Table Of ContentBeyond El Nifio
Decadal and Interdecadal Climate Variability
Springer-Verlag Berlin Heidelberg GmbH
Antonio Navarra (Ed.)
Beyond El Nifio
Decadal and Interdecadal
Climate Variability
With 168 Figures and 7 Tables
Springer
Editor
Dr. Antonio Navarra
IMGA-CNR
Via Gobetti 101
1-40129 Bologna
Italy
E-mail: [email protected]
ISBN 978-3-642-63556-4
Library of Congress Cataloging-in-Publication Data
Beyond El Nifio : decadal and interdecadal c1imate variability / Antonio Navarra, (ed.)
p. cm. Inc1udes bibliographical references and index.
ISBN 978-3-642-63556-4 ISBN 978-3-642-58369-8 (eBook)
DOI 10.1007/978-3-642-58369-8
1. Climatic changes. 1. Navarra, A. (Antonio), 1956- .
QC981.8.C5B46 1999 551.6 --dc21 99-18126 CIP
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Foreword
The interest and level of research into climate variability has risen dramatically
in recent years, and major breakthroughs have been achieved in the understanding
and modelling of seasonal to interannual climate variability and prediction. At the
same time, the documentation of longer term variability and its underlying mecha
nisms have progressed considerably.
Within the European Commission's Environment and Climate research programs
several important projects have been supported in these areas -including the "Dec
adal and Interdecadal Climate variability Experiment" (DICE) which forms the
basis of this book. Within the EC supported climate research, we see an increasing
importance of research into climate variability, as is evidenced in the upcoming
Fifth Framework Programme's Key Action on Global Change, Climate and Biodi
versity. This is because of the obvious potential socio-economic benefits from sea
sonal to decadal scale climate prediction and equally important for the fundamental
understanding of the climate system to help improve the quality and reliability of
future climate change and mankind's current interference with it.
The DICE group has performed important and pioneering work, and we hope
this book will receive the wide distribution and recognition it deserves. We wel
come the contributions from distinguished researchers from US, Japan and Canada
to the EC's DICE group towards completing the scope of the book and as an exam
ple of international cooperation which is essential in such a high-level scientific
endeavor.
Anver Ghazi and Ib Troen
Climate and Natural Hazards
European Commission
Brussels
Preface
Major progress on observations and modelling of the EI Nino/Southern Oscilla
tion (ENSO) have been made in recent years. We can now monitor the evolution of
the SST in real time and the modeling efforts have advanced to the point that sev
eral models used for climate studies now have intrinsic enso-like behavior on inter
annual scales and can simulate or predict ENSO impacts. The implications of such
developments are enormous. Precipitation and surface temperature in the extratrop
ics are influenced by the phase of ENSO and extratropical circulation anomalies
are correlated with the tropical sea surface temperatures (SST).
However, little attention has been paid to scales longer than ENSO, but shorter
than centuries. This segment of the climate variability is dominated by decadal
fluctuations whose dynamical nature is more elusive than the ENSO cycle, but
manifest themselves very clearly in the precipitation record, in the long-time statis
tics of the ENSO cycle and in the statistics of other atmospheric variables.
Decadal fluctuations show up clearly in the hydrological system, and regional
rainfall regimes have been identified as undergoing wide variability with very large
economic and societal impact. The decadal variations of precipitation in the tropics
have been well documented, and recently some evidence of decadal variability of
precipitation in Western Europe has also been proposed. The Indian monsoon
undergoes large decadal oscillations that might affect Southern Europe via a possi
ble connection with the Mediterranean surface pressure has been recently identi
fied.
The picture emerging from these studies seems to indicate that decadal fluctua
tions in rainfall, though most pronounced in the tropics, exist also in mid-latitude
areas and they are probably linked via some unknown teleconnection mechanism to
the equatorial variability. The full impact of this variability for the mid-latitude cli
mate remains to be assessed and the workings of the physical processes involved
are still largely obscure.
The evolution of the GeMs and the availability of high quality SST data sets,
have made possible the design of numerical experiments aimed at simulating
drought events. These experiments, performed with coupled models and with
atmospheric GeMs with prescribed SST, show that quantities as precipitation, soil
moisture and soil temperature exhibit some degree of reprodUcibility in GeM sim
ulations even outside the tropics. However, ensemble integrations, i.e. repeated
GeM simulations with slightly perturbed initial conditions, are necessary to extract
useful informations from the numerical experiments. The evidence is now suffi-
viii
cient to justify extensive investigations of the capability of GCMs to simulate dec
adal fluctuations of the climate variability.
