Essentials of meteorology an invitation to the atmosphere 8th edition ebook pdf

Essentials of Meteorology: An Invitation to the Atmosphere 8th Edition, (Ebook PDF) Visit to download the full and correct content document: https://ebookmass.com/product/essentials-of-meteorology-an-invitation-to-the-atmosp here-8th-edition-ebook-pdf/

ESSENTIALS OF

OROLOGY he Atmosphere EIGHTH EDITION

Tec

Robert Henson

Preface

xv

nm

Warming and Cooling Earth and Its Atmosphere 26

ee

Earth's Atmosphere

2

The Atmosphereand the Scientific Method Weather, Climate. and Meteorology

4

5

Meteorology—TheStudy of the Atmosphere A Glimpse ata Weather Map 7 Weather and Climate in Our Lives

FOCUS ONA SPECIAL TOPIC 1.1

WhatIs a Meteorologist?

14

22

Summary 24 Key Terms 24 24

Questions for Thought and Exploration

25

29

FOCUS ON SPECIAL TOPIC 2.1

Rising Air Cools and Sinking Air Warms

FOCUS ON AN OBSERVATION 1.2

Questions for Review

5

9

Components of Earth’s Atmosphere 15 The Early Atmosphere 15 Composition of Today’s Atmosphere 15 Vertical Structure of the Atmosphere 19 A Brief Look at Air Pressure and Air Density Layers of the Atmosphere 21 The Radiosonde

Temperature and Heat Transfer 28 Temperature Scales 28 Latent Heat—The Hidden Warmth Conduction 31 Convection 31

Radiant Energy

32

33

FOCUS ON AN ENVIRONMENTALISSUE 2.2

Sunburning and UV Rays

35

Radiation—Absorption, Emission, and Equilibrium

19

Selective Absorbers and the Atmospheric Greenhouse Effect 37 Enhancementof the Greenhouse Effect 38 Warmingthe Air from Below 40 Shortwave Radiation Streaming from the Sun Earth’s Annual Energy Balance 42 WhyEarth Has Seasons 44

FOCUS ONA SPECIALTOPIC 2.3

Space WeatherandIts Impact on Earth

44

Seasons in the Northern Hemisphere

46

FOCUS ON SPECIAL TOPIC 2.4

ls December 21 Really the First Day of Winter?

Seasons in the Southern Hemisphere Local Seasonal Variations 51 Summary 52 Key Terms 52 Questions for Review

52

Questions for Thought and Exploration

49

50

53

Se

Air Temperature

54

Warming and Cooling Air Near the Surface 56 Daytime Warming 56 Extreme High Temperatures 57 Nighttime Cooling 59 Cold Air Near the Surface 59 Protecting Crops from the Cold Night Air 60 Extreme Low Temperatures

62

Copyright 2018 CengageLearning.All Rights Reserved. Maynot be copied, scanned,or duplicated,in wholeorin part. WCN 02-200-202

36

41

KeyTerms 111 Questions for Review 111 Questions for Thought and Exploration

Daily Temperature Variations 63 Regional Temperature Variations 64 FOCUS ONA SPECIAL TOPIC 3.1

When It Comes to Temperature, What's Normal?

65

Applications of Air Temperature Data 67 Air Temperature and Human Comfort 70

Measuring Air Temperature

71

72

Atmospheric Stability 116 DeterminingStability 117 A Stable Atmosphere 117 An Unstable Atmosphere 118 A Conditionally Unstable Atmosphere Cloud Development and Stability 121 Convection and Clouds 121 Topography and Clouds 123

FOCUS ON AN OBSERVATION 3.3

Why Thermometers Must Be Readin the Shade 74

Summary 76 Key Terms 76 Questions for Review

76

Questions for Thought and Exploration

77

AE Circulation of Water in the Atmosphere

Atmospheric Stability and Windy Afternoons— Hold On to Your Hat 124 Precipitation Processes 126 Collision and Coalescence Process

80

Evaporation, Condensation, and Saturation

82

Vapor Pressure

120

FOCUS ONA SPECIAL TOPIC 5.1

Humidity, Condensation, and Clouds 7s Humidity

a Cloud Development and Precipitation 114

FOCUS ONA SPECIAL TOPIC 3.2

A Thousand Degrees and Freezing to Death

112

Ice-Crystal Process 127 Cloud Seeding and Precipitation

81

Precipitation in Clouds

82

Relative Humidity 83 Relative Humidity and Dew Point 85 Relative Humidity and Human Discomfort

131

126

129

88

FOCUS ONA SPECIAL TOPIC 4.1

Humid Air and Dry Air Do Not Weigh the Same

Measuring Humidity Dew and Frost 91 Fog

93

Foggy Weather

90

90

96

FOCUS ON AN ENVIRONMENTALISSUE 4.2

Fog Dispersal

97

Clouds 98 Classification of Clouds 98 High Clouds 98 Middle Clouds 99 Low Clouds 100 Clouds with Vertical Development Some Unusual Clouds 103

Clouds andSatellite Imagery

Summary

111

102

106

Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-200-202

CONTENTS

vii

Cc

FOCUS ON AN ENVIRONMENTALISSUE 5.2

Does Cloud Seeding EnhancePrecipitation?

Precipitation Types Rain 132 Snow 133

131

Air Pressure and Winds

132

Atmospheric Pressure 148 Horizontal Pressure Variations—a Tale of Two

FOCUS ON SPECIAL TOPIC 5.3

Are Raindrops Tear-Shaped?

134

Sleet and Freezing Rain

136

Cities 148 Measuring Air Pressure

Hail

The Atmosphere Obeys the Gas Law

138

Snow Grains and SnowPellets

138

140

Doppler Radar and Precipitation Summary 144 Key Terms 144 Questions for Review

144

Questions for Thought and Exploration

150

Pressure Readings 152 Surface and Upper-Air Charts 153 Whythe Wind Blows 154

138

MeasuringPrecipitation Instruments 140

150

FOCUS ON SPECIAL TOPIC 6.1

FOCUS ON AN OBSERVATION 5.4

Aircraft Icing

146

FOCUS ON SPECIAL TOPIC 6.2

Isobaric Maps

141

155

Newton's Laws of Motion 155 Forces That Influence the Wind Straight-Line Flow Aloft 159

156

FOCUS ON AN OBSERVATION 6.3

145

Estimating Wind Direction and Pressure Patterns Aloft by Watching Clouds 160

Curved Winds Around Lowsand Highs Aloft Winds On Upper-Level Charts 162 Surface Winds 163 FOCUS ON AN OBSERVATION 6.4

Winds Aloft in the Southern Hemisphere Winds andVertical Air Motions

164

164

Determining Wind Direction and Speed 165 The Influenceof 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

7

©C.Donald Ahrens

Atmospheric Circulations

viii__

CONTENTS

172

Scales of Atmospheric Motion 174 Eddies—Big and Small 175 Local Wind Systems 176 Thermal Circulations 176 FOCUS ON AN OBSERVATION 7.1

Eddies and “Air Pockets”

