Tropical Circulation Systems and Monsoons (eBook)

Tropical Circulation Systems and Monsoons 1
Preface 5
Acknowledgments 7
Contents 8
Guide to Numbering Figures and Equations 15
Part I Tropical Circulation Systems -- A Survey 16
1 Large-Scale Tropical Circulations Some General Aspects 17
1.1 Introduction 17
1.2 Tropical Circulation as Part of the Global General Circulation The Tradewinds 18
1.3 Poleward Boundary of the Tropical Circulation 20
1.4 Heat Sources and Sinks 21
1.4.1 Definition of Heat Sources/Sinks 21
1.4.2 Diabatic/Adiabatic Heat Sources/Sinks 22
1.4.2.1 Diabatic Heating/Cooling 22
1.4.2.2 Adiabatic Heating/Cooling 22
1.4.2.3 Temperature Change in the Atmosphere Due to Condensation Heating 22
1.4.2.4 Identification of Heat Sources and Sinks 23
1.5 Some Physical and Dynamical Constraints and Conservation Laws 23
1.5.1 Direct and Indirect Circulations 23
1.5.2 Energy Transformations 24
1.5.3 Energy Transfer Process ' Carnot's Cycle 25
1.5.4 Conditional Instability and Convection 25
1.5.5 Cellular Structure -- Shallow and Deep Convection 26
1.5.6 Coriolis Control-Variation with Latitude 26
1.5.7 Conservation Laws 27
1.6 Equatorial Circulations 27
1.6.1 Circulation with Heat Sources and Sinks Placed Alternately Along the Equator -- Walker Circulations 28
1.7 Meridional Circulation with Heat Source at the Equator and Heat Sinks in Higher Latitudes The Hadley Circulations 29
1.8 Seasonal Migration of the Equatorial Heat Source 30
1.8.1 Origin of Monsoon 31
1.8.2 The Wave Structure 32
1.8.3 Forcing for the Seasonal Movement of the Equatorial Heat Source 33
1.8.4 Intraseasonal Oscillation of Monsoon 35
1.9 Co-existence of Monsoon, Hadley and Walker Circulations Inclined Troughs 36
1.10 Definition of Monsoon 38
1.11 Global and Regional Distribution of Monsoons 39
1.11.1 Tropical Monsoons 39
1.11.2 Extratropical Monsoons 40
1.11.3 Zonal and Meridional Anomalies 41
1.12 Co-existence of Monsoon with Desert Circulation 43
2 Tropical Disturbances (Quasi-stationary Waves, Easterly/Westerly Waves, Lows and Depressions, Cyclonic Storms, and Meso-Scale Disturbances) 46
2.1 Introduction 46
2.2 Quasi-stationary Waves 47
2.2.1 Quasi-stationary Wave in Wind Field 48
2.2.2 Quasi-stationary Wave in Temperature Fields 49
2.2.3 Structure of the Quasi-stationary Wave in Circulations 50
2.2.3.1 Horizontal Circulation 50
2.2.3.2 Zonal-Vertical Circulation 50
2.3 Traveling Easterly (Ely) Waves 52
2.3.1 Easterly Waves in Tropical North Atlantic 52
2.3.2 Easterly Waves in Tropical North Pacific 53
2.3.3 Easterly Waves in the Indian Ocean Region 54
2.4 Development of Waves 56
2.4.1 Meaning of Development 56
2.4.2 Development of a Quasi-stationary Monsoon Trough into a Depression 58
2.4.2.1 Role of Tropical E'ly Waves 58
2.4.2.2 Role of Subtropical W'ly Waves 59
2.4.3 Development of a Depression into a Cyclonic Storm/Tropical Cyclone/Hurricane/Typhoon 61
2.5 Meso-Scale Disturbances and Severe Local Storms in the Tropics 63
2.5.1 General Considerations -- Source of Energy of the Storm 63
2.5.2 Thunderstorms 64
2.5.2.1 Cellular Structure of a Thundercloud and Vertical Currents 64
2.5.2.2 Hydrometeors Inside the Thundercloud 66
2.5.2.3 Precipitation, Downdraft and Squalls 66
2.5.2.4 Lightning and Thunder 66
2.5.2.5 Structure of a Thunderstorm 68
2.5.2.6 Squall Line 68
2.5.3 Hailstorms 68
2.5.4 Tornadoes 70
2.5.4.1 Tornado Circulation and Intensity 71
2.5.4.2 Geographical and Seasonal Distribution of Tornadoes 72
3 Tropical Cyclones/Hurricanes/Typhoons Their Structure and Properties 74
3.1 Introduction 74
3.2 Observed Structure of a Tropical Cyclone 74
3.2.1 Wind Structure 76
3.2.2 Radial and Tangential Components of the Wind 77
3.2.2.1 Radial Wind 77
