052182642X cambridge university press the global climate system patterns processes and teleconnections sep 2006

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The Global Climate System
Patterns, Processes, and Teleconnections
Over the last 20 years, developments in climatology have provided an amazing
array of explanations for the pattern of world climates. This textbook examines
the Earth’s climate systems in light of this incredible growth in data
availability, data retrieval systems, and satellite and computer applications.
It considers regional climate anomalies, developments in teleconnections,
unusual sequences of recent climate change, and human impacts on the climate
system. The physical climate forms the main part of the book, but social and
economic aspects of the global climate system are also considered. This textbook
has been derived from the authors’ extensive experience of teaching climatology
and atmospheric science. Each chapter contains an essay by a specialist in the
field to enhance the understanding of selected topics. An extensive bibliography
and lists of websites are included for further study. This textbook will be
invaluable to advanced students of climatology and atmospheric science.
H O W A R D A . B R I D G M A N is currently a Conjoint Professor at the University
of Newcastle in Australia, having retired at the Associate Professor level in
February 2005. He has held visiting scientist positions at Indiana University,
USA, the University of East Anglia, UK, the National Oceanographic and
Atmospheric Administration, Boulder, Colorado, USA, the Atmospheric
Environment Service in Canada, and the Illinois State Water Survey, USA.
He has written, edited or contributed to eleven other books on subjects
including air pollution, applied climatology and climates of the Southern
Hemisphere. He has published many articles in the field’s leading journals.
J O H N E . O L I V E R was educated in England and the United States, obtaining his
Ph.D. at Columbia University, where he served on the faculty, before joining
Indiana State University. Prior to his appointment as Emeritus Professor, he was

Professor of Physical Geography and Director of the University Climate
Laboratory at Indiana State. He also served as Department Chairperson and
Associate Dean of Arts and Sciences.
He has published twelve books and his work on applied climatology and
historic climates has appeared in a wide range of journals. He was founding
editor, with Antony Orme, of the journal Physical Geography, for which until
recently he served as editor for climatology. In 1998 he was awarded the first
Lifetime Achievement Award from the Climatology Group of the Association of
American Geographers.



The Global Climate System
Patterns, Processes, and Teleconnections

Howard A. Bridgman
School of Environmental and Life Sciences
University of Newcastle, Australia

John E. Oliver
Department of Geography, Geology and Anthropology
Indiana State University, USA

With contributions from
Michael Glantz, National Center for Atmospheric
Research, USA
Randall Cerveny, Arizona State University, USA
Robert Allan, Hadley Centre, UK
Paul Mausel, Indiana State University, USA
Dengsheng Lu, Indiana University, USA

Nelson Dias, Universidade de Taubate´, Brazil
Brian Giles, University of Birmingham, UK
Gerd Wendler, University of Alaska, USA
Gregory Zielinski, University of Maine, USA
Sue Grimmond, Indiana University, USA
and King’s College London, UK
Stanley Changnon, University of Illinois, USA
William Lau, NASA Goddard Space Flight Center, USA


  
Cambridge, New York, Melbourne, Madrid, Cape Town, Singapore, São Paulo
Cambridge University Press
The Edinburgh Building, Cambridge  , UK
Published in the United States of America by Cambridge University Press, New York
www.cambridge.org
Information on this title: www.cambridge.org/9780521826426
© H. Bridgman and J. Oliver 2006
This publication is in copyright. Subject to statutory exception and to the provision of
relevant collective licensing agreements, no reproduction of any part may take place
without the written permission of Cambridge University Press.
First published in print format 2006
-
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Cambridge University Press has no responsibility for the persistence or accuracy of s
for external or third-party internet websites referred to in this publication, and does not
guarantee that any content on such websites is, or will remain, accurate or appropriate.


