Essentials of Meteorology: An Invitation to the Atmosphere PDF
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2018
C. Donald Ahrens, Robert Henson
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Essentials of Meteorology: An Invitation to the Atmosphere, 8th Edition, is an introductory textbook on meteorology. The book covers various topics such as Earth's atmosphere, warming and cooling the Earth and its atmosphere, air temperature, humidity, condensation, clouds, precipitation, air pressure, winds, atmospheric circulations. It is a great resource for undergraduate students studying meteorology.
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Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-200-202 Want to turn your C into an A? Obviously, right? But the right way to go about it isn’t always so obvious. Go digital to get the grades. MindTap’s customizable study...
Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-200-202 Want to turn your C into an A? Obviously, right? But the right way to go about it isn’t always so obvious. Go digital to get the grades. MindTap’s customizable study tools and eTextbook give you everything you need all in one place. Engage with your course content, enjoy the flexibility of studying anytime and anywhere, stay connected to assignment due dates and instructor notifications with the MindTap Mobile app... and most of all…EARN BETTER GRADES. TO GET STARTED VISIT WWW.CENGAGE.COM/STUDENTS/MINDTAP Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-200-202 EIGHTH EDITION ESSENTIALS OF METEOROLOGY Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-200-202 Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-200-202 EIGHTH EDITION Essentials of Meteorology AN INVITATION TO THE ATMOSPHERE C. Donald Ahrens Robert Henson Emeritus, Modesto Junior College Australia Brazil Japan Korea Mexico Singapore Spain United Kingdom United States Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-200-202 Essentials of Meteorology © 2018, 2015, 2012 Cengage Learning An Invitation to the Atmosphere ALL RIGHTS RESERVED. No part of this work covered by the Eighth Edition copyright herein may be reproduced or distributed in any form or by any means, except as permitted by U.S. copyright law, without the C. Donald Ahrens and Robert Henson prior written permission of the copyright owner. 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Find your local representative at www.cengage.com. Cengage Learning products are represented in Canada by Nelson Education, Ltd. To learn more about Cengage Learning Solutions, visit www.cengage.com. Purchase any of our products at your local college store or at our preferred online store www.cengagebrain.com. Printed in the United States of America Print Number: 01 Print Year: 2016 Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-200-202 CONTENTS IN BRIEF CHAPTER 1 Earth’s Atmosphere 2 CHAPTER 2 Warming and Cooling Earth and its Atmosphere 26 CHAPTER 3 Air Temperature 54 CHAPTER 4 Humidity, Condensation, and Clouds 78 CHAPTER 5 Cloud Development and Precipitation 114 CHAPTER 6 Air Pressure and Winds 146 CHAPTER 7 Atmospheric Circulations 172 CHAPTER 8 Air Masses, Fronts, and Middle-Latitude Cyclones 208 CHAPTER 9 Weather Forecasting 242 CHAPTER 10 Thunderstorms and Tornadoes 272 CHAPTER 11 Hurricanes 318 CHAPTER 12 Global Climate 350 CHAPTER 13 Earth’s Changing Climate 380 CHAPTER 14 Air Pollution 414 CHAPTER 15 Light, Color, and Atmospheric Optics 442 APPENDICES A Units, Conversions, Abbreviations, and Equations 463 B Equations and Constants 466 C Weather Symbols and the Station Model 468 D Average Annual Global Precipitation 470 E Köppen’s Climatic Classification System 472 F Humidity and Dew-point Tables (Psychrometric Tables) 473 G Standard Atmosphere 477 H Beaufort Wind Scale (Over Land) 478 v Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-200-202 CONTENTS Preface xv CHAPTER 2 CHAPTER 1 Warming and Cooling Earth and Its Atmosphere 26 Earth’s Atmosphere 2 Temperature and Heat Transfer 28 The Atmosphere and the Scientific Method 4 Temperature Scales 28 Weather, Climate. and Meteorology 5 Latent Heat—The Hidden Warmth 29 Meteorology—The Study of the Atmosphere 5 Conduction 31 A Glimpse at a Weather Map 7 Convection 31 Weather and Climate in Our Lives 9 FOCUS ON A SPECIAL TOPIC 2.1 FOCUS ON A SPECIAL TOPIC 1.1 Rising Air Cools and Sinking Air Warms 32 What Is a Meteorologist? 14 Radiant Energy 33 Components of Earth’s Atmosphere 15 FOCUS ON AN ENVIRONMENTAL ISSUE 2.2 The Early Atmosphere 15 Sunburning and UV Rays 35 Composition of Today’s Atmosphere 15 Radiation—Absorption, Emission, and Equilibrium 36 Vertical Structure of the Atmosphere 19 Selective Absorbers and the Atmospheric A Brief Look at Air Pressure and Air Density 19 Greenhouse Effect 37 Layers of the Atmosphere 21 Enhancement of the Greenhouse Effect 38 FOCUS ON AN OBSERVAT RV ION 1.2 RVAT Warming the Air from Below 40 The Radiosonde 22 Shortwave Radiation Streaming from the Sun 41 Summary 24 Earth’s Annual Energy Balance 42 Key Terms 24 Why Earth Has Seasons 44 Questions for Review 24 FOCUS ON A SPECIAL TOPIC 2.3 Questions for Thought and Exploration 25 Space Weather and Its Impact on Earth 44 Seasons in the Northern Hemisphere 46 FOCUS ON A SPECIAL TOPIC 2.4 Is December 21 Really the First Day of Winter? 49 Seasons in the Southern Hemisphere 50 Local Seasonal Variations 51 Summary 52 Key Terms 52 Questions for Review 52 Questions for Thought and Exploration 53 CHAPTER 3 Air Temperature 54 Warming and Cooling Air Near the Surface 56 Daytime Warming 56 Extreme High Temperatures 57 Nighttime Cooling 59 © C. Donald Ahrens Cold Air Near the Surface 59 Protecting Crops from the Cold Night Air 60 Extreme Low Temperatures 62 vi Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-200-202 Daily Temperature Variations 63 Key Terms 111 Regional Temperature Variations 64 Questions for Review 111 FOCUS ON A SPECIAL TOPIC 3.1 Questions for Thought and Exploration 112 When It Comes to Temperature, What’s Normal? 