3.2.2.2 Tangential Wind 78
3.2.3 Vertical Motion in a Mean Typhoon 80
3.2.4 Pressure Distribution 81
3.2.5 Temperature Distribution 82
3.3 The Eye and the Eye-Wall 84
3.3.1 General Considerations -- Formation of the Hurricane Eye 84
3.3.2 Circulation Inside the Hurricane Eye -- Evidence of Meso-Scale Vortices 86
3.3.3 Concentric Multiple Eye-Walls 88
3.4 Spiral Bands Around the Eye-Wall 90
3.4.1 Structure 90
3.4.2 Origin and Direction of Propagation 91
3.5 Storm Surge 91
3.5.1 Introduction 91
3.5.2 Some General Aspects of Storm Surge 92
3.5.3 Mathematical Models of Storm Surge 93
3.6 Prediction of Cyclone Track and Intensity 95
3.6.1 Early Models -- The Steering Concept 96
3.6.2 Current Models 96
Part II Tropical Monsoons over Continents and Oceans 99
4 Monsoon over Southern Asia (Comprising Pakistan, India, Bangladesh, Myanmar and Countries of Southeastern Asia) and Adjoining Indian Ocean (Region I) 100
4.1 Introduction Physical Features and Climate 100
4.2 The Winter Season (DecemberFebruary) 102
4.2.1 General Climatic Conditions 102
4.2.2 Disturbances of the Winter Season 103
4.2.2.1 Western Disturbances (W.D.) 103
4.2.2.2 Easterly Waves and Cyclonic Storms of the Northern Indian Ocean 104
4.2.2.3 Easterly Waves and Cyclones of the Southern Indian Ocean 104
4.3 The Transition Season (MarchMay) 104
4.3.1 Western Disturbances 105
4.3.2 'Heat Lows' over Land and 'Cold Highs' over Ocean 105
4.3.3 Severe Local Storms 105
4.3.4 Developments over the Equatorial Indian Ocean 106
4.4 Advance of Summer Monsoon to the Indian Subcontinent General Remarks 109
4.4.1 Advance over the Indian Ocean (April--June) -- Stage 1 113
4.4.1.1 Retreat from the Southern Hemisphere 113
4.4.1.2 Advance over the Bay of Bengal 113
4.4.1.3 Advance over the Arabian Sea 114
4.4.1.4 Weather over the Northern Indian Ocean During Advance of Monsoon 114
4.4.2 Onset over the Indian Subcontinent (June--July) -- Stage 2 115
4.4.3 Advance to Western Himalayas (July--August) -- Stage 3 116
4.4.4 Source of Moisture for Monsoon Rainfall 117
4.5 Disturbances of the Summer Monsoon during the Onset Phase 117
4.5.1 Onset Vortex over the Arabian Sea and the Bay of Bengal 118
4.5.2 Monsoon Depressions and Cyclonic Storms 118
4.5.3 Interaction of Monsoon with W'ly Waves 119
4.6 Rainfall over the Indian Subcontinent during the Onset Phase 120
4.7 Summer Monsoon Withdrawal Phase (SeptemberNovember) 122
4.7.1 Dates of Withdrawal of Monsoon 122
4.7.2 Retreating Monsoon Rain over Tamil Nadu 122
4.7.3 Disturbances of the Withdrawal Phase 124
4.7.3.1 Western Disturbances 124
4.7.3.2 Depressions and Cyclonic Storms 124
4.8 Variability of the Indian Summer Monsoon Rainfall 125
4.8.1 Interannual Variability 126
4.8.1.1 Statistical Criteria 126
4.8.1.2 Floods and Droughts 128
4.8.2 Factors Likely Responsible for Interannual Variability 128
4.8.3 Intraseasonal Variability 132
4.8.3.1 Variability on Scale of 3--7 Days -- Active and Break Monsoons 132
4.8.3.2 Variability on 30--50 Day Time Scale 133
5 Monsoon over Eastern Asia (Including China, Japan, and Korea) and Adjoining Western Pacific Ocean 134
5.1 Introduction 134
5.2 Physical Features and Climate 135
5.3 The Winter Season over Eastern Asia (NovemberMarch) 136
5.3.1 Temperature, Pressure, and Wind 136
5.3.2 Quasi-stationary Wave in Westerlies -- Its Interaction with Traveling Waves -- Cold Surges 139
5.3.3 Winter Rainfall over Eastern Asia 141
5.4 Airmass Transformations and Cyclogenesis over the Oceans 141
5.4.1 Cyclonic Disturbances over Eastern Asia and Neighboring Ocean 141
5.5 Transition Period (April) 144
5.5.1 Development of 'Heat Low' over Eastern Asia 145
5.6 Origin of Monsoon over Eastern Asia 145