Contents

List of contributors
Preface
List of abbreviations

page viii
xi
xiv

1 Introduction
1.1 The climate system
1.2 Patterns, processes, and teleconnections
1.3 ESSAY: Problem climates or problem societies? (Glantz)
1.4 Examples of general climate websites
1.5 References

1
1
8
10
23
24

2 Oscillations and teleconnections
2.1 History and definitions
2.2 The North Atlantic Oscillation (NAO)
2.3 The North Pacific Oscillation (NPO)/Pacific Decadal
Oscillation (PDO)
2.4 The Pacific North American Oscillation (PNA)
2.5 The Madden–Julian Oscillation (MJO)
2.6 The Quasi-biennial Oscillation (QBO)
2.7 The Arctic Oscillation (AO) and the Antarctic Oscillation (AAO)
2.8 ESSAY: ENSO and related teleconnections (Allan)
2.9 Examples of oscillations and teleconnections websites
2.10 References

25
25
29

3 Tropical climates
3.1 Introduction
3.2 The climate controls
3.3 ESSAY: The Quasi-biennial Oscillation and tropical climate
variations (Cerveny)
3.4 Human activities and problem climates in the tropics

3.5 ESSAY: Remote sensing of Amazonia deforestation and
vegetation regrowth: inputs to climate change research
(Mausel, Lu and Dias)
3.6 Chapter summary

59
59
59

30
31
33
34
36
38
54
54

67
74

79
90
v


vi

Contents

3.7 Examples of tropical climates websites
3.8 References

91
91

4 Middle-latitude climates
4.1 Introduction
4.2 Data availability
4.3 ESSAY: Reanalysis (Giles)
4.4 Using reanalysis
4.5 The Northern Hemisphere
4.6 Mid-latitude circulation and teleconnections
in the Southern Hemisphere
4.7 Chapter summary
4.8 Examples of mid-latitude websites
4.9 References

96
96
96
97
104
106

5 Climate of the polar realms
5.1 Introduction (Wendler)
5.2 ESSAY: Antarctic climate (Wendler)
5.3 Upper air circulation and wind
5.4 Surface pressure variations

5.5 Cyclogenesis and cyclonicity
5.6 Antarctic climate and ENSO
5.7 Polar night jet and stratospheric ozone depletion
5.8 ESSAY: Arctic Climate (Wendler)
5.9 Arctic general circulation
5.10 Surface pressure and wind
5.11 Extra-tropical cyclones
5.12 Polar night jet and stratospheric ozone depeletion
5.13 Concerns about future warming
5.14 Chapter summary
5.15 Examples of polar websites
5.16 References

131
131
132
142
143
146
148
149
151
161
161
163
165
166
166
167
168

6 Post-glacial climatic change and variability
6.1 Introduction
6.2 Determining past climate through the use of proxies
6.3 ESSAY: Post-glacial climates in the Northern
Hemisphere (Zielinski)
6.4 Southern Hemisphere climate reconstructions
6.5 Chapter summary
6.6 Examples of paleoclimate websites
6.7 References

171
171
172

114
125
126
126

175
194
201
202
202


Contents

7 Urban impacts on climate

7.1 Introduction
7.2 Highlights in the history of urban climate research
7.3 ESSAY: Variability of urban climates (Grimmond)
7.4 Wind, cloud cover, and pressure
7.5 Urban canyons
7.6 Moisture and precipitation
7.7 Effects of air pollution
7.8 Remote sensing and the UHI
7.9 Mitigation of the UHI
7.10 Chapter summary
7.11 Examples of urban websites
7.12 References

205
205
207
210
223
227
230
232
234
238
239
239
240

8 Human response to climate change
8.1 Introduction
8.2 The Viking settlements in Greenland, AD 800–1450

8.3 Climate change and adaptation in Europe during the Little Ice Age
8.4 ESSAY: Economic impacts of climate conditions in the United
States (Changnon)
8.5 Conclusions
8.6 Examples of climate and history websites
8.7 References

