Contents
Preface..................................................xv
Abbreviations ......................................... xix
List of figures ........................................ xxi
List of tables ......................................... xxxi
List of abbreviations and names of satellites and sensors ............. xxxiii
List of symbols and nomenclature ............................ xli
1 Introduction ....................................... 1
1.1 An important observational tool for planetary science ....... 1
1.2 Putting remote sensing to work for oceanographers ........ 3
1.3 The oceanographic scope of the book ................. 4
1.4 Reference..................................... 6
2 The methods of satellite oceanography ...................... 7
2.1 Ocean remote-sensing techniques—a summary ............ 7
2.2 The unique sampling capabilities of sensors on satellites ..... 9
2.2.1 Creating image-like data fields from point samples .... 9
2.2.2 Satellite orbits and how they constrain remote sensing . 11
2.2.3 The space-time sampling capabilities of satellite sensors . 14
2.3 Generic processing tasks ....................... 16
2.3.1 Sensor calibration .......................... 17
2.3.2 Atmospheric correction ...................... 19
2.3.3 Positional registration ....................... 21
2.3.4 Geophysical product derivation ................ 21
2.3.5 Image resampling onto map projections ........... 23
2.3.6 Composite image maps ...................... 26
Preface .............................................2.4 Sensor types for observing the ocean .................. 28
2.4.1 Using the electromagnetic spectrum .............. 28
2.4.2 Ocean color radiometers ..................... 30
2.4.3 Thermal infrared radiometry for measuring sea surface
temperature .............................. 35
2.4.4 Microwave radiometry ...................... 42
2.4.5 Altimetry for measuring surface slope, currents, and wave
height ................................. 46
2.4.6 Oblique-viewing radars for measuring sea surface rough-
ness................................... 51
2.5 Platforms and sensors for satellite oceanography ........... 54
2.6 Satellite ocean data products ....................... 54
2.7 References .................................... 66
3 Mesoscale ocean features:Eddies ......................... 69
3.1 Discovering mesoscale variability from space ............. 69
3.2 Mesoscale ocean eddies ........................... 72
3.2.1 Eddies—ubiquitous phenomena in a turbulent ocean . . . 72
3.2.2 Lengthscales of mesoscale eddies—the Rossby radius . . 72
3.2.3 The dynamical structure of rings and eddies ........ 76
3.3 Detecting eddies from satellites....................... 78
3.4 Using SSHA from altimetry to observe eddies ............ 80
3.4.1 Revealing ocean eddies in altimeter SSHA data ...... 80
3.4.2 Present limitations of satellite altimetry ............ 86
3.4.3 Kinematic measurements from altimetric SSHA fields . . 88
3.4.4 The distribution of mesoscale turbulent energy ...... 89
3.5 Observation of eddies and mesoscale turbulence in the SST field 91
3.5.1 SST signatures of eddies in infrared imagery ........ 91
3.5.2 Microwave radiometry for viewing ocean eddies ..... 96
3.6 Views of mesoscale turbulence from ocean color ........... 98
3.7 Surface roughness signatures of eddies .................. 103
3.7.1 Hydrodynamic modulation patterns of eddies ........ 103
3.7.2 Slick-modulated signatures of eddies .............. 106
3.7.3 Sun glitter photography ...................... 109
3.7.4 Can imaging radar become a reliable tool for observing
turbulent eddies? ........................... 110
3.8 References .................................... 111
4 Mesoscale ocean features:Fronts.......................... 115
4.1 Boundaries in the ocean .......................... 115
4.2 The remote-sensing signatures of ocean fronts ............ 118
4.2.1 Sea surface temperature signatures of fronts ........ 118
4.2.2 Can fronts be detected by altimetry? ............. 124
4.2.3 Observing fronts in ocean color images ........... 126
vi Contents4.2.4 Frontal signatures in radar surface roughness images . . 129
4.2.5 Direct measurement of currents using Doppler analysis of
SARdata ............................... 134
4.3 Tracking fronts ................................ 136
4.3.1 Mapping frontal edges ...................... 136
4.3.2 Automatic parameterization of frontal structure ...... 140
4.4 Climatology of the major ocean fronts ................. 142
4.5 Mesoscale frontal variability ........................ 146
4.5.1 The Gulf Stream .......................... 146
4.5.2 The Southland Front ........................ 148
4.5.3 Antarctic Circumpolar Fronts .................. 148
4.6 Biological production associated with ocean fronts ......... 152
4.6.1 Antarctic Circumpolar Current ................. 152
