Meteorology Today An Introduction to Weather, Climate, and the Environment

Transcription

1 Meteorology Today Seventh Edition An Introduction to Weather, Climate, and the Environment C. Donald Ahrens Modesto Junior College THOMSON * ~ BROOKS/COLE i '''''»>*> i -- -' Australia Canada Mexico Singapore Spain United Kingdom United States

2 Contentf CHAPTER 1 The Earth and Itf Atmoffhere 1 Overview of the Earth's Atmosphere 2 Composition of the Atmosphere 3 A Breath of Fresh Air 4 The Early Atmosphere 7 Vertical Structure of the Atmosphere 8 A Brief Look at Air Pressure and Air Density Layers of the Atmosphere 10 The Atmospheres of Other Planets 12 The Radiosonde 14 The Ionosphere 15 Weather and Climate 16 Meteorology A Brief History 16 A Satellite's View of the Weather 17 Storms of All Sizes 17 A Look at a Weather Map 18 Weather and Climate in Our Lives 20 Summary 23 Key Terms 24 Questions for Review 24 Questions for Thought 25 Problems and Exercises 25 Questions for Exploration 25 The Fate of a Sunbeam 33 Rising Air Cools and Sinking Air Warms 34 Radiation 35 Radiation and Temperature 36 Radiation of the Sun and Earth 36 FOCUS ON AN ENVIRONMENTAL ISSUE Wave Energy, Sun Burning, and UV Rays 38 Balancing Act Absorption, Emission, and Equilibrium Selective Absorbers and the Atmospheric Greenhouse Effect 40 Enhancement of the Greenhouse Effect 42 Warming the Air from Below 43 FOCUS ON AN ADVANCED TOPIC Radiative Equilibrium and Forcing The Ins and Outs 44 Incoming Solar Energy 45 Scattered and Reflected Light 45 The Earth's Annual Energy Balance 46 Solar Particles and the Aurora 48 Characteristics of the Sun CHAPTER 2 Energy: Warming the Earth and the Atmoffhere 26 Energy, Temperature, and Heat 28 Temperature Scales 29 Specific Heat 30 Latent Heat The Hidden Warmth 30 Heat Transfer in the Atmosphere 31 Conduction 31 Convection 32 >.- '

3 Summary 51 Key Terms 52 Questions for Review 52 Questions for Thought 52 Problems and Exercises 53 Questions for Exploration 53 CHAPTER 3 Zeafonal and Daily Temferaturef 54 Why the Earth Has Seasons 56 Seasons in the Northern Hemisphere 57 Is December 21 Really the First Day of Winter? 57 Does the First Frost Cause the Leaves to Change Color in Autumn? 60 Seasons in the Southern Hemisphere 62 Local Seasonal Variations 62 The Changing Seasons and How We Feel It Could Be SAD 63 Daily Temperature Variations 64 FOCUS ON AN ENVIRONMENTAL ISSUE Solar Heating and the Noonday Sun 65 Daytime Warming 65 Nighttime Cooling 66 Radiation Inversions 67 Protecting Crops from the Cold 68 The Controls of Temperature 70 Air Temperature Data 72 Daily, Monthly, and Yearly Temperatures 72 When It Comes to Temperature, What's Normal? 73 The Use of Temperature Data 74 Air Temperature and Human Comfort 76 A Thousand Degrees and Freezing to Death 76 Measuring Air Temperature 78 Thermometers Should Be Read in the Shade 80 Summary 81 Key Terms 81 Questions for Review 82 Questions for Thought 82 Problems and Exercises 83 Questions for Exploration 83 CHAPTER 4 Light, Color, and Atmoffheric Ofticf White'and Colors 86 White Clouds and Scattered Light 86 Blue Skies and Hazy Days 87 Red Suns and Blue Moons 88 Twinkling, Twilight, and the Green Flash 91 The Mirage: Seeing Is Not Believing 94 The Fata Morgana 95 Halos, Sundogs, and Sun Pillars 96 Rainbows 98 Can It Be a Rainbow If It Is Not Raining? Coronas, Glories, and Heiligenschein 103 Summary 105 Key Terms 106 Questions for Review 106 Questions for Thought 106 Problems and Exercises 107 Questions for Exploration CHAPTER 5 Atmoffheric Moifture 108 Water in the Atmosphere 110! The Many Phases of Water 110 Circulation of Water in the Atmosphere 112 Absolute Humidity 113 Specific Humidity and Mixing Ratio 113

