Meteorology Today: An Introduction to Weather, Climate, and the Environment, Eleventh Edition
by C. Donald Ahrens, Robert Henson
by C. Donald Ahrens, Robert Henson
Contents
Preface xi
CHaPter 1
Earth and Its Atmosphere 3
The Atmosphere and the Scientific Method 4
Overview of Earth’s Atmosphere 4
The Early Atmosphere 5
Composition of Today’s Atmosphere 6
FOCUS ON A SPECIAL TOPIC 1.1
A Breath of Fresh Air 7
Vertical Structure of the Atmosphere 10
A Brief Look at Air Pressure and Air Density 11
Layers of the Atmosphere 12
FOCUS ON A SPECIAL TOPIC 1.2
The Atmospheres of Other Planets 14
FOCUS ON AN OBSERVATION 1.3
The Radiosonde 15
The Ionosphere 16
Weather and Climate 17
Meteorology—A Brief History 17
A Satellite’s View of the Weather 18
Weather and Climate in Our Lives 22
FOCUS ON A SPECIAL TOPIC 1.4
What is a Meteorologist? 26
Summary 27
Key Terms 27
CHaPter 1
Earth and Its Atmosphere 3
The Atmosphere and the Scientific Method 4
Overview of Earth’s Atmosphere 4
The Early Atmosphere 5
Composition of Today’s Atmosphere 6
FOCUS ON A SPECIAL TOPIC 1.1
A Breath of Fresh Air 7
Vertical Structure of the Atmosphere 10
A Brief Look at Air Pressure and Air Density 11
Layers of the Atmosphere 12
FOCUS ON A SPECIAL TOPIC 1.2
The Atmospheres of Other Planets 14
FOCUS ON AN OBSERVATION 1.3
The Radiosonde 15
The Ionosphere 16
Weather and Climate 17
Meteorology—A Brief History 17
A Satellite’s View of the Weather 18
Weather and Climate in Our Lives 22
FOCUS ON A SPECIAL TOPIC 1.4
What is a Meteorologist? 26
Summary 27
Key Terms 27
Questions for Review 27
Questions for Thought 28
Problems and Exercises 28
CHaPter 2
Energy: Warming Earth
and the Atmosphere 31
Energy, Temperature, and Heat 32
Temperature Scales 33
Specific Heat 34
Latent Heat—The Hidden Warmth 34
FOCUS ON A SPECIAL TOPIC 2.1
The Fate of a Sunbeam 36
Heat Transfer in the Atmosphere 36
Conduction 36
Convection 37
FOCUS ON A SPECIAL TOPIC 2.2
Rising Air Cools and Sinking Air Warms 38
Radiant Energy 39
Radiation and Temperature 40
Radiation of the Sun and Earth 40
Radiation—Absorption, Emission, and Equilibrium 41
FOCUS ON AN ENVIRONMENTAL ISSUE 2.3
Wave Energy, Sun Burning, and UV Rays 42
Selective Absorbers and the Atmospheric Greenhouse
Effect 43
Enhancement of the Greenhouse Effect 46
Warming the Air from Below 47
Shortwave Radiation Streaming from the Sun 47
FOCUS ON AN OBSERVATION 2.4
Blue Skies, Red Suns, and White Clouds 48
Earth’s Annual Energy Balance 49
Solar Particles, the Aurora, and Space Weather 51
FOCUS ON A SPECIAL TOPIC 2.5
Characteristics of the Sun 52
Solar Storms and Space Weather 54
Summary 55
Key Terms 55
Questions for Review 55
Questions for Thought 56
Problems and Exercises 56
Questions for Thought 28
Problems and Exercises 28
CHaPter 2
Energy: Warming Earth
and the Atmosphere 31
Energy, Temperature, and Heat 32
Temperature Scales 33
Specific Heat 34
Latent Heat—The Hidden Warmth 34
FOCUS ON A SPECIAL TOPIC 2.1
The Fate of a Sunbeam 36
Heat Transfer in the Atmosphere 36
Conduction 36
Convection 37
FOCUS ON A SPECIAL TOPIC 2.2
Rising Air Cools and Sinking Air Warms 38
Radiant Energy 39
Radiation and Temperature 40
Radiation of the Sun and Earth 40
Radiation—Absorption, Emission, and Equilibrium 41
FOCUS ON AN ENVIRONMENTAL ISSUE 2.3
Wave Energy, Sun Burning, and UV Rays 42
Selective Absorbers and the Atmospheric Greenhouse
Effect 43
Enhancement of the Greenhouse Effect 46
Warming the Air from Below 47
Shortwave Radiation Streaming from the Sun 47
FOCUS ON AN OBSERVATION 2.4
Blue Skies, Red Suns, and White Clouds 48
Earth’s Annual Energy Balance 49
Solar Particles, the Aurora, and Space Weather 51
FOCUS ON A SPECIAL TOPIC 2.5
Characteristics of the Sun 52
Solar Storms and Space Weather 54
Summary 55
Key Terms 55
Questions for Review 55
Questions for Thought 56
Problems and Exercises 56
CHaPter 3
Seasonal and Daily Temperatures 59
Why Earth Has Seasons 60
Seasons in the Northern Hemisphere 60
FOCUS ON A SPECIAL TOPIC 3.1
Is December 21 Really the First Day of Winter? 64
Seasons in the Southern Hemisphere 66
Local Seasonal Variations 66
FOCUS ON AN ENVIRONMENTAL ISSUE 3.2
Solar Heating and the Noonday Sun 67
Daily Warming and Cooling Air Near the Surface 68
Daytime Warming 68
Extreme High Temperatures 69
Nighttime Cooling 70
Record Low Temperatures 73
Daily Temperature Variations 75
FOCUS ON A SPECIAL TOPIC 3.3
When It Comes to Temperature, What’s Normal? 77
Applications of Air Temperature 80
Air Temperature and Human Comfort 82
FOCUS ON AN OBSERVATION 3.4
A Thousand Degrees and Freezing to Death 83
Measuring Air Temperature 84
FOCUS ON AN OBSERVATION 3.5
Why Thermometers Should Be Read in the Shade 86