4.6.2 Fronts in the southwest Atlantic ................ 153
4.7 References .................................... 155
5 Ocean mesoscale features:Upwelling and other phenomena ......... 159
5.1 Upwelling .................................... 159
5.1.1 The causes and consequences of upwelling ......... 159
5.1.2 Aspects of upwelling detected by satellites ......... 162
5.1.3 Upwelling regions of the world seen from space ..... 167
5.1.4 Using satellite data in upwelling research........... 171
5.2 Wind-driven, offshore, dynamical features ............... 174
5.3 Large river plumes .............................. 177
5.4 Island wakes .................................. 179
5.5 Ice edge phytoplankton blooms ...................... 181
5.6 Remote sensing in iron limitation studies ............... 184
5.7 Making the most of satellite data for mesoscale studies: conclu-
sions from Chapters 3–5 .......................... 187
5.8 References .................................... 190
6 Planetary waves and large-scale ocean dynamics ................ 195
6.1 Phenomena seen best from satellites ................... 195
6.2 Detecting planetary waves from space ................. 196
6.2.1 Producing composite anomaly datasets ............ 197
6.2.2 Producing Hovmoller diagrams to reveal propagating
features ................................ 200
6.2.3 Altimetry reveals the first compelling evidence of planet-
ary waves ............................... 202
6.2.4 Sea surface temperature signatures ............... 204
6.2.5 Evidence of planetary waves in ocean color ........ 206
6.3 The characteristics of Rossby waves ................... 206
6.3.1 A summary of planetary wave theory ............ 206
6.3.2 How can Rossby waves be seen at the sea surface? . . . 210
Contents vii6.4 Estimating planetary wave speed ..................... 212
6.4.1 Methods for analyzing Hovmoller diagrams ......... 212
6.4.2 Radon transform .......................... 213
6.4.3 Mapping the speed of planetary waves ............ 216
6.4.4 Meridional components of planetary wave propagation . 216
6.5 Understanding Rossby waves better ................... 220
6.5.1 Satellite data confirm the existence of Rossby waves . . . 220
6.5.2 Revisiting Rossby wave theory . . . .............. 221
6.5.3 The importance of Rossby waves . .............. 223
6.6 Other large-scale propagating phenomena . .............. 224
6.6.1 Equatorial Kelvin waves ..................... 225
6.6.2 Tropical instability waves .................... 227
6.6.3 The Madden–Julian Oscillation . . . .............. 231
6.6.4 The Antarctic circumpolar wave . . .............. 233
6.7 References .................................... 234
7 Ocean biology from space .............................. 239
7.1 Introduction ................................... 239
7.2 Phytoplankton blooms ........................... 240
7.2.1 An unfolding new view of phytoplankton distribution . . 240
7.2.2 The global distribution of chlorophyll ............. 246
7.2.3 Scientific exploitation of satellite ocean color data .... 251
7.2.4 Coccolithophores .......................... 254
7.3 Primary production ............................. 255
7.3.1 Theoretical background ...................... 255
7.3.2 Methods for estimating production from remote sensing 258
7.3.3 Estimating PARfrom space ................... 262
7.3.4 Measurements of primary production ............. 264
7.4 Fisheries ..................................... 267
7.4.1 General considerations ...................... 267
7.4.2 Fisheries management and research .............. 268
7.4.3 Operational applications to specific fisheries ........ 270
7.4.4 Aquaculture ............................. 271
7.5 Habitats in shallow tropical seas ..................... 272
7.6 Coral reefs—a wider role for satellite data .............. 279
7.7 Marine biology in the future ....................... 282
7.8 References .................................... 283
8 Ocean surface waves ................................. 293
8.1 Introduction ................................... 293
8.2 Measuring ocean waves—principles .................... 294
8.2.1 Characterizing ocean waves in terms of measurable
parameters............................... 294
8.2.2 Wave energy and spectra ..................... 295
8.2.3 Significant wave height ...................... 296
viii Contents8.2.4 Measuring ocean waves from an altimeter ......... 298
8.2.5 Observing waves with the synthetic aperture radar (SAR) 300
8.2.6 Wave spectrometry ......................... 304
8.3 Measuring ocean waves—practical systems .............. 307
8.3.1 Altimeters for measuring SWH ................. 307
8.3.2 SWH data products from altimeters ............. 309
8.3.3 Synthetic aperture radars ..................... 312
8.3.4 ASARwave-related products .................. 313
8.4 Applications of wave data from satellites ............... 317
