Clouds their Formation, Optical Properties, and Effects

501 Pages·1981·38.289 MB·English

by  Peter Hobbs (Eds.)

CLOUDS
THEIR FORMATION, OPTICAL
PROPERTIES, AND EFFECTS
Edited by
PETER V. HOBBS
Department of Atmospheric Sciences
University of Washington
Seattle, Washington
ADARSH DEEPAK
Institute for Atmospheric Optics and Remote Sensing
Hampton, Virginia
ACADEMIC PRESS 1981
A Subsidiary of Harcourt Brace Jovanovich, Publishers
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Library of Congress Cataloging in Publication Data
Symposium on Clouds: Their Formation, Optical Properties,
and Effects and (1980 : Williamsburg, Va.)
Clouds, their formation, optical properties, and
effects.
"Proceedings of Symposium on Clouds: Their Formation,
Optical Properties, and Effects, sponsored by Army Atmos­
pheric Sciences Laboratory and Army Research Office,
Williamsburg, Virginia, 13-14 May 1980"—Verso t.p.
Includes index.
Contents: Scales involved in the formation and organi­
zation of clouds and precipitation / Peter V. Hobbs —
Techniques for probing cloud microstructure / R. G.
Knollenberg — The microstructure of atmospheric clouds
and precipitation / H. R. Pruppacher — [etc.]
1. Cloud physics—Congresses. I. Hobbs, Peter Victor,
Date. II. Deepak, Adarsh. III. Atmospheric Sciences
Laboratory (U. S.) IV. United States. Army Research
Office. V. Title.
QC921.48.S95 1980 55l.57'6 81-3491
ISBN 0-12-350720-0 AACR2
PRINTED IN THE UNITED STATES OF AMERICA
81 82 83 84 9 8 7 6 5 4 3 2 1
PARTICIPANTS
Abdul Alkezweeny, Batteile, Pacific Northwest Laboratory, P. Ο. Box 999,
Richland, Washington 99352
Β. Jeffrey Anderson, NASA-Marshall Space Flight Center, ES 83, Marshall Space
Flight Center, Alabama 35812
Allan I. Carswell, York University, Department of Physics, 4700 Keele Street,
Downs view, Ontario, Canada M3J 1P3
Ronald M. Cionco, Atmospheric Sciences Laboratory, DELAS-BE-C, White Sands
Missile Range, New Mexico 88002
Stephen K. Cox, Department of Atmospheric Science, Colorado State University,
Fort Collins, Colorado 80524
William E. Cummins II, TRADOC Weather Office, Building P-173, United States
Air Force, Fort Monroe, Virginia 23651
M. H. Davis, USRA, P. O. Box 3006, Boulder, Colorado 80307
Adarsh Deepak, Institute for Atmospheric Optics and Remote Sensing, P. O. Box
P, Hampton, Virginia 23666
James E. Dye, NC AR, P. Ο. Box 3000, Boulder, Colorado 80303
Usamah O. Farrukh, Institute of Atmospheric Optics and Remote Sensing, P. O.
Box P, Hampton, Virginia 23666
B. Richard Fow, Geo-Atmospheric Corporation, Box 117, Lincoln, Maryland
01773
M. Geller, Naval Ocean System Center, Code 813, 271 Catalina Boulevard, San
Diego, California 92152
Hermann E. Gerber, Naval Research Laboratory, Washington, D. C. 20375
Richard B. Gomez, Atmospheric Sciences Laboratory, Atten: DELAS-EO-MO,
White Sands Missile Range, New Mexico 88002
Andrew Heymsfield, NC AR, P. Ο. Box 3000, Boulder, Colorado 80303
Peter V. Hobbs, Department of Atmospheric Sciences, AK-40, University of
Washington, Seattle, Washington 98195
Gerald Hoist, Chemical Systems Laboratory, DRDAR-CLB-PS, Aberdeen Proving
Ground, Maryland 21005
vii
viii PARTICIPANTS
Jim Hudson, Desert Research Institute, P. O. Box 60220, Reno, Nevada 89506
Garry E. Hunt, University College London, Gower Street, London, England
WC1E 6BT
Edwin C. Hutter, RCA Astro-Electronics, P. O. Box 800, Princeton, New Jersey
08640
Dave Ingram, TRADOC, Fort Monroe, Virginia 23651
Casimir Jachimowski, NASA-Langley Research Center, MS 404B, Hampton,
Virginia 23665
Kolf Jayaweera, Geophysics Institute, University of Alaska, Fairbanks, Alaska
99701
James E. Jiusto, Atmospheric Sciences Research Center, State University of New
York, 1400 Washington Avenue, Albany, New York 12222
Marvin Kays, Atmospheric Sciences Laboratory, White Sands Missile Range, New
Mexico 88002
Geoffrey Kent, Institute for Atmospheric Optics and Remote Sensing, P. O. Box P,
Hampton, Virginia 23666
Michael King, NASA-Goddard Space Flight Center, Code 915, Greenbelt,
Maryland 20771
Robert G. Knollenberg, Particle Measuring Systems, Inc., 1855 South 57th Court,
Boulder, Colorado 80301
Kuo-Nan Liou, Department of Meteorology, University of Utah, Salt Lake City,
Utah 84112
John D. Mill, AFGL/OPA, Hanscom AFB, Massachusetts 01731
G. C. Mooradian, Naval Ocean System Center, Code 811, 271 Catalina Boulevard,
San Diego, California 92152
C. Martin R. Platt, CSIRO, Division of Atmospheric Physics, P.O. Box 77,
Mordialloc, Victoria, Australia 3195
H. R. Pruppacher, Division of Atmospheric Sciences, University of California at