177

Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-200-202

161

Seaand Land Breezes

178

Mountain and Valley Breezes Katabatic Winds

180

Chinook (Foehn) Winds

Mid-Latitude Cyclonic Storms 229 Polar Front Theory 229 Where Do Mid-Latitude Cyclones Tend to Form? 231 Developing Mid-Latitude Cyclones and Anticyclones 232

180

181

FOCUS ON SPECIAL TOPIC 7.2

Snow Eaters and Rapid Temperature Changes

182

Santa Ana Winds 182 Desert Winds 184 Seasonally Changing Winds—The Monsoon 186 Global Winds 188 General Circulation ofthe Atmosphere 188 Single-Cell Model 188 Three-Cell Model 189 Average Surface Windsand Pressure: The Real World 192 The General Circulation andPrecipitation Patterns

192

Westerly Winds andthe Jet Stream 194 Atmosphere-OceanInteractions 197 Global WindPatterns and Surface Ocean Currents 197 Winds and Upwelling 198

Questions for Review

206

Questions for Thought and Exploration

Nor'easters

233

FOCUS ONA SPECIALTOPIC 8.4

A Closer Look at Convergence and Divergence

Summary 239 Key Terms 239 Questions for Review 239 Questions for Thought and Exploration

203

199

242

Weather Observations 244 Acquisition of Weather Information Weather Forecasting Tools 245

244

FOCUS ON AN OBSERVATION 9.1

TV Weathercasters—How DoThey Do It?

Weather Forecasting Methods

247

207

ee Air Masses, Fronts, and

Middle-Latitude Cyclones

Air Masses

208

210

Source Regions 210 Classification 211 Air Masses of North America

212

FOCUS ONA SPECIAL TOPIC 8.1

Lake-Effect (Enhanced) Snows

213

FOCUS ONA SPECIAL TOPIC 8.2

The Return of the Siberian Express Fronts 220 Stationary Fronts

215

221

Cold Fronts 222 Warm Fronts 224

Drylines

226

Occluded Fronts

240

J Weather Forecasting

El Nifio , La Nifia, and the Southern Oscillation

Other Atmosphere-Ocean Interactions Summary 206 Key Terms 206

FOCUS ON A SPECIALTOPIC 8.3

227

Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned,or duplicated, in wholeorin part. WCN 02-200-202

246

234

The Computer and Weather Forecasting: Numerical WeatherPrediction 247 Why Computer-Based Forecasts Can Go Awry and Steps to Improve Them 249 OtherForecasting Techniques 252

Time Rangeof Forecasts

Squall-Line Thunderstorms 280 Supercell Thuderstorms 282 Thunderstormsand Flooding 286 Distribution of Thunderstorms 288 FOCUS ONA SPECIAL TOPIC 10.1

255

TheTerrifying Flash Flood in the Big Thompson Canyon

FOCUS ON SPECIAL TOPIC 9.2

WeatherPrediction and The Marketplace

Distribution of Thunderstorms

257

FOCUS ON AN OBSERVATION 10.2

Accuracy and Skill in Weather Forecasting 257 Weather Forecasting Using Surface Charts 259 Determing the Movementof Weather Systems 259 A Forecast for Six Cities 259 Using Forecasting Tools to Predict the Weather 264 Help from the 500-mb Chart 264 The Models Provide Assistance 266 A Valid Forecast 267 Satellite and Upper-Air Assistance 267 A Day of Rain and Wind 268 Summary 270 Key Terms 270 Questions for Review

270

Questions for Thought and Exploration

Thunderstorms and the Dryline

Lightning and Thunder Tornadoes 296

274

Ordinary Cell Thunderstorms Multicell Thunderstorms

290

Don’t Sit Under the Apple Tree

TornadoLife Cycle

297

297

Tornado Occurrence and Distribution Tornado Winds 300

298

FOCUS ONA SPECIAL TOPIC 10.4

The Weird World of Tornado Damage

302

FOCUS ONA SPECIAL TOPIC 10.3

The Evolution of Tornado Watches and Warnings

Tornado Outbreaks 305 Tornado Formation 305 Supercell Tornadoes 305 Nonsupercell Tornadoes 309

Se Thunderstorms

290

FOCUS ONA SPECIAL TOPIC 10.3

271

Thunderstorms and Tornadoes

288

272

Waterspouts

310

Observing Tornadoes and Severe Weather Storm Chasing and Mobile Radar 314

275

311

Summary 315 Key Terms 315

277

Questions for Review

315

Questions for Thought and Exploration

Hurricanes

316

318

Tropical Weather 320 Anatomy of a Hurricane

© Robert Henson

320 Hurricane Formation and Dissipation

The Right Environment 324 The Developing Storm 324 The Storm Dies Out 325 Hurricane Stages of Development Investigating the Storm 326 Hurricane Movement

323

325

327

Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-200-202

304

287

Moist Subtropical Mid-Latitude Climates (Group C) 366

FOCUS ON SPECIAL TOPIC 11.1

How Do Hurricanes Compare with Middle-Latitude Cyclones? 328

Naming Hurricanes and Tropical Storms 331 Devastating Winds, the Storm Surge, and Flooding

FOCUS ON AN OBSERVATION 12.2

A Desert with Clouds and Drizzle

331

Moist Continental Climates (Group D)

FOCUS ONA SPECIAL TOPIC 11.2

When Doesa DrySpell Become a Drought?

FOCUS ON AN ENVIRONMENTALISSUE 12.4

Are Plant Hardiness ZonesShifting Northward?

Questions for Review

378

Questions for Thought and Exploration 339

FOCUS ON AN OBSERVATION 11.3

SUR

2005

Earth's Changing Climate

The Record-Setting Atlantic Hurricane Seasons of 2004 and 340

341

Devastating Tropical Cyclones Around the World Hurricane Watches and Warnings 343

Reconstructing Past Climates Climate Throughout the Ages

342

380

382 384

The Ocean's Influence on Rapid Climate Change

386

344

Hurricane Forecasting Techniques Modifying Hurricanes 347 Summary 348 Key Terms 348 Questions for Review

379

FOCUS ONA SPECIALTOPIC 13.1

FOCUS ON AN ENVIRONMENTALISSUE 11.4

Hurricanes ina Warmer World

376

Summary 378 Key Terms 378

Hugo, 1989 337 Andrew, 1992 338

Sandy, 2012

372

Polar Climates (Group E) 374 Highland Climates (Group H) 375

334 336

Some Notable Hurricanes 337 Galveston, 1900 337 New England, 1938 337 Camille, 1969 337

Katrina and Rita, 2005

370

FOCUS ONA SPECIAL TOPIC 12.3

Devastation from a Tropical Storm—The Case of Allison 334

Classifying Hurricane Strength Hurricane-Spawned Tornadoes Hurricane Fatalities 336

367

345

348

Questions for Thought and Exploration

349

2.

