Many climatic extremes around the globe, such as severe droughts and floods, can be attributed to the periodic warming of the equatorial Pacific sea surface, termed the El NiГ±o or Southern Oscillation (ENSO). Advances in our understanding of ENSO, in which Edward Sarachik and Mark Cane have been key participants, have led to marked improvements in our ability to predict its development months or seasons, allowing adaptation to global impacts. The book introduces basic concepts and builds to more detailed theoretical treatments. Chapters on the structure and dynamics of the tropical ocean and atmosphere place ENSO in a broader observational and theoretical context. Chapters on ENSO prediction, past and future, and impacts introduce broader implications of the phenomenon. This book provides an introduction to all aspects of this most important mode of global climate variability, for research workers and students of all levels in climate science, oceanography and related fields.
Author(s): Edward S. Sarachik, Mark A. Cane
Publisher: CUP
Year: 2010
Language: English
Pages: 385
Cover......Page 1
Half-title......Page 3
Title......Page 5
Copyright......Page 6
Contents......Page 7
Preface......Page 11
Abbreviations......Page 14
1.2 The normal tropical Pacific......Page 17
1.3 The phases of ENSO......Page 20
1.4 Evolution of phases of ENSO......Page 24
1.5.1 The processes that change SST......Page 25
1.5.2 The process by which warm SST anchors regions of persistent precipitation......Page 26
1.5.4 The processes by which surface winds change thermocline depth......Page 27
1.5.5 The processes by which regions of persistent precipitation affect regions remote from the tropical Pacific......Page 29
1.6 Modeling ENSO......Page 31
1.7 Observing and predicting ENSO......Page 33
1.8 Towards a theory of ENSO......Page 35
1.9 The past and future of ENSO......Page 37
1.10 What is ENSO information good for?......Page 39
2.1 The nature and source of climate observations relevant to ENSO......Page 41
2.2 Solar forcing and fluxes at the surface......Page 43
2.3 The annually averaged tropical Pacific......Page 49
2.5 The evolution of ENSO......Page 57
2.6 ENSO effects......Page 65
2.7 Variability at periods of less than a year......Page 73
2.8 Decadal variability......Page 76
3.1 Equations governing the ocean and atmosphere......Page 77
3.1.1 Equations of motion on a rotating sphere......Page 79
3.1.3 Constituent equations......Page 84
3.1.5 Boundary conditions......Page 85
3.2 The f-plane and the beta-plane......Page 86
3.3 The hydrostatic approximation......Page 87
3.3.1 The hydrostatic equations, with formalities......Page 88
3.3.2 Boussinesq equations......Page 92
3.3.3 Hydrostatic balance and pressure coordinates......Page 93
3.3.4 Ocean dynamic height......Page 95
3.4 Geostrophy......Page 96
3.5.1 Shallow-water equations......Page 99
3.5.2 Transport equations......Page 100
3.5.3 1½-Layer model......Page 101
3.5.4 2-Layer model......Page 103
3.6 Vertical ocean modes in a continuously stratified fluid......Page 106
3.7 The shallow-water equations on a sphere and equatorial beta-plane......Page 110
4 Boundary layers on both sides of the tropical ocean surface......Page 113
4.1 Mixing, inversions and entrainment: general concepts......Page 114
b. Friction velocity......Page 116
c. Monin–Obukhov length......Page 117
4.2.2 The surface layer......Page 118
4.2.3 Fluxes and entrainment in the convectively mixed layer......Page 120
4.3.1 Bulk mixed-layer models......Page 122
a. The critical Richardson number......Page 124
b. Turbulent kinetic energy balance......Page 127
4.3.3 Non-bulk models – mixing at all z......Page 128
a. The simplest: kH, km = constant......Page 129
d. KPP, a profile parameterization with nonlocal mixing......Page 130
5 Atmospheric processes......Page 133
5.1.1 Virtual temperature Tv......Page 135
5.1.3 Dry adiabatic ascent......Page 136
5.1.4 Moist adiabatic ascent......Page 139
5.1.5 Buoyancy flux from the surface......Page 142
5.2 The diagnosis of Reed and Recker......Page 143