4 Vapor Pressure 114 Vapor Pressure and Boiling The Higher You Go, the Longer Cooking Takes 115 Relative Humidity 116 Relative Humidity and Dew Point 117 Comparing Humidities 120 Relative Humidity in the Home 121 Computing Relative Humidity and Dew Point Relative Humidity and Human Discomfort 123 Measuring Humidity 124 N Is Humid Air or Dry Air More Dense? 126 Summary 127 Key Terms 127 Questions for Review 127 Questions for Thought 128 Problems and Exercises 128 Questions for Exploration 128 CHAPTER 6 Condensation: Pew, Fog, and Cloud} The Formation of Dew and Frost 132 Condensation Nuclei 133 Haze 133 Fog 134 Radiation Fog 135 Advection Fog 135 Why Are Headlands Usually Foggier Than Beaches? 137 Upslope Fog 138 Evaporation (Mixing) Fog 138 Fog that Forms by Mixing 139 Foggy Weather 140 FOCUS ON AN ENVIRONMENTAL ISSUE Fog Dispersal 141 Clouds 142 Classification of Clouds 142 Cloud Identification 143 High Clouds 143 Middle Clouds 144 Low Clouds 144 Clouds with Vertical Development 147 Some Unusual Clouds 151 Cloud Observations 154 Determining Sky Conditions 154 Satellite Observations Measuring Cloud Ceilings 156 Satellites Do More than Observe Clouds Summary 161 Key Terms 162 Questions for Review, 162 Questions for Thought 162 Problems and Exercises 163 Questions for Exploration 163 CHAPTER 7 Stability and Cloud Development 164 Atmospheric Stability 166 Determining Stability 167 Stable Air 167 A Stable Atmosphere 167 Unstable Air 169 Causes of Instability 170 Cloud Development 173 Convection and Clouds 173 Determining Convective Cloud Bases 177 Topography and Clouds 178 FOCUS ON AN ADVANCED TOPIC Adiabatic Charts 180 i Widespread Ascent and Clouds 182 Changing Cloud Forms 182 \ x Mixing and Stratocumulus 183 Summary 184 Key Terms