Summary 88
Key Terms 88
Questions for Review 88
Questions for Thought 89
Problems and Exercises 90
Seasonal and Daily Temperatures 59
Why Earth Has Seasons 60
Seasons in the Northern Hemisphere 60
FOCUS ON A SPECIAL TOPIC 3.1
Is December 21 Really the First Day of Winter? 64
Seasons in the Southern Hemisphere 66
Local Seasonal Variations 66
FOCUS ON AN ENVIRONMENTAL ISSUE 3.2
Solar Heating and the Noonday Sun 67
Daily Warming and Cooling Air Near the Surface 68
Daytime Warming 68
Extreme High Temperatures 69
Nighttime Cooling 70
Record Low Temperatures 73
Daily Temperature Variations 75
FOCUS ON A SPECIAL TOPIC 3.3
When It Comes to Temperature, What’s Normal? 77
Applications of Air Temperature 80
Air Temperature and Human Comfort 82
FOCUS ON AN OBSERVATION 3.4
A Thousand Degrees and Freezing to Death 83
Measuring Air Temperature 84
FOCUS ON AN OBSERVATION 3.5
Why Thermometers Should Be Read in the Shade 86
Summary 88
Key Terms 88
Questions for Review 88
Questions for Thought 89
Problems and Exercises 90
CHaPter 4
Atmospheric Humidity 93
Circulation of Water in the Atmosphere 94
The Many Phases of Water 95
Evaporation, Condensation, and Saturation 95
Humidity 97
Absolute Humidity 97
Specific Humidity and Mixing Ratio 97
Vapor Pressure 98
Relative Humidity 99
FOCUS ON A SPECIAL TOPIC 4.1
Vapor Pressure and Boiling—The Higher You Go,
the Longer Cooking Takes 100
Relative Humidity and Dew Point 101
Comparing Humidities 104
Relative Humidity in the Home 105
Relative Humidity and Human Discomfort 106
FOCUS ON A SPECIAL TOPIC 4.2
Computing Relative Humidity and Dew Point 107
Measuring Humidity 109
FOCUS ON A SPECIAL TOPIC 4.3
Which Is “Heavier”—Humid Air or Dry Air? 110
Summary 111
Key Terms 111
Questions for Review 111
Questions for Thought 112
Problems and Exercises 112
Atmospheric Humidity 93
Circulation of Water in the Atmosphere 94
The Many Phases of Water 95
Evaporation, Condensation, and Saturation 95
Humidity 97
Absolute Humidity 97
Specific Humidity and Mixing Ratio 97
Vapor Pressure 98
Relative Humidity 99
FOCUS ON A SPECIAL TOPIC 4.1
Vapor Pressure and Boiling—The Higher You Go,
the Longer Cooking Takes 100
Relative Humidity and Dew Point 101
Comparing Humidities 104
Relative Humidity in the Home 105
Relative Humidity and Human Discomfort 106
FOCUS ON A SPECIAL TOPIC 4.2
Computing Relative Humidity and Dew Point 107
Measuring Humidity 109
FOCUS ON A SPECIAL TOPIC 4.3
Which Is “Heavier”—Humid Air or Dry Air? 110
Summary 111
Key Terms 111
Questions for Review 111
Questions for Thought 112
Problems and Exercises 112
CHaPter 5
Condensation: Dew, Fog,
and Clouds 115
The Formation of Dew and Frost 116
Condensation Nuclei 117
Haze 117
Fog 118
Radiation Fog 119
Advection Fog 120
FOCUS ON AN OBSERVATION 5.1
Why Are Headlands Usually Foggier Than Beaches? 121
Upslope Fog 122
Evaporation (Mixing) Fog 122
Foggy Weather 123
FOCUS ON A SPECIAL TOPIC 5.2
Fog That Forms by Mixing 124
FOCUS ON AN ENVIRONMENTAL ISSUE 5.3
Fog Dispersal 126
Clouds 127
Classification of Clouds 127
Cloud Identification 127
Some Unusual Clouds 132
Cloud Observations 135
Satellite Observations 135
FOCUS ON AN OBSERVATION 5.4
Measuring Cloud Ceilings 137
FOCUS ON A SPECIAL TOPIC 5.5
Satellites Do More Than Observe Clouds 141
Summary 142
Key Terms 142
Questions for Review 142
Questions for Thought 143
Problems and Exercises 143
CHaPter 6
Stability and Cloud Development 145
Atmospheric Stability 146
Determining Stability 147
A Stable Atmosphere 147
An Unstable Atmosphere 149
A Conditionally Unstable Atmosphere 151
Causes of Instability 151
FOCUS ON A SPECIAL TOPIC 6.1
Subsidence Inversions—Put a Lid on It 152
Cloud Development 154
Convection and Clouds 154
FOCUS ON A SPECIAL TOPIC 6.2
Atmospheric Stability and Windy Afternoons —
Hold On to Your Hat 155
FOCUS ON AN OBSERVATION 6.3
Determining Convective Cloud Bases 159
Topography and Clouds 159
Clouds That Form Downwind of Mountains 161
FOCUS ON AN ADVANCED TOPIC 6.4
Adiabatic Charts 162
Changing Cloud Forms 162
Summary 166
Key Terms 166
Questions for Review 166
Questions for Thought 166
Problems and Exercises 167
CHaPter 7
Precipitation 169
Precipitation Processes 170
How Do Cloud Droplets Grow Larger? 170
Collision and Coalescence Process 171
Ice-Crystal (Bergeron) Process 173
FOCUS ON A SPECIAL TOPIC 7.1
The Freezing of Tiny Cloud Droplets 174
Cloud Seeding and Precipitation 176
Precipitation in Clouds 178
FOCUS ON AN ENVIRONMENTAL ISSUE 7.2
Does Cloud Seeding Enhance Precipitation? 178
Precipitation Types 179
Rain 179
Snow 180
FOCUS ON A SPECIAL TOPIC 7.3
Are Raindrops Tear-Shaped? 181
FOCUS ON A SPECIAL TOPIC 7.4
