Coupled Ocean-Atmosphere Models (eBook)

Front Cover 1
Coupled Ocean-Atmosphere Models 4
Copyright Page 5
Contents 12
List of contributors 6
Preface 10
CHAPTER 1. A COUPLED OCEAN–ATMOSPHERE AND THE RESPONSE TO INCREASING ATMOSPHERIC CO 26
Plan of the numerical experiments 26
The equilibrium calculations 28
Results of the “switch-on” experiment 29
References 31
CHAPTER 2. MODELLING THE ATMOSPHERIC RESPONSE TO THE 1982/83 EL NIÑO 32
Abstract 32
Introduction 32
Themodel 33
The experiment 33
The divergent component 34
The rotational component 38
Concluding remarks 41
Acknowledgements 42
References 42
CHAPTER 3. SENSITNITY OF JANUARY CLIMATE RESPONSE TO THE POSITION OF PACIFIC SeA-SURFACE TEMPERATURE ANOMALIES 44
References 52
CHAPTER 4. SUBSEASONAL SCALE OSCILLATION. BIMODAL CLIMATIC STATE AND THE EL NIÑO/SOUTHERN OSCILLATION 54
Abstract 54
Introduction 54
Observations 55
Air–sea interaction 60
A hypothesis 60
A simple nonlinear oscillator relevant t o ENSO 61
Conclusion 64
Acknowledgment 64
References 64
CHAPTER 5. RESULTS FROM A MOIST EQUATORIAL ATOMOSPHERE MODEL 66
Abstract 66
Introduction 66
The Model 66
Zonally independent forcing 68
Zonally varying forcing 70
References 74
CHAPTER 6. LARGE-SCALE MOMENTUM EXCHANGE IN THE COUPLED ATMOSPHERE–OCEAN 76
Abstract 76
Introduction 76
The surface shearing stress 77
Horizontal averaging 79
Consequences for the general circulation dynamics in the ocean and the atmosphere 81
Oceanic meridional heat transport 83
Conclusions 85
References 85
CHAPTER 7. CLIMATE VARIABILITY STUDIES WITH A PRIMITIVE EQUATION MODEL OF THE EQUATORIAL PACIFIC 88
Abstract 88
Introduction 88
The model 89
The wind field 90
The experiments 92
El NiÑo events 100
Discussion 105
Acknowledgements 105
References 106
CHAPTER 8. RESPONSE OF THE UK METEOROLOGICAL OFFICE GENERAL CIRCULATION MODEL TO SEA-SURFACE TEMPERATURE ANOMALIES IN THE TROPICAL PACIFIC OCEAN 108
Abstract 108
Introduction 108
Experiments 110
Comparison of results with linear theory 126
Conclusions 130
Acknowledgements 131
References 131
CHAPTER 9. TRANSIENT EFFECTS DUE TO OCEANIC THERMAL INERTIA IN AN ATMOSPHERIC MODEL COUPLED TO TWO OCEANS 134
Abstract 134
Introduction 134
Model description 135
Experiments 135
Results 137
Discussion 143
Acknowledgements 131
References 131
CHAPTER 10. GCM SENSITIVITY TO 1983-83 EQUATORIAL PACIFIC SEA–SURFACE TEMPERATURE ANOMALIES 146
Abstract 146
Introduction 146
Model and integrations 147
Results 150
Acknowledgements 154
References 154
CHAPTER 11. THE GLOBAL CLIMATE SIMULATED BY A COUPLED ATMOSPHERE–OCEAN GENERAL CIRCULATION MODEL PRELIMINARY RESULTS 156
Abstract 156
Introduction 156
Overview of model 158
Uncoupled models’ performance 160
Results from an extended coupled integration 164
Concluding remarks 173
Acknowledgements 174
References 174
CHAPTER 12. FREE EQUATORIAL INSTABILITIES IN SIMPLE COUPLED ATMOSPHERE-OCEAN MODELS 178
Abstract 178
Introduction 178
Model and method 179
Stability and dispersion 182
Structure of free modes 188
Conclusion 189
Acknowledgements 190
References 190
