Earth Observations from Space: The First 50 Years of Scientific Achievements (2008)

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EARTH OBSERVATIONS FROM SPACE THE FIRST 5O YEARS OF SCIENTIFIC ACHIEVEMENTS Committee on Scientific Accomplishments of Earth Observations from Space Board on Atmospheric Sciences and Climate Division on Earth and Life Studies 

THE NATIONAL ACADEMIES PRESS   500 Fifth Street, N.W.   Washington, DC 20001 NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the committee responsible for the report were chosen for their special competences and with regard for appropriate balance. Support for this project was provided by the National Aeronautics and Space Administration under Contract No. NNG06GF62G. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the organizations or agencies that provided support for the project. International Standard Book Number-13:  978-0-309-11095-2 International Standard Book Number-10:  0-309-11095-5 Additional copies of this report are available from the National Academies Press, 500 Fifth Street, N.W., Lockbox 285, Washington, DC 20055; (800) 624-6242 or (202) 334-3313 (in the Washington metropolitan area); Internet, http://www.nap.edu. Cover design by Van Nguyen, National Academies Press. Copyright 2008 by the National Academy of Sciences. All rights reserved. Printed in the United States of America 

The National Academy of Sciences is a private, nonprofit, self-perpetuating society of distinguished scholars engaged in scientific and engineering research, dedicated to the furtherance of science and technology and to their use for the general welfare. Upon the authority of the charter granted to it by the Congress in 1863, the Academy has a mandate that requires it to advise the federal government on scientific and technical matters. Dr. Ralph J. Cicerone is president of the National Academy of Sciences. The National Academy of Engineering was established in 1964, under the charter of the National Academy of Sciences, as a parallel organization of outstanding engineers. It is autonomous in its administration and in the selection of its members, sharing with the National Academy of Sciences the responsibility for advising the federal government. The National Academy of Engineering also sponsors engineering programs aimed at meeting national needs, encourages education and research, and recognizes the superior achievements of engineers. Dr. Charles M. Vest is president of the National Academy of Engineering. The Institute of Medicine was established in 1970 by the National Academy of Sciences to secure the services of eminent members of appropriate professions in the examination of policy matters pertaining to the health of the public. The Institute acts under the responsibility given to the National Academy of Sciences by its congressional charter to be an adviser to the federal government and, upon its own initiative, to identify issues of medical care, research, and education. Dr. Harvey V. Fineberg is president of the Institute of Medicine. The National Research Council was organized by the National Academy of Sciences in 1916 to associate the broad community of science and technology with the Academy’s purposes of furthering knowledge and advising the federal government. Functioning in accordance with general policies determined by the Academy, the Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in providing services to the government, the public, and the scientific and engineering communities. The Council is administered jointly by both Academies and the Institute of Medicine. Dr. Ralph J. Cicerone and Dr. Charles M. Vest are chair and vice chair, respectively, of the National Research Council. www.national-academies.org 



COMMITTEE ON SCIENTIFIC ACCOMPLISHMENTS OF EARTH OBSERVATIONS FROM SPACE JEAN BERNARD MINSTER (Chair), Scripps Institution of Oceanography, La Jolla, California JANET W. CAMPBELL (Vice Chair), University of New Hampshire, Durham JEFF DOZIER, University of California, Santa Barbara JAMES R. FLEMING, Colby College, Waterville, Maine JOHN C. GILLE, National Center for Atmospheric Research, Boulder, Colorado DENNIS L. HARTMANN, University of Washington, Seattle KENNETH JEZEK, The Ohio State University, Columbus STANLEY Q. KIDDER, Colorado State University, Fort Collins NAVIN RAMANKUTTY, McGill University, Montreal, Quebec ANNE M. THOMPSON, Pennsylvania State University, University Park SUSAN L. USTIN, University of California, Davis JAMES A. YODER, Woods Hole Oceanographic Institution, Massachusetts NRC Staff CLAUDIA MENGELT, Study Director MARIA UHLE, Program Officer LEAH PROBST, Research Associate KAtherine WELLER, Senior Program Assistant  