Snowing When the Air Temperature Is Well Above Freezing 182
Sleet and Freezing Rain 185
FOCUS ON A SPECIAL TOPIC 7.5
Sounds and Snowfalls 185
FOCUS ON AN OBSERVATION 7.6
Aircraft Icing 187
Snow Grains and Snow Pellets 188
Hail 188
Measuring Precipitation 191
Instruments 191
Doppler Radar and Precipitation 192
Measuring Precipitation from Space 193
Summary 195
Key Terms 195
Questions for Review 195
Questions for Thought 196
Problems and Exercises 196
CHaPter 8
Air Pressure and Winds 199
Atmospheric Pressure 200
Horizontal Pressure Variations—A Tale of Two
Cities 200
Daily Pressure Variations 201
Pressure Measurements 202
FOCUS ON A SPECIAL TOPIC 8.1
The Atmosphere Obeys the Gas Law 204
Pressure Readings 205
Surface and Upper-Level Charts 206
FOCUS ON AN OBSERVATION 8.2
Flying on a Constant Pressure Surface—High to Low, Look Out
Below 209
Newton’s Laws of Motion 210
Forces That Influence the Winds 211
Pressure Gradient Force 211
Coriolis Force 211
Straight-Line Flow Aloft—Geostrophic Winds 214
FOCUS ON AN ADVANCED TOPIC 8.3
A Mathematical Look at the Geostrophic Wind 216
Curved Winds Around Lows and Highs Aloft—
Gradient Winds 216
FOCUS ON AN OBSERVATION 8.4
Estimating Wind Direction and Pressure Patterns Aloft by
Watching Clouds 218
Winds on Upper-Level Charts 218
Surface Winds 220
FOCUS ON AN OBSERVATION 8.5
Winds Aloft in the Southern Hemisphere 220
Winds and Vertical Air Motions 222
FOCUS ON AN ADVANCED TOPIC 8.6
The Hydrostatic Equation 224
Summary 225
Key Terms 225
Questions for Review 225
Questions for Thought 226
Problems and Exercises 226
CHaPter 9
Wind: Small-Scale and Local
Systems 229
Scales of Motion 230
Small-Scale Winds Interacting with the Environment 231
Friction and Turbulence in the Boundary Layer 231
Eddies—Big and Small 233
The Strong Force of the Wind 234
Wind and Soil 234
FOCUS ON AN OBSERVATION 9.1
Eddies and “Air Pockets” 235
Wind and Snow 236
Wind and Vegetation 237
Wind and Water 238
Local Wind Systems 239
FOCUS ON A SPECIAL TOPIC 9.2
Pedaling into the Wind 240
Thermal Circulations 240
Sea and Land Breezes 241
Mountain and Valley Breezes 243
Katabatic Winds 244
Chinook (Foehn) Winds 245
FOCUS ON A SPECIAL TOPIC 9.3
Snow Eaters and Rapid Temperature Changes 246
Santa Ana Winds 246
Desert Winds 249
Seasonally Changing Winds—The Monsoon 251
Determining Wind Direction and Speed 254
The Influence of Prevailing Winds 255
Wind Measurements 257
FOCUS ON A SPECIAL TOPIC 9.4
Wind Energy 257
Summary 260
Key Terms 260
Questions for Review 260
Questions for Thought 261
Problems and Exercises 262
CHaPter 10
Wind: Global Systems 265
General Circulation of the Atmosphere 266
Single-Cell Model 266
Three-Cell Model 267
Average Surface Winds and Pressure:
The Real World 269
The General Circulation and Precipitation Patterns 271
Average Wind Flow and Pressure Patterns Aloft 272
FOCUS ON AN OBSERVATION 10.1
The “Dishpan” Experiment 274
Jet Streams 274
The Formation of Jet Streams 276
Other Jet Streams 277
Atmosphere-Ocean Interactions 278
Global Wind Patterns and Surface Ocean Currents 278
Upwelling 280
El Niño, La Niña, and the Southern Oscillation 281
Pacific Decadal Oscillation 286
FOCUS ON A SPECIAL TOPIC 10.2
The Challenge of Predicting El Niño and La Niña 287
North Atlantic Oscillation and Arctic Oscillation 289
Summary 291
Key Terms 291
Questions for Review 291
Questions for Thought 292
Problems and Exercises 292
CHaPter 11
Air Masses and Fronts 295
Air Masses 296
Source Regions 296
Classification 296
Air Masses of North America 297
FOCUS ON A SPECIAL TOPIC 11.1
Lake-Effect (Enhanced) Snows 299
FOCUS ON A SPECIAL TOPIC 11.2
The Return of the Siberian Express 302
Fronts 306
Stationary Fronts 307
Cold Fronts 307
Warm Fronts 311
Drylines 313
FOCUS ON A SPECIAL TOPIC 11.3
The Wavy Warm Front 314
Occluded Fronts 315
Upper-Air Fronts 316
Summary 318
Key Terms 318
Questions for Review 318
Questions for Thought 319
Problems and Exercises 319
CHaPter 12
Middle-Latitude Cyclones 321
Polar Front Theory 322
Where Do Mid-Latitude Cyclones Tend to Form? 325
FOCUS ON A SPECIAL TOPIC 12.1
Nor’easters 326
Vertical Structure of Deep Dynamic Lows 326
The Roles of Converging and Diverging Air 327
FOCUS ON A SPECIAL TOPIC 12.2
A Closer Look at Convergence and Divergence 328
Upper-Level Waves and Mid-Latitude Cyclones 329
The Necessary Ingredients for a Developing Mid-Latitude
Cyclone 330
Upper-Air Support 330
The Role of the Jet Stream 331
FOCUS ON A SPECIAL TOPIC 12.3
Jet Streaks and Storms 332
Conveyor Belt Model of Mid-Latitude Cyclones 333
A Developing Mid-Latitude Cyclone—The March
Storm of 1993 334
Vorticity, Divergence, and Developing Mid-Latitude
Cyclones 337
FOCUS ON A SPECIAL TOPIC 12.4