65 Applications of Air Temperature Data 67 CHAPTER 5 Air Temperature and Human Comfort 70 FOCUS ON A SPECIAL TOPIC 3.2 Cloud Development and A Thousand Degrees and Freezing to Death 71 Precipitation 114 Measuring Air Temperature 72 Atmospheric Stability 116 FOCUS ON AN OBSERVAT RV ION 3.3 RVAT Determining Stability 117 Why Thermometers Must Be Read in the Shade 74 A Stable Atmosphere 117 Summary 76 An Unstable Atmosphere 118 Key Terms 76 A Conditionally Unstable Atmosphere 120 Questions for Review 76 Cloud Development and Stability 121 Questions for Thought and Exploration 77 Convection and Clouds 121 Topography and Clouds 123 CHAPTER 4 FOCUS ON A SPECIAL TOPIC 5.1 Atmospheric Stability and Windy Afternoons— Humidity, Condensation, Hold On to Your Hat 124 and Clouds 78 Precipitation Processes 126 Collision and Coalescence Process 126 Circulation of Water in the Atmosphere 80 Ice-Crystal Process 127 Evaporation, Condensation, and Saturation 81 Cloud Seeding and Precipitation 129 Humidity 82 Precipitation in Clouds 131 Vapor Pressure 82 Relative Humidity 83 Relative Humidity and Dew Point 85 Relative Humidity and Human Discomfort 88 FOCUS ON A SPECIAL TOPIC 4.1 Humid Air and Dry Air Do Not Weigh the Same 90 Measuring Humidity 90 Dew and Frost 91 Fog 93 Foggy Weather 96 FOCUS ON AN ENVIRONMENTAL ISSUE 4.2 Fog Dispersal 97 Clouds 98 Classification of Clouds 98 High Clouds 98 Middle Clouds 99 Low Clouds 100 Clouds with Vertical Development 102 © C. Donald Ahrens Some Unusual Clouds 103 Clouds and Satellite Imagery 106 Summary 111 CONTENTS vii Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-200-202 FOCUS ON AN ENVIRONMENTAL ISSUE 5.2 CHAPTER 6 Does Cloud Seeding Enhance Precipitation? 131 Precipitation Types 132 Air Pressure and Winds 146 Rain 132 Snow 133 Atmospheric Pressure 148 Horizontal Pressure Variations—a Tale of Two FOCUS ON A SPECIAL TOPIC 5.3 Cities 148 Are Raindrops Tear-Shaped? 134 Measuring Air Pressure 150 Sleet and Freezing Rain 136 FOCUS ON A SPECIAL TOPIC 6.1 FOCUS ON AN OBSERVAT RV ION 5.4 RVAT The Atmosphere Obeys the Gas Law 150 Aircraft Icing 138 Pressure Readings 152 Snow Grains and Snow Pellets 138 Surface and Upper-Air Charts 153 Hail 138 Why the Wind Blows 154 Measuring Precipitation 140 FOCUS ON A SPECIAL TOPIC 6.2 Instruments 140 Isobaric Maps 155 Doppler Radar and Precipitation 141 Summary 144 Newton’s Laws of Motion 155 Key Terms 144 Forces That Influence the Wind 156 Questions for Review 144 Straight-Line Flow Aloft 159 Questions for Thought and Exploration 145 FOCUS ON AN OBSERVAT RV ION 6.3 RVAT Estimating Wind Direction and Pressure Patterns Aloft by Watching Clouds 160 Curved Winds Around Lows and Highs Aloft 161 Winds On Upper-Level Charts 162 Surface Winds 163 FOCUS ON AN OBSERVAT RV ION 6.4 RVAT Winds Aloft in the Southern Hemisphere 164 Winds and Vertical Air Motions 164 Determining Wind Direction and Speed 165 The Influence of Prevailing Winds 166 Wind Instruments 167 FOCUS ON A SPECIAL TOPIC 6.5 Wind Energy 169 Summary 170 Key Terms 170 Questions for Review 170 Questions for Thought and Exploration 171 CHAPTER 7 Atmospheric Circulations 172 Scales of Atmospheric Motion 174 Eddies—Big and Small 175 © C. Donald Ahrens Local Wind Systems 176 Thermal Circulations 176 FOCUS ON AN OBSERVAT RV ION 7.1 RVAT Eddies and “Air Pockets” 177 viii CONTENTS Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-200-202 Sea and Land Breezes 178 Mid-Latitude Cyclonic Storms 229 Mountain and Valley Breezes 180 Polar Front Theory 229 Katabatic Winds 180 Where Do Mid-Latitude Cyclones Tend to Chinook (Foehn) Winds 181 Form? 231 FOCUS ON A SPECIAL TOPIC 7.2 Developing Mid-Latitude Cyclones and Snow Eaters and Rapid Temperature Changes 182 Anticyclones 232 Santa Ana Winds 182 FOCUS ON A SPECIAL TOPIC 8.3 Desert Winds 184 Nor’easters 233 Seasonally Changing Winds—The Monsoon 186 FOCUS ON A SPECIAL TOPIC 8.4 Global Winds 188 A Closer Look at Convergence and Divergence 234 General Circulation of the Atmosphere 188 Summary 239 Single-Cell Model 188 Key Terms 239 Three-Cell Model 189 Questions for Review 239 Average Surface Winds and Pressure: The Real Questions for Thought and Exploration 240 World 192 The General Circulation and Precipitation CHAPTER 9 Patterns 192 Westerly Winds and the Jet Stream 194 Atmosphere-Ocean Interactions 197 Weather Forecasting 242 Global Wind Patterns and Surface Ocean Weather Observations 244 Currents 197 Acquisition of Weather Information 244 Winds and Upwelling 198 Weather Forecasting Tools 245 El Niño , La Niña, and the Southern Oscillation 199 FOCUS ON AN OBSERVAT RV ION 9.1 RVAT Other Atmosphere-Ocean Interactions 203 TV Weathercasters—How Do They Do It? 246 Summary 206 Key Terms 206 Weather Forecasting Methods 247 Questions for Review 206 Questions for Thought and Exploration 207 CHAPTER 8 Air Masses, Fronts, and Middle-Latitude Cyclones 208 Air Masses 210 Source Regions 210 Classification 211 Air Masses of North America 212 FOCUS ON A SPECIAL TOPIC 8.1 Lake-Effect (Enhanced) Snows 213 FOCUS ON A SPECIAL TOPIC 8.2 The Return of the Siberian Express 215 Fronts 220 Stationary Fronts 221 Cold Fronts 222 Warm Fronts 224 Drylines 226 NASA Occluded Fronts 227 CONTENTS ix Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-200-202 The Computer and Weather Forecasting: Numerical Squall-Line Thunderstorms 280 Weather Prediction 247 Supercell Thuderstorms 282 Why Computer-Based Forecasts Can Go Awry and Thunderstorms and Flooding 286 Steps to Improve Them 249 Distribution of Thunderstorms 288 Other Forecasting Techniques 252 FOCUS ON A SPECIAL TOPIC 10.1 Time Range of Forecasts 255 The Terrifying Flash Flood in the Big Thompson Canyon 287 FOCUS ON A SPECIAL TOPIC 9.2 Distribution of Thunderstorms 288 Weather Prediction and The Marketplace 257 FOCUS ON AN OBSERVAT RV ION 10.2 RVAT Accuracy and Skill in Weather Forecasting 257 Thunderstorms and the Dryline 290 Weather Forecasting Using Surface Charts 259 Lightning and Thunder 290 Determing the Movement of Weather Tornadoes 296 Systems 259 FOCUS ON A SPECIAL TOPIC 10.3 A Forecast for Six Cities 259 Using Forecasting Tools to Predict the Weather 264 Don’t Sit Under the Apple Tree 297 Help from the 500-mb Chart 264 Tornado Life Cycle 297 The Models Provide Assistance 266 Tornado Occurrence and Distribution 298 A Valid Forecast 267 Tornado Winds 300 Satellite and Upper-Air Assistance 267 FOCUS ON A SPECIAL TOPIC 10.4 A Day of Rain and Wind 268 The Weird World of Tornado Damage 302 Summary 270 Key Terms 270 FOCUS ON A SPECIAL TOPIC 10.3 Questions for Review 270 The Evolution of Tornado Watches and Warnings 304 Questions for Thought and Exploration 271 Tornado Outbreaks 305 Tornado Formation 305 CHAPTER 10 Supercell Tornadoes 305 Nonsupercell Tornadoes 309 Thunderstorms and Tornadoes 272 Waterspouts 310 Observing Tornadoes and Severe Weather 311 Thunderstorms 274 Storm Chasing and Mobile Radar 314 Ordinary Cell Thunderstorms 275 Summary 315 Multicell Thunderstorms 277 Key Terms 315 Questions for Review 315 Questions for Thought and Exploration 316 CHAPTER 11 Hurricanes 318 Tropical Weather 320 Anatomy of a Hurricane 320 Hurricane Formation and Dissipation 323 The Right Environment 324 The Developing Storm 324 The Storm Dies Out 325 Hurricane Stages of Development 325 Investigating the Storm 326 © Robert Henson Hurricane Movement 327 x CONTENTS Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-200-202 FOCUS ON A SPECIAL TOPIC 11.1 Moist Subtropical Mid-Latitude Climates How Do Hurricanes Compare with Middle-Latitude (Group C) 366 Cyclones? 