BOARD ON ATMOSPHERIC SCIENCES AND CLIMATE F. SHERWOOD ROWLAND (Chair), University of California, Irvine M. JOAN ALEXANDER, NorthWest Research Associates, Boulder, Colorado MICHAEL L. BENDER, Princeton University, Princeton, New Jersey ROSINA M. BIERBAUM, University of Michigan, Ann Arbor CAROL ANNE CLAYSON, Florida State University, Tallahassee WALTER F. DABBERDT, Vaisala, Inc., Boulder, Colorado KERRY A. EMANUEL, Massachusetts Institute of Technology, Cambridge DENNIS L. HARTMANN, University of Washington, Seattle PETER R. LEAVITT, Weather Information, Inc., Newton, Massachusetts VERNON R. MORRIS, Howard University, Washington, D.C. THOMAS H. VONDER HAAR, Colorado State University/CIRA, Fort Collins Ex Officio Member ANTONIO J. BUSALACCHI, JR., University of Maryland, College Park NRC Staff CHRIS ELFRING, Director IAN KRAUCUNAS, Program Officer CURTIS H. MARSHALL, Program Officer CLAUDIA MENGELT, Program Officer ELIZABETH A. GALINIS, Research Associate LEAH PROBST, Research Associate ROB GREENWAY, Senior Program Assistant KATHERINE WELLER, Senior Program Assistant DIANE GUSTAFSON, Administrative Coordinator SHUBHA BANSKOTA, Financial Associate vi 

Preface Over the past five decades, space-faring nations have was organized through the American Geophysical Union to developed impressive capabilities for observing Earth from elicit comments and opinions. From this process emerged a satellite platforms. This has resulted in rapid advances in fun- long list of scientific accomplishments, each singularly con- damental science and improved our ability to understand and vincing, unique, and sometimes amazing that could not have predict the dynamics of Earth systems, to the great benefit been achieved without orbital observations. From this list the of society. Global geophysical observations covering a wide committee chose some of the most compelling and illustra- range of disciplines have provided unprecedented insight tive examples to showcase the value of satellite observations into the physics of Earth systems. Exquisitely accurate space and argue the central importance of sustaining the effort to geodetic measurements have yielded a global reference sys- develop and deploy these observational tools. The examples tem that is three orders of magnitude more accurate than that presented in this report capture the committee’s subjective of a half-century ago. Today, our ability to forecast weather, view of the most important accomplishments, yet we believe climate, and natural hazards depends critically on satellite- that another committee’s short list would overlap consider- based observations of the planet. ably with the present selection. These accomplishments The Earth science community is currently engaged in demonstrate clearly that the advent of satellite observations major efforts to plan directions for future observations and has revolutionized the Earth sciences. research that depend on space-based platforms. One essen- Many individuals contributed essential information tial study—the first of its kind in the Earth sciences—is the and helped in writing the examples of accomplishments recent “decadal survey” led by the National Academies: (Chapters 3-11) and added to the committee members’ own Earth ­ Science and Applications from Space: National expertise, and they are recognized in the Acknowledgments. Imperatives for the Next Decade and Beyond (NRC 2007a). I am also grateful to the committee members; they volun- This is a ­forward-looking report that provides guidance to teered countless hours to this study. I would like particu- the U.S. government—particularly the National Aeronautics larly to acknowledge the dedication of Janet Campbell, the and Space Administration (NASA), the U.S. Geological committee’s vice chair, who “stepped into the breach” more Survey, and the National Oceanic and Atmospheric Admin- than once to keep our momentum. istration—about future priorities. It recommends a renewal Finally, I am most grateful to the National Research of the national commitment to support ongoing observations Council (NRC) staff—Study Director Claudia Mengelt; from space in order to face scientific and societal challenges Research Associate Leah Probst, who managed the circula- over the next decades and to understand and manage natural tion of drafts and supporting documents via the Web and resources. To complement this decadal survey, NASA asked staffed all of our meetings; Maria Uhle, who pitched in the National Academies to illustrate the value of a half- during the busiest periods of the study; and Senior Program c ­ entury of Earth observations from space. That is the topic Assistant Katie Weller, who handled the logistics of all meet- of this report. ings, cheerfully managing the travel requirements of all par- The committee addressed this task by meeting with ticipants. As is usual for NRC studies, the staff was a critical expert scientists from various disciplines who offered their element in completing the study on time and on budget. perspectives on crucial discoveries and scientific achieve- ments enabled by satellite observations. Suggestions were Bernard Minster, Chair also solicited from the Earth science community at large Committee on Scientific Accomplishments through various distribution lists, and a town hall meeting of Earth Observations from Space vii 