5 Questions for Review 185 Questions for Thought 185 Problems and Exercises 186 Questions for Exploration 186 CHAPTER 8 Frecijritation i88 Precipitation Processes 190 How Do Cloud Droplets Grow Larger? 190 Collision and Coalescence Process 192 Ice-Crystal Process 193 Cloud Seeding and Precipitation 196 Precipitation in Clouds 197 Does Cloud Seeding Enhance Precipitation? 198 Precipitation Types 199 Rain 199 Are Raindrops Tear-Shaped? 200 Snow 201 Snowflakes and Snowfall 201 When Is It Too Warm to Snow? 203 A Blanket of Snow 205 Sounds of Snow 205 Sleet and Freezing Rain 205 Aircraft Icing 206 Snow Grains and Snow Pellets 208 Hail 208 Measuring Precipitation 211 Instruments 211 Doppler Radar and Precipitation 212 Summary 213 Key Terms 213 Questions for Review 214 Questions for Thought 214 Problems and Exercises 215 Questions for Exploration 215 CHAPTER 9 The Atmosphere in Motion: Air Fressure, Forcef, and Winds 217 Atmospheric Pressure 218 The Atmosphere Obeys the Gas Law 220 Pressure Measurements 220 Pressure Readings 223 Surface and Upper-Level Charts 224 Flying on a Constant Pressure Surface High to Low, Look Out Below 228 Newton's Laws of Motion 228 Forces that Influence the Winds 230 Pressure Gradient Force 230 Coriolis Force 231 Straight-Line Flow Aloft Geostrophic Winds 233 FOCUS ON AN ADVANCED TOPIC A Mathematical Look at the Geostrophic Wind 235 Curved Winds Around Lows and Highs Aloft Gradient Winds 236 Estimating Wind Direction and Pressure Patterns Aloft 237 Winds on Upper-Level Charts 238 Winds Aloft in the Southern Hemisphere 239 Surface Winds 240 Winds and Vertical Air Motions 241 FOCUS ON AN ADVANCED TOPIC -- The Hydrostatic Equation 243 Summary 244 Key Terms 244 j Questions for Review 244 Questions for Thought 245 Problems and Exercises 246 Questions for Exploration 246 CHAPTER 10 Wind: Small-Scale and Local Systems 248 Small-Scale Winds Interacting with the Environment 250 Scales of Motion 250 Friction and Turbulence in the Boundary Layer 250 Eddies Big and Small 253 Eddies and "Air Pockets" 254 The Force of the Wind 255 Microscale Winds Blowing over the Earth's Surface 256 Wind and Exposed Soil 256 Wind and Snow Surfaces 257 Wind and Vegetation 257 Wind and Waves 258 Pedaling into the Wind 259 j Determining Wind Direction and Speed 259 The Influence of Prevailing Winds 260 Wind Instruments 261 Wind Power 262

6 Local Wind Systems 264 Thermal Circulations 264 Sea and Land Breezes 264 Florida's Fires and the Sea Breeze 266 Local Winds and Water 267 Seasonally Changing Winds The Monsoon 268 Mountain and Valley Breezes 270 Katabatic Winds 270 Snow Eaters and Rapid Temperature Changes 272 Chinook (Foehn) Winds 273 Santa Ana Winds 273 Desert Winds 274 Other Local Winds of Interest 276 Dust Storms on Mars 277 Summary 278 Key Terms 279 Questions for Review 279 Questions for Thought 280 Problems and Exercises 280 Questions for Exploration 281 CHAPTER 11 Wind: (flobal Systems 282 General Circulation of the Atmosphere 284 Single-Cell Model 284 Three-Cell Model 284 Average Surface Winds and Pressure: The Real World 286 Dynamic General Circulation Models 287 The General Circulation and Precipitation Patterns 290 Average Wind Flow and Pressure Patterns Aloft 291 Jet Streams 292 The "Dishpan" Experiment 294 The Formation of the Polar Front Jet. and the Subtropical Jet 295 Other Jet Streams 297 FOCUS ON AN ADVANCED TOPIC Momentum A Case of Give and Take 298 Atmosphere-Ocean Interactions 300 Global Wind Patterns and Surface Ocean Currents 300 Upwelling 301 El Nino and the Southern Oscillation 303 Other Ocean Temperature Fluctuations and Climate Patterns 307 Summary 309 Key Terms 310 Questions for Review 310 Questions for Thought 310 " Problems and Exercises 311 Questions for Exploration 311 CHAPTER 1 2 Air Masses and Fronts 312 Air Masses 314 Source Regions 314 Classification 314 Air Masses of North America 315 cp (Continental Polar) and ca (Continental Arctic) Air Masses 315 Lake Effect Snows 316 mp (Maritime Polar) Air Masses 319 The Return of the Siberian Express 320 mt (Maritime Tropical) Air Masses 320 ct (Continental Tropical) Air Masses 322 Fronts 324 Stationary Fronts 324 Cold-Fronts 325 Warm Fronts 329 Occluded Fronts- 331 Drylines 332 Upper Air Fronts 335 Summary 335 Key Terms 335 Questions for Review 336 Questions for Thought 336 Problems and Exercises 337 Questions for Exploration 337