244
244
245
250
260
275
277
277

9 ESSAY: Model interpretation of climate signals: an application
to Asian monsoon climate (Lau)
9.1 Introduction
9.2 A climate model primer
9.3 Modeling the Asian monsoon climate
9.4 Future challenges
9.5 Acknowledgement
9.6 Examples of climate modeling websites
9.7 References

281
281
282
292

303
305
305
305

10 Conclusions and the future of climate research
10.1 Introduction
10.2 Understanding the global climate system
10.3 The importance of communication
10.4 References

309
309
311
318
320

Other books on climatology and the climate system
Index
The color plates are situated between pages 170 and 171

321
325

vii


Contributors

Michael Glantz is a senior scientist at the National Center for Atmospheric

Research, Boulder, Colorado, USA, and is an expert on climate change
impacts on society and lifestyle.
Robert Allan is a senior scientist at the Hadley Centre, Met Office, United
Kingdom, and is an expert on E1 Nin˜o–Southern Oscillation, its teleconnections and its climate impacts.
Randall Cerveny is a Professor in Geography at Arizona State University,
Phoenix, Arizona, USA, and is an expert on tropical circulations and
climates of South America.
Paul Mausel is a Professor at Indiana State University, Terre Haute, Indiana,
USA, and is an expert on remote sensing, and interpretations of biospheric
and atmospheric changes from satellite data.
Dengsheng Lu is a research scientist in the Center for the Study of Institutions,
Population, and Environmental Change at Indiana University and is an
expert in remote sensing.
Nelson Dias is a research associate at the Universidade de Taubate´ in Brazil, and
researches changes to the Amazon rainforest using remote sensing
techniques.
Brian Giles is a retired Professor from the School of Geography, Geology
and Environmental Sciences at the University of Birmingham, UK, and is
an expert on synoptic meteorology and NCEP/NCAR reanalysis. He
currently lives in Takapuna, New Zealand.
Gerd Wendler is a Professor and Director of the Arctic Research Institute at
the University of Alaska, Fairbanks, Alaska, USA, and is an expert on
synoptic climatology of the Arctic and Antarctic regions.
Gregory Zielinski is a scientist at the Institute for Quaternary and Climate
Studies at the University of Maine, Orono, Maine, USA, and is an expert on
Holocene paleoclimates and proxy interpretations of climate change.

viii

List of contributors

Sue Grimmond is a Professor in the Environmental Monitoring and Modelling
Group, Department of Geography, King’s College London, UK, and is an
expert on urban climate and urban impacts on energy and water balances.
Stanley Changnon is retired as Director of the Illinois State Water Survey,
Champaign-Urbana, Illinois, USA, and is currently Emeritus Professor of
Geography at the University of Illinois. His expertise is in water and
climate change, and the impacts of weather hazards on economics and
society.
William Lau is Head of the Climate and Radiation Branch, NASA Goddard
Space Flight Center, Greenbelt, Maryland, USA, and is an expert on
climate modeling.

ix



Preface

As graduate students in the 1960s and 1970s, the authors became attracted to the
exciting world of the atmosphere and climatology through both lectures and
textbooks. The approach to climatology at that time is best described as ‘‘global
descriptive,’’ where we were introduced to climate patterns and regimes across
the Earth, and what then were known as the explanations behind them. One of
the best books for studying advanced climatology was The Earth’s Problem
Climates (University of Wisconsin Press, 1966), by Glenn Trewartha, a wellknown and respected climatologist from the University of Wisconsin. In this
book we explored, both geographically and systematically, the climate patterns
and anomalies across the continents. We were introduced to the nature of the
Atacama Desert, the climatic anomalies of northeast Brazil, the temperature

