Scattered and Filtered Solar UV Measurements

199 Pages·2004·5.779 MB·English

by  Alfio V. Parisi, Jeff Sabburg, Michael G. Kimlin (auth.)

SCATTERED AND FILTERED SOLAR UV MEASUREMENTS
ADVANCES IN GLOBAL CHANGE RESEARCH
VOLUME 17
Editor-in-Chief
Martin Beniston, Institute of Geography, University of Frihourg, PeroUes,
Switzerland
Editorial Advisory Board
B. Allen-Diaz, Department ESPM-Ecosystem Sciences, University ()f California, Berkeley,
CA, US.A.
R.S. Bradley, Department of Geosciences, University of Massachusetts, Amherst, MA,
US.A.
W. Cramer, Department of Global Change and Natural Systems, Potsdam Institute for
Climate Impact Research, Potsdam, Germany.
H.E Diaz, Climate Diagnostics Center, Oceanic and Atmospheric Research, NOAA,
Boulder, CO, US.A.
S. Erkman, Institute for Communication and Analysis of Science and Technology -ICAST,
Geneva, Switzerland.
M. Lal, Centre for Atmospheric Sciences, Indian Institute ()fTechnology, New Delhi, India.
U. Luterbacher, The Graduate Institute of International Studies, University of Geneva.
Geneva, Switzerland.
I. Noble, CRC for Greenhouse Accounting and Research School ofB iological Sciences,
Australian National University, Canberra, Australia.
L. Tessier, Institut Mediterraneen d'Ecologie et Paleoecologie, Marseille, France.
F. Toth, International Institute for Applied Systems Analysis, Laxenburg, Austria.
M.M. Verstraete, Space Applications Institute, EC Joint Research Centre, Ispra (VA),
Italy.
The titles published in this series are listed at the end of this volume.
SCATTERED AND FILTERED SOLAR
UV MEASUREMENTS
by
Altlo V. Parisi
Centerfor Astronomy. Solar Radiation and Climate.
Faculty of Sciences. University of Southern Queensland.
Toowoomba. Australia
Jeff Sabburg
Centerfor Astronomy. Solar Radiation and Climate.
Faculty of Sciences. University of Southern Queensland.
Toowoomba. Australia
and
Michael G. Kimlin
Center,l()r Astronomy. Solar Radiation and Climate.
Faculty of Sciences. University of Southern Queensland.
Toowoomba. Australia
National Ultraviolet Monitoring Center;
Department of Physics and Astronomy.
University of Georgia. Athens. U.S.A.
KLUWER ACADEMIC PUBLISHERS
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A C.I.P. Catalogue record for this book is available from the Library of Congrcss.
ISBN 978-90-481-6519-3 ISBN 978-94-015-1246-6 (eBook)
DOI 10.1007/978-94-015-1246-6
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CONTENTS
PREFACE ............................................................................... .ix
Chapter 1 INTRODUCTION ................................................. 1
1. Solar Ultraviolet Radiation ................................... 1
1.1 Introduction .................................................................... 1
1.2 Electromagnetic Radiation .............................................. 2
1.3 UV Wavebands ............................................................... 4
1.4 Radiometric Units ........................................................... 5
1.5 Solar UV ......................................................................... 6
l.6 UV Index ........................................................................ 9
2. Atmospheric Ozone and Aerosols ...................... 11
2.1 Ozone ............................................................................ 11
2.2 Scattering Processes ..................................................... 18
3. Solar Zenith Angle ............................................... 20
4. Earth's Orbit ........................................................ 21
5. Surface Albedo ..................................................... 22
6. Altitude ................................................................. 25
7. Summary .............................................................. 26
Chapter 2 DIFFUSE AMBIENT SOLAR UV ..................... 27
1. Introduction .......................................................... 27
2. Diffuse UV Spectral Irradiances ........................ 28
2.1 Diffuse UV ................................................................... 28
2.2 Spectral Measurement .................................................. 28
2.3 Spectra .......................................................................... 34
2.4 Biologically Damaging UV .......................................... 43
3. Summary .............................................................. 51
VI
Chapter 3 PERSONAL SOLAR UV EXPOSURES IN
DIFFUSE UV SETTINGS .................................. 53
1. Introduction .......................................................... 53
2. UV in Tree Shade ................................................. 54
2.1 Global UV in Tree Shade ............................................. 54
2.2 Diffuse Irradiances in Tree Shade ................................ 61
3. Personal UV Exposure Distribution ................... 65
3.1 Polysulphone Dosimeters ............................................. 65
3.2 Personal UV Exposures in Tree Shade ......................... 73