Global Climate

350

A World with Many Climates 352 Global Temperatures 352 Global Precipitation 354 FOCUS ONA SPECIAL TOPIC 12.1

Extreme Wet and Dry Regions

356

Climatic Classification—The Képpen System 357 The Global Pattern of Climate 359 Tropical Moist Climates (Group A) 359 Dry Climates (Group B) 362

= 8 3 e

CONTENTS

xi

Temperature Trends During the Past 1000 Years

385

Temperature Trends During the Past 100-Plus Years 386 Climate Change Caused by Natural Events 388 Climate Change: Feedback Mechanisms 389 Climate Change:Plate Tectonics and Mountain Building 390 Climate Change:Variations in the Earth's Orbit

391

Climate Change:Variations in Solar Output 394 Climate Change: Atmospheric Particles 394 Climate Change Caused by Human(Anthropogenic) Activities 397 Climate Change: Greenhouse Gases 397

FOCUS ON AN ENVIRONMENTALISSUE 13.2

Nuclear Winter—Climate Change Induced by Nuclear War 398

Climate Change: Land Use Changes 398 Climate Change: Global Warming 399 Recent Global Warming: Perspective 399 FOCUS ON AN ENVIRONMENTALISSUE 13.3

Climate Change and Extreme Weather

Future Climate Change: Projections FOCUS ON SPECIAL TOPIC 13.4

Climate Models—A Quick Look

404

400

401

FOCUS ON AN ENVIRONMENTALISSUE 13.5

The Impact of Ozone on the Greenhouse Effect and Climate Change 406

Consequencesof Climate Change: The Possibilties 406 Climate Change: A Final Note 410

Summary 411 Key Terms 411

Questions for Review

411

Questions for Thought and Exploration

412

el

Air Pollution

414

A Brief History of Air Pollution 416 Types and Sourcesof Air Pollutants 418 FOCUS ON AN ENVIRONMENTALISSUE 14.1

IndoorAir Pollution

418

Principal Air Pollutants 419 Ozone inthe Troposphere 422 Ozonein the Stratosphere 422 FOCUS ONA SPECIAL TOPIC 14.2

The Formation of Ground-Level Ozonein Polluted Air FOCUS ON AN ENVIRONMENTALISSUE 14.3

The Ozone Hole

425

Air Pollution: Trends and Patterns Factors That Affect Air Pollution The Role of the Wind 429

426

429

The RoleofStability and Inversions The Role of Topography 431

429

FOCUS ON AN OBSERVATION 14.4

Smokestack Plumes

432

Severe Air Pollution Potential 433 Air Pollution and the Urban Environment

433

FOCUS ON AN OBSERVATION 14.5

Five Days in Donora—AnAir Pollution Episode

Acid Deposition

434

436

FOCUS ON AN ENVIRONMENTALISSUE 14.6

Heat WavesandAir Pollution: A Deadly Team Summary 439 Key Terms 439 Questions for Review

439

Questions for Thought and Exploration

437

440

mH

Copyright 2018 Cengage Learning.All Rights Reserved. Maynot be copied, scanned,or duplicated,in wholeorin part. WCN 02-200-202

423

RES

Light, Color, and Atmospheric Optics 442

Units, Conversions, Abbreviations, and

Twinkling, Twilight, and the Green Flash

The Mirage: Seeing Is Not Believing

451

449

FOCUS ON AN OBSERVATION 15.1

The Fata Morgana

453

Halos, Sundogs, and Sun Pillars Rainbows 456 Coronas and Cloud Iridescence

™m™OoOn wD

Equations

463

Equations and Constants 466 Weather Symbols andthe Station Model 468 Average Annual Global Precipitation 470 K6ppen’s Climatic Classification System 472 Humidity and Dew-point Tables (Psychrometric Tables)

=o)

White and Colors 444 Clouds and Scattered Light 444 Blue Skies and Hazy Days 445 Red Suns and Blue Moons 447

>

ce

473

Standard Atmosphere

Beaufort Wind Scale (Over Land)

Additional Reading Material Glossary 481 Index 496

453

459

477

478

479

FOCUS ON AN OBSERVATION 15.2

Glories and the Heiligenschein

460

Summary 461 Key Terms 461 Questions for Review

461

Questions for Thought and Exploration

462

Copyright 2018 Cengage Learning. All Rights Reserved. Maynot be copied, scanned, or duplicated, in whole or in part. WCN 02-200-202

CONTENTS xiii

Copyright 2018 CengageLearning.All Rights Reserved. Maynotbe copied, scanned,or duplicated, in whole orin part. WCN 02-200-202

PREFACE The world is an ever-changing picture of naturally occurring events. From drought and famine to devastating floods, someof the greatest challenges we face come

in the form of natural disasters created by weather. Yet,

dealing with weather and climate is an inevitable part of our lives. Sometimes it is as small as deciding what to wear for the day or howto plan a vacation. But it can also have life-shattering consequences, especially for those whoare victims of a hurricane or a tornado.

In recent years, weather and climate have become

front page news, from record-setting extreme weather events to environmental issues such as global warming and ozonedepletion. The dynamic nature of the atmosphere seems to demandourattention and understanding more these days than ever before. Almost daily, there are newspaperarticles describing some weather event or impending climate change. For this reason, and the fact that weather influences our daily lives in so many ways, interest in meteorology (the study of the atmosphere) has been growing. This rapidly developing and popular science is giving us more information about the workings of the atmosphere than ever before.

Oneofthe reasons that meteorology is such an engaging science to study is that the atmosphereis a universally accessible laboratory for everyone. Although the atmosphere will always provide challenges for us, as research and technology advance, our ability to understand our atmosphere improvesas well. The informationavailable to you in this book, therefore, is intended to aid in your

own personal understanding and appreciation of our Earth’s dynamic atmosphere.

About This Book Essentials of Meteorology is written for students taking an introductory course on the atmospheric environment.

The main purposeofthe text is to convey meteorological conceptsin a visual, practical, and nonmathematical manner. In addition, the intent of the book is to stim-

ulate curiosity in the reader and to answer questions about weather andclimate that arise in our day-to-day lives. Although introductory in nature, this eighth edition maintains scientific integrity and includes up-todate information on large-scale topics, such as global warming, ozone depletion, and El Nifio, as well as dis-

cussion of recent high-profile weather events. As in previous editions, no special prerequisites are necessary for understanding.

Written expressly for the student, this book emphasizes the understanding andapplication of meteorological principles. The text encourages watching the weather so that it becomes “alive,” allowing readers to immedi-

ately apply textbook material to the world around them.

To assist with this endeavor, a color Cloud Chart ap-

pears at the back of the text. The Cloud Chart can be separated from the book and usedas a learning tool at any place one choosesto observethe sky. To strengthen points and clarify concepts, illustrations are rendered in full color throughout. Color photographs were carefully selected to illustrate features, stimulate interest,

and show how exciting the study of weather can be. To enhancethe value of the book, several appendices that were only available online in the seventh edition have been reincorporated.

Organized into fifteen chapters, Essentials of Meteorology is designed to provide maximum flexibility to instructors of weather and climate courses. Thus, chap-

ters can be covered in any desired order. For example, Chapter 15, “Light, Color, and Atmospheric Optics,” is

self-contained and can be coveredearlier if so desired.

Instructors, then,are able to tailor this text to their par-

ticular needs. This book basically follows a traditional approach. After an introductory chapter on theorigin, composition, and structure of the atmosphere,it covers solar energy, air temperature, humidity, clouds, precipitation, and winds. Then comesa chapter on air masses, fronts, and middle-latitude cyclonic storms. Weather

prediction and severe storms are next. A chapter on

hurricanesis followed by a chapter on global climate. A chapter on climate changeis next. A chapter onair pollution precedesthe final chapter on atmosphericoptics.