extremes of central Siberia, and the monsoon variations in India and China,
among other aspects. Trewartha’s book was reprinted in 1981, but sadly the new
version did not properly include new research and findings on global climate
patterns. For example, despite recognition by the mid 1970s of its essential
importance to global climatic variability, there was no discussion of the
El Nin˜o–Southern Oscillation!
During the decades of the 1970s, 1980s, and 1990s, there has been an explosion
in climatic research and a new breadth and depth of understanding about climatology and the atmosphere. There have also been a number of excellent books
published in the area of climatology. Almost all of these can be grouped into one
of two categories: (a) introductory to intermediate textbooks, to support teaching,
which basically assume little or no background knowledge in climate or atmospheric studies; and (b) detailed books on either a climatic topic or a geographical
area, based on extensive summaries of research publications. Examples of the
latter include Elsevier’s World Survey of Climatology series; El Ni~
no: Historical
and Palaeoclimatic Aspects of the Southern Oscillation (editors Diaz and
Markgraf ); Antarctic Meteorology and Climatology (King and Turner); El
Ni~
no Southern Oscillation and Climate Variability (Allen, Lindesay, and
Parker); and Climates of the Southern Continents (editors Hobbs, Lindesay, and
Bridgman). There is currently no book that provides a synthesis and overview of
this information, filling the gap left by The Earth’s Problem Climates.
It is our purpose in The Global Climate System to fill this gap, providing a
book that can be used as background to climate research, as well as a text for
xi


xii

Preface

advanced climatology studies at senior undergraduate and graduate levels. We
have, combined, over 50 years teaching experience in climate, atmospheric
sciences and weather, and written or co-authored 12 books on climate, climatology, and the atmosphere.
Global climates mostly follow a semi-predictable pattern based upon the
receipts of energy and moisture distribution, with modifications based upon
the non-homogeneity of the Earth’s surface. But within these arrangements of
climate are areas that are atypical of the expected pattern. In the preface to the
second edition of The Earth’s Problem Climates, Glenn Trewartha wrote, ‘‘In
the nearly two decades that have elapsed since the initial publication of this
book, new information as well as new climatic data have become available
concerning some of the earth’s unusual climates.’’ As noted, in the more than
two decades since Trewartha wrote these words there has been an incredible
growth in information, information technology, data availability, and rapid data
retrieval systems. Satellite and computer applications have led to a modern
climatology whose methods were not available when Trewartha penned his
first edition. Given such developments, it is appropriate that a timely reexamination of the Earth’s climate system should be undertaken. Some examples
include:
1. Regional climates that cannot be well explained in the context of their surrounding
climates. Such anomalies are dealt with by considering continental areas within the
division of tropical, middle-latitude and polar climates.
2. The recent developments in teleconnections open an array of climatic observations
that are not readily explained. Thus, new understandings of climate interactions, such
as those arising for example from possible impacts of ENSO events, are explored.
3. Intense inquiry into processes and nature of climate change has opened new vistas for
its study. However, within the sequence of change there are times and events that do
not appear to follow an expected pattern.
4. Both the human inputs into climate and the impacts of climate upon humans provide an
extensive area of study. In the urban environment, massive interruptions of the natural
systems provide an arena in which many seemingly anomalous conditions occur. At
the same time, problem climates also influence the social and economic well-being of

many people.

We cannot cover the full details of the entire climate system in this book. The
range of knowledge about the climate system is increasing too rapidly. Instead,
we explore a range of aspects and topics, to show current understanding, but also
to encourage interest and further research, from both the scientist and the
student. To help achieve this aim, we have enlisted the input of respected
scholars who contribute essays dealing with their areas of expertise. These
essays are merged into each chapter in the hope that the text is a continuum of
information. Each author was given some very general instructions about the
aim of the book, the expected size of the essay, and the number of supporting


Preface

figures and tables. Further specifics were intentionally left out, to allow the
authors freedom to develop their essays in their own style. Initially we had
hoped to have essayists from a range of different geographical locations
around the world. The final list, nine from the USA, two from the UK, and
one from Brazil, does not quite meet that aim, but we are very pleased with
the outcome. The essays are shaded, to distinguish them from the material
written by us.
We would like to thank the University of Newcastle and Indiana State
University for their support, especially for study leave trips for both authors.
We thank our support cartographers, Olivier Rey-Lescure at Newcastle and Lu
Tao at Indiana State. Last, but not least, we thank our wives, who had a
wonderful time socializing in the second half of 2004, allowing us to work
uninterrupted on the manuscript.