Starting in 1994, the European Union supported a research project within the
Environment Program of Fourth Framework Program of Research and Develop
ment called DICE (Decadal and Interdecadal Climate variability: dynamics and
predictability Experiments) in which some of these puzzles have been investigated
using global numerical models. The plan was to assess the reliability of present
GCMs at simulating present climate variations on the decadal timescale, to evalu
ate the reproducibility of the simulations by performing ensemble integrations and
to carry out model validation through comparison with the observed decadal fluctu
ations. The members of the DICE partnership included nine groups from seven
european countries and the major effort was to construct and analyze ensemble
simulations with the GCM of participating institutions, by perturbing initial condi
tions. The results of DICE are widely distributed in the literature in major scientific
journals, but at the end of the project it was also felt that it would be useful to bring
together in a single place the cultural advances that DICE had fostered. The inter
national collaboration was an experience not only scientific, but also human and
personal, forging lasting links of collaboration and friendship. This book represent
the results of trying to put together the overall experience of DICE and to pass on
"what we have learned" in a more coherent fashion than what is possible in special
ized papers. The book is mostly based on contribution from DICE partners (IMGA
CNR, Italy; Max-Planck-Institute, Germany; Hadley Center, UK Meteorological
Office; Laboratoire de Meteorologie Dynamique, France; KNMI, Holland; Univer
sity of Alcala, Spain), but we have happily hosted contributions from Japanese and
North American colleagues that have provided expertise not present in DICE, or
different and complimentary views.
The first six chapter of the book contains observational studies on decadal vari
ability. The variability of the arctic is discussed in first chapter by Larry Mysak,
that illustrates how complex mechanisms can be at work in the arctic that could
interact with the general circulation of the Atlantic, the following chapter, by
Claude Frankignoul, extends the process in investigating the puzzling relationship
between the atmosphere and the SST in the North Atlantic. The discussion of extra
tropical variability is completed by the Chapter 3, by Hisashi Nakamura and Toshio
Yamagata, on the decadal variability in the North Pacific. Chris Folland and collab
orators describes thoroughly the variability of the Sea Surface Temperatures, dis
cussing the quality and availability of the data sets and the space-time behavior of
the global patterns of variability of SST. The chapter is also giving a lucid discus
sion of the teleconnections between SST and rainfall at a global level and in
selected areas at decadal time scales. An important component of the climate vari
ability is the Indian Summer Monsoon, that is also a phenomenon for which we can
have a very long time series of observations. Julia Slingo is discussing in Chapter 5
the decadal variability of the Indian Monsoon and some of its relation with the
Pacific ENSO variability. One of the most famous problem involving decadal vari
ability, the Sahel drought, is discussed in Chapter 6, by Neil Ward and collabora-
ix
tors. In this chapter the problem of the variability of rainfall over the Sahelian
region is discussed in the wider context of the North African climate system.
The following chapter, by Antonio Navarra, introduces the chapters devoted to
the description of numerical simulations of decadal and interannual variability. The
chapter discusses the basic concepts that are important for these class of applica
tions: ensembles, skill, reproducibility. The discussion is based on simulations per
formed with the T30 version of the ECHAM4 model for the period 1961-1994.
Similar experiments are discussed in Chapter 8, by Z. Li, with the LMD finite dif
ference model. Chapter 9, by Tett and collaborators, comparisons are made of
observed behavior with simulations of interannual to decadal variability in coupled
Hadley Center models. The same topic is the subject of Chapter 10, by Seiji Yuki
moto, in which the performance of the Japan Meteorological Research Institute
global coupled model is discussed. Chapter 11 contains an extensive discussion of
the dynamics of the interdecadal variability in coupled ocean atmosphere models
by Mojib Latif. The tropical variability is the subject of Chapter 12, by Ortiz-bevia
and collaborators, that is discussed defining various indices of the ocean tempera
ture in the Gulf of Guinea. Chapter 13, by Haarsma and collaborators, contains the
discussion of an idealized coupled model developed at KNMI that is suitable for
very long simulations. A more theoretical outlook of decadal variability is offered
by Gu and Philander in Chapter 14. A discussion of the relevance of decadal vari
ability in the thermohaline circulation by Stefan Rahmstorf in Chapter 15 con
cludes the book.
