Climates of the Oceans

World Survey of Climatology Volume 15 Climates of the Oceans edited by H. VAN LOON National Center for Atmospheric Research P.O. Box 3000 Boulder, Colo. 80307 (U.S.A.) ELSEVIER Amsterdam-Oxford-New York-Tokyo 1984

PREFACE IX Chapter 1. CLIMATE OF THE SOUTH ATLANTIC OCEAN by O. HOFLICH Basic principles 1 Historical review 1 Climatology, 2 Synoptic meteorology, 3 Problems of the data 5 Origin of data, 5 Problems inherent in the data, 6 Inhomogeneities, 6 Selected ocean areas, 8 Fundamentals of climate 8 Climate-producing processes, 9 Planetary circulation, 10 Characteristics of marine climate, 11 Climate classification of the South Atlantic, 12 Climatic elements 13 Air pressure 14 Mean pressure field, 14 Annual variation, 15 Variability, 16 Wind 17 Wind speed, 17 Wind direction, 19 Wind roses, 21 Strong winds and gales, 22 Oceanic elements 22 Sea and swell, 23 Ocean currents, 25 Subsurface conditions, 27 Temperature 30 Sea surface temperature, 30 Air temperature over the ocean, 34 Air-sea temperature difference, 36 Humidity 37 Vapour pressure, 38 Equivalent temperature, 39 Relative humidity, 40 Visible weather phenomena 42 Cloudiness, 42 Visibility, 46 Precipitation frequencies, 47 Thunderstorms, 48 Water and heat balance 48 Water balance 49 Precipitation amounts, 49 Evaporation, 51 Water balance, 53 Vertical heat flux at the sea surface 56 Latent heat flux, 57 Sensible heat flux, 57 Total heat flux, 59 Radiation balance 60 Insolation at sea level, 60 Terrestrial radiation, 62 Atmospheric counter radiation, 62 Net long-wave radiation at the sea surface, 63 Radiation balance at the sea surface, 64 Radiation balance in the atmosphere, 65 XI

, Heat balance 66 Heat balance at the sea surface, 66 Heat balance of the earth-atmosphere system, 68 Climatic stations 70 Sao Tome 71 Fernando de Noronha 73 Ascension Island 75 St. Helena 77 Tristan da Cunha 78 Gough Island 80 Falkland Islands 81 South Georgia 83 Off-shore climates 86 South American off-shore areas 86 North coast of Brazil, 87 Northeast coast of Brazil, 88 Southeast coast of Brazil, 89 Rio de la Plata, 91 Patagonian Shelf, 93 African off-shore areas 94 Coast of Gabon, 94 Coast of Angola, 95 Coast of Southwest Africa, 96 Coast of the Cape Province, 98 Aerology 100 Geopotential heights 101 Absolute topographies, 101 Meridional profiles, 102 Zonal profiles, 103 Wind 105 Zonal winds, 105 Meridional winds, 107 Temperature 107 Relative topographies, 107 Meridional profiles, 107 Zonal profiles, 109 Humidity... 110 Vapour pressure, 110 Relative humidity, 111 Several humidity elements, 112 Synoptic climatology 113 Tropics 113 Intertropical Convergence Zone, 114 Trade winds, 114 Disturbances, 114 Anticyclones 116 High-pressure centres, 116 High-pressure tracks, 116 Cyclones of the westwind zone 117 Frontal zone, 118 Low-pressure centres, 118 Low-pressure tracks, 119 Weather systems, 121 References 123 Appendix Climatic tables and charts 132 Chapter 2. CLIMATE OF THE NORTH ATLANTIC OCEAN by G. B. TUCKER AND R. G. BARRY Introduction 193 Main climatic features 193 XII