Vorticity and Longwaves 339
Vorticity Advection and Shortwaves 340
Putting It All Together—A Monstrous Snowstorm 341
Polar Lows 342
Summary 343
Key Terms 343
Questions for Review 343
Questions for Thought 344
Problems and Exercises 344
CHaPter 13
Weather Forecasting 347
Weather Observations 348
Surface and Upper-Air Data 348
Satellite Products 348
Doppler Radar 348
FOCUS ON A SPECIAL TOPIC 13.1
The Forecast Funnel 349
Acquisition of Weather Information 350
Weather Forecasting Tools 350
FOCUS ON A SPECIAL TOPIC 13.2
The Forecast in Words and Pictures 351
Forecast Production 352
Time Range of Forecasts 353
FOCUS ON A SPECIAL TOPIC 13.3
The Thickness Chart—A Forecasting Tool 354
Forecasting Techniques 355
FOCUS ON AN OBSERVATION 13.4
TV Weathercasters—How Do They Do It? 356
The Computer and Weather Forecasting: Numerical
Weather Prediction 358
Why Forecasts Go Awry and Steps to Improve
Them 360
Accuracy and Skill in Forecasting 363
FOCUS ON SOCIAL AND ECONOMIC IMPACTS 13.5
Weather Prediction and the Marketplace 364
Predicting the Weather from Local Signs 366
Weather Forecasting Using Surface Charts 366
FOCUS ON AN OBSERVATION 13.6
Forecasting Temperature Advection by
Watching the Clouds 368
Determining the Movement of Weather Systems 369
A Forecast for Six Cities 370
A Meteorologist Makes a Prediction 373
Help from the 500-mb Chart 374
The Models Provide Assistance 375
A Valid Forecast 376
Satellite and Upper-Air Assistance 376
A Day of Rain and Wind 377
Summary 379
Key Terms 379
Questions for Review 379
Questions for Thought 380
Problems and Exercises 380
CHaPter 14
Thunderstorms 383
Thunderstorm Types 384
Ordinary Cell Thunderstorms 385
Multicell Thunderstorms 387
Supercell Thunderstorms 394
Thunderstorms and the Dryline 398
Thunderstorms and Flooding 399
FOCUS ON A SPECIAL TOPIC 14.1
The Terrifying Flash Flood in the Big Thompson Canyon 400
Distribution of Thunderstorms 401
Lightning and Thunder 403
How Far Away Is the Lightning?— Start Counting 403
Electrification of Clouds 404
FOCUS ON AN OBSERVATION 14.2
ELVES in the Atmosphere 405
The Lightning Stroke 405
Lightning Detection and Suppression 408
FOCUS ON AN OBSERVATION. 14.3
Don’t Sit Under the Apple Tree 409
Summary 411
Key Terms 411
Questions for Review 411
Questions for Thought 412
Problems and Exercises 412
CHaPter 15
Tornadoes 415
Tornadoes: A Few Facts 416
Tornado Life Cycle 416
Tornado Occurrence and Distribution 417
Tornado Winds 419
FOCUS ON A SPECIAL TOPIC 15.1
The Evolution of Tornado Watches and Warnings 422
Tornado Outbreaks 423
Tornado Formation 424
Supercell Tornadoes 424
FOCUS ON A SPECIAL TOPIC 15.2
Forecasting Severe Thunderstorms and Tornadoes 428
Nonsupercell Tornadoes 429
Waterspouts 431
Observing Tornadoes and Severe Weather 432
Storm Chasing and Field Research 434
Summary 436
Key Terms 436
Questions for Review 436
Questions for Thought 436
Problems and Exercises 437
CHaPter 16
Hurricanes 439
Tropical Weather 440
Anatomy of a Hurricane 440
Hurricane Formation and Dissipation 443
The Right Environment 443
The Developing Storm 444
The Storm Dies Out 445
Hurricane Stages of Development 445
Investigating the Storm 446
Hurricane Movement 447
FOCUS ON A SPECIAL TOPIC 16.1
How Do Hurricanes Compare with
Middle-Latitude Cyclones? 448
Naming Hurricanes and Tropical Storms 450
Devastating Winds, the Storm Surge, and Flooding 452
Classifying Hurricane Strength 453
FOCUS ON A SPECIAL TOPIC 16.2
Devastating Tropical Storms 454
Hurricane Spawned Tornadoes 455
Hurricane Fatalities 456
Some Notable Hurricanes 456
Galveston, 1900 456
New England, 1938 456
Camille, 1969 457
Hugo, 1989 457
Andrew, 1992 457
Ivan, 2004 458
Katrina and Rita, 2005 459
FOCUS ON AN OBSERVATION 16.3
The Record-Setting Atlantic Hurricane Seasons
of 2004 and 2005 460
Sandy, 2012 461
Devastating Tropical Cyclones Around the World 462
Hurricane Watches and Warnings 464
FOCUS ON AN ENVIRONMENTAL ISSUE 16.4
Hurricanes in a Warmer World 465
Hurricane Forecasting Techniques 466
Modifying Hurricanes 467
Summary 468
Key Terms 468
Questions for Review 468
Questions for Thought 469
Problems and Exercises 469
CHaPter 17
Global Climate 471
A World with Many Climates 472
Global Temperatures 472
Global Precipitation 473
FOCUS ON A SPECIAL TOPIC 17.1
Precipitation Extremes 476
Climatic Classification 477
The Ancient Greeks 477
The Köppen System 477
Thornthwaite’s System 477
The Global Pattern of Climate 478
Tropical Moist Climates (Group A) 478
Dry Climates (Group B) 484
Moist Subtropical Mid-Latitude Climates
(Group C) 486
FOCUS ON AN OBSERVATION 17.2
A Desert with Clouds and Drizzle 487
FOCUS ON A SPECIAL TOPIC 17.3