328 FOCUS ON AN OBSERVAT RV ION 12.2 RVAT Naming Hurricanes and Tropical Storms 331 A Desert with Clouds and Drizzle 367 Devastating Winds, the Storm Surge, and Flooding 331 Moist Continental Climates (Group D) 370 FOCUS ON A SPECIAL TOPIC 11.2 FOCUS ON A SPECIAL TOPIC 12.3 Devastation from a Tropical Storm—The —The Case of Allison 334 When Does a Dry Spell Become a Drought? 372 Classifying Hurricane Strength 334 Polar Climates (Group E) 374 Hurricane-Spawned Tornadoes 336 Highland Climates (Group H) 375 Hurricane Fatalities 336 FOCUS ON AN ENVIRONMENTAL ISSUE 12.4 Some Notable Hurricanes 337 Are Plant Hardiness Zones Shifting Northward? 376 Galveston, 1900 337 Summary 378 New England, 1938 337 Key Terms 378 Camille, 1969 337 Questions for Review 378 Hugo, 1989 337 Andrew, 1992 338 Questions for Thought and Exploration 379 Katrina and Rita, 2005 339 CHAPTER 13 FOCUS ON AN OBSERVAT RV ION 11.3 RVAT The Record-Setting Atlantic Hurricane Seasons of 2004 and 2005 340 Earth’s Changing Climate 380 Sandy, 2012 341 Reconstructing Past Climates 382 Devastating Tropical Cyclones Around the World 342 Climate Throughout the Ages 384 Hurricane Watches and Warnings 343 FOCUS ON A SPECIAL TOPIC 13.1 FOCUS ON AN ENVIRONMENTAL ISSUE 11.4 The Ocean’s Influence on Rapid Climate Change 386 Hurricanes in a Warmer World 344 Hurricane Forecasting Techniques 345 Modifying Hurricanes 347 Summary 348 Key Terms 348 Questions for Review 348 Questions for Thought and Exploration 349 CHAPTER 12 Global Climate 350 A World with Many Climates 352 Global Temperatures 352 Global Precipitation 354 FOCUS ON A SPECIAL TOPIC 12.1 Extreme Wet and Dry Regions 356 Climatic Classification—The Köppen System 357 The Global Pattern of Climate 359 © C. Conald Ahrens Tropical Moist Climates (Group A) 359 Dry Climates (Group B) 362 CONTENTS xi Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-200-202 Temperature Trends During the Past 1000 FOCUS ON AN ENVIRONMENTAL ISSUE 13.5 Years 385 The Impact of Ozone on the Greenhouse Effect and Climate Temperature Trends During the Past 100-Plus Change 406 Years 386 Consequences of Climate Change: Climate Change Caused by Natural Events 388 The Possibilties 406 Climate Change: Feedback Mechanisms 389 Climate Change: A Final Note 410 Climate Change: Plate Tectonics and Mountain Summary 411 Building 390 Key Terms 411 Climate Change: Variations in the Earth’s Questions for Review 411 Orbit 391 Questions for Thought and Exploration 412 Climate Change: Variations in Solar Output 394 Climate Change: Atmospheric Particles 394 CHAPTER 14 Climate Change Caused by Human (Anthropogenic) Activities 397 Climate Change: Greenhouse Gases 397 Air Pollution 414 FOCUS ON AN ENVIRONMENTAL ISSUE 13.2 A Brief History of Air Pollution 416 Nuclear Winter—Climate Change Induced by Nuclear Types and Sources of Air Pollutants 418 War 398 FOCUS ON AN ENVIRONMENTAL ISSUE 14.1 Climate Change: Land Use Changes 398 Indoor Air Pollution 418 Climate Change: Global Warming 399 Principal Air Pollutants 419 Recent Global Warming: Perspective 399 Ozone in the Troposphere 422 FOCUS ON AN ENVIRONMENTAL ISSUE 13.3 Ozone in the Stratosphere 422 Climate Change and Extreme Weather 400 FOCUS ON A SPECIAL TOPIC 14.2 Future Climate Change: Projections 401 The Formation of Ground-Level Ozone in Polluted Air 423 FOCUS ON A SPECIAL TOPIC 13.4 FOCUS ON AN ENVIRONMENTAL ISSUE 14.3 Climate Models—A Quick Look 404 The Ozone Hole 425 Air Pollution: Trends and Patterns 426 Factors That Affect Air Pollution 429 The Role of the Wind 429 The Role of Stability and Inversions 429 The Role of Topography 431 FOCUS ON AN OBSERVAT RV ION 14.4 RVAT Smokestack Plumes 432 Severe Air Pollution Potential 433 Air Pollution and the Urban Environment 433 FOCUS ON AN OBSERVAT RV ION 14.5 RVAT Five Days in Donora—An Air Pollution Episode 434 Acid Deposition 436 FOCUS ON AN ENVIRONMENTAL ISSUE 14.6 Heat Waves and Air Pollution: A Deadly Team 437 Summary 439 Key Terms 439 © Robert Henson Questions for Review 439 Questions for Thought and Exploration 440 xii CONTENTS Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-200-202 CHAPTER 15 APPENDIXES Light, Color, and Atmospheric A Units, Conversions, Abbreviations, and Equations 463 Optics 442 B Equations and Constants 466 White and Colors 444 C Weather Symbols and the Station Model 468 Clouds and Scattered Light 444 D Average Annual Global Precipitation 470 Blue Skies and Hazy Days 445 E Köppen’s Climatic Classification System 472 Red Suns and Blue Moons 447 F Humidity and Dew-point Tables (Psychrometric Twinkling, Twilight, and the Green Flash 449 Tables) 473 The Mirage: Seeing Is Not Believing 451 G Standard Atmosphere 477 FOCUS ON AN OBSERVAT RV ION 15.1 RVAT H Beaufort Wind Scale (Over Land) 478 The Fata Morgana 453 Additional Reading Material 479 Halos, Sundogs, and Sun Pillars 453 Glossary 481 Rainbows 456 Index 496 Coronas and Cloud Iridescence 459 FOCUS ON AN OBSERVAT RV ION 15.2 RVAT Glories and the Heiligenschein 460 Summary 461 Key Terms 461 Questions for Review 461 Questions for Thought and Exploration 462 CONTENTS xiii Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-200-202 Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-200-202 PREFACE The world is an ever-changing picture of naturally oc- Written expressly for the student, this book empha- curring events. From drought and famine to devastat- sizes the understanding and application of meteorologi- ing floods, some of the greatest challenges we face come cal principles. The text