Los Angeles, Los Angeles, California 90024
Lary Radke, Department of Atmospheric Sciences, AK-40, University of
Washington, Seattle, Washington 98195
G. D. Robinson, The Center for the Environment and Man, Inc., 275 Windsor
Street, Hartford, Connecticut 06120
Kenneth Sassen, University of Utah, 819 Browning Building, Salt Lake City, Utah
84112
Michael Starks, USAMSAA, DRXSY-GS, Aberdeen Proving Ground, Aberdeen,
Maryland 21005
Graeme Stephens, Department of Atmospheric Sciences, Colorado State Univer­
sity, Fort Collins, Colorado 80523
Z. G. Sztankay, Harry Diamond Laboratories, DELHD-R-CM-NM, 2800 Powder
Mill Road, Adelphi, Maryland 20783
Robert Vaglio-Laurin, Department of Applied Sciences, New York University,
23-36 Stuyvesant Street, New York, New York 10003
PARTICIPANTS ιχ
Paul Wang, Department of Atmospheric Sciences, University of California, 405
Hilgard Avenue, Los Angeles, California 90024
Pi Wang, Institute for Atmospheric Optics and Remote Sensing, P. O. Box P,
Hampton, Virginia 23666
James A. Weinman, Department of Meteorology, University of Wisconsin,
Madison, Wisconsin 53706
Christian Werner, DFVLR, 8031 Oberpfoffenhofen, West Germany
David Wu, Institute for Atmospheric Optics and Remote Sensing, P. O. Box P,
Hampton, Virginia 23666
Man-Li C. Wu, NASA-Goddard Space Flight Center, Code 915, Greenbelt,
Maryland 20771
Glenn K. Yue, Institute for Atmospheric Optics and Remote Sensing, P. O. Box P,
Hampton, Virginia 23666
FOREWORD
The papers contained in this volume present the reader with an excellent assess­
ment and concise summary of our current knowledge and the theoretical and experi­
mental aspects of the microphysical, and optical properties of clouds. This tutorial
program on the Symposium on Clouds: Their Formation, Optical Properties, and Ef­
fects was held in Williamsburg, Virginia, May 13-14, 1980. Understanding the
physics and radiative properties of clouds and fogs is essential for acquiring the know
how for estimating and predicting the effects of the cloudy environments on the per­
formance of various sensor systems deployed in different fields, such as, defense,
communications, and weather, and for developing valid models for realistic atmos­
pheric conditions containing clouds, fogs, hazes, rain, snow, etc.
I feel that these papers and the follow-up discussions will provide the initiate, the
advanced researcher, as well as the program manager, with the concise review of the
state of the art and will help identify those areas in which further research efforts are
needed in the near future.
Richard Β. Gomez
xi
PREFACE
This volume contains the technical proceedings of the Symposium on Clouds:
Their Formation, Optical Properties, and Effects, held in Williamsburg, Virginia,
May 13-14, 1980. The symposium consisted of a tutorial program of eleven invited
review papers on the subject of clouds presented to a select audience of forty-two in­
vited participants from universities, nonprofit institutions, research laboratories, and
government agencies in the United States, Canada, West Germany, England, and
Australia. The invited papers were grouped under the headings of structure of clouds,
interaction of passive radiation with clouds, and interaction of active radiation with
clouds.
During the past few years, significant advances have been made in our ability to
characterize the properties of clouds through detailed in site and remote sensing tech­
niques, and these have led to improvements in our understanding of cloud processes.
In the next few years, we should see these techniques and new knowledge applied
with increasing effectiveness to many areas of meteorology—weather forecasting,
weather modification, climate, atmospheric chemistry, and to many areas of technol­
ogy that interface with the atmosphere—aviation and satellite meteorology, remote
sensing, communication systems, to mention only a few.
One of the most profound effects of clouds on the meteorology of our planet is in
their interactions with radiation. These interactions play crucial roles in determining
long-term climatic trends, as well as daily weather. In addition, many important
areas of technology involving man-made sources of radiation (for example, lasers)
and communication systems are presently limited in their reliability and applications
by insufficient understanding of the ways in which they interact with clouds. On the
other hand, these same technologies are providing new means of probing clouds
which may, in the future, prove as valuable to meteorology as radar.