> Main oceanic features 194 History of observations 196 Climatic change.. 199 Representative data 201 Use of January and July maps 202 Mean circulation patterns 203 Surface pressure field 203 Winds 206 Synoptic climatology 210 Annual cycle of synoptic events 210 Winter, 210 Spring, 211 Summer, 212 Autumn, 213 Circulation patterns and synoptic events in the westerlies 213 Climatology of blocking action, 215 Coastal storms of eastern United States, 217 Thermal troughs over the northeastern Atlantic, 218 Trade-wind region 218 Intertropical Convergence Zone, 220 Tropical storms, 224 Air-sea interactions 225 Air temperature 227 Air-sea temperature difference 231 Interactions between the ocean and atmospheric circulation 233 Moisture conditions 234 Humidity 234 Cloudiness 237 Visibility 238 Precipitation 238 Evaporation 241 Heat balance 243 General remarks 243 Solar radiation 244 Terms in the heat balance equation 245 Climatic zones 248 Equatorial zone, 249 Tropical and subtropical zone, 252 Temperate zone, 252 Subpolar zone, 252 References 253 Appendix Climatic tables 258 Chapter 3. CLIMATE OF THE SOUTH PACIFIC OCEAN by N. A. STRETEN AND J. W. ZILLMAN Introduction 263 History of climatic description 263 Data sources 266 Surface climatic data, 266 Upper-air data, 266 Satellite data, 267 Synoptic analyses, 267 Tabulated data, 267 Treatment 267 XIII

v The ocean 268 Circulation 269 Temperature 273 Salinity 274 Ocean fronts 275 Sea ice 277 Icebergs. 280 Synoptic climatology 281 The data base 281 Synoptic regimes of the South Pacific 284 The tropical easterlies 285 Tropical cyclones 288 The tropical anticyclone belt 292 The westerlies 296 The Antarctic trough 307 The Pacific cloud band 308 Main climatic elements 310 Surface air temperatures 310 Surface dew point 312 Surface pressure 312 Surface wind 314 Cloudiness and fog 317 Precipitation 319 Climate of the upper air 323 Geopotential height and temperature 323 Moisture distribution 329 Wind 329 Jet streams and tropopause 329 Meridional cross-sections 331 The heat budget 332 Surface heat budget 335 Surface radiation balance, 335 Latent heat flux, 338 Sensible heat flux, 339 Heat available for storage and transport by the ocean, 341 Influence of ocean fronts, 342 Diurnal variation of the surface heat budget, 343 Atmospheric heat budget 344 Radiation budget, 345 Condensation heating, 346 Net diabatic heating, 348 Large-scale circulations 348 The Southern Oscillation 349 Walker Circulation 355 El Nino 358 Conclusion 361 Acknowledgements 361 References 362 Appendix Climatic tables 375 XIV

Chapter 4. CLIMATE OF THE NORTH PACIFIC OCEAN by K. TERADA AND M. HANZAWA Introduction 431 Geographic features 431 Early data summaries 431 Ocean currents 432 Mean pressure field 434 High pressure 434 Low pressure 437 Wind and depression tracks 438 Major wind systems 438 Monsoons 441 Gale statistics and cyclogenesis 444 Extratropical depression tracks 445 Tropical and subtropical cyclones 447 Temperature and humidity 453 Temperature distribution 453 Difference between air and sea surface temperature 457 Humidity 458 Cloudiness, visibility, fog, and precipitation 459 Cloudiness 459 Visibility 463 Fog 464 Precipitation 465 Snow and ice 467 Large-scale energy exchange between ocean and atmosphere 470 Evaporation 470 Marine climate studies 471 Acknowledgements 475 References 475 Appendix Climatic tables for ocean weather ships and land or island stations.... 478 Chapter5. CLIMATE OF THE INDIAN OCEAN SOUTH OF 35 S by J. J. TALJAARD AND H. VAN LOON Introduction 505 General 505 Geographical setting and bottom topography 505 Currents, convergences, and pack ice 507 Historical survey and data used 511 Temperature 514 Sea surface temperature 514 March-September range of sea temperature, 517 Anomalies of sea temperature XV