encourages watching the weather in the form of natural disasters created by weather. Yet, so that it becomes “alive,” allowing readers to immedi- dealing with weather and climate is an inevitable part ately apply textbook material to the world around them. of our lives. Sometimes it is as small as deciding what To assist with this endeavor, a color Cloud Chart ap- to wear for the day or how to plan a vacation. But it pears at the back of the text. The Cloud Chart can be can also have life-shattering consequences, especially for those who are victims of a hurricane or a tornado. separated from the book and used as a learning tool at In recent years, weather and climate have become any place one chooses to observe the sky. To strengthen front page news, from record-setting extreme weather points and clarify concepts, illustrations are rendered events to environmental issues such as global warming in full color throughout. Color photographs were care- and ozone depletion. The dynamic nature of the atmos- fully selected to illustrate features, stimulate interest, phere seems to demand our attention and understand- and show how exciting the study of weather can be. To ing more these days than ever before. Almost daily, enhance the value of the book, several appendices that there are newspaper articles describing some weather were only available online in the seventh edition have event or impending climate change. For this reason, been reincorporated. and the fact that weather influences our daily lives in Organized into fifteen chapters, Essentials of Meteo- so many ways, interest in meteorology (the study of the rology is designed to provide maximum flexibility to in- atmosphere) has been growing. This rapidly develop- structors of weather and climate courses. Thus, chap- ing and popular science is giving us more information ters can be covered in any desired order. For example, about the workings of the atmosphere than ever before. Chapter 15, “Light, Color, and Atmospheric Optics,” is One of the reasons that meteorology is such an engaging self-contained and can be covered earlier if so desired. science to study is that the atmosphere is a universally Instructors, then, are able to tailor this text to their par- accessible laboratory for everyone. Although the atmos- ticular needs. This book basically follows a traditional phere will always provide challenges for us, as research approach. After an introductory chapter on the origin, and technology advance, our ability to understand our composition, and structure of the atmosphere, it covers atmosphere improves as well. The information available solar energy, air temperature, humidity, clouds, precipi- to you in this book, therefore, is intended to aid in your tation, and winds. Then comes a chapter on air masses, own personal understanding and appreciation of our fronts, and middle-latitude cyclonic storms. Weather Earth’s dynamic atmosphere. prediction and severe storms are next. A chapter on hurricanes is followed by a chapter on global climate. A chapter on climate change is next. A chapter on air pol- About This Book lution precedes the final chapter on atmospheric optics. Essentials of Meteorology is written for students taking an Each chapter contains at least two Focus sections, introductory course on the atmospheric environment. which either expand on material in the main text or ex- The main purpose of the text is to convey meteorologi- plore a subject closely related to what is being discussed. cal concepts in a visual, practical, and nonmathematical Focus sections fall into one of three distinct categories: manner. In addition, the intent of the book is to stim- Observations, Special Topics, and Environmental Issues. ulate curiosity in the reader and to answer questions Some include material that is not always found in intro- about weather and climate that arise in our day-to-day ductory meteorology textbooks—subjects such as space lives. Although introductory in nature, this eighth edi- weather, the scientific method, and wind energy. Others tion maintains scientific integrity and includes up-to- help to bridge theory and practice. This edition contains date information on large-scale topics, such as global several new or rewritten Focus sections, including an up- warming, ozone depletion, and El Niño, as well as dis- dated discussion of nor’easters in Chapter 8 and a new cussion of recent high-profile weather events. As in pre- Focus section on tornado damage patterns in Chapter 10. vious editions, no special prerequisites are necessary for Set apart as “Did You Know?” features in each chap- understanding. ter is weather information that may not be commonly xv Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-200-202 known, yet pertains to the topic under discussion. Supplemental Material Designed to bring the reader into the text, most of these weather highlights relate to some interesting weather and Technology Support fact or astonishing event. Each chapter incorporates other effective learn- TECHNOLOGY FOR THE INSTRUCTOR ing aids: Instructor Companion Website Everything you need A major topic outline begins each chapter. for your course in one place! This collection of book- Interesting introductory pieces draw the reader natu- specific lecture and class tools is available online via rally into the main text. www.cengage.com/login. Access and download Power- Important terms are boldfaced, with their definitions Point presentations, images, instructor’s manual, vid- appearing in the glossary or in the text. eos, and more. Key phrases are italicized. Cognero Test Bank Cengage Learning Testing Pow- English equivalents of metric units are immediately ered by Cognero is a flexible, online system that allows provided in parentheses. you to: A brief review of the main points is placed toward the author, edit, and manage test bank content from mul- middle of most chapters. tiple Cengage Learning solutions Each chapter ends with a summary of the main create multiple test versions in an instant ideas. deliver tests from your LMS, your classroom, or wher- A list of key terms with page references follows each ever you want chapter, allowing students to review and reinforce their knowledge of key concepts. Global Geoscience Watch Updated several times a Questions for Review act to check how well students