CHAPTER 13. AN ANALYSIS OF THE AIR-SEA-ICE INTERACTION SIMULATED BY THE OSU–COUPLED ATMOSPHERE-OCEAN GENERAL CIRCULATION MODEL 192
Abstract 192
Introduction 192
Design of the coupled model experiment 193
Simulated SST and sea ice 196
Local upper-ocean heat budget analysis 202
Discussion and concluding remarks 204
Acknowledgements 206
References 206
CHAPTER 14. OBSERVED LONG-TERM VARIABILITY IN THE GLOBAL SURFACE TEMPERATURES OF THE ATMOSPHERE AND OCEANS 208
Abstract 208
Introduction 208
Data 209
Results 214
Summary and concluding remarks 217
Acknowledgements 219
References 223
CHAPTER 15. MULTIVARIATE ANALYSIS OF SENSITIVITY STUDIES WITH ATMOSPHERIC GCMS 224
Abstract 224
Introduction 224
The SST anomaly experiments 225
Univariate analysis 226
Multivariate analysis 227
The atmospheric response to the SST anomaly 229
Discussion 233
Acknowledgements 234
References 234
CHAPTER 16. INTERANNUAL AND SEASONAL VARIABILITY OF THE TROPICAL ATLANTIC OCEAN DEPICTED BY SIXTEEN YEARS OF SEA- SURFACE TEMPERATURE AND WIND STRESS 236
Abstract 236
Introduction 236
Data processing 237
Variability of SST 242
Variability of wind stress 251
Discussion 253
Summary and conclusions 260
Acknowledgements 261
References 262
CHAPTER 17. AN ATMOSPHERE-OCEAN COUPLED MODEL FOR LONG–RANGE NUMERICAL FORECASTS 264
The principle of the model 264
Examples of a one-month prediction 271
Conclusion 272
References 272
CHAPTER 18. ON THE SPECIFICATION OF SURFACE FLUXES IN COUPLED ATMOSPHEREOCEAN GENERAL CIRCULATION MODELS 274
Abstract 274
Introduction 274
The Model 275
Results and discussion 276
Concluding remarks 282
References 287
CHAPTER 19. IMPORTANCE OF COUPLING BETWEEN DYNAMIC AND THERMODYNAMIC PROCESSES AT THE SEA SURFACE: THE LARGE- SCALE OCEANIC POINT OF VIEW 288
Abstract 288
Introduction 288
The subtropical front 289
Thermocline theory 291
Application to the North Pacific Ocean 294
Discussion 297
Acknowledgements 298
References 298
CHAPTER 20. THE SIGNIFICANT TROPOSPHERIC MIDLATITUDINAL EL NIÑO RESPONSE PATTERNS OBSERVED IN JANUARY 1983 AND SIMULATED BY A GCM 300
Abstract 300
Introduction 300
Statistical assessment tools 302
January 1983 - Extraordinary with respect to its predecessors 303
Significant El Nhio response simulation with the ECMWF GCM 307
The coincidence of the simulated and observed response patterns 309
Discussion: The linearity hypothesis 310
References 312
CHAPTER 21. RESPONSE OF A GFDL GENERAL CIRCULATION MODEL TO SST FLUCTUATIONS OBSERVED IN THE TROPICAL PACIFIC OCEAN DURING THE PERIOD 1962-1976 314
Abstract 314
Introduction 314
Model characteristics and experimental design 315
Comparison of model results with observations 315
Summary and conclusions 326
Acknowledgements 327
References 327
CHAPTER 22. ELEMENTS OF COUPLED OCEAN–ATMOSPHERE MODELS FOR THE TROPICS 328
Abstract 328
Introduction 328
The ocean model 329
The sea-surface temperature anomaly 331
The atmosphere model 332
Relation between the surface temperature and heating anomalies 333
Behaviour in the uncoupled model 335
Results for the coupled model 336
Relating precipitation to SST 339
