Clear Air Turbulence and Its Detection: Proceedings of a Symposium on Clear Air Turbulence and Its Detection, Organized and Sponsored by the Flight Sciences Laboratories, Boeing Scientific Research Laboratories, Office of the Vice President — Research and PDF
Preview Clear Air Turbulence and Its Detection: Proceedings of a Symposium on Clear Air Turbulence and Its Detection, Organized and Sponsored by the Flight Sciences Laboratories, Boeing Scientific Research Laboratories, Office of the Vice President — Research and
Yih-Ho Pao Arnold Goldburg E ditors Clear air turbulence and its detection Proceedings of a symposium on Clear Air Turbulence and Its Detection, Organized and Sponsored by the Flight Sciences Laboratories, Office of the Vice Precident – Research and Development, The Boeing Company, Seattle, Washington, August 14–16, 1968 CLEAR AIR TURBULENCE AND ITS DETECTION CLEAR AIR TURBULENCE AND ITS DETECTION Proceed1ngs of a Sympos1um on Clear Air Turbulence and Its Detection, Organ1zed and Sponsored by the Flight Sciences Laboratory, Boeing Scientific Research Laboratories, Office of the Vice President - Research and Develop- ment. The Boeing Company, Seattle, Washington, August 14-16, 1968 Edited by Yih-Ho Pao and Arnold 6oldburg Boeing Scientific Research Laboratories Seattle, Washington, U.S.A SPRINGER SCIENCE+B USINESS MEDIA, LLC 1969 Library of Congress Catalog Card Number 73-76507 © 1969 Springer Science+Business Media New York Originally published by Plenum Press in 1969 Softcover reprint of the hardcover 1st edition 1969 ISBN 978-1-4899-5617-0 ISBN 978-1-4899-5615-6 (eBook) DOI 10.1007/978-1-4899-5615-6 All rights reserved No part of this publication may be reproduced in any form without written permission from the publisher PREFACE Clear air turbulence is a part of the atmospheric environment in which aircraft and aerospace vehicles func tion and hence is of interest to The Boeing Company. The characteristics of clear air turbulence can be important in the design for structural strength and for stability and control characteristics of airplanes and aerospace vehicles. The detection and avoidance of clear air turbulence can be important to airfleet operation for passenger safety and comfort as well as for economic and mission performance. This Symposium brought together for meaningful dis cussion three different groups of research workers in clear air turbulence: those interested in fundamental aspects of clear air turbulence; those measuring clear air turbu lence; and those attempting to detect clear air turbulence at remote distance. The success of the Symposium is due in direct measure to the quality of the papers and the seriousness of purpose of those participating. We wish to thank the invited speakers, the session chairmen, and the participants for their efforts towards this goal. George S. Schairer Vice President Research and Development Guilford L. Hollingsworth Director Boeing Scientific Research Laboratories FOREWORD Clear air turbulence and the related atmospheric motions have attracted much attention in recent years. The clear air turbulence problem becomes more acute with the advent of high-speed, high-flying and large (thus, more flexible) jet airplanes which interact with clear air turbulence in terms of structure, stability, and control across an increasing range of wavelength scales. Clear air turbulence also presents a problem in communication since it scatters signals transmitted by electro-magnetic waves. Clear air turbulence studies have become an integral part of the Glo bal Atmospheric Research Program because energy dissipated at the small scale by clear air turbulence influences global weather phenomena. Important as the problem is, however, the term "clear air turbulence" is not universally agreed upon. The pheno menon is also often referred to as "critical atmospheric turbulence" and as "internal (to the atmospheric layer) turbulence." In the published literature it seems to en compass a variety of irregular fluctuating motions in a clear atmosphere at high altitude. Some of these motions are undulant rather than truly turbulent. For simplicity, we use the popular term "clear air turbulence" to represent undulant and turbulent motions in a clear atmosphere. It has been three years since the 1965 Boeing Scienti fic Research Laboratories "Lecture Series on Atmospheric Turbulence and Its Detection (Seattle, Washington, June October 1965)". It has been two-and-a-half years since the "National Conference on Clear Air Turbulence (Washington, D. C., February 1966)". Since these meetings, considerable research has been accomplished contributing to a better knowledge of clear air turbulence (CAT). It was the purpose of this Symposium to present a comprehensive picture of and to review the recent developments in CAT, especially: (i) theories and measurements concerning the origin and the structure of CAT, (ii) methods for forecasting CAT, and (iii) methods for the remote detection of CAT. Special emphasis was placed on clear air turbulence in the upper troposphere and in the stratosphere. We believe that the principal conclusions reached at the Symposium on the nature of CAT and its detection methods were: vi FOREWORD vii (i) The energy dissipated at small-scale by clear air turbulence influences the large-scale atmospheric motion. (ii) The vigorous mixing caused by clear air turbulence changes the meso-scale structure of the atmosphere. (iii) Clear air turbulence derive~ from the ordered meso-scale motion of the atmosphere. The larger and faster airplanes tend to interact with the longer wavelengths of the clear air turbulence which is strongly influenced by the meso-scale motion. The relation between CAT and this ordered motion