8.4.1 Applications of SWH ....................... 317
8.4.2 Applications of SAR ....................... 318
8.5 Using satellite data in wave prediction models ............ 319
8.5.1 Wave prediction models ..................... 319
8.5.2 Use of satellite data with wave models ............ 320
8.5.3 Assimilating satellite data into models ............ 321
8.6 Wave climate .................................. 322
8.7 Assessment and future perspectives ................... 326
8.8 References .................................... 328
9 Wind over the sea ................................... 333
9.1 Measuring wind over the sea from satellites .............. 333
9.1.1 Scatterometry . . . .......................... 334
9.1.2 Wind data from SAR ....................... 336
9.1.3 Wind data from altimeters .................... 336
9.1.4 Microwave radiometry ....................... 337
9.1.5 The alternatives to satellite measurements .......... 340
9.2 Oceanography and wind data ....................... 341
9.2.1 Differences between analysis winds and satellite winds . . 342
9.2.2 Which type of wind data should be used to study ocean
phenomena? . . . .......................... 342
9.3 Tropical cyclones over the ocean ..................... 344
9.3.1 Detecting and predicting tropical cyclones ......... 344
9.3.2 Use of ocean remote sensing to study hurricane–ocean
interaction ............................... 347
9.4 Satellite winds for offshore wind farms ................. 350
9.5 References .................................... 354
10 Fluxes through the air–sea interface ........................ 359
10.1 Introduction ................................... 359
10.2 Determining fluxes .............................. 361
10.2.1 General principles ......................... 361
10.2.2 Theoretical basis of flux parameterizations .......... 362
10.3 Satellite data available for surface fluxes ................ 363
10.3.1 Sea surface temperature ..................... 364
10.3.2 Wind .................................. 365
Contents ix10.3.3 Sea surface roughness ....................... 366
10.3.4 Significant wave height and wave age ............. 367
10.3.5 Water vapor ............................. 368
10.3.6 Air temperature at sea level ................... 369
10.3.7 Gas concentrations in the surface sea and the ABL . . . 369
10.4 Measuring fluxes from space ........................ 370
10.4.1 Radiative flux ............................ 370
10.4.2 Gas flux ................................ 372
10.4.3 Turbulent heat flux ........................ 378
10.5 Satellite flux measurements in future? .................. 382
10.6 References .................................... 386
11 Large ocean phenomena with human impact................... 391
11.1 Introduction ................................... 391
11.2 El Nino ..................................... 393
11.2.1 The ENSO phenomenon...................... 393
11.2.2 Observing an El Nino from satellites ............. 402
11.2.3 Observing an El Nino in sea surface temperature from
satellites ................................ 404
11.2.4 Applying altimetry to the study of El Nino......... 407
11.2.5 Satellite-observed wind fields and ocean surface currents . 410
11.2.6 Chlorophyll .............................. 415
11.2.7 Rainfall over the ocean ...................... 418
11.2.8 Synergy ................................ 419
11.3 Monsoons .................................... 421
11.3.1 Introduction ............................. 421
11.3.2 Illustrating the Indian monsoon using satellite data .... 422
11.3.3 Interannual variability of the Indian monsoon ....... 424
11.4 Sea ice distribution .............................. 426
11.4.1 Introduction ............................. 426
11.4.2 Measuring sea ice from space .................. 427
11.4.3 How is the distribution of sea ice changing? ........ 431
11.5 Tides, sea level, surges, and tsunamis .................. 435
11.5.1 A surveyor’s benchmark in the sky .............. 435
11.5.2 Mean sea level ............................ 437
11.5.3 Storm surges ............................. 441
11.5.4 Tsunamis ............................... 442
11.6 Conclusion ................................... 444
11.7 References .................................... 447
12 Internal waves...................................... 453
12.1 Introduction ................................... 453
12.1.1 Ocean internal and interfacial waves ............. 453
12.1.2 The importance of internal waves in physical and bio-
logical oceanography ....................... 456
x Contents12.2 Internal wave signatures detected with SAR ............. 457
12.2.1 Introduction.............................. 457
12.2.2 Internal, solitary wave packets observed by SAR ..... 459
12.2.3 Identification of internal wave trains and their propaga-
tion direction . . . .......................... 462