Each chapter contains at least two Focus sections,

which either expand on material in the main text or explore a subjectclosely related to whatis being discussed.

Focussections fall into one of three distinct categories: Observations, Special Topics, and Environmental Issues.

Someinclude material that is not always found in introductory meteorology textbooks—subjects such as space weather, the scientific method, and wind energy. Others

help to bridge theory andpractice. This edition contains several new orrewritten Focussections, including an updated discussion of noreasters in Chapter 8 and a new Focussection on tornado damagepatterns in Chapter 10.

Set apart as “Did You Know?”features in each chapter is weather information that may not be commonly XV.

known, yet pertains to the topic under discussion.

Designedto bring the readerinto thetext, mostof these weather highlights relate to someinteresting weather fact or astonishing event.

Each chapter incorporates other effective learning aids:

e A majortopic outline begins each chapter. e Interesting introductory pieces draw the reader naturally into the maintext. e Important termsare boldfaced, with their definitions

appearingin the glossary orin thetext. e Key phrasesareitalicized. e English equivalents of metric units are immediately provided in parentheses. e A brief review of the main points is placed toward the middle of most chapters. e Each chapter ends with a summary of the main ideas.

e A list of key terms with page references follows each chapter, allowing students to review and reinforce their knowledge of key concepts. e Questions for Review act to check how well students

assimilate the material. e Questions for Thought and Exploration encourage students to synthesize learned concepts for deeper understanding. e References to 19 concept animations are compiled on pp. Xx-xxi. These animations convey an immediate appreciation of how a process works and help students visualize the more difficult concepts in meteorology.

Animationscan be found on the Meteorology CourseMate, accessed through Cengagebrain.com. e At the end of each chapter are questions thatrelate to articles found on the Global Geoscience Watch website, available on its own or via the Meteorology CourseMate.

Eight appendices conclude the book. In addition, at the endof the book, a compilation of supplementary reading material is presented, as is an extensive glossary. On the endsheetat the back of the bookis a geophysical map of North America. The map serves as a quick reference for locating states, provinces, and geographical features, such as mountain ranges and large bodiesof water.

XVi__

PREFACE

Supplemental Material and Technology Support TECHNOLOGYFOR THE INSTRUCTOR

Instructor Companion Website

Everything you need

for your course in one place! This collection of bookspecific lecture and class tools is available online via www.cengage.com/login. Access and download PowerPoint presentations, images, instructor’s manual, vid-

eos, and more.

Cognero Test Bank Cengage Learning Testing Powered by Cognerois a flexible, online system that allows youto: e author, edit, and managetest bank content from mul-

tiple Cengage Learningsolutions e create multiple test versions in an instant

e deliver tests from your LMS,yourclassroom,or wherever you want

Global Geoscience Watch Updated several times a day, the Global Geoscience Watch is a focused portal into GREENR—ourGlobal Reference on the Environment, Energy, and Natural Resources—an ideal one-

stop site for classroom discussion and research projects for all things geoscience! Broken into the four key course areas (Geography, Geology, Meteorology, and Oceanography), you can easily get to the mostrelevant contentavailable for your course. You and yourstudents will have access to the latest information from trusted academic journals, news outlets, and magazines. You also will receive access to statistics, primary sources, case studies, podcasts, and much more!

TECHNOLOGYFOR THE STUDENT

Earth Science MindTap for Essentials of Meteorology MindTap is well beyond an eBook, a homework solu-

tion or digital supplement, a resource center website, a course delivery platform, or a Learning Management System. Morethan 70 percent of students surveyed said that it was unlike anything they have ever seen before.

MindTap is a new personal learning experience that combinesall of your digital assets—readings, multimedia, activities, study tools, and assessments—into a sin-

gular learning path to improve student outcomes.

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 Climatological Survey (OCS) research and service facility, in concert with the University of Oklahoma, Explorationsin

Meteorology places a strong emphasis on helping students understand weather and climate by using real meteorological data. Theactivities in this lab manual require that students tap into the OCSarchives of meteorological data in order to complete meteorological exercises.

Full-color pictures and data graphs help students visually understand weather and severe weather topics. The lab manual also challenges students by providing optional questions intended for honors students, making

this lab manual appropriate for both introductory and honors meteorology courses.

Eighth Edition Changes This edition of Essentials of Meteorology includes a coauthor—meteorologist and science journalist Robert Henson (Weather Underground). For more than 20 years, Henson produced publications and websites for the University Corporation for Atmospheric Research, which manages the National Center for Atmospheric Research. He is an expert on severe weather, including tornadoes, thunderstorms, and hurricanes. He has

also analyzed how television weathercasters cover major storms andreport on climate change. Hensonis the author of four trade books on meteorology, including The Thinking Person’s Guide to Climate Change (previously The Rough Guide to Climate Change, thefirst edition of which wasshortlisted for the United Kingdom’s Royal Society Prize for Science Books).

The authors have carried out extensive updates and revisions to this eighth edition of Essentials of Meteorology, reflecting the ever-changing natureof the field and the atmosphereitself. Dozens of new photos and new or revised colorillustrations help students visualize the excitementof the atmosphere. e Chapter 1, “Earth's Atmosphere,’ continuesto serve as

a broad overview of the atmosphere. The text now begins with a discussion of the scientific method andits importance. To help draw students into the material, the introduction to meteorology and the summary of extreme weather types has been placed earlier in the chapter, followed by discussion of the chemistry and vertical structure of Earth’s atmosphere. Among

recent events now included are the severe flooding

over the Southern Plains and Southeast in 2015 and the Houstonflash flood of April 2016.

Chapter 2, “Warming and Cooling Earth andIts Atmosphere,’ contains up-to-date statistics and background on greenhouse gases and climate change, topics covered in more detail later in the book.

Discussionofthe potential impact of clouds on future global warminghas been updated.

In Chapter 3, “Air Temperature,” several figures and

tables have been updated so that they refer to normals drawn from the most recent reference period (1981-2010).

Chapter 4, “Humidity, Condensation, and Clouds,’ includes updated material on satellite observations,

including new background and artwork from the

Global Precipitation Mission satellite. Also included is a “Did You Know?”box onthe high-impact Atlanta snowstorm of January 2014.

Chapter 5, “Cloud Development and Precipita-

tion,” includes a new graphic. Newsatellite observing techniquesare also noted andillustrated in this chapter.

Chapter6, “Air Pressure and Winds,” includes a sub-

stantially enhanced description andrevised illustrations of the interplay between the pressure gradient and Coriolis forces in cyclonic and anticyclonic flow.

Several otherillustrations have been revised for clarity, and the discussion of scatterometers has been up-

dated. A box on windenergy features the most recent data on wind energy adoption.

Chapter7, “Atmospheric Circulations, features a major restructuring, update, and expansion ofsections dealing with the El Nifio/Southern Oscillation, Pacific Dec-

adal Oscillation, North Atlantic Oscillation, and Arctic Oscillation,including several new and updated images.

The openingsection, which introducesscales of atmospheric motion,hasalso beenrevised forclarity.

