Atmosphere-ocean Modeling: Coupling And Couplers

by Carlos Roberto Mechoso, Soon-il An, Sophie Valcke

Overview

Coupled atmosphere-ocean models are at the core of numerical climate models. There is an extraordinarily broad class of coupled atmosphere-ocean models ranging from sets of equations that can be solved analytically to highly detailed representations of Nature requiring the most advanced computers for execution. The models are applied to subjects including the conceptual understanding of Earth's climate, predictions that support human activities in a variable climate, and projections aimed to prepare society for climate change. The present book fills a void in the current literature by presenting a basic and yet rigorous treatment of how the models of the atmosphere and the ocean are put together into a coupled system. The text of the book is divided into chapters organized according to complexity of the components that are coupled. Two full chapters are dedicated to current efforts on the development of generalist couplers and coupling methodologies all over the world.

Product Details

ISBN-13:	9789811234460
Publisher:	World Scientific Publishing Company, Incorporated
Publication date:	08/13/2021
Pages:	204
Product dimensions:	6.69(w) x 9.61(h) x 0.43(d)

Table of Contents

Preface vii

1 Atmosphere-Ocean Interactions and Feedbacks 1

1.1 Introduction 1

1.2 Basic concepts 1

1.2.1 The vertical temperature profile in the ocean 1

1.2.2 The global distribution of sea surface temperature and precipitation 1

1.2.3 Momentum and heat fluxes at the atmosphere-ocean interface 5

1.2.4 Net energy fluxes at the atmosphere-ocean interface 5

1.3 Atmosphere-ocean feedbacks 8

1.3.1 Bjerknes feedback 8

1.3.2 Wind evaporation SST feedback 9

1.3.3 Ekman feedback 9

1.3.4 Water vapor feedback 10

1.3.5 Cloud-SST feedback 10

1.3.6 Thermocline feedback 10

1.3.7 Ice-albedo feedback 11

1.3.8 Land surface conditions feedback 11

1.3.9 Reemergence 12

2 A Classification of Coupled Atmosphere-Ocean Models 13

2.1 Introduction 13

2.2 Conceptual models of coupled atmosphere-ocean processes 14

2.3 Models of intermediate complexity and ENSO prediction 15

2.4 AGCMs coupled to simpler ocean models (HCM1s) 15

2.4.1 AGCMs coupled to a swamp ocean model 15

2.4.2 AGCMs coupled to a slab ocean model 16

2.5 OGCMs coupled to simpler atmospheric models (HCM2s) 16

2.6 Coupled atmosphere-ocean GCMs (CGCMs) 17

2.7 Perspectives 17

3 Conceptual Models of Interannttal Variability 18

3.1 Introduction 18

3.2 Basic aspects of ENSO 18

3.3 The recharge-oscillator model 21

3.4 The delayed oscillator model 24

3.5 General comments on the recharge and delayed oscillator models 24

3.6 Perspectives 26

4 Models of Intermediate Complexity and ENSO Prediction 29

4.1 Introduction 29

4.2 Gill-type model of the tropical atmosphere 30

4.3 One- and two-layer shallow water systems 32

4.3.1 One-layer shallow-water system 32

4.3.1.1 Governing equations 32

4.3.1.2 Energy equation 34

4.3.1.3 Vorticity equation 36

4.3.2 Two-layer shallow-water system (linearized) 36

4.3.3 Reduced gravity ocean model 37

4.4 Oscillations in a reduced gravity ocean model coupled to a conceptual atmosphere 39

4.5 Zebiak and Cane model (ZC87) 40

4.5.1 Atmospheric component 41

4.5.2 Ocean component 42

4.5.3 Atmosphere-ocean coupling 45

4.5.4 ENSO predictions with the ZC87 model 45

4.6 Preconditions and initialization 46

4.6.1 Preconditions 46

4.6.2 Initialization 48

4.7 Another example of an intermediate-complexity model for El Niño prediction 49

4.8 Perspectives 51

5 AGCMs Coupled to Simpler Ocean Models 53

5.1 Introduction 53

5.2 AGCMs 53

5.3 Fluxes at the atmosphere-ocean interface 55

5.4 Calculation of fluxes at the atmosphere-ocean interface 56

5.5 The surface layer in the atmosphere 58

5.5.1 The Monin-Obukhov theory and fluxes at the surface 59