day, the Global Geoscience Watch is a focused portal assimilate the material. into GREENR—our Global Reference on the Environ- Questions for Thought and Exploration encourage ment, Energy, and Natural Resources—an ideal one- students to synthesize learned concepts for deeper stop site for classroom discussion and research pro- understanding. jects for all things geoscience! Broken into the four key References to 19 concept animations are compiled on course areas (Geography, Geology, Meteorology, and pp. xx-xxi. These animations convey an immediate ap- Oceanography), you can easily get to the most relevant preciation of how a process works and help students content available for your course. You and your students visualize the more difficult concepts in meteorology. will have access to the latest information from trusted Animations can be found on the Meteorology Course- academic journals, news outlets, and magazines. You Mate, accessed through Cengagebrain.com. also will receive access to statistics, primary sources, At the end of each chapter are questions that relate case studies, podcasts, and much more! to articles found on the Global Geoscience Watch TECHNOLOGY FOR THE STUDENT website, available on its own or via the Meteorology Earth Science MindTap for Essentials of Meteorology CourseMate. MindTap is well beyond an eBook, a homework solu- Eight appendices conclude the book. In addition, tion or digital supplement, a resource center website, a at the end of the book, a compilation of supplementary course delivery platform, or a Learning Management reading material is presented, as is an extensive glos- System. More than 70 percent of students surveyed said sary. On the endsheet at the back of the book is a geo- that it was unlike anything they have ever seen before. physical map of North America. The map serves as a MindTap is a new personal learning experience that quick reference for locating states, provinces, and geo- combines all of your digital assets—readings, multime- graphical features, such as mountain ranges and large dia, activities, study tools, and assessments—into a sin- bodies of water. gular learning path to improve student outcomes. xvi PREFACE Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-200-202 Lab Manual Developed by the Oklahoma Climato- recent events now included are the severe flooding logical Survey (OCS) research and service facility, in over the Southern Plains and Southeast in 2015 and concert with the University of Oklahoma, Explorations in the Houston flash flood of April 2016. Meteorology places a strong emphasis on helping students Chapter 2, “Warming and Cooling Earth and Its At- understand weather and climate by using real meteor- mosphere,” contains up-to-date statistics and back- ological data. The activities in this lab manual require ground on greenhouse gases and climate change, that students tap into the OCS archives of meteorologi- topics covered in more detail later in the book. cal data in order to complete meteorological exercises. Discussion of the potential impact of clouds on future Full-color pictures and data graphs help students visu- global warming has been updated. ally understand weather and severe weather topics. The In Chapter 3, “Air Temperature,” several figures and lab manual also challenges students by providing op- tables have been updated so that they refer to nor- tional questions intended for honors students, making mals drawn from the most recent reference period this lab manual appropriate for both introductory and (1981–2010). honors meteorology courses. Chapter 4, “Humidity, Condensation, and Clouds,” includes updated material on satellite observations, including new background and artwork from the Eighth Edition Changes Global Precipitation Mission satellite. Also included is a “Did You Know?” box on the high-impact Atlanta This edition of Essentials of Meteorology includes a snowstorm of January 2014. coauthor—meteorologist and science journalist Robert Chapter 5, “Cloud Development and Precipita- Henson (Weather Underground). For more than 20 years, tion,” includes a new graphic. New satellite observ- Henson produced publications and websites for the ing techniques are also noted and illustrated in this University Corporation for Atmospheric Research, chapter. which manages the National Center for Atmospheric Chapter 6, “Air Pressure and Winds,” includes a sub- Research. He is an expert on severe weather, includ- stantially enhanced description and revised illustra- ing tornadoes, thunderstorms, and hurricanes. He has tions of the interplay between the pressure gradient also analyzed how television weathercasters cover ma- and Coriolis forces in cyclonic and anticyclonic flow. jor storms and report on climate change. Henson is the Several other illustrations have been revised for clar- author of four trade books on meteorology, including ity, and the discussion of scatterometers has been up- The Thinking Person’s Guide to Climate Change (previously dated. A box on wind energy features the most recent The Rough Guide to Climate Change, the first edition of data on wind energy adoption. which was shortlisted for the United Kingdom’s Royal Chapter 7, “Atmospheric Circulations,” features a major Society Prize for Science Books). restructuring, update, and expansion of sections deal- The authors have carried out extensive updates and ing with the El Niño/Southern Oscillation, Pacific Dec- revisions to this eighth edition of Essentials of Meteorol- adal Oscillation, North Atlantic Oscillation, and Arctic ogy, reflecting the ever-changing nature of the field and Oscillation, including several new and updated images. the atmosphere itself. Dozens of new photos and new The opening section, which introduces scales of atmos- or revised color illustrations help students visualize the pheric motion, has also been revised for clarity. excitement of the atmosphere. Chapter 8, “Air Masses, Fronts, and Middle-Latitude Chapter 1, “Earth’s Atmosphere,” continues to serve as Cyclones,” now includes discussion of atmospheric a broad overview of the atmosphere. The text now be- rivers and an illustration of their impacts. In line gins with a discussion of the scientific method and its with recent research, the section on occluded fronts importance. To help draw students into the material, stresses the