7 CHAPTER 13 Middle-Latitude Cyclones 338 Polar Front Theory 340 Where Do Mid-Latitude Storms Tend to Form? 341 Vertical Structure of Deep-Pressure Systems 342 Northeasters 343 A Closer Look at Convergence and Divergence 345 Upper-Level Waves and Surface Storms 346 The Necessary Ingredients for a Developing Wave Cyclone 348 Upper-Air Support 348 The Role of the Jet Stream 349 Jet Streaks and Storms 350 The Conveyor Belt Model of Rising and Descending Air 351 A Developing Wave-Cyclone The March Storm of Polar Lows 355 Vorticity, Divergence, and Developing Storm Systems 356 Vorticity and Longwaves 359 Summary 362 Key Terms 362 Questions for Review 362 Questions for Thought 362 Problems and Exercises 363 Questions for Exploration 363 CHAPTER 14 Weather Forecasting 364 Acquisition of Weather Information 366 Watches, Warnings, and Advisories 367 Weather Forecasting Methods 368 The Computer and Weather Forecasting: Numerical Weather Prediction 368 Forecasting Tools 368 Why Forecasts Go Awry and Steps to Improve Them 371 Other Forecasting Methods 373 Types of Forecasts 375 Accuracy and Skill in Forecasting 375 Predicting the Weather from Local Signs 377 Weather Forecasting Using Surface Charts 379 Determining the Movement of Weather Systems 379 A Forecast for Six Cities 381 Forecasting Temperature Advection by Watching the Clouds 382 \ Weather Forecast for Augusta, Georgia 382 Rain or Snow for Washington, D.C.? 384 Big Snowstorm for Chicago 384 Mixed Bag of Weather for Memphis 385 Cold Wave for Dallas 385 Clear but Cold for Denver 385 ' A Meteorologist Makes a Prediction 386 Help from the 500-mb Chart 387 The Computer Provides Assistance 388 A Valid Forecast 388 Assistance from the Satellite 390 A Day of Rain arid Wind 391 Summary 392 Key Terms 393 Questions for Review 393 Questions for Thought 394 Problems and Exercises 394 Questions for Exploration 394, CHAPTER 1 5 Thunderstorms and Tornadoes 396 Thunderstorms 398 Ordinary Thunderstorms 398 Severe Thunderstorms 400 The Gust Front and Microburst 402 j Mesoscale Convective Systems 404 Squall Lines 405 Mesoscale Convective Complexes (MCCs) 406

8 Dryline Thunderstorms 407 Thunderstorm Movement 408 Floods and Flash Floods 408 The Terrifying Flash Flood in the Big Thorripson Canyon 409 Distribution of Thunderstorms 410 Lightning and Thunder 412 Electrification of Clouds 413 The Lightning Stroke 414 Red Sprites and Blue Jets 414 Lightning Detection and Suppression 417 Don't Sit Under the Apple Tree 417 Tornadoes 419 Tornado Occurrence 419 Tornado Winds 421 Seeking Shelter All The Fujita Scale 411 Tornadic Thunderstorms 423 Favorable Atmospheric Conditions 424 Supercell Tornadoes 425 Nonsupercell Tornadoes 428 Severe Weather and Doppler Radar 430 Waterspouts 431 Summary 433 Key Terms 433 Questions for Review 433 Questions for Thought 434 Problems and Exercises 434 Questions for Exploration 434 CHAPTER 16 Hurricanes 436 Tropical Weather 438 Anatomy of a Hurricane 438 Hurricane Formation and Dissipation 440 Hurricane Stages of Development 443 Hurricane Movement 444 Destruction and Warning 446 How Do Hurricanes Compare with Middle Latitude Storms? 447 A Tropical Storm Named Allison 450 Modifying Hurricanes 455 Naming Hurricanes 456 Summary 457 Key Terms 457 Questions for Review 457 Questions for Thought 458 Problems and Exercises 458 Questions for Exploration 458 CHAPTER 17 AirFollution 4<so A Brief History of Air Pollution 462 Types and Sources of Air Pollutants 463 Principal Air Pollutants 463 Ozone in the Troposphere 467 Ozone in the Stratosphere 468 Stratospheric Ozone: Production-Destruction 469 Stratospheric Ozone Upsetting the Balance 469~ FOCUS ON AN ENVIRONMENTAL ISSUE The Ozone Hole 471 Air Pollution: Trends and Patterns 472 FOCUS ON AN ENVIRONMENTAL ISSUE Indoor Air Pollution 475 Factors That Affect Air Pollution 476 The Role of the Wind 476 The Role of Stability and Inversions 476 The Role of Topography 478 Smoke-Stack Plumes 479, Severe Air Pollution Potential 480 Air Pollution and the Urban Environment 480 Five Days in Donora An Air Pollution Episode 481