5.3 How clouds heat......Page 146
5.4 A model for the vertical structure of the tropical atmosphere......Page 157
5.5.1 The zonally averaged Hadley circulation......Page 163
a. The linear Hadley circulation......Page 165
b. The nonlinear Hadley circulation......Page 168
5.5.2 The Gill model......Page 173
5.5.3 Linear theory of thermal forcing by an isolated heat source on an equatorial beta-plane......Page 178
The atmosphere has no discrete free-vertical modes......Page 181
5.6 The processes that anchor regions of persistent precipitation to SST......Page 190
5.7 Surface winds for simple atmospheric models......Page 194
6 Ocean processes......Page 201
6.1 The processes that change SST......Page 202
6.2 The barotropic adjustment problem......Page 203
6.2.1 Free planetary waves......Page 204
6.2.2 The steady response......Page 205
6.2.3 Adjustment to the steady response......Page 209
6.3 Equatorial ocean dynamics: free waves......Page 212
6.3.2 Midlatitude beta-plane......Page 213
6.3.3 Equatorial beta-plane......Page 215
6.4.1 Scaling the equations......Page 220
6.4.2 A simple example of our method......Page 222
6.4.3 Calculating forced motions on an equatorial beta-plane......Page 224
6.5 Equatorial ocean dynamics: adjustment......Page 231
6.5.1 Adjustment in the absence of boundaries......Page 232
6.5.2 Calculating the effects of meridional boundaries......Page 236
a. Westernoundary response......Page 238
b. Easternoundary response......Page 239
6.5.3 Steady-state solutions......Page 241
6.5.4 Adjustment to the steady state in a basin......Page 242
6.6 Periodically forced motions......Page 246
6.7 The role of the ocean in ENSO......Page 248
7 ENSO mechanisms......Page 251
7.1 Pioneers of the study of ENSO: Bjerknes and others......Page 253
7.2.1 Formulation......Page 254
7.2.2 Stable and unstable coupled solutions......Page 257
7.3 The Zebiak–Cane model......Page 263
7.4. The delayedscillator equation......Page 272
7.5 The recharge oscillator and other conceptual models......Page 287
7.6 Stochastically forced models......Page 291
7.7 Noise or chaos? Stable or unstable? Linear or nonlinear? Does it matter and can we tell?......Page 296
7.7.2 The cause of equilibration at finite amplitude......Page 297
7.7.4 Does it matter and can we tell?......Page 298
7.8 Modeling ENSO by state-of-the-art coupled climate models......Page 299
7.8.2 Simulation of the mean climate and annual cycle......Page 300
7.8.3 Simulations of ENSO......Page 304
8 ENSO prediction and short-term climate prediction......Page 307
8.1 Weather prediction......Page 309
8.2.1 General concepts......Page 310
8.2.2 One-fiered and two-fiered short-range climate prediction......Page 313
8.2.4 Multiodel ensembles......Page 315
8.3 The current status of ENSO prediction and short-term climate prediction......Page 316
8.4 Improvements to ENSO and short-term climate prediction......Page 318
9 ENSO, past and future: ENSO by proxy and ENSO in the tea leaves......Page 321
9.1.1 ENSO in the Pliocene......Page 322
9.1.2 ENSO in the Holocene......Page 323
9.1.3 ENSO in the Pleistocene......Page 327
9.1.4 ENSO in the last millennium: the response to solar and volcanic variations......Page 328
9.2 ENSO in the twentieth century......Page 331
9.3 ENSO in the future......Page 333
9.4 Conclusions......Page 334
10 Using ENSO information......Page 337
10.1 General considerations......Page 338
10.2 Using past ENSO information......Page 339
10.3 Using ENSO nowcasts......Page 342
10.4 End-to-end forecasting......Page 343
10.5 Using forecasts – some potential examples......Page 345
10.6 Improving the use of climate information......Page 346
11.1 Looking back......Page 349
11.2 Looking ahead......Page 351
Derived quantities......Page 353
Appendix 2: The parabolic-cylinder functions......Page 355
A3.1 Context......Page 357
A3.2.2 General matrices......Page 358
A3.2.3 System evolution......Page 360
A3.3.2 Asymmetric matrix......Page 362
A3.4 Error evolution......Page 365
References......Page 367
Index......Page 380