Acknowledgments Over the course of this study, the committee met five Annemarie Schneider, University of California, Santa times to gather information and conduct deliberations. In Barbara the process, many members of the Earth science community Bill Smith, Hampton University, Virginia were invited to provide input and contribute descriptions Dave Smith, NASA of scientific accomplishments. In addition, the community Omar Torres, NASA responded to a broad solicitation for input, which also helped Lucia Tsaoussi, NASA shape the committee’s thinking. In particular, the committee Bruce Wielicki, NASA wants to acknowledge the following individuals for provid- Carl Wunsch, Massachusetts Institute of Technology, ing invaluable information to this study: Cambridge Charles Yentsch, Bigelow Laboratory for Ocean Tad Anderson, University of Washington, Seattle Sciences, West Boothbay Harbor, Maine Rick Anthes, University Corporation for Atmospheric Howard Zebker, Stanford University, California Research, Boulder, Colorado Robert Bindschadler, National Aeronautics and Space This report has been reviewed in draft form by indi- Administration (NASA) viduals chosen for their diverse perspectives and technical Kenneth Casey, National Oceanic and Atmospheric expertise, in accordance with procedures approved by the Administration (NOAA) National Research Council’s Report Review Committee. The Yi Chao, NASA purpose of this independent review is to provide candid and Dudley Chelton, Oregon State University, Corvallis critical comments that will assist the institution in making its James Coakley, Oregon State University, Corvallis published report as sound as possible and to ensure that the Peter Cornillon, University of Rhode Island, report meets institutional standards for objectivity, evidence, Narragansett and responsiveness to the study charge. The review com- Diane Evans, NASA ments and draft manuscript remain confidential to protect Jonathan A. Foley, University of Wisconsin, Madison the integrity of the deliberative process. We wish to thank the Mark Friedl, Boston University, Massachusetts following individuals for their review of this report: Randy Friedl, NASA Ralph Kahn, NASA Gregory Asner, Carnegie Institution, Stanford, Jack Kaye, NASA California Dennis Lettenmaier, University of Washington, Seattle Sheldon Drobot, University of Colorado, Boulder Ulrike Lohmann, Institute for Atmospheric and Dara Entekabi, Massachusetts Institute of Technology, Climate Science, Eidgenössische Technische Cambridge Hochschule, Zurich, Switzerland Inez Fung, University of California, Berkeley Stephen Lord, NOAA Bradford Hager, Massachusetts Institute of Tom Loveland, U.S. Geological Survey Technology, Cambridge Michael Mishchenko, NASA Charles Kolb, Aerodyne Research, Inc., Billerica, Lorraine Remer, NASA Massachusetts Sassan Saatchi, NASA Kuo-Nan Liou, University of California, Los Angeles ix 

 ACKNOWLEDGMENTS Anne Nolin, Oregon State University, Corvallis endorse the report’s conclusions or recommendations, nor David Siegel, University of California, Santa Barbara did they see the final draft of the report before its release. The Lynn Talley, Scripps Institution of Oceanography, La review of this report was overseen by Elbert W. Friday, Jr., Jolla, California University of Oklahoma, Norman. Appointed by the National Byron Tapley, University of Texas, Austin Research Council, he was responsible for making certain that Thomas Vonder Haar, Colorado State University, Fort an independent examination of this report was carried out in Collins accordance with institutional procedures and that all review comments were carefully considered. Responsibility for the Although the reviewers listed above provided construc- final content of this report rests entirely with the authoring tive comments and suggestions, they were not asked to committee and the institution. 