Chapter 8, “Air Masses, Fronts, and Middle-Latitude

Cyclones,” now includes discussion of atmospheric rivers and anillustration of their impacts. In line with recent research, the section on occluded fronts

stresses the prevalence of warm-type over cold-type occluded fronts. The discussion of drylines has been expanded, and the Focus box on noreasters has been

reworked to spotlight the record-setting East Coast snowstorm of January 2016.

PREFACE

XVii

e “Weather Forecasting” (Chapter 9) has undergone substantial revision, with several updated graphics.

Three majortypesofsatellite imagery are introduced near the beginning of the chapter. Explanations of watches, warnings, and forecasts of various durations

(including seasonal outlooks) are now incorporated in a new section, “Time Rangeof Forecasts.” The con-

ceptofthe forecast funnel is also introduced.

e Chapter 10, “Thunderstorms and Tornadoes,” in-

cludes several new and updatedillustrations, depicting low- and high-precipitation supercells, a roll cloud, and shelf cloud. An expandedsection covers

both flash flooding andriver flooding andtheir connection to thunderstorms, including examples from Colorado (2013) and Texas and Oklahoma(2015).

A new Focus box explores the baffling damage patterns that tornadoes can produce. Theeffort to accommodate new waysofestimating and reporting tornado wind speed (such as mobile radar reports) is also noted. e The chapter on “Hurricanes” (Chapter 11) includes a new openingsection that introduces students to the terrible impacts of Hurricane Katrina. Several graphics that use satellite imagery to explain basic concepts have been updated with recent tropical cyclones. Charts on hurricane climatology have been broughtup to date, and an expandedrange of both historical and recent examples are discussed, including the Galveston hurricane of 1900, the New

England hurricane of 1938, and Typhoon Haiyan from 2013.

e Chapter 12, “Global Climate,” includes a number

of updates to climatological charts and discussion, drawing on the mostrecent set of United Statescli-

mate normals (1981-2010). e Chapter 13, “Earth's Changing Climate,’ has been

revised throughoutto reflect increasing confidence on a variety of climate change indicators and impacts. Also incorporated are graphics, conclusions, and emission pathways from the Fifth Assessment Report (2013-14) of the Intergovernmental Panel on Climate Change. The extremely quiet solar cycle of the late 2000s andearly 2010sis noted, along with a variety of weather extremesfrom recentyears that are relevant to climate change. The Paris Accord is discussed in the context of the Kyoto Protocol

that preceded it. A number of diagrams have been updated. e The chapter on “Air Pollution” (Chapter 14) has been revised to includethelatest air pollution trends across the United States as well as the latest information on ozone depletion in the Arctic and Antarctic. The US. Clean PowerPlan is introduced, and the devastating

impacts of both indoorand outdoorair pollution are discussed, includingtheeffects of tiny particulates on cardiovascular health. e Several of the photos in Chapter 15, “Light, Color, and

Atmospheric Optics” have been replaced with spectacular new examples (e.g., anticrepuscular rays and double rainbows).

Acknowledgments Many people have contributed to the eighth edition of Essentials of Meteorology. A very special and most grateful thank-you goes to Lita Ahrens who proofread each chapter. Special thank you to Charles Preppernau for rendering the beautiful art and to Janet Hansen for careful proofreading.

Weare indebted to Janet Alleyn, who notonly designed the book but, once again, took the art, photos,

and manuscript and turned them into a beautiful book.

Thanks goes to Judith Chaffin for her careful and conscientious editing. Special thanks to all the people at Cengage Learning who worked on this edition, including Lauren Oliveira, Morgan Carney, Hal Humphrey, and Dawn Giovanniello.

Thanksto our friends who provided photos and to those reviewers whooffered comments and suggestions for this edition, including:

Fidel Gonzalez Rouco Universidad Complutense de Madrid

Redina Herman WesternIllinois University Bette Otto-Bliesner National Center for Atmospheric Research

David Schultz University of Manchester Alex Huang University of North Carolina at Asheville

Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-200-202

AnthonySantorelli Anne Arundel Community College Dan Ferandez Anne Arundel Community College Dean G Butzow Western Michigan University

Douglas K. Miller Purdue University EdwardJ. Perantoni

Lindenwood University

To the Student Learning about the atmosphere can be a fascinating and enjoyable experience. This book is intended to give you someinsight into the workings of the atmosphere. However, for a real appreciation of your atmospheric environment, you must go outside and observe.

Although mountains take millions of years to form, a cumulus cloud can develop into a raging thunderstorm in less than an hour. The atmosphere is always producing something newforus to behold. To help with your observations, a color Cloud Chartis at the back of the

Ronald A Dowey Harrisburg Area Community College

bookfor easy reference. Removeit and keep it with you.

Shaunna L. Donaher

book are manifested out there for you to discover and enjoy. Please take the time to look.

Troy Kimmel University of Texas

Donald Ahrens and Robert Henson

University of Miami

And, remember,all of the concepts and ideas in this

Copyright 2018 Cengage Learning. All Rights Reserved. Maynot be copied, scanned, or duplicated, in whole or in part. WCN 02-200-202

PREFACE

Xix

These animations have beencarefully created to bring to life key points in the chapters. They are also the perfect tool to help refresh students’ memories ofprevious concepts, so they can keep building on knowledge already

acquired. Concept Animationsare accessed through the MindTapplatform, which can be acquired separately or together with print or looseleaf versions of this book.

Some examples of Concept Animations are shownhere.

Doppler radar images are used extensively throughoutthis book.

To better understand Doppler radar images, watchall 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 pressure and sinks above an area of high atmospheric pressure. Converging andDiverging Air (Chapters 1 and 8).

Additional Animations: @ Ice Crystals (Bergeron) Process (Chapter 5) @ General Circulation of the Atmosphere (Chapter 7) @ Geostrophic Wind (Chapter 6) @ Temperature versus Molecular Movement (Chapter 2) @ Condensation (Chapter 4)

@ Air Temperature, Dew Point, and Relative Humidity (Chapter 4) @ Daily Temperature Changes Abovethe Surface (Chapter 3)

Seasons provides a complete picture of Earth revolving around the sun while it is tilted on its axis. While viewing this animation, look closely at how the sun is viewed by a mid-latitude observer at various times of the year (Chapter 2).

To view air rising over a mountain and the formation ofa rain shadowdesert, watchAirRising Up and Over a Mountain (Chapters 5 and 7).

For a visual presentation of the Coriolis force, watch Coriolis Force (Chapter6).

The concept of atmospheric stability can be a bit confusing, especially when comparing the temperatureinside a rising air parcel to that of its surroundings. Watch Stable Atmosphere (Chapter5) 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 ColdFront in Winter (Chapters 8 and 9), To see a warm front actually move across the surface, watch Warm Frontin 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

=-

—

ae Atmosphere rememberwell a brilliant red balloon which kept me com-

_ The Atmosphere and

_ the Scientific Method : Weather, Climate, and | Meteorology

pletely happy for a whole afternoon,until, while | was playing, a clumsy movementallowedit to escape. Spellbound, | gazedafterit as it drifted silently away, gently swaying, growing smaller and smaller until it was only a red point ina

blue sky. At that moment| realized, for the first time, the

Componentsof Earth’s Atmosphere

vastness aboveus: a huge space withoutvisible limits. It was

Vertical Structure of

poweroverall the Earth’s inhabitants. | believe that many

an apparentvoid,full of secrets, exerting an inexplicable people, consciously or unconsciously, have beenfilled with

awe bythe immensity of the atmosphere.All our knowledge

aboutthe air, gathered over hundredsof years, has not diminishedthis feeling.