Working in DICE was an exciting experience and I would like to thank here the
support of my partners in DICE (C. Frankignoul, M. Latif, T. Opsteegh, J.Slingo,
C. Folland, S. Bassini, M. Sciortino, H. Le Treut and M. OrtizBevia) and have
made the whole effort a pleasant enterprise. I would also like to thank the other
contributors to the book that have joined enthusiastically the enlarged DICE com
munity. It is also a pleasure to acknowledge the continous support and encourage
ment of the Commission Officers Ib Troen, R. Fantechi, and A. Ghazi.
A Navarra
Editor,
Coordinator of the European Union Project
"Decadal and Interdecadal Climate Variability: Dynamics and Predictability
Experiments" --DICE
Table of Contents
List of Contributors ...................................................................................... xvii
1 Interdecadal Variability at Northern High Latitudes ................... 1
LAWRENCE A. MYSAK
1.1 Introduction ........................................................................................ 1
1.2 A feedback loop for interdecadal climate variability
in the Arctic ........................................................................................ 8
1.3 Evidence for a Great Ice and Salinity Anomaly (GISA)
event in the late 1980s ........................................................................ 9
1.4 Possible sources for the precipitation and runoff anomalies in the
Mackenzie basin: An attempt to verify the cyclogenesis-related
links in the feedback loop ................................................................. 13
1.5 Models of the "Great Salinity Anomaly" (GSA) and other
interdecadal variability in the Arctic and northern North Atlantic ... 18
1.5.1 Simulations of the GSA .................................................................... 18
1.5.2 Models of coupled ice-ocean interdecadal oscillations .................... 22
1.5.3 Interdecadal variability in ocean GeMs ........................................... 23
1.5.4 The 50-year oscillation in the North Atlantic THC .......................... 23
2 Sea Surface Temperature Variability in the North Atlantic:
Monthly to Decadal Time Scales ................................................... 25
CLAUDE FRANKIGNOUL
2,1 Introduction ....................................................................................... 25
2.2 Short-term variability ........................................................................ 27
2.3 Decadal variability ............................................................................ 34
2.3.1 Observations ..................................................................................... 34
2.3.2 Coupled ocean-atmosphere models .................................................. 39
2.3.3 Thermocline response to stochastic wind stress forcing .................. .44
2.3.4 Ocean-atmosphere feedback ............................................................. 46
2.4 Conclusions ....................................................................................... 47
xii
3 Recent Decadal SST Variability in the Northwestern
Pacific and Associated Atmospheric Anomalies ......................... .49
HISASHI NAKAMURA AND TOSHIO YAMAGATA
3.1 Introduction ....................................................................................... 49
3.2 Data ................................................................................................... 51
3.3 Characteristics of SST Variability over the NW Pacific ................... 54
3.4 Dominant Decadal Variability in Winter .......................................... 55
3.4.1 Spatial Structure ................................................................................ 55
3.4.2 Time Evolution ................................................................................. 59
3.4.3 Comparison with ENSO-Scale Variability ....................................... 63
3.5 Dominant Decadal Variability in Summer. ....................................... 65
3.6 Discussion ......................................................................................... 70
4 Large Scale Modes of Ocean Surface Temperature Since
the Late Nineteenth Century ......................................................... 73
C. K. FOLLAND, D. E. PARKER, A. W. COLMAN
R. WASHINGTON
4.1 Introduction ....................................................................................... 73
4.2 Data ................................................................................................... 74
4.3 Low Frequency Variability in Marine Surface Temperatures ........... 75
4.3.1 Global and Regional Time Series of SST and
NMAT Anomalies ............................................................................. 75
4.3.2 Power spectra .................................................................................... 75
4.3.3 Spatial patterns of near bidecadal ocean surface
temperature variability ...................................................................... 81
4.3.4 Synthesis of variability: Empirical Orthogonal Function
(EOF) analysis .................................................................................. 83
4.3.5 Extended EOF analysis ofLF SST ................................................... 90
4.3.6 Stability ofthe all seasons EOF analyses ......................................... 92
4.4 Relationships between marine surface temperatures and
tropic-wide rainfall on multi decadal time-scales ............................. 93
4.5 Low Frequency relationships between marine surface
temperatures and southern African rainfall ...................................... 96
4.6 Discussion and conclusions .............................................................. 99
4.7 Appendix: Enhancement OfEOF Time Series
For Missing Data ............................................................................ 100
5 The Indian Summer Monsoon and its Variability ..................... 103
JULIA SLINGO
5.1 Introduction .................................................................................... 103
5.2 Mean behavior of the Indian Summer Monsoon ............................ 105
5.3 Interannual to decadal variability and its relationship
with EI Nino ................................................................................... 106
