systematically, an introduction to the science of meteorology in its pres ent stage of development. My primary purpose is to set forth the facts and principles concerning the behavior and responses of the atmosphere in such a way as to enable the reader to acquire an elementary understanding of the physical processes underlying observed weather phenom ena. An importantsecondary object is to present that general body of information about the weather and the present state of our knowledge concerning it, which it is believed that every intelligent person should possess in relation to this most important element of his environment. Attention is given to the instruments and methods used in observing and measuring atmospheric conditions, to the complex effects of solar radiation, and to the interrelations of the various weather elements. Other subjects treated are the general circulation of the atmosphere and its modi fications, the basis of weather forecasting, the general geo graphic distribution of the weather elements, and some of the relations of weather and climate to man and his varied life. A brief account is given of the electrical and optical phenomena of the atmosphere, and of the organization and activities of the United States Weather Bureau. Some knowledge of such matters is a necessary foundation for the study of geography, agriculture, and ecology, and of aeronautics, hydrology, and other branches of engineering. In addition, such knowledge is useful in a great variety of professions and occupations, notably in medicine, law, and viii PREFACE TO FIRST EDITION business. It is hoped, therefore, that the book will prove of value to persons of widely varying interests. The discussions are necessarily brief and incomplete, and much interesting and valuable material has been omitted, but it is hoped that the most important phases of the sub ject have been treated in such a way as to arouse an abiding interest and lead to further reading. Meteorology is a growing science and at the present time is undergoing a rather rapid development andtransition. An effort is made to present the modern aspects of the subject and to indicate the lines along which research is being conducted and progress being made. The author of a book on elementary meteorology is in evitably indebted to the pioneers and leaders in the science of the weather in past generations, and also to a great number of contemporary students and investigators. No one can write such a book without becoming aware of mete orologys debt to Sir Napier Shaw and Dr. W. J. Hum phreys, among present-day scientists. Dr. H. C. Willett and Mr...