Solution for the one dimensional non-rotating case 342
Solutions for the one dimensional rotating case: An ITCZ 344
Two dimensional solutions for the tropics 347
Conclusions 350
Acknowledgements 351
Appendix 351
References 351
CHAPTER 23. THE MEAN RESPONSE OF THE ECMWF GLOBAL MODEL TO THE COMPOSITE EL NINO ANOMALY IN EXTENDED RANGE PREDICTION EXPERIMENTS 354
Introduction 354
The experiment 354
Results 357
Conclusions 366
References 367
CHAPTER 24. SIMPLE MODELS OF EL NIÑO AND THE SOUTHERN OSCILLATION 370
Abstract 370
Introduction 370
A coupled model with two equilibrium states 372
A coupled model that develops slowly propagating disturbances 381
Summary and discussion 392
Acknowledgements 394
References 394
CHAPTER 25. THE RESPONSE OF THE OSU TWO-LEVEL ATMOSPHERIC GENERAL CIRCULATION MODEL TO A WARM SEA-SURFACE TEMPERATURE ANOMALY OVER THE EASTERN EQUATORIAL PACIFIC OCEAN 396
Abstract 396
Introduction 396
Experimental design 399
Approach towards equilibrium 400
The local equatorial response 402
The remote response 405
Year-to-year variability 411
Acknowledgements 414
References 414
CHAPTER 26. A PRELIMINARY STUDY OF INTERMONTHLY CHANGES IN SEA-SURFACE TEMPERATURE ANOMALIES THROUGHOUT THE WORLD OCEAN 416
Abstract 416
Introduction 416
Intermonthly local area sea-surface temperature anomaly changes–A global view 417
Intermonthly regional scale sea-surface temperature anomaly changes 423
Conclusion 428
Acknowledgements 428
Rererences 428
CHAPTER 27. MORPHOLOGY OF SOMALI CURRENT SYSTEM DURING THE SOUTHWEST MONSOON 430
Abstract 430
Introduction 430
The model 432
The wind forcing 434
Results 446
Discussion and conclusion 457
Acknowledgements 461
References 461
CHAPTER 28. A MODEL FOR THE SEA-SURFACE TEMPERATURE AND HEAT CONTENT IN THE NORTH ATLANTIC OCEAN 464
Abstract 464
Introduction 464
The mixed layer model 465
Modelling of an upper ocean basin 467
Comparison with data 468
Conclusions 469
Acknowledgments 470
References 470
CHAPTER 29. THE ROLE OF THE OCEAN IN CO2 INDUCED CLIMATE CHANGE: PRELIMINARY RESULTS FROM THE OSU COUPLED ATMOSPHERE-OCEAN GENERAL CIRCULATION MODEL 472
Abstract 472
Introduction 473
Description of the model and simulations 478
Results 482
Analysis of the climate response function 493
Summary and concluding remarks 497
Acknowledgements 499
Appendix 499
References 501
CHAPTER 30. ATMOSPHERIC RESPONSE OF A GENERAL CIRCULATION MODEL FORCED BY A SEA-SURFACE TEMPERATURE DISTRIBUTION ANALOGOUS TO THE WINTER 1982–83 EL NINO 504
Abstract 504
Introduction 504
Method and data 504
Results 506
Conclusion 514
Acknowledgements 514
References 514
CHAPTER 31. THE RESPONSE OF AN EQUATORIAL PACIFIC MODEL TO WIND FORCING 516
Abstract 516
Introduction 516
The model 517
Conclusions and summary 536
Acknowledgements 536
References 537
CHAPTER 32. A SIMPLE WIND- AND BUOYANCY-DRIVEN THERMOCLINE MODEL (Extended Abstract) 538
References 541
CHAPTER 33. SIMULATION OF EL NIÑO OF 1982–1983 542
Abstract 542
Introduction 542
The measurements 543
The model 549
Results 551
Summary 562
Acknowledgements 565
References 565
CHAPTER 34. THE PHYSICS OF THERMOCLINE VENTILATION 568