When Does a Dry Spell Become a Drought? 490
Moist Continental Climates (Group D) 490
Polar Climates (Group E) 493
FOCUS ON AN ENVIRONMENTAL ISSUE 17.4
Are Plant Hardiness Zones Shifiting Northward? 496
Highland Climates (Group H) 497
Summary 498
Key Terms 498
Questions for Review 498
Questions for Thought 499
Problems and Exercises 499
CHaPter 18
Earth’s Changing Climate 501
Reconstructing Past Climates 502
Climate Throughout the Ages 504
Temperature Trends during the Past 1000 Years 505
FOCUS ON A SPECIAL TOPIC 18.1
The Ocean’s Influence on Rapid Climate Change 506
Temperature Trends during the Past 100-Plus
Years 507
Climate Change Caused by Natural Events 508
Climate Change: Feedback Mechanisms 508
Climate Change: Plate Tectonics, and
Mountain Building 509
Climate Change: Variations in Earth’s Orbit 511
Climate Change: Variations in Solar Output 514
Climate Change: Atmospheric Particles 514
Climate Change Caused by Human (Anthropogenic)
Activities 516
Climate Change: Aerosols Injected into the Lower
Atmosphere 516
Climate Change: Greenhouse Gases 517
Climate Change: Land Use Changes 517
FOCUS ON AN ENVIRONMENTAL ISSUE 18.2
Nuclear Winter, Cold Summers, and Dead Dinosaurs 518
Climate Change: Global Warming 519
Recent Global Warming: Perspective 519
FOCUS ON A SPECIAL TOPIC 18.3
The Sahel—An Example of Climatic Variability and Human
Existence 520
FOCUS ON AN ENVIRONMENTAL ISSUE 18.4
The Extremes of 2011 and 2012: Did Climate Change Play a
Role? 521
Future Climate Change: Projections 522
FOCUS ON A SPECIAL TOPIC 18.5
Climate Models —A Quick Glance 524
Consequences of Climate Change: The
Possibilities 527
FOCUS ON AN ENVIRONMENTAL ISSUE 18.6
Ozone and the Ozone Hole: Their Influence on Climate
Change 527
Climate Change: Efforts to Curb 530
Summary 532
Key Terms 532
Questions for Review 532
Questions for Thought 533
Problems and Exercises 533
CHaPter 19
Air Pollution 535
A Brief History of Air Pollution 536
Types and Sources of Air Pollutants 537
FOCUS ON AN ENVIRONMENTAL ISSUE 19.1
Indoor Air Pollution 538
Principal Air Pollutants 540
Ozone in the Troposphere 542
Ozone in the Stratosphere 543
FOCUS ON AN ENVIRONMENTAL ISSUE 19.2
The Ozone Hole 546
Air Pollution: Trends and Patterns 547
Factors That Affect Air Pollution 550
The Role of the Wind 550
The Role of Stability and Inversions 550
FOCUS ON SPECIAL TOPIC 19.3
Smokestack Plumes 553
The Role of Topography 554
Severe Air Pollution Potential 554
FOCUS ON AN OBSERVATION 19.4
Five Days in Donora—An Air Pollution Episode 556
Air Pollution and the Urban Environment 556
FOCUS ON SOCIAL AND ECONOMIC IMPACT 19.5
Heat Waves and Air Pollution: A Deadly Team 558
Acid Deposition 559
Summary 561
Key Terms 561
Questions for Review 561
Questions for Thought 562
Problems and Exercises 562
CHaPter 20
Light, Color, and Atmospheric
Optics 565
White and Colors 566
Scattered Light 566
Blue Skies and Hazy Days 566
White Clouds and Dark Bases 567
Crepuscular and Anticrepuscular Rays 569
Red Suns and Blue Moons 569
Twinkling, Twilight, and the Green Flash 571
The Mirage: Seeing Is Not Believing 573
FOCUS ON AN OBSERVATION 20.1
The Fata Morgana 575
Halos, Sundogs, and Sun Pillars 575
Rainbows 578
Coronas, Glories, and Heiligenschein 581
FOCUS ON AN OBSERVATION 20.2
Can It Be a Rainbow If It Is Not Raining? 581
Summary 584
Key Terms 584
Questions for Review 584
Questions for Thought 585
Problems and Exercises 585
aPPeNdIX a
Units, Conversions, Abbreviations, and Equations A-1
aPPeNdIX B
Weather Symbols and the Station Model A-4
aPPeNdIX C
Global Average Annual Precipitation A-6
Glossary G-1
Additional Reading Material R-1
Index I-1
Condensation: Dew, Fog,
and Clouds 115
The Formation of Dew and Frost 116
Condensation Nuclei 117
Haze 117
Fog 118
Radiation Fog 119
Advection Fog 120
FOCUS ON AN OBSERVATION 5.1
Why Are Headlands Usually Foggier Than Beaches? 121
Upslope Fog 122
Evaporation (Mixing) Fog 122
Foggy Weather 123
FOCUS ON A SPECIAL TOPIC 5.2
Fog That Forms by Mixing 124
FOCUS ON AN ENVIRONMENTAL ISSUE 5.3
Fog Dispersal 126
Clouds 127
Classification of Clouds 127
Cloud Identification 127
Some Unusual Clouds 132
Cloud Observations 135
Satellite Observations 135
FOCUS ON AN OBSERVATION 5.4
Measuring Cloud Ceilings 137
FOCUS ON A SPECIAL TOPIC 5.5
Satellites Do More Than Observe Clouds 141
Summary 142
Key Terms 142
Questions for Review 142
Questions for Thought 143
Problems and Exercises 143
CHaPter 6
Stability and Cloud Development 145
Atmospheric Stability 146
Determining Stability 147
A Stable Atmosphere 147
An Unstable Atmosphere 149
A Conditionally Unstable Atmosphere 151
Causes of Instability 151
FOCUS ON A SPECIAL TOPIC 6.1