5.7 Seasonal March of the Summer Monsoon 147
5.8 Stationary States and Jumps 148
5.9 Meteorological Developments Associated with the Jump to Central China 148
5.9.1 Tibetan Plateau Monsoon 149
5.9.2 The Meiyu (Plum Rain) Front over China 150
5.9.2.1 Formation of the Meiyu Front 150
5.9.2.2 Interaction of the Meiyu Front with Traveling Disturbances 151
5.9.2.3 Structure of the Meiyu--Baiu Front 152
5.10 Jump of East Asian Monsoon to Extratropical Latitudes 153
5.10.1 Evidence of Jump in Climatological Fields 154
5.10.2 Zonal Anomaly in Seasonal Variations 156
5.10.3 Climatological Rainfall over Eastern Asia During July 157
5.11 Monsoon over Japan 158
5.11.1 Geographical Location and Climate 158
5.11.2 The Baiu Front -- Its Seasonal Movement and Activity 158
5.12 Monsoon over Korea 160
5.12.1 Historical Background 161
5.12.2 Physical Features and Climate 161
5.12.3 Winter Monsoon over Korea 161
5.12.4 Summer Monsoon over Korea -- Changma Season 162
5.12.5 Korea's Climatic Zones (After McCune, 1941) 163
6 Meteorology of the Maritime Continent (Region III) (Comprising Philippines, Indonesia and Equatorial Western Pacific Ocean) 165
6.1 Introduction 165
6.2 Climate of the Maritime Continent 166
6.2.1 Pressure 166
6.2.2 Temperature 167
6.2.3 Relative Humidity and Cloudiness 168
6.2.4 Rainfall 168
6.3 Factors Affecting the Climate of the Maritime Continent 169
6.3.1 Geographical Location and Topography 169
6.3.2 Ocean Currents 170
6.3.3 Equatorial Trough, the ITCZ and Monsoons 170
6.3.3.1 The Equatorial Trough and Its Movement 170
6.3.3.2 ITCZ 171
6.3.3.3 Monsoons 172
6.3.3.4 SPCZ 172
6.3.3.5 Tropical Cyclones/Typhoons 174
6.4 The Maritime Continent A Heat Source 174
6.5 The Maritime Continent and the ENSO 178
7 Monsoon over Australia (Region IV) 180
7.1 Introduction Location and Physical Features 180
7.2 Early Studies 180
7.3 Climate of Australia and Surrounding Oceans 182
7.3.1 Ocean Surface Temperature (SST, C) 182
7.3.2 Air Temperatures 183
7.3.3 Atmospheric Pressure (Isobaric Height) 185
7.3.4 Wind and Circulation 186
7.3.4.1 Low-Level Cross-Equatorial Airflow 188
7.3.4.2 Jetstreams 188
7.4 Monsoon over Australia 191
7.4.1 Onset of Monsoon 191
7.4.2 Co-existence of Monsoon and Hadley Circulations -- Interhemispheric Movement 192
7.4.3 Summer Monsoon Rainfall over Australia 194
7.5 Annual Rainfall of Australia and Its Seasonal Variability 196
7.5.1 Annual Rainfall 196
7.5.2 Seasonal Variability 197
7.6 Variability of Australian Rainfall with ENSO 197
7.7 Tropical Disturbances in the Australian Region Depressions and Cyclones 198
7.8 Tropical-Midlatitude Interaction in the Australian Region 200
7.8.1 Northerly and Southerly Bursters 201
8 Monsoon over Africa (Region V) 204
8.1 Introduction 204
8.2 Physical Features and Environment 204
8.3 Climates of Africa and Surrounding Oceans 207
8.3.1 Sea Surface Temperature and Wind 207
8.3.2 Air Temperature 207
8.3.3 Isobaric Height (gpm) 208
8.3.4 Wind and Circulation 210
8.3.5 Rainfall over Africa 214
8.4 Equatorial Westerlies over Africa 216
8.5 The Equatorial Trough over North Africa Its Zonal Anomaly 217
8.6 Structure of the Circulation Associated with the Equatorial Trough 219
8.6.1 Zonal Circulation 220
8.6.2 Meridional Circulation 220
8.7 Origin of African Wave Disturbances 221
8.7.1 Early Studies 221
8.7.2 Influence of Midlatitude Forcing 222
8.7.3 Sudan -- The Breeding Ground 226
8.7.4 Role of Topography 228
8.8 Structure, Development and Movement of the Waves 228
8.9 Interaction of South African Monsoon with Midlatitude Waves of the Southern Hemisphere 229
9 Monsoon over South America (Region VI) 231
9.1 Introduction 231
9.2 Physical Features and Environment 231