must be better understood. (iv) Severe clear air turbulence at high altitude often occurs in sloping flows. How disturbances amplify in these sloping flows is crucial to the understanding of the origin of clear air turbulence. (v) Clear air turbulence at high altitude is often sporadic and patchy, and often occurs in a strongly stable region. (vi) It is believed that the severe clear air turbu lence is essentially non-stationary and inhomogeneous. Fundamental understanding of these stochastic processes is lacking. (vii) From the airborne measurements of severe CAT, gaps occur in the low wavenumber portion of the turbulent velocity spectra, while the spectra at high wavenumbers, where CAT is expectea to be locally homogeneous and tem porally stationary, follows the Kolmogorov -5/3 law. It is believed that the gaps in the spectra are caused by the presence of internal waves. (viii) There appears to be some correlation between CAT and certain meteorological patterns. Synaptical analyses of these relations results in CAT forecasting techniques. However, CAT also occurs in situations with no apparent significant meteorological pattern. There is an urgent need to understand the origin of CAT in relation to the meso-scale and macro-scale atmospheric structure. viii FOREWORD (ix) Very sensitive radars which are capable of sensing refractive index fluctuations in the atmosphere appear to be a promising method for detecting clear air turbulence. How ever, the correlation between the intensity spectrum of the clear air turbulence and the radar return signature remains to be investigated and synthesized in detail. At present, it is too expensive to have a network of such radars for CAT detection for routine operational airline use. (x) IR detection methods may have promise, but present IR detectors for CAT sense the overall temperature variation in a relatively large volume of air, and do not measure the local temperature fluctuations. (xi) Coordinated simultaneous measurements of CAT with sensitive radars, IR detection equipment, ~n ~~u measure ments with airplanes, radiosondes, and Jimspheres at a given spatial region, should be encouraged in the future. These investigations, when carried out, will yield perti nent information as to: the origin and the structure of CAT, its relation to the meteorological conditions, and the relation between the intensity spectrum of CAT and the signaLs from remote detection. The Symposium was organized and sponsored by the Flight Sciences Laboratory, Boeing Scientific Research Laboratories. All papers were by invitation only. This Symposium Proceed ings contains 27 papers, with discussions at the end of each paper, and the Panel Discussion. Since the field of clear air turbulence is a rapidly evolving one, the editors felt it was important at this time to include all three types of papers: the review article presenting introduction to the subject; the report on finished research presenting phenomena now understood; and the report on research in progress presenting phenomena which are not yet explained. The Symposium Proceedings is divided into five parts: Part I is concerned with the origin and the structure of CAT; Part II contains the recent observational results and data analyses of CAT; Part III is devoted to methods for forecasting CAT; Part IV is concerned with the methods for the remote detection of CAT; Part V is the log of Panel and Floor Discussions and the Conclusion. FOREWORD ix The editors wish to thank Miss Edna R. Holmes for com piling the Authors' Index and Mr. J. Michael Hall for com piling the Subject Index. The editors wish to express their appreciation to Professor Ronald F. Probstein for suggesting that these Proceedings be collected in permanent form and to Mr. Robert Ubell and Plenum Press for their aid and cooperation. Yih-Ho Pao and Arnold Goldburg Editors Seattle, Washington October 1968 ACKNOWLEDGMENTS I wish to thank the following persons whose suggestions and comments have helped to form the Symposium program: Professor Hans A. Panofsky, Professor David Atlas, Mr. Neal V. Loving, Professor John A. Dutton, and Messrs. William Moreland and E. M. Hansen. I particularly appreciate the cooperative response of the invited speakers in agreeing to participate in the Symposium and in providing so promptly the summaries of their papers before the Symposium and the final manuscripts after the Symposium. I would like to thank the Session Chairmen, Professor Robert G. Fleagle, Professor Robert W. Stewart, Professor Joost A. Businger, Professor Leslie S. G. Kovasznay, and Professor David Atlas, for the smooth operation of their sessions. I am grateful to Mr. Michael E. Callahan for his superb effort in coordinating the Symposium and for arrang ing the Symposium social functions, and to Mr. Robert Carlsen for handling the discussion sessions and arranging the questions and comments in sequence. I am indebted to Miss Sarajane Beal for her assistance in distributing the Symposium programs and for typing the pre-symposium communi cation, and editing the Summaries of Papers, and to Mr. Donald Fenton for handling the printing of the Summaries of Papers and arranging figures for the Proceedings. The final manuscripts of the Proceedings were retyped by the secretarial staff of Boeing Scientific Research Laboratories, in particular, I wish to thank Miss Edna R. Holmes, Mrs. Pat Easthom, Miss Sarajane Beal and Hiss Victoria A. Caraway for their typing effort. I would also like to thank Dr. M. E. Smithmeyer for her help in proof reading some of the retyped manuscripts. Finally, I would like to thank Dr. Arnold Goldburg for his encouragement and support. Yih-Ho Pao Symposium Chairman X
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