12.2.4 Hydrodynamic and film modulation .............. 463
12.2.5 Internal wave mean propagation speed ............ 468
12.2.6 Inversion of polarity in SARsignatures of internal waves 468
12.3 Internal waves and ocean color ...................... 471
12.3.1 Observations . . . .......................... 471
12.3.2 Remote sensing and depth distribution of ocean
chlorophyll .............................. 474
12.3.3 A model for interpreting ocean color signatures of
internal tides . . . .......................... 475
12.3.4 Internal waves and primary production ............ 477
12.4 Impact of remote sensing on our knowledge of internal waves . . 479
12.5 References .................................... 480
13 Shelf seas, estuaries, and coasts .......................... 485
13.1 Introduction ................................... 485
13.2 Observing shelf seas from space ..................... 486
13.2.1 What is distinct about the remote sensing of shelf seas? 486
13.2.2 Variability scales in shelf seas .................. 488
13.2.3 Shelf edge phenomena ....................... 492
13.2.4 Thermal signatures of shelf sea dynamical phenomena . . 497
13.2.5 Remote sensing of suspended sediments in shelf seas . . 508
13.2.6 Monitoring ecosystems and water quality .......... 516
13.3 Coastal altimetry ............................... 523
13.3.1 Challenges and opportunities for altimetry in coastal seas 523
13.3.2 Potential applications of coastal and shelf altimetry . . . 524
13.3.3 Practical approaches to improving altimeter accuracy in
shelf seas ............................... 527
13.4 Coastal and estuarine remote sensing .................. 528
13.4.1 Important edges of the ocean .................. 528
13.4.2 A mismatch of scales? ...................... 529
13.4.3 Coastal remote-sensing applications using satellite data. . 532
13.5 References .................................... 534
14 Putting ocean remote sensing to work ...................... 539
14.1 Satellites and applied oceanography ................... 539
14.1.1 Introduction . . . .......................... 539
14.1.2 The fundamental importance of ocean monitoring and
forecasting .............................. 540
14.1.3 Motivation for scientists to engage in applied ocean
remote sensing . .......................... 541
Contents xi14.2 Integrated ocean-forecasting systems ................... 543
14.2.1 What is operational oceanography? .............. 543
14.2.2 Combining satellite oceanography and ocean models for
operational tasks........................... 547
14.2.3 Assimilating satellite data into ocean-dynamical models . 551
14.3 Ecosystem modeling ............................. 555
14.3.1 How can satellite ocean color data support operational
applications? ............................. 555
14.3.2 Marine ecosystem models, scientific principles, and
operational purpose ........................ 555
14.3.3 Ways in which ocean color data are used in ocean
modeling ............................... 558
14.3.4 Sequential assimilation to constrain ecosystem state
variables ............................... 562
14.3.5 Characterizing light penetration in numerical models . . 564
14.3.6 Alternative approaches to ocean color assimilation .... 565
14.4 Preparing satellite data for operational use .............. 569
14.4.1 Providing merged data from multiple sensors/satellites . 570
14.4.2 GHRSST: A case study on preparing SST data for
operational applications ..................... 575
14.5 Oil spill monitoring ............................. 583
14.5.1 Introduction ............................. 583
14.5.2 How can oil spills be monitored routinely from space? . 584
14.5.3 CleanSeaNet, a European service for oil spill detection . 586
14.6 Using satellite data for climate monitoring .............. 588
14.6.1 Introduction ............................. 588
14.6.2 The ocean’s role in the climate system ............ 589
14.6.3 Essential climate variables .................... 591
14.6.4 Ocean datasets used for climate . . . .............. 597
14.7 References .................................... 602
15 Looking forward .................................... 607
15.1 Achievements ................................. 607
15.1.1 Oceanographic discoveries from satellite data ....... 607
15.1.2 Does ocean science need remote sensing? .......... 609
15.2 Securing the future for ocean remote sensing ............. 610
15.2.1 Essential satellite oceanography . . .............. 610
15.2.2 Limitations of existing sensors and platforms ....... 611
15.2.3 Future sensors, platforms, and systems for observing the
ocean ................................. 613
15.3 Challenges for satellite oceanographers . . . .............. 617
15.4 References .................................... 619
Index .............................................. 621
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