9.2.1 Physical Dimension of the Continent 232
9.2.2 Topography 233
9.2.3 Oceanic Environment and Its Influence on Climate 233
9.3 Climatological Features 234
9.3.1 Air Temperature and Pressure 235
9.3.2 Atmospheric Circulation -- Monsoon 238
9.3.3 Co-existence of Monsoon and Hadley Circulations 241
9.3.3.1 Summer (January ) 242
9.3.3.2 Winter (July) 243
9.3.4 Rainfall over South America 243
9.4 Quasi-stationary Waves and Their Associated Weather 243
9.4.1 Weather Phenomena Related to the Northern Boundary 246
9.4.1.1 Low Level Jet (LLJ) 246
9.4.1.2 Zonal Anomaly of Rainfall over NE Brazil 247
9.4.2 Weather Phenomena Associated with the Southern Boundary 248
9.4.2.1 Southwest Atlantic Convergence Zone (SACZ) 248
9.4.2.2 Semi-arid Conditions over Patagonia 249
9.5 Tropical Disturbances over South America 249
9.5.1 Types of Disturbances 249
9.5.2 Monsoon Lows and Depressions 250
9.5.2.1 Case Study: Monsoon Low/Depression of 7--11 January 2002 251
9.5.3 Upper-Tropospheric Cyclonic Vortices 251
9.5.3.1 Case Study: Upper-Tropospheric Cyclonic Vortex of 1--6 January 2001 251
9.6 A Tropical Cyclone over the South Atlantic Ocean 255
9.6.1 Introduction 256
9.6.2 Formation of the Initial Vortex ' Interaction with W'ly Waves 258
9.6.3 Structure, Movement and Development of the Vortex 259
Part III Extratropical Monsoons 261
10 Monsoon over Central America and Adjoining Southwestern North America (Region VII) 262
10.1 Introduction 262
10.2 Heat Sources and Sinks and Their Seasonal Movement 263
10.3 The Climate of Central America and Adjoining North America 264
10.3.1 Surface Temperatures and Winds 264
10.3.2 Upper Air Temperatures 266
10.3.3 Upper Air Height (gpm) 267
10.3.4 Upper Air Wind Field and Circulation 269
10.4 Rainfall over Central America and Adjoining Areas 271
10.4.1 Annual Rainfall over Mexico 274
10.4.2 Source of Moisture for Rainfall over the Arizona-Sonoran Desert 275
10.5 Some Characteristic Features of Weather over Central America 277
10.5.1 Weather Associated with W'ly Waves 277
10.5.2 Weather Associated with 'Northers' 277
10.5.3 Land and Sea Breezes on the Pacific Coast of Mexico 278
10.5.4 Temporales of the Caribbean Sea and the Gulf of Mexico 279
10.5.5 Hurricanes and Tropical Storms 279
11 Extratropical Monsoon over North America 281
11.1 Introduction 281
11.2 Climatological Background of North American Monsoon 281
11.2.1 Physical Features of the Land 282
11.2.2 Semi-permanent High and Low Pressure Systems over Oceans 283
11.2.2.1 The Subtropical High Pressure System of the Pacific Ocean 283
11.2.2.2 The Subtropical High Pressure System over the Atlantic Ocean 283
11.2.2.3 The Arctic Ocean High Pressure System 283
11.2.2.4 Semi-permanent 'Aleutian Low' and 'Icelandic Low' 284
11.3 The Seasonal Movement of Heat Sources and Sinks 284
11.4 Seasonal Circulations Monsoons 285
11.4.1 The Winter Monsoon (December--February) 285
11.4.2 The Spring Transition Season (March--May) 287
11.4.3 The Summer Monsoon (June--August) 287
11.4.3.1 Structure of the Monsoon Boundary Layer 289
11.4.3.2 Moisture Budget and Precipitation 290
11.4.3.3 Seasonality in the Distribution of Orographic Precipitation 291
11.4.4 The Autumn Transition Season (September--November) 292
11.5 Interaction of Monsoons with Wly Wave Disturbances 292
11.6 Some Characteristic Features of East Coast Monsoon 293
11.6.1 Seasonal Variations and Reversals 293
11.6.2 Monsoonal Characteristics of the East Coast Region 294
11.7 Role of the Appalachian Mountain Range Leeside Cyclogenesis Northeast Storms 294
11.8 Interaction of Monsoon with Storms and Hurricanes 295
Appendix Meanings of Uncommon Words/Terms Used in the Book 297
References 304
Author Index 317
Subject Index 321