xiii

Abbreviations

AAO
ABRACOS
ACSYS
ACW
AGB
AGCM
ALPEX
AM
AMIP
AMO
AO
AUHI
AVHRR
AWS
BUFR
CACGP
CCN
CCSP
CET
CliC
CLIVAR
CMAP
CMIP
COADS
CPC
CPT

CPV
CRU
DOE
ECA
xiv

Antarctic Oscillation
Anglo-Brazilian Amazonian Climate Observation
Study
Arctic Climate System Study
Antarctic Circumpolar Wave
Above Ground Biomass
Atmospheric General Circulation Model
Alpine Experiment of 1982
Asian Monsoon
Atmospheric Model Intercomparison Project
(NCEP/DOE)
Atlantic Multidecadal Oscillation
Arctic Oscillation
Atmospheric Urban Heat Island
Advanced Very High Resolution Radiometer (satellite)
Automatic Weather Station
Binary Universal Format Representation of the WMO
Commission on Atmospheric Chemistry and Global
Pollution
Cloud Condensation Nuclei
Climate Change Science Program
Central England Temperature Series
Climate and Cryosphere
Climate Variability and Predictability

CPC Merged Analysis of Precipitation
Coupled Model Intercomparison Project
Comprehensive Ocean-Atmosphere Data Set
Climate Prediction Center
Circumpolar Trough
Circumpolar Vortex
Climatic Research Unit, University of East Anglia
Department of Energy
European Climate Assessment


List of abbreviations

ECMWF
ENSO
EOF
FGGE
GAIM
GARP
GATE
GCM
GCTE
GDP
GEOS
GEWEX
GIS
GISP2
GNP
GRIB
GRIP

GURME
HadCRUT
HadSST
HRC
H/W
IAMAS
ICSU
IGAC
IGBP
IGY
IHDP
ILEAPS
INPE
IPCC
IPCC DDC
IPO

European Centre for Medium-Range Weather
Forecasts
El Nin˜o–Southern Oscillation
Empirical Orthogonal Function
First GARP Global Experiment
Global Analysis, Integration, and Modelling Program
Global Atmospheric Research Program
GARP Global Atlantic Experiment
General Circulation Model
Global Climate Model
Global Chemistry Tropospheric Experiment
Gross Domestic Product
Goddard Earth Observing System

Global Energy and Water Cycle Experiment
Geographic Information System(s)
Greenland Ice Sheet Project 2
Gross National Product
Grided Binary representation (WMO)
Greenland Ice Core Project
Global Urban Research Meteorology and
Environmental Project
Climatic Research Unit’s land surface air temperatures
Hadley Centre monthly gridded Sea Surface
Temperatures
Highly Reflective Clouds
Height to Width ratio
International Association of Meteorology and
Atmospheric Science
International Council for Science
International Global Atmospheric Chemistry
Program
International Geosphere/Biosphere Program
International Geophysical Year
International Hydrological Development Program
Integrated Land Ecosystem–Atmospheric Processes
Study
Instituto Nacional de Pesquisas Espaciais (National
Institute for Space Research, the Brazilian government)
Intergovernmental Panel on Climate Change
Intergovernmental Panel on Climate Change Data
Distribution Centre
Interdecadal Pacific Oscillation