Theo Loebsack, Our Atmosphere

O ur atmosphereis a delicate life-giving blanketof air that surroundsthe fragile Earth. In one way or another,it influences everything we see and hear—itis intimately connected to ourlives. Air is with us from birth,

and we cannot detach ourselves from its presence. In the openair, we can travel for many thousandsofkilometers 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 without water for a few days, but, without our atmosphere, we would not survive more than a few minutes.Just as fish are

confined to an environmentof water, so we are confined

to an ocean of air. Anywhere we go, air must go with us.

Earth without an atmosphere would have nolakes or oceans. There would be no sounds,no clouds,no red sun-

sets. The beautiful pageantry of the sky would be absent.It would be unimaginablycold at night and unbearably hot duringthe day. All things on Earth would be at the mercy of an intense sun beating down upona planetutterly parched.

LivingonthesurfaceofEarth, we have adapted so completely to our environmentofair that we sometimes forget howtruly remarkable this substance is. Even thoughair is tasteless, odorless, and (most ofthe time)invisible,it protects

us from the scorching rays of the sun and provides us with a mixtureof gasesthat allowslife to flourish. Because we cannotsee, smell, or taste air, it may seem surprising that

between youreyes and these wordsaretrillions of air molecules. Someofthese mayhavebeenin cloudonlyyesterday, or over another continentlast week, or perhaps part of the life-givingbreath ofa person wholived hundredsofyears ago.

Warmth for ourplanet is provided primarily by the suns energy. At an average distance from the sun ofnearly 150 million kilometers (km), or 93 million miles (mi),

Earth intercepts only a very small fraction of the sun’s total energy output. However,it is this radiant energy* that drives the atmosphereinto the patterns of everyday wind and weather, andallowslife to flourish.

Atits surface, Earth maintains an average temperature of about 15°C (59°F).** Although this temperature is mild, Earth experiences a wide range of temperatures, as readings can drop below — 85°C (—121°F) during a frigid Antarctic night and climb during the day to above 50°C (122°F) on the oppressively hot, subtropical desert.

Noteveryonewill experience such extremes where they live, butall of us have a chance to observe the day-to-day changesin the atmospherethat werefer to as weather.

In this chapter, we will examine a number of

important concepts and ideas about Earth’s atmosphere, manyof which will be expanded in subsequent chapters.

*Radiantenergy, or radiation,is energy transferred in the form of wavesthat haveelectrical and magnetic properties. The light that weseeis radiation,as is ultraviolet light. More on this importanttopic is given in Chapter2. **The abbreviation °C is used when measuring temperature in degrees

These concepts andideasare partofthe foundationfor understanding the atmosphere and howit produces weather.

They are built on knowledge acquired andapplied through the scientific method, which allows us to make informed predictions about how thenatural world will behave.

The Atmosphere and the Scientific Method For hundredsof years, the scientific method has served as the backbone for advances in medicine, biology,

engineering, and many otherfields. In the field of atmospheric science, the scientific method has paved the way for the production ofweatherforecasts that have steadily improvedovertime.

Investigators use the scientific method by posing a question, putting forth a hypothesis,* predicting what the hypothesis would imply if it were true, and carrying outtests to see if the prediction is accurate. Many commonsayings about the weather, such as “red sky at morning, sailor take warning; red sky at night, sailor’s delight” (see @ Fig. 1.1) are rooted in careful observation, and there

are grains oftruth in someofthem. However,they are not considered to be productsofthe scientific method because they are nottested andverified in a standardrigorousway.

To be accepted,a hypothesis has to be shownto be correct througha series of quantitative tests. In many areas of science, suchtesting is carried out in a laboratory, where it can bereplicated again and again. Studying the atmosphere, however,is somewhatdifferent, because our Earth

has only one atmosphere. Despite this limitation,scientists have madevastprogress by studyingthe physics and chemistry ofair in the laboratory (for instance, studying the way in which moleculesabsorb energy) andby extending those understandings to the atmosphere as a whole. Observations using weather instruments allow us to quantify how the atmosphere behaves and to determine whethera prediction is accurate. If a particular kind of weatheris being studied,such as hurricanesor snowstorms,a field study can

gatheradditional observationsto test specific hypotheses.

Overthelastfifty years, computers have given atmospheric scientists a tremendous boost. The physical laws that control atmospheric behaviorcan berepresented in software packages known as numerical models. Forecasts can be madeand tested manytimesover. The atmospheredescribed by a model can beused to depict weather conditions from thepast andto project them into the future. When a model can accurately simulate past weatherconditions and provide confidenceinits portrayal oftomorrow's weather,the model can provide valuable information about the weather and climate we may expectdecades from now.

Celsius, and °F is the abbreviation for degrees Fahrenheit. More information

about temperaturescales is given in Appendix A and in Chapter 2.

4

CHAPTER

*A hypothesis is an assertion subjectto verification or proof.

@ FIGURE 1.1 Observing the natural world is a critical part of the scientific method. Here a vibrantredskyis visible at sunset. One mightuse scientific method to verify the old proverb: “Red sky at morning,sailor take warning;red sky at night,sailor's delight.”

s3

8 2 3 8> 3 23 £

< S5 B 23 23 B g 5

=

s S s s5 e 35 = e3 g= 5 8

Weather, Climate, and Meteorology Whenwetalk aboutthe weather, we are talking aboutthe

condition of the atmosphereat any particular time and place. Weather—whichis always changing—is comprised of the elementsof: 1. air temperature—the degree of hotness or coldness of the air 2. air pressure—theforceofthe air above an area 3. humidity—a measureof the amountof watervaporin the air 4. clouds—visible massesof tiny water droplets and ice crystals or both thatare above Earth's surface 5. precipitation—any form ofwater,eitherliquid orsolid (rain or snow), that falls from clouds and reaches the

ground 6. visibility—the greatest distance one can see 7. wind—thehorizontal movementofair

If we measure andobserve these weather elements over a specified interval of time, say, for many years, we would obtain the “average weather,” or the climate, of

a particular region. Climate, therefore, represents the accumulation of daily and seasonal weatherevents (the average range of weather) over a long period oftime.

The concept of climate is much more than this, however, for it also includes the extremes of weather—the

heat waves of summerandthecold spells of winter— that occurin a particular region. The frequency of these extremes is what helps us distinguish among climates that have similar averages.

If we were able to watch Earth for many thousands of years, even the climate would change. We would see rivers of ice moving down stream-cut valleys and huge glaciers—sheets ofmoving snow and ice—spreadingtheir

icy fingers over large portions ofNorth America. Advancing slowly from Canada, a single glacier might extend as far south as Kansas andIllinois, with ice several thousands of metersthick covering the region now occupiedby Chicago.