9 Acid Deposition 483 Summary 485 Key Terms 485 Questions for Review 485 Questions for Thought 486 Problems and Exercises 486 Questions for Exploration 487 CHAPTER 18 global Climate 488 A World with Many Climates 490 Global Temperatures 490 The Hottest and Coldest Places on Earth Global Precipitation 492 Climatic Classification 495 The Ancient Greeks 495 The Koppen System 495 Precipitation Extremes 496 Thornthwaite's System 496 The Global Pattern of Climate" 497 Tropical Moist Climates (Group A) 500 Dry Climates (Group B) 502 Moist Subtropical Mid-Latitude Climates (Group C) A Desert with Clouds and Drizzle 507 Moist Continental Climates (Group D) 509 Polar Climates (Group E) 513 Highland Climates (Group H) 515 Summary 516 Key Terms 516 Questions for Review 516 Questions for Thought 516 Problems and Exercises 517 Questions for Exploration 517 CHAPTER 19 Climate Change sis The Earth's Changing Climate 520 Determining Past Climates 520 Climate Through the Ages 522 Climate During the Last 1000 Years The Ocean Conveyor Belt and Climate Change 524, Possible Causes of Climatic Change 526 Climate Change and Feedback Mechanisms 527 i Climate Change, Plate Tectonics, and Mountain Building 527 Climate Change and Variations in the Earth's Orbit 529 Climate Change and Atmospheric Particles 531 Aerosols in the Troposphere 531 Volcanic Eruptions and Aerosols in the Stratosphere 532 Nuclear Winter Climate Change Induced by Nuclear War 533 Climate Change and Variations in Solar Output 534 Global Warming 536 The Recent Warming 536 Radiative Forcing Agents 536 Climate Models and Recent Temperature Trends 536 Future Warming Projections, Questions and Uncertainties 537 Possible Consequences of Global Warming 539 The Sahel An Example of Climatic Variability and Human Existence 540 In Perspective 542 Summary 543 Key Terms 543 \ Questions for Review 543 Questions for Thought 544 Problems and Exercises 544 Questions for Exploration 544

10 APPENDIX A Units, Conversions, Abbreviations, and Equations APPENDIX B Weather Symbols and the Station Model A-4 APPENDIX C Beaufort Wind Scale A-6 APPENDIX D Humidity and Dew-Point Tables A-7 APPENDIX E Instant Weather Forecast Chart A-ll APPENDIX F Changing GMT and UTC to Local Time A-12 APPENDIX G Heat Index (HI) Table A-13 A-i APPENDIX H Standard Atmosphere A-14 APPENDIX I Hurricane Tracking Chart A-15 APPENDIX J Adiabatic Chart A-16 APPENDIX K Koppen's Climatic Classification System A-17 APPENDIX L Annual Global Pattern of Precipitation A-18 Additional Reading Material Glossary G-1 Index 1-1 R-l