xv


xvi

List of abbreviations

IRD
ISL
ITC or ITCZ
IUGG
JMA
JRA-25
LBA
LF ENSO
LFV
LIA
LULC
MAP
MC
METROMEX
MIP
MJO
MMIP
MSLP
MTM-SVD
MWP
NAO
NASA/DAO

NCAR
NCEP/DOE AMIP-II
NCEP/NCAR
NCEP/NCAR-40
NEE
NGDC
NH
NMC
NOAA
NPO
NWS
OLR
PAGES
PDO
PDV

Ice-Rafted Debris
Inertial Sub-Layer (urban)
Intertropical Convergence Zone
International Union of Geodesy and Geophysics
Japanese Meteorological Agency
Japanese Re-Analysis 25 years
Large-scale Biosphere–Atmosphere Experiment in
Amazonia
Low-Frequency ENSO, 2.5 to 7 years
Local Fractional Variance
Little Ice Age
Land Use/Land Cover
Merged Analysis of Precipitation
Maritime Continent

METROpolitan Meteorological EXperiment
Model Intercomparison Projects
Madden–Julian Oscillation
Monsoon Model Intercomparison Project
Mean Sea Level Pressure
Multi-Taper Method Singular Value Decomposition
Medieval Warm Period
North Atlantic Oscillation
National Aeronautics and Space Administration/Data
Assimilation Office of the Goddard Laboratory
for Atmospheres
National Center for Atmospheric Research
Reanalysis or Reanalysis 2
National Centers for Environmental Prediction/
National Center for Atmospheric Research
Reanalysis project 1957–1996
Net Ecosystem Exchange (of CO2)
National Geophysical Data Center
Northern Hemisphere
National Meteorological Center, USA
National Oceanographic and Atmospheric
Administration, USA
North Pacific Oscillation
National Weather Service, USA
Outgoing Longwave Radiation
Past Global Changes
Pacific Decadal Oscillation
Pacific Decadal Variation

List of abbreviations

PILPS
PMIP
PNA
PNJ
PSCs
QB ENSO
QBO
RSL
SAM
SAO
SAR
SCORE
SEAM
SEB
SH
SMIP
SO
SOI
SOLAS
SPARC
SPCZ
SS1
SS2
SS3
SST
STHP
SUHI
SVF

THC
TM
TOGA
TOMS
TOVS/SSU
TPI
TRMM
TRUCE
UBL
UCI
UCL

Project of Intercomparison of Land Parameterization
Schemes
Paleoclimate Model Intercomparison Project
Pacific North American Oscillation
Polar Night Jet
Polar Stratospheric Clouds
Quasi-Biennial ENSO, 2 to 2.5 years
Quasi-Biennial Oscillation
Roughness Sub-Layer (urban)
South Asian Monsoon
Semi-Annual Oscillation
Synthetic Aperture Radar
Scientific Committee on Ocean Research
South East Asian Monsoon
Surface Energy Balance
Southern Hemisphere
Seasonal Model Intercomparison Project
Southern Oscillation

Southern Oscillation Index
Surface Ocean–Lower Atmosphere Study
Stratospheric Processes and their Role in Climate
South Pacific Convergence Zone
Initial secondary succession
Secondary succession forest
Succession to mature forest
Sea Surface Temperature
Subtropical High Pressure
Surface Urban Heat Island
Sky View Factor (urban)
Global Thermohaline Circulation
Thematic Mapper, Landsat satellite sensor,
resolution 30 m
Tropical Ocean Global Atmosphere
Total Ozone Monitoring Spectrometer
TIROS Operational Vertical Sounder/Stratospheric
Sounding Unit
Trans-Polar Index (Southern Hemisphere)
Tropical Rainfall Measuring Mission
Tropical Urban Climate Experiment
Urban Boundary Layer
Urban Cool Island
Urban Canopy Layer

xvii


xviii

List of abbreviations

UHI
UHIC
UME
UNCCD
UNCED
UNEP
VOC
WCRP
WETAMC
WMO
See also Table 10.1.