Overan interval of two million years or so, we would see the ice advance and retreat many times. Of course, for

this phenomenonto happen,the average temperature of North America would have to decrease andthen rise in a cyclic manner.

Suppose we could photograph Earth once every thousandyears for many hundredsof millionsofyears. In time-lapse film sequence, these photos would show that not only is the climate altering, but the whole Earthitself is changing as well: Mountains wouldrise up only to be torn down byerosion;isolated puffs of smoke and steam would appear as volcanoes spew hotgases andfine dust into the atmosphere; andthe entire surface ofEarth would

undergo a gradual transformation as some ocean basins widen and someof them shrink.* In summary, Earth andits atmosphere are dynamic systemsthat are constantly changing. While major transformationsofEarth’s surface are completedonly after long spansof time, the state of the atmosphere can change in a matter of minutes. Hence, a watchful eye turned skyward will be able to observe many of these changes.

Upto this point, we have looked at the concepts of weather and climate without discussing the word meteorology. What doesthis word actually mean, and where did it originate?

METEOROLOGY—THE STUDY OF THE ATMOSPHERE

Meteorology is the study of the atmosphere and its phenomena. The term itself goes back to the Greek *The movementofthe ocean floor andcontinents is explained in the theory ofplate tectonics.

ATMOSPHERE

Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-200-202

philosopher Aristotle, who, about 340 B.c., wrote a book

on natural philosophytitled Meteorologica. This work represented the sum of knowledge on weather and climate at that time, as well as material on astronomy, geography, and chemistry. Someofthe topics covered included clouds,

rain, snow, wind,hail, thunder, and hurricanes. In those days,all substancesthatfell from the sky, and anything seen in theair, were called meteors, hence the term meteorology, whichactually comes from the Greek word meteoros, meaning“highin the air” Today, wedifferentiate between those meteors that comefrom extraterrestrial sources outside our atmosphere (meteoroids) and particles of water atmospheric phenomenain a philosophical and speculative manner. Even though manyofhis ideas were foundto be erroneous,Aristotle’s work remained a dominantinfluencein thefield of meteorology for almost two thousand years.In fact, the birth ofmeteorology as a genuine natural science did nottake place until the invention of weather

Columbus

NOAA

and ice observed in the atmosphere (hydrometeors).

In Meteorologica, Aristotle attempted to explain

aleiFetatel collie

a

Cincinnati

@ FIGURE 1.2 Doppler radar image showing precipitation over portions of Indiana. The areas shadedlight green indicate lighter rain, whereasyellow indicates heavier rain. The dark red shaded areas represent the heaviest rain and the possibility of hail and intense thunderstorms.

instruments, such as the hygrometer in the mid-1400s, the thermometerin the late 1500s, and the barometer(for

severe thunderstorm and unveil its wind, as well as show precipitation intensity (see @ Fig. 1.2). Recent upgrades to these Doppler radars makeit possible for them todistin-

measuringair pressure) in the mid-1600s. With the newly available observations from instruments, attempts were

guish raindrops, snowflakes,and hailstones.

In 1960, the first weather satellite, Tiros 1, was

then madeto explain certain weather phenomena employing scientific experimentation and the physical laws that were being developedat the time. As more and better

launched,usheringin space-age meteorology. Subsequent satellites provided a wide range of useful information, ranging from day andnight time-lapse images of clouds and stormsto images that depict swirling ribbons ofwater vapor flowing aroundthe globe, as shownin e Fig. 1.3.

instruments were developed, in the 1800s,the science of

meteorology progressed. The invention of the telegraph in 1843 allowedfor the transmission of routine weather observations. The understanding of the concepts of wind

Overthelast several decades, even more sophisticatedsat-

flow and storm movement becameclearer, and in 1869

ellites have been developed. Thesesatellites are supplying computers with a far greater networkofdata so that more accurate forecasts—perhaps extendingupto two weeksor more—will be available in the future.

crude weather mapswith isobars (lines of equal pressure)

were drawn. Around 1920 in Norway, the conceptsofair masses and weatherfronts were formulated. By the 1940s,

daily upper-air balloon observations of temperature, humidity, and pressure gave a three-dimensional view of the atmosphere, and high-flying military aircraft discoveredthe existence ofjet streams.

Meteorology took another step forward in the 1950s, whenscientists converted the mathematical equations that describe the behavior ofthe atmosphereinto software called numerical models that could be run on new highspeed computers. These calculations were the beginning of numerical weatherprediction. Today, computers plot the observations, draw the lines on the map,andforecast the

World War II, surplus military radars becameavailable,

and manyweretransformedintoprecipitation-measuring tools. In the mid-1990s, the National Weather Servicereplaced these conventional radars with the more sophisticated Doppler radars, which havetheability to peer into a 6

CHAPTER

NOAA

state ofthe atmosphere for somedesired timein thefuture.

Meteorologists evaluate the results from different numerical models and use them to issue public forecasts. After

@ FIGURE 1.3 This satellite image shows the dynamic nature of the atmosphereas ribbons of water vapor (gray regions) swirl counterclockwise about huge storms over the North Pacific Ocean.

Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-200-202

A Satellite’s View of the Weather

A good view

of the weather can be obtained from a weathersatellite.

e Figure 1.4 is a satellite image showing a portion of the

Pacific Ocean and the North American continent. The

image wasobtained from a geostationary satellite situated about 36,000 km (22,300 mi) above Earth. At this elevation, the satellite travels at the same rate as Earth spins, which

allows it to remain positioned above the samespotso it can continuously monitor whatis taking place beneathit.

The thin, solid black lines running from north-to-

south onthesatellite image are called meridians,or lines oflongitude. Since the zero meridian (or prime meridian) runs through Greenwich, England, the longitude of any place on Earth is simply howfar it is in degrees from the prime meridian up to 180° east or west. North America is west of Great Britain and mostof the UnitedStateslies between 75°W and 125°W longitude.

Thethin,solid black lines thatparallel the equator are called parallels oflatitude. Thelatitudeof any place is how far north or south,in degrees,it is from the equator. Thelatitudeof the equatoris 0°, whereas thelatitude ofthe North

Poleis 90°N andthatof the South Pole is 90°S. Most of the UnitedStates is located between latitude 30°N and 50°N, a region commonly referred to as the middle latitudes.

Storms of All Sizes Probably the most prominentfeature in @ Fig. 1.4 is the whirling cloud massesofall shapes andsizes. The clouds appear white because sunlightis reflected back to space from their tops. The largestofthe organized cloud massesare the sprawling storms. One such storm showsas an extensive band ofclouds, over 2000 km long, west of the Great Lakes. Superimposed onthesatellite image is the storm's center (indicated by the large red L) andits adjoining weather fronts in red, blue, and

purple. This middle-latitude cyclonic storm system (or extratropical cyclone) formsoutside thetropics and,in the Northern Hemisphere,has winds spinning counterclockwise aboutits center, which is presently over Minnesota.