4. Summary .............................................................. 80
Chapter 4 INFLUENCE OF CLOUDS ON SOLAR UV ... 81
1. Introduction .......................................................... 81
2. CLOUD DETECTION ........................................ 83
2.1 Introduction .................................................................. 83
2.2 Satellite-based ............................................................... 84
2.3 Ground-based ................................................................ 86
2.4 Case Study .................................................................... 93
3. UV and Cloud Studies ......................................... 96
3.1 Introduction .................................................................. 96
3.2 Inferred Cloud Detection .............................................. 98
3.3 Direct Cloud Detection ................................................. 99
3.4 Spectral Dependency .................................................. 104
4. Summary ............................................................ 107
Chapter 5 UV ENHANCEMENT BY CLOUD ................. I09
1. Introduction ........................................................ 10 9
2. Literature Review .............................................. 110
2.1 Overview .................................................................... 110
2.2 UVA Case study ......................................................... 117
3. UVB Enhancement ............................................ 120
3.1 UVB Case Study ......................................................... 120
3.2 Postulated Mechanism ................................................ 122
4. Spectral Dependency Revisited ........................ 125
Vll
5. Summary ............................................................ 127
Chapter 6 GLASS FILTERED SOLAR UV ..................... 131
1. Introduction ........................................................ 131
2. Glass Transmitted UV Spectrum ..................... 132
2.1 Standard Window Glass ............................................. 132
2.2 Automobile Window Glass ......................................... 138
2.3 Special Types of Glasses ............................................ 142
3. Filtered UV in a Greenhouse: Case Study ....... 146
3.1 Spectral Transmission ................................................. 146
3.2 UV A Irradiances ......................................................... 147
3.3 Erythemal UV lrradiances .......................................... 149
3.4 Six Hour Erythemal Exposures .................................. 151
4. Summary ............................................................ 152
Chapter 7 SOLAR UV IN AUTOMOBILES: AMBIENT
AND PERSONAL EXPOSURES ..................... 155
1. Introduction ........................................................ 155
2. UV Radiation in Automobiles ........................... 156
2.1 UV Radiation in Automobiles: An Overview ............. 156
3. Measurement of UV in Automobiles ................ 157
3.1 Experimental Design: Laboratory vs. Field Based ..... 157
3.2 Broad Band Filtered UV in an Automobile ................ 159
3.3 Spectral UV Irradiances in an Automobile ................. 163
4. Annual UV A Exposure in an Automobile ....... 166
4.1 Estimates of Long-term UVA ..................................... 166
4.2 Estimates of Seasonal UV A ........................................ 168
4.3 Estimates of Annual UV A .......................................... 168
4.4 Personal Ultraviolet-A Exposure in an Automobile ... 173
5. Summary ............................................................ 175
References . ............................................................................ 177
Index ............................................................................. 191
PREFACE
Personal UV exposure is due to sunlight received as direct radiation,
scattered radiation and filtered radiation. The definitions of scattered and
filtered UV as used in this book are that scattered UV refers to the UV that
has been scattered and reflected by the atmosphere, for example clouds, and
physical environment, for example snow, and filtered UV refers to the UV
that is present after passing through a material, for example glass, or shade
material. There is very little information available about the scattered and
filtered solar UV environment and the resulting UV exposures to humans.
The incidence of skin cancer and sun-related eye disorders can be reduced
by the minimization of exposures to UV radiation. For this to occur, a
greater understanding of the solar UV exposure to humans for varying
conditions and in different environments is necessary. Furthermore, the
impact of UV absorption and its effects must be understood as one
component of the complex interactions between human systems and climate,
in the changing context. Accordingly, this book aims to quantify, understand
and provide information on the filtered and scattered solar UV.