Subsidence Inversions—Put a Lid on It 152
Cloud Development 154
Convection and Clouds 154
FOCUS ON A SPECIAL TOPIC 6.2
Atmospheric Stability and Windy Afternoons —
Hold On to Your Hat 155
FOCUS ON AN OBSERVATION 6.3
Determining Convective Cloud Bases 159
Topography and Clouds 159
Clouds That Form Downwind of Mountains 161
FOCUS ON AN ADVANCED TOPIC 6.4
Adiabatic Charts 162
Changing Cloud Forms 162
Summary 166
Key Terms 166
Questions for Review 166
Questions for Thought 166
Problems and Exercises 167
CHaPter 7
Precipitation 169
Precipitation Processes 170
How Do Cloud Droplets Grow Larger? 170
Collision and Coalescence Process 171
Ice-Crystal (Bergeron) Process 173
FOCUS ON A SPECIAL TOPIC 7.1
The Freezing of Tiny Cloud Droplets 174
Cloud Seeding and Precipitation 176
Precipitation in Clouds 178
FOCUS ON AN ENVIRONMENTAL ISSUE 7.2
Does Cloud Seeding Enhance Precipitation? 178
Precipitation Types 179
Rain 179
Snow 180
FOCUS ON A SPECIAL TOPIC 7.3
Are Raindrops Tear-Shaped? 181
FOCUS ON A SPECIAL TOPIC 7.4
Snowing When the Air Temperature Is Well Above Freezing 182
Sleet and Freezing Rain 185
FOCUS ON A SPECIAL TOPIC 7.5
Sounds and Snowfalls 185
FOCUS ON AN OBSERVATION 7.6
Aircraft Icing 187
Snow Grains and Snow Pellets 188
Hail 188
Measuring Precipitation 191
Instruments 191
Doppler Radar and Precipitation 192
Measuring Precipitation from Space 193
Summary 195
Key Terms 195
Questions for Review 195
Questions for Thought 196
Problems and Exercises 196
CHaPter 8
Air Pressure and Winds 199
Atmospheric Pressure 200
Horizontal Pressure Variations—A Tale of Two
Cities 200
Daily Pressure Variations 201
Pressure Measurements 202
FOCUS ON A SPECIAL TOPIC 8.1
The Atmosphere Obeys the Gas Law 204
Pressure Readings 205
Surface and Upper-Level Charts 206
FOCUS ON AN OBSERVATION 8.2
Flying on a Constant Pressure Surface—High to Low, Look Out
Below 209
Newton’s Laws of Motion 210
Forces That Influence the Winds 211
Pressure Gradient Force 211
Coriolis Force 211
Straight-Line Flow Aloft—Geostrophic Winds 214
FOCUS ON AN ADVANCED TOPIC 8.3
A Mathematical Look at the Geostrophic Wind 216
Curved Winds Around Lows and Highs Aloft—
Gradient Winds 216
FOCUS ON AN OBSERVATION 8.4
Estimating Wind Direction and Pressure Patterns Aloft by
Watching Clouds 218
Winds on Upper-Level Charts 218
Surface Winds 220
FOCUS ON AN OBSERVATION 8.5
Winds Aloft in the Southern Hemisphere 220
Winds and Vertical Air Motions 222
FOCUS ON AN ADVANCED TOPIC 8.6
The Hydrostatic Equation 224
Summary 225
Key Terms 225
Questions for Review 225
Questions for Thought 226
Problems and Exercises 226
CHaPter 9
Wind: Small-Scale and Local
Systems 229
Scales of Motion 230
Small-Scale Winds Interacting with the Environment 231
Friction and Turbulence in the Boundary Layer 231
Eddies—Big and Small 233
The Strong Force of the Wind 234
Wind and Soil 234
FOCUS ON AN OBSERVATION 9.1
Eddies and “Air Pockets” 235
Wind and Snow 236
Wind and Vegetation 237
Wind and Water 238
Local Wind Systems 239
FOCUS ON A SPECIAL TOPIC 9.2
Pedaling into the Wind 240
Thermal Circulations 240
Sea and Land Breezes 241
Mountain and Valley Breezes 243
Katabatic Winds 244
Chinook (Foehn) Winds 245
FOCUS ON A SPECIAL TOPIC 9.3
Snow Eaters and Rapid Temperature Changes 246
Santa Ana Winds 246
Desert Winds 249
Seasonally Changing Winds—The Monsoon 251
Determining Wind Direction and Speed 254
The Influence of Prevailing Winds 255
Wind Measurements 257
FOCUS ON A SPECIAL TOPIC 9.4
Wind Energy 257
Summary 260
Key Terms 260
Questions for Review 260
Questions for Thought 261
Problems and Exercises 262
CHaPter 10
Wind: Global Systems 265
General Circulation of the Atmosphere 266
Single-Cell Model 266
Three-Cell Model 267
Average Surface Winds and Pressure:
The Real World 269
The General Circulation and Precipitation Patterns 271
Average Wind Flow and Pressure Patterns Aloft 272
FOCUS ON AN OBSERVATION 10.1
The “Dishpan” Experiment 274
Jet Streams 274
The Formation of Jet Streams 276
Other Jet Streams 277
Atmosphere-Ocean Interactions 278
Global Wind Patterns and Surface Ocean Currents 278
Upwelling 280
El Niño, La Niña, and the Southern Oscillation 281
Pacific Decadal Oscillation 286
FOCUS ON A SPECIAL TOPIC 10.2
The Challenge of Predicting El Niño and La Niña 287
North Atlantic Oscillation and Arctic Oscillation 289
Summary 291
Key Terms 291
Questions for Review 291
Questions for Thought 292
Problems and Exercises 292
CHaPter 11
Air Masses and Fronts 295
Air Masses 296
Source Regions 296
Classification 296
Air Masses of North America 297
FOCUS ON A SPECIAL TOPIC 11.1
Lake-Effect (Enhanced) Snows 299
FOCUS ON A SPECIAL TOPIC 11.2
The Return of the Siberian Express 302