Abstract 568
Introduction 568
The seasonal boundary layer 571
Sources and sinks of potential vorticity 579
Parameterizing diurnal variation 580
The subduction of isopycnals 584
Regional variation of D 590
Changes in the potential vorticity profile 602
Discussion 608
Conclusion 612
References 613
CHAPTER 35. PRELIMINARY EXPERIMENTS ON THE SENSITIVITY OF ATMOSPHERIC MONTHLY MEAN PREDICTION TO SEA-SURFACE TEMPERATURE SPECIFICATION 616
Abstract 616
Introduction 616
The model 616
Numerical experiments 617
Discussion: Tropics and subtropics 631
Discussion: Mid-latitudes 632
Conclusions and prospects 635
Acknowledgements 635
References 635
CHAPTER 36. THE PARAMETRIZATION OF THE UPPER OCEAN MIXED LAYER IN COUPLED OCEAN–ATMOSPHERE MODELS 638
Abstract 638
Introduction 638
The mixed-layer model 641
Experiments with climatological fluxes 642
Experiments with modelled fluxes 645
Conclusions 655
Acknowledgements 659
References 659
CHAPTER 37. STABILITY OF A SIMPLE AIR–SEA COUPLED MODEL IN THE TROPICS 662
Abstract 662
Introduction 662
The model 663
Some simple solutions of the model equations 665
Summary and discussion 678
Appendix 679
References 681
CHAPTER 38. NUMERICAL EXPERIMENTS ON A FOUR-DIMENSIONAL ANALYSIS OF POLYMODE AND ‘SECTIONS PROGRAMMES OCEANO–GRAPHIC DATA 684
Abstract 684
Introduction 684
Four dimensional analysis scheme 685
Model numerical experiments 688
Numerical experiments with the assimilation of Polymode programme data 691
Numerical experiments with the assimilation of the ‘Sections’ programme data 692
Conclusions 697
References 698
CHAPTER 39. EFFECTS OF VARYING SEA-SURFACE TEMPERATURE ON 10-DAY ATMOSPHERIC MODEL FORECASTS 700
Abstract 700
Introduction 700
Models and experimental procedures 702
SST fields and surface fluxes 705
Storm track comparison 712
Summary and conclusions 718
Acknowledgements 719
References 719
CHAPTER 40. INTERANNUAL CLIMATE VARIABILITY ASSOCIATED WITH THE EL NIÑO/SOUTHERN OSCILLATION 722
Abstract 722
Introduction 722
Data and analyses 724
Mean annual cycle 725
Evolution of ENSO 732
1982/83 ENSO anomalies 734
Concluding remarks 744
References 748
CHAPTER 41. MODELING TROPICAL SEA-SURFACE TEMPERATURE: IMPLICATIONS OF VARIOUS ATMOSPHERIC RESPONSES 752
Abstract 752
Introduction 752
A simple thermodynamic model 753
Eigenmodes and eigenvalues 755
Scaling of the thermal damping factors 757
Conclusions 759
References 759
CHAPTER 42. MODELS OF INTERACTIVE MIXED LAYERS 760
Abstract 760
Introduction 760
The model equations 761
The effect of the atmospheric mixed-layer depth on the surface wind stress 763
The effect of sea-surface temperature changes on the atmospheric mixed-layer depth and moisture content 767
The interactive evolution of the oceanic and atmospheric mixed layers in the source region of the trades 769
Summary 772
Acknowledgements 772
Appendix 773
References 773
CHAPTER 43. A GCM STUDY OF THE ATMOSPHERIC RESPONSE TO TROPICALSST ANOMALIES 774
Abstract 774
Introduction 774
The GCM and its climatology 775
Results 780
References 788
List of participants to the 16th Liège Colloquium 790