prevalence of warm-type over cold-type the introduction to meteorology and the summary occluded fronts. The discussion of drylines has been of extreme weather types has been placed earlier in expanded, and the Focus box on nor’easters has been the chapter, followed by discussion of the chemistry reworked to spotlight the record-setting East Coast and vertical structure of Earth’s atmosphere. Among snowstorm of January 2016. PREFACE xvii Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-200-202 “Weather Forecasting” (Chapter 9) has undergone that preceded it. A number of diagrams have been substantial revision, with several updated graphics. updated. Three major types of satellite imagery are introduced The chapter on “Air Pollution” (Chapter 14) has been near the beginning of the chapter. Explanations of revised to include the latest air pollution trends across watches, warnings, and forecasts of various durations the United States as well as the latest information on (including seasonal outlooks) are now incorporated ozone depletion in the Arctic and Antarctic. The U.S. in a new section, “Time Range of Forecasts.” The con- Clean Power Plan is introduced, and the devastating cept of the forecast funnel is also introduced. impacts of both indoor and outdoor air pollution are Chapter 10, “Thunderstorms and Tornadoes,” in- discussed, including the effects of tiny particulates on cludes several new and updated illustrations, depict- cardiovascular health. ing low- and high-precipitation supercells, a roll Several of the photos in Chapter 15, “Light, Color, and cloud, and a shelf cloud. An expanded section covers Atmospheric Optics,” have been replaced with spec- both flash flooding and river flooding and their con- tacular new examples (e.g., anticrepuscular rays and nection to thunderstorms, including examples from double rainbows). Colorado (2013) and Texas and Oklahoma (2015). A new Focus box explores the baffling damage patterns that tornadoes can produce. The effort to Acknowledgments accommodate new ways of estimating and reporting Many people have contributed to the eighth edition of tornado wind speed (such as mobile radar reports) Essentials of Meteorology. A very special and most grate- is also noted. ful thank-you goes to Lita Ahrens who proofread each The chapter on “Hurricanes” (Chapter 11) includes chapter. Special thank you to Charles Preppernau for a new opening section that introduces students to rendering the beautiful art and to Janet Hansen for care- the terrible impacts of Hurricane Katrina. Several ful proofreading. graphics that use satellite imagery to explain ba- We are indebted to Janet Alleyn, who not only de- sic concepts have been updated with recent tropi- signed the book but, once again, took the art, photos, cal cyclones. Charts on hurricane climatology have and manuscript and turned them into a beautiful book. been brought up to date, and an expanded range of Thanks goes to Judith Chaffin for her careful and con- both historical and recent examples are discussed, scientious editing. Special thanks to all the people at including the Galveston hurricane of 1900, the New Cengage Learning who worked on this edition, includ- England hurricane of 1938, and Typhoon Haiyan ing Lauren Oliveira, Morgan Carney, Hal Humphrey, from 2013. and Dawn Giovanniello. Chapter 12, “Global Climate,” includes a number Thanks to our friends who provided photos and to of updates to climatological charts and discussion, those reviewers who offered comments and suggestions drawing on the most recent set of United States cli- for this edition, including: mate normals (1981–2010). Chapter 13, “Earth’s Changing Climate,” has been Fidel González Rouco revised throughout to reflect increasing confidence Universidad Complutense de Madrid on a variety of climate change indicators and im- Redina Herman pacts. Also incorporated are graphics, conclusions, Western Illinois University and emission pathways from the Fifth Assessment Bette Otto-Bliesner Report (2013-14) of the Intergovernmental Panel National Center for Atmospheric Research on Climate Change. The extremely quiet solar cycle of the late 2000s and early 2010s is noted, along with David Schultz a variety of weather extremes from recent years that University of Manchester are relevant to climate change. The Paris Accord Alex Huang is discussed in the context of the Kyoto Protocol University of North Carolina at Asheville xviii PREFACE REFACE Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-200-202 Anthony Santorelli To the Student Anne Arundel Community College Learning about the atmosphere can be a fascinating Dan Ferandez and enjoyable experience. This book is intended to Anne Arundel Community College give you some insight into the workings of the atmos- Dean G Butzow phere. However, for a real appreciation of your atmos- Western Michigan University pheric environment, you must go outside and observe. Douglas K. Miller Although mountains take millions of years to form, a Purdue University cumulus cloud can develop into a raging thunderstorm Edward J. Perantoni in less than an hour. The atmosphere is always produc- Lindenwood University ing something new for us to behold. To help with your observations, a color Cloud Chart is at the back of the Ronald A Dowey book for easy reference. Remove it and keep it with you. Harrisburg Area Community College And, remember, all of the concepts and ideas in this Shaunna L. Donaher book are manifested out there for you to discover and University of Miami enjoy. Please take the time to look. Troy Kimmel Donald Ahrens and Robert Henson University of Texas PREFACE xix Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-200-202 EXP XPLORE LORE THE CONCEP CONCEPT ANIMATIONS These animations have been carefully created to bring to acquired. Concept Animations are accessed through the life key points in the chapters. They are also the perfect MindTap platform, which can be acquired separately or tool to help refresh students’ memories of previous con- together with print or looseleaf versions of this book. cepts, so they can keep building on knowledge already Some examples of Concept Animations are shown here. Doppler radar images are used extensively throughout this book. To better understand Doppler radar images, watch all 4 parts of this Doppler Radar animation (Chapters 