5.5.2 The turbulent mixing coefficients as a function of Ri 61

5.6 Planetary boundary layer structure and height 62

5.7 Turbulence above the surface layer 65

5.8 Examples of PBL parameterizations 66

5.8.1 The PBL parameterization in CAM4 67

5.8.2 The PBL parameterization in the UCLA AGCM 69

5.9 Radiation fluxes at the atmosphere lower boundary 71

5.10 Surface fluxes over sea-ice and land surfaces 71

5.11 Examples of AGCMs coupled to simple ocean models 72

5.11.1 AGCMs coupled to swamp ocean models 73

5.11.2 AGCMs coupled to slab ocean models 73

5.12 Appendix A: Classical mixing length theory 75

6 OGCMs Coupled to Simpler Atmospheric Models 77

6.1 Introduction 77

6.2 OGCMs 77

6.2.1 Discretization of the equations of oceanic motions 77

6.2.2 The sea surface temperature equation 80

6.2.3 Incorporation of a sea-ice model to the OGCM 82

6.2.4 Wind stress on the ocean surface 82

6.3 Examples of OGCMs coupled to simple models 84

6.3.1 Tropical Atlantic OGCM coupled to an empirical atmosphere 84

6.3.2 OGCM coupled to a two-level atmosphere for ENSO studies 86

6.3.3 Reduced gravity ocean model coupled to a statistical atmosphere 87

6.3.4 Primitive equation ocean model coupled to an empirical atmosphere for ENSO studies 89

6.3.5 OGCM coupled to a statistical atmosphere for AMOC studies 89

6.3.6 AGCM coupled to a Slab Ocean Model in the tropical Atlantic and to an OGCM elsewhere 91

6.4 Perspectives 91

7 Atmosphere-Ocean Coupled General Circulation Models 93

7.1 Introduction 93

7.2 Fundamentals of AGCM and OGCM coupling 93

7.3 Current issues on CGCM performance 95

7.4 CGCMs as laboratories for hypothesis-testing experimentation 98

7.4.1 Testing hypothesis on the causes of the tropical SST biases 98

7.4.2 Simulations that address enhancing prediction skill 100

7.5 Long-term predictions 101

7.5.1 Seasonal predictions 102

7.5.2 Multi-year predictions 103

7.5.3 Predictions of ENSO changes with global warming 103

7.5.4 Climate change predictions 105

7.6 Perspectives 107

8 Coupling Software and Technologies 109

8.1 Historical overview 109

8.2 Coupling software used in contemporary atmosphere-ocean coupled models 113

8.2.1 OASIS3-MCT 114

8.2.1.1 Initialization and definition 115

8.2.1.2 Coupling send and receive 116

8.2.1.3 Communication and component layout 116

8.2.1.4 Configuration 117

8.2.1.5 Regridding and other transformations 117

8.2.1.6 Performance 117

8.2.2 ESMF 118

8.2.2.1 Using ESMF superstructure to assemble coupled applications 119

8.2.2.2 Interoperability, NUOPC and ESPS 120

8.2.2.3 ESMF Infrastructure 122

8.2.2.4 Users and user support 123

8.2.3 MCT 124

8.2.4 FMS 125

8.2.5 CPL7 126

8.2.6 YAC 128

8.2.7 C-Coupler2 130

8.2.8 MOAB-TempestRemap 131

8.3 Analysis of coupler or coupling software 131

8.3.1 Basic coupling functions 132

8.3.1.1 Data transfer and coordinated execution of components 132

8.3.1.2 Coupling field regridding and transformation 133

8.3.2 Advantages and disadvantages of the different coupler implementations 135

8.4 Perspectives 137

9 Coupling Algorithms and Specific Coupling Features in CGCMs 140

9.1 Introduction 140

9.2 Coupling algorithms in selected CGCMs 140

9.2.1 Implementation in European CGCMs 140

9.2.2 ECMWF-IFS coupling algorithm 142

9.2.3 RPN coupling algorithm 143

9.2.4 CESM2 and CMCC-CM2 coupling algorithm 144

9.3 PRISM revised ocean-atmosphere physical coupling interface 146

9.3.1 Exchanges of energy 147

9.3.2 Exchanges of mass 148

9.3.3 Exchanges of momentum 149

9.3.4 Subgrid scale computations 149

9.3.5 Time sequence 149

9.4 Discussion on specific coupling features and their implementation 150

9.4.1 Component sequencing and time inconsistency 150

9.4.2 Regridding and spatial inconsistencies 153

9.4.2.1 Flux computation 153

9.4.2.2 Sea-land mask issue 154

9.4.2.3 Merging and cell fractions 155

9.5 Perspectives 156

Bibliography 157

Index 181