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Optical instruments are routinely employed to obtain a wealth of information about the atmosphere, including its composition, temperature, and winds. A bewildering variety of optical instruments have been proposed over the years, making it difficult to decide which instrument should be chosen to make a specific measurement. Spectral Imaging of the Atmosphere traces the historical development of both spectral and imaging methods and places them in a unified framework relevant to observations of the troposphere, stratosphere, mesosphere and thermosphere. The underlying concepts of various measurement methodologies are presented and paired with appropriate applications. A selection of specific spectral imaging instruments, appropriate to illustrate each conceptual type, is described in detail.Shepherd's work provides both scientists and engineers with an in-depth understanding of the fundamental concepts they need to know in order to plan a program of atmospheric measurements. Expected future methods and developments are also presented. Problems designed to test and enhance the reader's understanding of the material are included in each chapter.
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Spectral Imaging of the Atmosphere
This is Volume 82 in the INTERNATIONAL GEOPHYSICS SERIES A series of monographs and textbooks Edited by RENATA DMOWSKA, JAMES R. HOLTON and H. THOMAS ROSSBY A complete list of books in this series appears at the end of this volume
Spectral Imaging of the Atmosphere Gordon G. Shepherd Centre for Research in Earth and Space Science, York University, Toronto, Canada
Amsterdam Boston London New York Oxford Paris San Diego San Francisco Singapore Sydney Tokyo
This book is printed on acid-free paper. Copyright 2002, Elsevier Science Ltd. All Rights Reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Academic Press An Imprint of Elsevier Science 84 Theobald’s Road, London WC1X 8RR, UK http://www.academicpress.com Academic Press An Imprint of Elsevier Science 525 B Street, Suite 1900, San Diego, California 92101-4495, USA http://www.academicpress.com ISBN 0-12-639481-4 Library of Congress Catalog Number: 2002107237 A catalogue record for this book is available from the British Library
Typeset by Newgen Imaging Systems (P) Ltd., Chennai, India Printed and bound in Great Britain by MPG Books Limited, Bodmin, Cornwall 02 03 04 05 06 07 MP 9 8 7 6 5 4 3 2 1
DEDICATED TO IRENE AND GEORGE SHEPHERD in memory of their unfailing love and encouragement
Who has seen the Wind? Neither you nor I: But when the trees bow down their heads, The wind is passing by. Christina Rossetti (1830–1894)
“Here was the least common denominator of nature, the skeleton requirements simply, of land and sky – Saskatchewan prairie. It lay wide around the town, stretching tan to the far line of the sky, shimmering under the June sun and waiting for the unfailing visitation of wind, gentle at first, barely stroking the long grasses and giving them life; later, a long hot gusting that would lift the black topsoil and pile it in barrow pits along the roads, or in deep banks against the fences.” “High above the prairie, platter-flat, the wind wings on, bereft and wild its lonely song. It ridges drifts and licks their ripples off; it smoothens crests, piles snow against the fences. The tinting green of Northern Lights slowly shades and fades against the prairie nights, dying here, imperceptibly reborn over there.” Who Has Seen the Wind W.O. Mitchell (1914–1998)
CONTENTS
Preface
xiii
1
Observing Atmospheric Radiation 1.1 Atmospheric Radiation 1.2 Measuring Atmospheric Radia