1, 5, and 10). For a visual interpretation of the energy emitted by the earth without and with a greenhouse effect, watch the Greenhouse animation (Chapter 2). Learn about how air rises above an area of low atmospheric pres- sure and sinks above an area of high atmospheric pressure. Con- verging and Diverging Air (Chapters 1 and 8). Additional Animations: Ice Crystals (Bergeron) Process (Chapter 5) Seasons provides a complete picture of Earth revolving around General Circulation of the Atmosphere (Chapter 7) the sun while it is tilted on its axis. While viewing this animation, Geostrophic Wind (Chapter 6) look closely at how the sun is viewed by a mid-latitude observer Temperature versus Molecular Movement (Chapter 2) at various times of the year (Chapter 2). Condensation (Chapter 4) Air Temperature, Dew Point, and Relative Humidity (Chapter 4) Daily Temperature Changes Above the Surface (Chapter 3) Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-200-202 To view air rising over a mountain and the formation of a rain shadow desert, watch Air Rising Up and Over a Mountain (Chapters 5 and 7). For a visual presentation of the Coriolis force, watch Coriolis Force (Chapter 6). The concept of atmospheric stability can be a bit confusing, espe- cially when comparing the temperature inside a rising air parcel to that of its surroundings. Watch Stable Atmosphere (Chapter 5) and the two animations Unstable Atmosphere and Conditionally Unstable Atmosphere (Chapters 5 and 10). For a visualization of a cold front moving across the landscape, watch Cold Front in Winter (Chapters 8 and 9), To see a warm front actually move across the surface, watch Warm Front in Winter (Chapters 8 and 9). For a visualization of the stages that a wave cyclone goes through from birth to decay, watch the animation entitled Cyclogenesis (Chapter 8). Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-200-202 © Foto2rich/Shutterstock.com Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-200-202 CHAPTER 1 Earth’s Atmosphere Contents The Atmosphere and I remember well a brilliant red balloon which kept me com- com pletely happy for a whole afternoon, until, while I was playing, a clumsy movement allowed it to escape. Spellbound, the Scientific Method I gazed after it as it drifted silently away, gently swaying, Weather, Climate, and growing smaller and smaller until it was only a red point in a Meteorology blue sky. Att that moment I realized, for the first time, the Components of vastness above us: a huge space without visible limits. It was Earth’s Atmosphere an apparent void, full of secrets, exerting an inexplicable Vertical Structure of power over all the Earth’s inhabitants. I believe that many the Atmosphere people, consciously or unconsciously, have been filled with awe by the immensity of the atmosphere. All ll our knowledge about the air, gathered over hundreds of years, has not diminished this feeling. Theo Loebsack, Our Atmosphere 3 EARTH’S ATMOSPHERE 3 Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-200-202 O ur atmosphere is a delicate life-giving blanket of air These concepts and ideas are part of the foundation for un- that surrounds the fragile Earth. In one way or an- derstanding the atmosphere and how it produces weather. other, it influences everything we see and hear—it is They are built on knowledge acquired and applied through intimately connected to our lives. Air is with us from birth, the scientific method, which allows us to make informed and we cannot detach ourselves from its presence. In the predictions about how the natural world will behave. open air, we can travel for many thousands of kilometers in any horizontal direction, but should we move a mere eight kilometers above the surface, we would suffocate. We may be able to survive without food for a few weeks, or with- The Atmosphere and out water for a few days, but, without our atmosphere, we would not survive more than a few minutes. Just as fish are the Scientific Method confined to an environment of water, so we are confined For hundreds of years, the scientific method has served to an ocean of air. Anywhere we go, air must go with us. as the backbone for advances in medicine, biology, Earth without an atmosphere would have no lakes or engineering, and many other fields. In the field of oceans. There would be no sounds, no clouds, no red sun- atmospheric science, the scientific method has paved sets. The beautiful pageantry of the sky would be absent. It the way for the production of weather forecasts that have would be unimaginably cold at night and unbearably hot steadily improved over time. during the day. All things on Earth would be at the mercy of Investigators use the scientific method by posing a an intense sun beating down upon a planet utterly parched. question, putting forth a hypothesis,* predicting what Living on the surface of Earth, we have adapted so com- the hypothesis would imply if it were true, and carrying pletely to our environment of air that we sometimes forget out tests to see if the prediction is accurate. Many com- how truly remarkable this substance is. Even though air is mon sayings about the weather, such as “red sky at morn- tasteless, odorless, and (most of the time) invisible, it protects ing, sailor take warning; red sky at night, sailor’s delight” us from the scorching rays of the sun and provides us with (see Fig. 1.1) are rooted in careful observation, and there a mixture of gases that allows life to flourish. Because we are grains of truth in some of them. However, they are not cannot see, smell, or taste air, it may seem surprising that considered to be products of the scientific method because between your eyes and these words are trillions of air mol- they are not tested and verified in a standard rigorous way. ecules. Some of these may have been in a cloud only yesterday, To be accepted, a hypothesis has to be shown to be cor- or over another continent last week, or perhaps part of the rect through a series of quantitative tests. In many areas of life-giving breath of a person who lived hundreds of years ago. science, such testing is carried out in a laboratory, where Warmth for our planet is provided primarily by the it can be replicated again and again. Studying the atmo- sun’s energy. At an average distance from the sun of nearly sphere, however, is somewhat different, because our Earth 150 million kilometers (km), or 93 million miles (mi), has only one atmosphere. Despite this limitation, scientists Earth intercepts only a very small fraction of the sun’s have made vast progress by studying the physics and chem- total energy output. However, it is this radiant energy*that istry of air in the laboratory (for instance, studying the way drives the atmosphere into the patterns of everyday wind in which molecules absorb energy) and by extending those and weather, and allows life to flourish. understandings to the atmosphere as a whole. Observa- At its surface, Earth maintains an average tempera- tions using weather instruments allow us to quantify how ture of about 15°C (59°F).