Contents SUMMARY 1 A Unique Vantage Point, 1 Fundamental Contributions to Science, 2 Societal Applications of Satellite Data, 4 Infrastructure Requirements to Advance Science, 6 Conclusions, 6 1 INTRODUCTION 8 The Study’s Approach, 8 2 EARTH OBSERVATIONS FROM SPACE: THE EARLY HISTORY 10 Early Satellites and Pioneers, 11 Instrument and Technology Development, 15 Conclusion, 16 3 WEATHER 18 Weather Imagery, 18 Atmospheric Properties, 21 Numerical Weather Prediction, 23 4 Earth’s Radiation Budget and the Role of Clouds and Aerosols in the Climate System 26 Earth’s Radiation Budget, 26 Global Distribution of Cloud Properties, 27 Aerosols from Natural Processes and Human Activities, 31 Indirect Effects of Aerosols, 31 Stratospheric Particles, 32 Global Climatologies of Aerosols, 35 5 Atmospheric Composition: Ozone Depletion and Global Pollution 37 Understanding and Removing the Threat of Stratospheric Ozone Depletion, 38 Observing Stratospheric Dynamics, 38 Determining the Causes of Antarctic Ozone Depletion, 39 Ozone Depletion Over the Northern Hemisphere, 43 Tropospheric Ozone and Trace Gases, 44 xi 

xii CONTENTS 6 HYDROLOGY 50 Precipitation Estimates from the Tropical Rainfall Measuring Mission, 50 Seasonal Snow Cover, 51 Discovery of Ancient Buried River Channels, 54 Analysis of Groundwater from Gravity Data, 55 Use of Satellite-Derived Elevation Data in Hydrology, 55 7 CRYOSPHERE 58 Nonuniform and Dynamic Ice Streams in Antarctica, 58 Accelerating Ice Sheet Flow in Antarctica and Greenland, 59 Declining Arctic Summer Sea Ice, 60 Glacier Extent and Position of Equilibrium Line, 62 8 OCEAN DYNAMICS 64 The Ocean’s Role in Climate Change, 64 Prevalence of Dynamic Features, 66 Understanding Ocean Tides: New Solutions to an Old Scientific Question, 68 The Turbulent Ocean, 68 Ocean Wind Measurements Reveal Two-Way Ocean-Atmosphere Interaction, 71 9 ECOSYSTEMS AND THE CARBON CYCLE 73 Terrestrial Primary Productivity, 73 Marine Primary Productivity, 75 Global Marine and Terrestrial Primary Production, 78 The Ocean Carbon Cycle, 78 Long-Term Ecosystem Record Reveals Atmosphere-Biosphere Coupling, 79 Studying Plant Physiology from Space, 80 10 LAND-USE AND LAND-COVER CHANGE 84 Monitoring Agricultural Lands, 85 Estimating Tropical Deforestation, 86 Mapping Global Land Cover, 86 Mapping Global Fires, 86 Understanding Desertification, 91 11 SOLID EARTH 92 Geodesy, 92 Structure and Dynamics of Earth’s Deep Interior, 92 The Global Positioning System, 94 Plate Tectonics, Topography, Seismology, and Volcanology, 94 12 CONCLUSIONS 98 The Emergence of Integrated Earth System Science, 98 Integrated Global View of the Carbon Cycle and Climate System, 99 Maximizing the Return on Investment in Earth Observations from Space, 101 Opportunities for the Future of Earth Observations from Space, 105 REFERENCES 107 APPENDIXES A Examples of Scientific Accomplishments and Relevant Satellite Missions 121 B Acronyms 123 C Biographical Sketches of Committee Members and Staff 126