In view of these considerations, it seems particularly opportune at this time to re­
view our knowledge of clouds and their optical properties and to assess the nature and
scope of the new research programs that are needed to advance our understanding of
these subjects. This was the purpose of this symposium and workshop.
xiii
xiv PREFACE
The symposium was followed by a two-day workshop in which twenty experts on
clouds and their optical properties were asked to identify the principal gaps in our
knowledge of the optical properties of clouds and the types of research efforts that
should be mounted to remove these gaps. The deliberations and recommendations of
the workshop participants are contained in a separately published workshop report.
In order to ensure that major disciplines involved were properly represented, a Sci­
entific Program Committee composed of the following scientists was set up: Profes­
sor P. V. Hobbs, University of Washington, Chairman; Professor A. I. Carswell,
York University, Toronto, Canada; Professor S. Κ. Cox, Colorado State University;
Dr. A. Deepak, Institute for Atmospheric Optics and Remote Sensing; and Professor
H. Pruppacher, University of California at Los Angeles.
The editors wish to acknowledge the cooperation of the authors, members of the
Scientific Program Committee, and the participants for making this a successful and
valuable symposium. It is a pleasure to acknowledge the valuable assistance of the
symposium coordinator, Miss Susan K. Woodfin, Institute for Atmospheric Optics
and Remote Sensing, for the smooth organization of the symposium and the typing of
the final manuscripts. Special thanks are due to Dr. Richard B. Gomez, U. S. Army
Atmospheric Sciences Laboratory, who not only conceived the idea for the sympo­
sium and arranged the financial support, but also participated in various aspects of its
organization. Thanks are also due Dr. Leo Alpert, Army Research Office, for the
additional financial support that was needed to enhance the scope and quality of the
symposium.
Peter V. Hobbs
Adarsh Deepak
SCALES INVOLVED IN THE FORMATION AND ORGANIZATION
OF CLOUDS AND PRECIPITATION1
Peter V. Hobbs
Atmospheric Sciences Department
University of Washington
Seattle, WA
The spatial and temporal scales involved in the formation
and organization of clouds and precipitation range from the micro-
physical up to the planetary. This enormous range of scales may
be divided into three main categories (macro, meso, and micro)
and eleven subcategories. Consideration of scales is important
in evaluating cloud and precipitation processes and their effects.
The formation and organization of the clouds and precipitation
in extratropical cyclones is used to illustrate the role and
importance of various scales of phenomena.
I. INTRODUCTION
The processes involved in the formation and organization of
clouds and precipitation range from the very small-scale physical
and chemical processes involved in the nucleation and growth of
cloud particles up to the very large-scale dynamical processes
that are associated with synoptic weather systems. Awareness and
^Research supported by the Atmospheric Research Section of the
National Science Foundation (ATM74-14726-A02 and ΆΤΜ77-01344;
U. S. Army Research Office (DAAG29-79-G-0005), and the U. S. Air
Force Office of Scientific Research (F49620-77-C-0057').
Copyright © 1981 by Academic Press, Inc.
Clouds: Their Formation, Optical Properties, and Effects 1 All rights of reproduction in any form reserved.
ISBN 0-12-350720-0
PETER V. HOBBS
2
proper consideration of scale is important, not only in deter­
mining the effects of a particular phenomenon but in planning
field programs. For example, the areal density of measurements
should be at least sixteen times greater than the areal scale of
the phenomenon under investigation.
II. DISCUSSION
Shown on the right-hand side of Fig. 1 is a classification
of atmospheric processes based on their horizontal spatial scale
(indicated on the left-hand side of Fig. 1). Phenomena with
horizontal scales > 1000 km are referred to as macroscale (or
synoptic-scale, since they are resolved by synoptic data).
Phenomena with horizontal spatial scales ranging from a few
kilometers up to about 1000 km are called mesoscale. Smaller
scale phenomena (< 1 km) are termed microscale. To provide
further refinement, the macroscale may be divided into two
subdivisions (a and β), the mesoscale into three subdivisions
(a, 3, and γ) and the microscale into six subdivisions (α, β, γ,
ό, ξ, and ζ) as shown in Fig. 1.
To impress upon the reader the enormous extent of the fifteen
orders of magnitude covered by the horizontal spatial scales shown
in Fig. 1, it might be noted that the ratio of the linear dimen­
sions of the Milky Way to that of the earth is also about 10"*"^!
It is a most remarkable achievement that technological advances
over the past decade now allow observations and measurements
over this entire size range of atmospheric phenomena to be made.
In the remainder of this paper the concept of scales of
phenomena are illustrated by considering the organization of
clouds and precipitation in extratropical cyclones, which dominate
the weather throughout the mid-latitudes of the world.
On the macroscale, extratropical cyclones may be viewed as
cyclonic circulations embedded within baroclinic waves in the