** Although this temperature the atmosphere behaves and to determine whether a pre- is mild, Earth experiences a wide range of temperatures, diction is accurate. If a particular kind of weather is being as readings can drop below 85°C ( 121°F) during a studied, such as hurricanes or snowstorms, a field study can frigid Antarctic night and climb during the day to above gather additional observations to test specific hypotheses. 50°C (122°F) on the oppressively hot, subtropical desert. Over the last fifty years, computers have given atmo- Not everyone will experience such extremes where they spheric scientists a tremendous boost. The physical laws that live, but all of us have a chance to observe the day-to-day control atmospheric behavior can be represented in software changes in the atmosphere that we refer to as weather. packages known as numerical models. Forecasts can be In this chapter, we will examine a number of made and tested many times over. The atmosphere described important concepts and ideas about Earth’s atmosphere, by a model can be used to depict weather conditions from many of which will be expanded in subsequent chapters. the past and to project them into the future. When a model can accurately simulate past weather conditions and provide *Radiant energy, or radiation, is energy transferred in the form of waves that have electrical and magnetic properties. The light that we see is radiation, as is confidence in its portrayal of tomorrow’s weather, the model ultraviolet light. More on this important topic is given in Chapter 2. can provide valuable information about the weather and **The abbreviation °C is used when measuring temperature in degrees climate we may expect decades from now. Celsius, and °F is the abbreviation for degrees Fahrenheit. More information about temperature scales is given in Appendix A and in Chapter 2. *A hypothesis is an assertion subject to verification or proof. 4 CHAPTER 1 Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-200-202 FIGURE 1.1 Observing the natural world FI is a critical part of the scientific method. Here a vibrant red sky is visible at sunset. One might use scientific method to verify the old proverb: “Red sky at morning, sailor take warning; red sky at night, sailor’s delight.” © University Corporation for Atmospheric Research, Photo by Carlye Calvin icy fingers over large portions of North America. Advanc- Weather, Climate, and Meteorology ing slowly from Canada, a single glacier might extend as far south as Kansas and Illinois, with ice several thousands of When we talk about the weather, we are talking about the meters thick covering the region now occupied by Chicago. condition of the atmosphere at any particular time and Over an interval of two million years or so, we would see place. Weather—which is always changing—is comprised the ice advance and retreat many times. Of course, for of the elements of: this phenomenon to happen, the average temperature of . air temperature—the degree of hotness or coldness of North America would have to decrease and then rise in a the air cyclic manner. . air pressure—the force of the air above an area Suppose we could photograph Earth once every . humidity—a measure of the amount of water vapor in thousand years for many hundreds of millions of years. In the air time-lapse film sequence, these photos would show that . clouds—visible masses of tiny water droplets and ice not only is the climate altering, but the whole Earth itself crystals or both that are above Earth’s surface is changing as well: Mountains would rise up only to be . precipitation—any form of water, either liquid or solid torn down by erosion; isolated puffs of smoke and steam (rain or snow), that falls from clouds and reaches the would appear as volcanoes spew hot gases and fine dust ground into the atmosphere; and the entire surface of Earth would . visibility—the greatest distance one can see undergo a gradual transformation as some ocean basins . wind—the horizontal movement of air widen and some of them shrink.* In summary, Earth and its atmosphere are dynamic If we measure and observe these weather elements systems that are constantly changing. While major trans- over a specified interval of time, say, for many years, we formations of Earth’s surface are completed only after long would obtain the “average weather,” or the climate, of spans of time, the state of the atmosphere can change in a a particular region. Climate, therefore, represents the matter of minutes. Hence, a watchful eye turned skyward accumulation of daily and seasonal weather events (the will be able to observe many of these changes. average range of weather) over a long period of time. Up to this point, we have looked at the concepts of The concept of climate is much more than this, how- weather and climate without discussing the word meteo- ever, for it also includes the extremes of weather—the rology. What does this word actually mean, and where did heat waves of summer and the cold spells of winter— it originate? that occur in a particular region. The frequency of these extremes is what helps us distinguish among climates METEOROLOGY—THE STUDY OF THE ATMOSPHERE that have similar averages. Meteorology is the study of the atmosphere and If we were able to watch Earth for many thousands its phenomena. The term itself goes back to the Greek of years, even the climate would change. We would see rivers of ice moving down stream-cut valleys and huge *The movement of the ocean floor and continents is explained in the theory glaciers—sheets of moving snow and ice—spreading their of plate tectonics.