Urban Heat Island
Urban Heat Island Circulation
Urban Moisture Excess
United Nations Convention to Combat Desertification
United Nations Conference on Environment and
Development
United Nations Environment Programme
Volatile Organic Compounds
World Climate Research Programme
Wet season Atmospheric Mesoscale Campaign
(Amazon Basin)
World Meteorological Organization


Chapter 1

Introduction

1.1 The climate system
Climate is a function not only of the atmosphere but is rather the response to
linkages and couplings between the atmosphere, the hydrosphere, the biosphere,
and the geosphere. Each of these realms influences any prevailing climate and
changes in any one can lead to changes in another. Figure 1.1 provides in
schematic form the major couplings between the various components of the
climate system. A climate-systems approach avoids the isolation of considering
only individual climatic or atmospheric components. This approach recognizes
the importance of forcing factors, which create changes on scales from longterm transitional to short-term sudden, and that the climate system is highly nonlinear. According to Steffen (2001), a systems approach also recognizes the
complex interaction between components, and links between the other great
systems of the Earth, and the ways in which humans affect climate through the
socioeconomic system. Ignoring such interactions may create inaccuracies and
misinterpretations of climate system impacts at different spatial scales.
In examining any component of the Earth’s atmosphere, its systems and
its couplings, basic knowledge of the energy and mass budgets is critical.
Information concerning these is given in most introductory texts (Oliver and
Hidore 2002; Barry and Chorley 1998) and they are not reiterated in detail here.
Rather, the following provides a brief summary of major concepts.

1.1.1 Energy and mass exchanges
Energy
Every object above the temperature of absolute zero À273 8C radiates energy to
its environment. It radiates energy in the form of electromagnetic waves that
travel at the speed of light. Energy transferred in the form of waves has
characteristics that depend upon wavelength, amplitude, and frequency.
The characteristics of the radiation emitted by an object vary as the fourth
power of the absolute temperature (degrees Kelvin). The hotter an object, the
greater the flow of energy from it. The Stefan–Boltzmann Law expresses this

1


2

Figure 1.1 A simplified
and schematic
representation of the Earth’s
climate system.

1 Introduction

ATMOSPHERE
Terrestrial
radiation

Solar
radiation

Atmospheric
gases and aerosols
Clouds
Advection
1

2
Evaporation

Heat
Sea ice

exchange 3

4
Ice sheets

LAND
OCEAN
1 Atmosphere–land coupling
2 Atmosphere–biosphere coupling

3 Atmosphere–sea ice coupling
4 Atmosphere–ice coupling

relationship by the equation F ¼ T 4 where F is the flux of radiation emitted per
square meter,  is a constant (5.67 Â 10À8 W mÀ2 kÀ4 in SI units), and T is
an object’s surface temperature in degrees Kelvin.
Applying this law, the average temperature at the surface of the Sun is 6000 K.
The average temperature of Earth is 288 K. The temperature at the surface of the
Sun is more than 20 times as high as that of Earth. Twenty raised to the fourth
power is 160 000. Therefore, the Sun emits 160 000 times as much radiation per
unit area as the Earth. The Sun emits radiation in a continuous range of electromagnetic waves ranging from long radio waves with wavelengths of 105 meters
down to very short waves such as gamma rays, which are less than 10À4
micrometers in length.
Another law of radiant energy (Wien’s Law) states that the wavelength of
maximum intensity of radiation is inversely proportional to the absolute temperature. Thus the higher the temperature, the shorter the wavelength at which
maximum radiation intensity occurs. This is given by lmax ¼ 2897/T where
T ¼ temperature in degrees Kelvin, and wavelength is in micrometers.
For the Sun, lmax is 2897/6000 which equals 0.48 mm. For the Earth lmax is given
by 2897/288, a wavelength of 10 mm. Thus the Sun radiates mostly in the visible
portion of the electromagnetic spectrum and the Earth in the infrared (Figure 1.2).