The initial chapter will provide information on the solar UV and the
factors influencing solar UV on the earth. This is followed by chapters on
the diffuse ambient solar UV in different settings and the resulting personal
solar UV exposures. These chapters also provide details of the technical
aspects of the instrumentation and techniques required for the UV
measurements in these settings. As clouds have the greatest range of effects
on UV compared to all other parameters, the next two chapters consider in
detail the interaction of cloud on solar UV, including the possibility that on
some occasions, particular configurations of cloud can produce greater than
clear sky UV irradiances. Finally, the last two chapters provide information
on filtered solar UV and the associated measuring techniques.
This book is based on research by the authors over a number of years. All
previous publishers arc thanked for permission to use material from earlier
works. Many colleagues and granting organizations acknowledged in the
authors' previous research publications have assisted in the research over the
years and the authors gratefully acknowledge their help.
Chapter 1
INTRODUCTION
1. SOLAR ULTRAVIOLET RADIATION
1.1 Introduction
The risk of skin cancer and sun-related eye disorders, including,
cataracts, conjunctivitis, pterygium may be lowered by the reduction of
human exposures to solar ultraviolet (UV) radiation (Longstreth et aI., 1995;
Young, 1994). UV radiation is also responsible for suppression of the
immune system (Longstreth et aI., 1995), which in tum may lead to the
development of other disorders. In order to minimize the UV exposure of
humans, a complete understanding of the solar UV environment is
necessary. On the beneficial side, exposures to UV are required for the
production of vitamin D (Matsuoka et aI., 1989). Again this requires an
understanding of the solar UV environment.
Human UV exposure is due to sunlight received as direct radiation,
scattered radiation and filtered radiation - all 3 contribute together to the UV
exposure. The definitions as used in this book are that scattered UV refers to
the UV that has been scattered and reflected by the atmosphere and physical
environment. The scattering in the atmosphere is due to the interaction with
molecules and aerosols suspended in the air. Any particle in the UV
radiation's path causes redirection of the UV so that the particle is now the
point source of the scattered UV. The filtered UV refers to the UV that is
present after passing through a material, for example glass, or shade
2 Chapter I
material. The erythemal (sunburning) irradiance of filtered solar UV is only
a small fraction of that of natural solar radiation, however it is still very
important as the cumulative exposure of filtered solar UV can become
significant. The focus of this monograph is scattered and filtered solar UV
measurements. Prior to reviewing scattered and filtered UV measurements in
the following chapters, solar UV and the factors that influence solar UV on
the earth will be discussed.
1.2 Electromagnetic Radiation
The energy radiated from the sun is necessary to sustain life on earth and
also is responsible for influencing the earth's climate. The energy travels
from the sun and through the vacuum of space in the form of
electromagnetic radiation. This radiation consists of two sinusoidal waves:
an electric wave and a magnetic wave that are perpendicular to each other
and also to the direction of propagation. This form of energy has a wide
range of energies and wavelengths and forms the electromagnetic spectrum.
The wavebands comprising the spectrum are radio waves, mIcrowaves,
infrared, visible light, ultraviolet, X-rays and gamma rays.
For electromagnetic radiation, the photon energy, E, in units of Joules (1)
is related to the frequency,f, by:
E=hxf J
where h = 6.63 X 10-34 J s is Planck's constant. The frequency is the number
of waves passing a fixed point per unit time and has units of Hertz (Hz). One
Hertz is equal to one complete wave per second. The frequency is related to
the velocity of propagation, c, by:
c = fXA m
S-1
where A is the wavelength of the radiation or the distance from one wave
peak to the next. The value of c in a vacuum is 2.99792 x 108 m S-I. The unit
of wavelength is the meter (m) and common submultiples for
electromagnetic radiation are the nanometer (om) and the micrometer (/-lm).
Another unit is the angstrom (A) where I A = I X 10-10 m. For example, for
the most familiar waveband of the electromagnetic spectrum, namely the
visible light detected by the human eye, the wavelengths are from
approximately 0.4 /-lm to 0.7 /-lm, or 400 nm to 700 om, or 4000 A to
7000 A. The shorter wavelength corresponds to violet in the visible spectrum
and the longer wavelength corresponds to red.