Fronts 306
Stationary Fronts 307
Cold Fronts 307
Warm Fronts 311
Drylines 313
FOCUS ON A SPECIAL TOPIC 11.3
The Wavy Warm Front 314
Occluded Fronts 315
Upper-Air Fronts 316
Summary 318
Key Terms 318
Questions for Review 318
Questions for Thought 319
Problems and Exercises 319
CHaPter 12
Middle-Latitude Cyclones 321
Polar Front Theory 322
Where Do Mid-Latitude Cyclones Tend to Form? 325
FOCUS ON A SPECIAL TOPIC 12.1
Nor’easters 326
Vertical Structure of Deep Dynamic Lows 326
The Roles of Converging and Diverging Air 327
FOCUS ON A SPECIAL TOPIC 12.2
A Closer Look at Convergence and Divergence 328
Upper-Level Waves and Mid-Latitude Cyclones 329
The Necessary Ingredients for a Developing Mid-Latitude
Cyclone 330
Upper-Air Support 330
The Role of the Jet Stream 331
FOCUS ON A SPECIAL TOPIC 12.3
Jet Streaks and Storms 332
Conveyor Belt Model of Mid-Latitude Cyclones 333
A Developing Mid-Latitude Cyclone—The March
Storm of 1993 334
Vorticity, Divergence, and Developing Mid-Latitude
Cyclones 337
FOCUS ON A SPECIAL TOPIC 12.4
Vorticity and Longwaves 339
Vorticity Advection and Shortwaves 340
Putting It All Together—A Monstrous Snowstorm 341
Polar Lows 342
Summary 343
Key Terms 343
Questions for Review 343
Questions for Thought 344
Problems and Exercises 344
CHaPter 13
Weather Forecasting 347
Weather Observations 348
Surface and Upper-Air Data 348
Satellite Products 348
Doppler Radar 348
FOCUS ON A SPECIAL TOPIC 13.1
The Forecast Funnel 349
Acquisition of Weather Information 350
Weather Forecasting Tools 350
FOCUS ON A SPECIAL TOPIC 13.2
The Forecast in Words and Pictures 351
Forecast Production 352
Time Range of Forecasts 353
FOCUS ON A SPECIAL TOPIC 13.3
The Thickness Chart—A Forecasting Tool 354
Forecasting Techniques 355
FOCUS ON AN OBSERVATION 13.4
TV Weathercasters—How Do They Do It? 356
The Computer and Weather Forecasting: Numerical
Weather Prediction 358
Why Forecasts Go Awry and Steps to Improve
Them 360
Accuracy and Skill in Forecasting 363
FOCUS ON SOCIAL AND ECONOMIC IMPACTS 13.5
Weather Prediction and the Marketplace 364
Predicting the Weather from Local Signs 366
Weather Forecasting Using Surface Charts 366
FOCUS ON AN OBSERVATION 13.6
Forecasting Temperature Advection by
Watching the Clouds 368
Determining the Movement of Weather Systems 369
A Forecast for Six Cities 370
A Meteorologist Makes a Prediction 373
Help from the 500-mb Chart 374
The Models Provide Assistance 375
A Valid Forecast 376
Satellite and Upper-Air Assistance 376
A Day of Rain and Wind 377
Summary 379
Key Terms 379
Questions for Review 379
Questions for Thought 380
Problems and Exercises 380
CHaPter 14
Thunderstorms 383
Thunderstorm Types 384
Ordinary Cell Thunderstorms 385
Multicell Thunderstorms 387
Supercell Thunderstorms 394
Thunderstorms and the Dryline 398
Thunderstorms and Flooding 399
FOCUS ON A SPECIAL TOPIC 14.1
The Terrifying Flash Flood in the Big Thompson Canyon 400
Distribution of Thunderstorms 401
Lightning and Thunder 403
How Far Away Is the Lightning?— Start Counting 403
Electrification of Clouds 404
FOCUS ON AN OBSERVATION 14.2
ELVES in the Atmosphere 405
The Lightning Stroke 405
Lightning Detection and Suppression 408
FOCUS ON AN OBSERVATION. 14.3
Don’t Sit Under the Apple Tree 409
Summary 411
Key Terms 411
Questions for Review 411
Questions for Thought 412
Problems and Exercises 412
CHaPter 15
Tornadoes 415
Tornadoes: A Few Facts 416
Tornado Life Cycle 416
Tornado Occurrence and Distribution 417
Tornado Winds 419
FOCUS ON A SPECIAL TOPIC 15.1
The Evolution of Tornado Watches and Warnings 422
Tornado Outbreaks 423
Tornado Formation 424
Supercell Tornadoes 424
FOCUS ON A SPECIAL TOPIC 15.2
Forecasting Severe Thunderstorms and Tornadoes 428
Nonsupercell Tornadoes 429
Waterspouts 431
Observing Tornadoes and Severe Weather 432
Storm Chasing and Field Research 434
Summary 436
Key Terms 436
Questions for Review 436
Questions for Thought 436
Problems and Exercises 437
CHaPter 16
Hurricanes 439
Tropical Weather 440
Anatomy of a Hurricane 440
Hurricane Formation and Dissipation 443
The Right Environment 443
The Developing Storm 444
The Storm Dies Out 445
Hurricane Stages of Development 445
Investigating the Storm 446
Hurricane Movement 447
FOCUS ON A SPECIAL TOPIC 16.1
How Do Hurricanes Compare with
Middle-Latitude Cyclones? 448
Naming Hurricanes and Tropical Storms 450
Devastating Winds, the Storm Surge, and Flooding 452
Classifying Hurricane Strength 453
FOCUS ON A SPECIAL TOPIC 16.2
Devastating Tropical Storms 454
Hurricane Spawned Tornadoes 455
Hurricane Fatalities 456
Some Notable Hurricanes 456
Galveston, 1900 456
New England, 1938 456
Camille, 1969 457