There is a thus a fundamental difference between solar and terrestrial radiation and
the ways in which each interacts with the atmosphere and Earth’s surface.
Utilization of these laws, and knowledge of Earth–Sun relations, enables the
computation of the amount of energy arriving, the solar constant, and the nature
of solar and terrestrial radiation. These are used to derive budgets of energy
exchanges over the Earth’s surface. Box 1.1 provides basic information on this
using the customary symbols.


1.1 The climate system

3

Figure 1.2 Wavelength
characteristics of solar and
terrestrial radiation. Note
the difference between
extraterrestrial solar
radiation and that incident
at the Earth’s surface
indicating atmospheric
absorption of both shortwave ultraviolet and infrared
radiant energy. Earth emits
energy largely in the infrared
portion of the spectrum.
(After Sellers 1965)

The climate at any location is ultimately related to net radiation (Q*) and is a
function of a number of interacting variables. First, incoming solar radiation
varies with latitude, being greatest at the equator and least at the poles. Hence,

climate varies with latitude. Second, energy transformations at the surface
are completely different over ice, water, and land, while also varying with
topography, land use, and land cover. Climates will thus vary between such
surfaces. The variation associated with such surfaces is seen in the heat budget
equation.
The heat budget explains the relative partitioning between sensible heat and
latent heat transfers in a given environment. In a moist environment a large part
of available energy is used for evaporation with less available for sensible heat.


4

1 Introduction

Background Box 1.1

Energy flow representation
The exchanges and flows associated with energy inputs into the Earth-atmosphere
system is represented by a series of symbolic equations. Use of the equations permits
easy calculation once values are input.
Shortwave solar radiation (K#) reaching the surface is made up of the vertical
radiation (S) and diffuse radiation (D):
K#¼ S þ D
Some of the energy is reflected back to space (K") so that net shortwave radiation
(K*) is the difference between the two:
K* ¼ K # À K "
Net longwave, terrestrial radiation (L*) comprises downward atmospheric
radiation (L#) less upward terrestrial radiation (L"):
L* ¼ L # À L "
The amount of energy available at any surface is thus the sum of K* and L*. This is

net all-wave radiation (Q*):
Q* ¼ K* þ L*
which may also be given as
Q* ¼ ðK # À K "Þ þ ðL # À L "Þ
Q* may be positive or negative.
High positive values will occur during high sun periods when K# is at its
maximum and atmospheric radiation, L#, exceeds outgoing radiation, L".
Negative values require outgoing values to be greater than incoming. This
happens, for example, on clear nights when L" is larger than other values.
On a long-term basis, Q* will vary with latitude and surface type.

The heat budget
Consider a column of the Earth’s surface extending down to where vertical heat
exchange no longer occurs (Figure 1.3). The net rate (G) at which heat in this column
changes depends upon the following:
Net radiation (K " À K #) þ (L" À L #)
Latent heat transfer (LE)
Sensible heat transfer (H)
Horizontal heat transfer (S)


1.1 The climate system

5

Figure 1.3 Model of
energy transfer in the
atmospheric system.

In symbolic form:

G ¼ ðK " À K #Þ þ ðL " À L #Þ À LE À H Æ S
Since
ðK " À K #Þ þ ðL " À L #Þ ¼ Q*
then
G ¼ Q* À LE À H Æ S
in terms of Q*
Q* ¼ G þ LE þ H Æ S
The column will not experience a net change in temperature over an annual period;
that is, it is neither gaining nor losing heat over that time, so G ¼ 0 and can be
dropped from the equation.
Q* ¼ LE þ H Æ S
This equation will apply to a mobile column, such as the oceans. On land, where
subsurface flow of heat is negligible, S will be unimportant. The land heat budget
becomes
Q* ¼ LE þ H
The ratio between LE and H is given as the Bowen Ratio.
(After Oliver and Hidore 2002)

The opposite is true in dry environments. The ratio of one to another is expressed
by the Bowen Ratio; a high value would indicate that large amounts of energy
are available for sensible heat, a low value indicates that much available energy
is used for latent heat transfer. This partially explains why desert regions, which