in March and September, 518 The annual variation of sea temperature along 43 S, 519 Sea temperature extremes, 520 Surface air temperature 521 Surface air temperature in January and July, 521 The annual variation of air temperature, 523 Difference between air and sea temperature, 526 Summer to winter air temperature range, 527 January and July air temperature anomalies, 528 Air temperature extremes, 529 Temperature variability at Marion, New Amsterdam, and Kerguelen, 531 Upper-air temperature 531 General, 531 Mean monthly, seasonal, and annual upper-air temperatures and standard deviations at Marion, New Amsterdam, Kerguelen, and Heard islands, 532 The temperature distribution at 500 mbar in January and July, 533 Temperature change from January to July at 500 mbar, 533 Temperature deviations from the hemispheric zonal means at 500 mbar, 534 Annual variation of upper-air temperature, 535 Meridional temperature gradient at 500 mbar, 537 Zonal temperature anomaly profiles along 35 and 55 S in January and July, 539 Pressure 539 Sea-level pressure 539 Mean sea-level pressure in January and July, 539 The subtropical ridge, 539 The circumpolar trough, 541 Annual course of pressure at the islands and at Mawson, 542 Mid-seasonal fluctuations of pressure, 543 Variability of daily, monthly, seasonal, and annual mean sea-level pressures, 546 Upper-air pressure 547 General, 547 Mean monthly, seasonal, and annual heights of constant-pressure surfaces and standard deviations, 547 Contour charts for 500 mbar in January and July, 547 January-July height change and zonal anomalies at 200 mbar, 549 Variability of pressure heights, 549 Wind 551 Surface wind 551 Wind in the troposphere 556 Precipitation and clouds 560 Synoptic climatology 563 General 563 Anticyclones 564 Anticyclogenesis, 564 Anticyclone movement, 565 Anticyclone frequency, 566 Cyclones 570 Cyclogenesis, 570 Cyclone movement, 573 Cyclone frequency, 573 Speeds of cyclones, 575 Fronts, 575 Movement of deep cold and warm air masses, 577 Heat balance 578 Data 578 The equations used, 579 Results and discussion, 581 Acknowledgements 588 References 588 Appendix Climatic tables 592 XVI

Chapter 6. CLIMATE OF THE INDIAN OCEAN NORTH OF 35 S by C. S. RAMAGE Introduction 603 Sea surface currents 605 Monsoon region, 606 Non-monsoon region, 606 Data 607 Typical synoptic situations 608 Subtropical cyclone 608 Subtropical cyclone of 12 and 13 August 1964, 609 Near-equatorial troughs 610 Near-equatorial troughs of April-May 1964, 612 Air-sea interaction over the western Arabian Sea 617 Weather off Somalia in August 1964, 618 Conditions during January and July 627 January 627 Monsoon region, 627 Australian summer monsoon, 628 Non-monsoon region 628 July 630 \g. Monsoon region, 630 Non-monsoon region, 638 Winter-summer differences 640 ^ Heat balance, 640 Trough and ridge shifts, 641 Trans-equatorial flow, 641 Tropical cyclones 641 TropicaliCyclones over the northern Indian Ocean 644 Tropical cyclones over the southern Indian Ocean 644 Tropical cyclone movement 644 March of climate through the year 645 Northern Hemisphere monsoon region 649 November to April, 649 May to mid-september, 649 Mid-September to October, 650 Equatorial region 651 Southern Hemisphere monsoon region 652 Western Indian Ocean, 652 Eastern Indian Ocean, 653 Central Indian Ocean, 653 Southern Hemisphere non-monsoon region 653 Trade winds, 653 Acknowledgements 654 References 654 Appendix Climatic tables 659 Chapter 7. CLIMATE OF ICELAND by MARKUS A. EINARSSON Introduction 673 Climatic factors 674 XVII

* Weather types 676 Southeastern 676 Southwestern or western 677 Southern with warm air mass 677 Warm air mass originating in Europe 677 Eastern 677 Northeastern 677 Northern 678 A high over Iceland 678 Climatic variations 678 Temperature 680 Precipitation 684 Snow 686 Wind 687 Humidity 689 Cloudiness 689 Visibility and fog 691 Sunshine and radiation 691 Potential evapotranspiration 692 Acknowledgements 693 References 693 Appendix Climatic tables 695 REFERENCE INDEX 699 GEOGRAPHICAL INDEX 709 SUBJECT INDEX 713 XVIII