Hugo, 1989 457
Andrew, 1992 457
Ivan, 2004 458
Katrina and Rita, 2005 459
FOCUS ON AN OBSERVATION 16.3
The Record-Setting Atlantic Hurricane Seasons
of 2004 and 2005 460
Sandy, 2012 461
Devastating Tropical Cyclones Around the World 462
Hurricane Watches and Warnings 464
FOCUS ON AN ENVIRONMENTAL ISSUE 16.4
Hurricanes in a Warmer World 465
Hurricane Forecasting Techniques 466
Modifying Hurricanes 467
Summary 468
Key Terms 468
Questions for Review 468
Questions for Thought 469
Problems and Exercises 469
CHaPter 17
Global Climate 471
A World with Many Climates 472
Global Temperatures 472
Global Precipitation 473
FOCUS ON A SPECIAL TOPIC 17.1
Precipitation Extremes 476
Climatic Classification 477
The Ancient Greeks 477
The Köppen System 477
Thornthwaite’s System 477
The Global Pattern of Climate 478
Tropical Moist Climates (Group A) 478
Dry Climates (Group B) 484
Moist Subtropical Mid-Latitude Climates
(Group C) 486
FOCUS ON AN OBSERVATION 17.2
A Desert with Clouds and Drizzle 487
FOCUS ON A SPECIAL TOPIC 17.3
When Does a Dry Spell Become a Drought? 490
Moist Continental Climates (Group D) 490
Polar Climates (Group E) 493
FOCUS ON AN ENVIRONMENTAL ISSUE 17.4
Are Plant Hardiness Zones Shifiting Northward? 496
Highland Climates (Group H) 497
Summary 498
Key Terms 498
Questions for Review 498
Questions for Thought 499
Problems and Exercises 499
CHaPter 18
Earth’s Changing Climate 501
Reconstructing Past Climates 502
Climate Throughout the Ages 504
Temperature Trends during the Past 1000 Years 505
FOCUS ON A SPECIAL TOPIC 18.1
The Ocean’s Influence on Rapid Climate Change 506
Temperature Trends during the Past 100-Plus
Years 507
Climate Change Caused by Natural Events 508
Climate Change: Feedback Mechanisms 508
Climate Change: Plate Tectonics, and
Mountain Building 509
Climate Change: Variations in Earth’s Orbit 511
Climate Change: Variations in Solar Output 514
Climate Change: Atmospheric Particles 514
Climate Change Caused by Human (Anthropogenic)
Activities 516
Climate Change: Aerosols Injected into the Lower
Atmosphere 516
Climate Change: Greenhouse Gases 517
Climate Change: Land Use Changes 517
FOCUS ON AN ENVIRONMENTAL ISSUE 18.2
Nuclear Winter, Cold Summers, and Dead Dinosaurs 518
Climate Change: Global Warming 519
Recent Global Warming: Perspective 519
FOCUS ON A SPECIAL TOPIC 18.3
The Sahel—An Example of Climatic Variability and Human
Existence 520
FOCUS ON AN ENVIRONMENTAL ISSUE 18.4
The Extremes of 2011 and 2012: Did Climate Change Play a
Role? 521
Future Climate Change: Projections 522
FOCUS ON A SPECIAL TOPIC 18.5
Climate Models —A Quick Glance 524
Consequences of Climate Change: The
Possibilities 527
FOCUS ON AN ENVIRONMENTAL ISSUE 18.6
Ozone and the Ozone Hole: Their Influence on Climate
Change 527
Climate Change: Efforts to Curb 530
Summary 532
Key Terms 532
Questions for Review 532
Questions for Thought 533
Problems and Exercises 533
CHaPter 19
Air Pollution 535
A Brief History of Air Pollution 536
Types and Sources of Air Pollutants 537
FOCUS ON AN ENVIRONMENTAL ISSUE 19.1
Indoor Air Pollution 538
Principal Air Pollutants 540
Ozone in the Troposphere 542
Ozone in the Stratosphere 543
FOCUS ON AN ENVIRONMENTAL ISSUE 19.2
The Ozone Hole 546
Air Pollution: Trends and Patterns 547
Factors That Affect Air Pollution 550
The Role of the Wind 550
The Role of Stability and Inversions 550
FOCUS ON SPECIAL TOPIC 19.3
Smokestack Plumes 553
The Role of Topography 554
Severe Air Pollution Potential 554
FOCUS ON AN OBSERVATION 19.4
Five Days in Donora—An Air Pollution Episode 556
Air Pollution and the Urban Environment 556
FOCUS ON SOCIAL AND ECONOMIC IMPACT 19.5
Heat Waves and Air Pollution: A Deadly Team 558
Acid Deposition 559
Summary 561
Key Terms 561
Questions for Review 561
Questions for Thought 562
Problems and Exercises 562
CHaPter 20
Light, Color, and Atmospheric
Optics 565
White and Colors 566
Scattered Light 566
Blue Skies and Hazy Days 566
White Clouds and Dark Bases 567
Crepuscular and Anticrepuscular Rays 569
Red Suns and Blue Moons 569
Twinkling, Twilight, and the Green Flash 571
The Mirage: Seeing Is Not Believing 573
FOCUS ON AN OBSERVATION 20.1
The Fata Morgana 575
Halos, Sundogs, and Sun Pillars 575
Rainbows 578
Coronas, Glories, and Heiligenschein 581
FOCUS ON AN OBSERVATION 20.2
Can It Be a Rainbow If It Is Not Raining? 581
Summary 584
Key Terms 584
Questions for Review 584
Questions for Thought 585
Problems and Exercises 585
aPPeNdIX a
Units, Conversions, Abbreviations, and Equations A-1
aPPeNdIX B
Weather Symbols and the Station Model A-4
aPPeNdIX C
Global Average Annual Precipitation A-6
Glossary G-1
Additional Reading Material R-1
Index I-1