A slightly smaller but morevigorous storm is located over the Pacific Ocean near latitude 12°N and longitude 116°W. This tropical storm system,with its swirling band ofrotating clouds andsustained surface winds of65 knots*

(74 mi/hr) or more, is known asa hurricane. The diameter of the hurricane, as measured bythe presenceof windsof at least 34 knots (39 mi/hr),is about 800 km (500 mi). The

tiny dotatits centeris called the eye. Near the surface, in the eye, windsare light, skies are generally clear, and the atmospheric pressureis lowest. Aroundthe eye, however,

is an extensive region where heavy rain and high surface winds are reaching peak gusts of 100 knots.

Smaller stormsare seen as bright spots over the Gulf of Mexico. These spots represent clusters of towering *A knotis a nautical mile per hour whereone knotequals 1.15 miles per hour (mi/hr)or 1.9 kilometers per hour (km/hr).

Whenit rains, it rains pennies from heaven—sometimes. On July 17, 1940, a tornado reportedly picked up a treasure of over 1000 sixteenth-century silver coins, carried them into a thunderstorm, then dropped them on the village of Merchery in the Gorki region of Russia.

cumulus cloudsthat have grown into thunderstorms,that is, tall churning clouds accompanied bylightning, thunder,

strong gusty winds, and heavy rain.If you lookclosely at Fig. 1.4, you will see similar cloud forms in manyregions.

There were probably more than a thousand thunderstorms occurring throughout the world at that very moment.

Although they cannotbeseenindividually, there are even some thunderstorms embeddedin the cloud mass west of the Great Lakes. Later in the day on which this image was taken,a few ofthese storms spawnedthe mostviolent disturbance in the atmosphere, tornadoes.

A tornadois an intenserotating column ofair that usually extends downward from the baseofa thunderstorm with acirculation reachingthe ground. Sometimescalled twisters, or cyclones, they may appear as ropesoras large cylinder.

They can be more than 2 km (1.2 mi) in diameter, although mostareless than a football field wide. Most tornadoes have sustained winds below 100 knots, but some can pack winds

exceeding 200 knots (230 mi/hr). Sometimesa visibly rotating funnel cloud dips part of the way down from a thunderstorm, then rises withoutever forming a tornado.

A GLIMPSE AT A WEATHER MAP Wecan obtain a better picture of the middle-latitude storm system by examining a simplified surface weather map for the same day thatthe satellite image was taken. The weightof the air above different regions varies and, hence, so does

the atmospheric pressure. In @ Fig. 1.5, the red letter L on the mapindicates a region of low atmospheric pressure, often called a low, which marksthe center of the middlelatitude cyclonic storm. (Comparethecenterofthe storm in Fig. 1.5 with that in Fig. 1.4.) The twolarge blueletters H on the map represent regions of high atmospheric pressure,called highs, or anticyclones. Thecircles on the maprepresentother individual weatherstationsorcities whereobservationsare taken. The windis the horizontal movementofair. The wind direction—thedirectionfrom which the windis blowing*—is given by wind barbs,lines that parallel the wind and extend outward from the center ofthe station. The wind speed—therate at which theairis movingpast a stationary observer—is indicated byflags, the shortlines that extend off each windbarb.

Notice how the wind blows aroundthe highs and the lows. The horizontal pressure differences create a force *If you are facing north and the windis blowing in your face, the wind would be called a “north wind”

ATMOSPHERE

@

F

This

NOAA/National Weather Service

satellite image (taken in visible reflected light) showsa variety of cloud patterns and storms in Earth’s atmosphere.

that starts the air moving from higher pressure toward lower pressure. Because of Earth’s rotation, the winds

are deflected from their path toward the right in the Northern Hemisphere.* This deflection causes the windsin the Northern Hemisphere to blow clockwise and outward from the center of the highs, and counterclockwise and inward towardthe centerofthe low.

As the surface air spins into the low,it flows to-

getherandis forced upward,like toothpaste squeezed out of an upward-pointing tube. Therising air cools, and the water vaporin the air condensesinto clouds.

Notice on the weather mapthat the area ofprecipitation (the shaded green area) in the vicinity of the low corresponds to an extensive cloudy region in the satellite imageofFig. 1.4.

Also notice by comparing Figs. 1.4 and 1.5 that, in the regions of high pressure, skies are generally clear. As the surface air flows outward away from the centerof a high, air sinking from above mustreplacethelaterally spreading surfaceair. Since sinking air does not usually produce *This deflecting force, known as the Coriolis force, is discussed more completely in Chapter6, as are the winds.

8

CHAPTER

clouds, we find generally clear skies and fair weather associated with the regions of high atmosphericpressure.

Areas of high andlowpressure, and the swirling air around them, are the major weather producers for the middle latitudes. Look at the middle-latitude storm and the surface temperatures in Fig. 1.5 and noticethat, to the southeast of the storm, southerly winds from the Gulf of

Mexico are bringing warm, humid air northward over muchof the southeastern portion of the nation. On the storm’s western side, cool dry northerly breezes combine with sinkingair to create generally clear weather over the Rocky Mountains. The boundarythat separates the warm andcoolair appearsas a heavy,colored line on the map—a front, across whichthereis a sharp change in temperature, humidity, and winddirection.

Wherethe cool air from Canadareplaces the warmer

air from the Gulf of Mexico, a coldfrontis drawnin blue,

with arrowheads showingthe front’s general direction of movement. Where the warm Gulfair is replacing cooler air to the north, a warm front is drawn in red, with half

circles showingits general direction ofmovement. Where the cold front has caught up to the warm front and cold air is now replacing coolair, an occludedfront is drawn

wey Cold front

@28 Warm front

\82_

@™ Stationary front

\ 4 F

b

wey Occluded front

Warm, humidair

© Cengage Learning?

3

Gulf of Mexico

&

Thunderstorm

ee

Light rain

2

Vv

Rain shower

- Wind direction (N) i

Windspeed (10 knots)

@ FIGURE 1.5 Simplified surface weather map that roughly correlates with the satellite image shown in Fig. 1.4. Because this map showsconditions several hoursafter those in Fig. 1.4, the frontal system across the Midwest is farther east. The shaded green area represents precipitation. The numbers on the map represent air temperaturesin °F.

in purple, with alternating arrowheads andhalf circles to show howit is moving. Along each of the fronts, warm air is rising, producing clouds andprecipitation. In the satellite image (Fig. 1.4), the occluded frontand the cold front appear as an elongated, curling cloud band that stretches from the low pressure area over Minnesota into the northernpartof Texas.

Noticein Fig. 1.5 that the frontal system is to the west ofChicago.As the westerly windsaloft pushthefront eastward, a person onthe outskirts of Chicago might observe the approachingfrontas a line oftowering thunderstorms similar to those shownin @ Fig. 1.6. On a Doppler radar image, the advancing thunderstorms might appear similar to those shown in e Fig. 1.7. In a few hours, Chicago should experience heavy showers with thunder,lightning, and gusty windsas the front passes. All of this weather, however, should give way to clearing skies and surface winds from the west or northwest after the front has movedonby.

Observing storm systems, we see that not only do they movebutthey also constantly change. Steered by the upper-level westerly winds, the middle-latitude storm in Fig. 1.5 gradually weakens and moveseastward, carrying

its clouds and weatherwithit. In advanceofthis system,

a sunny day in Ohio will gradually cloud over andyield heavy showers and thunderstormsby nightfall. Behind the storm,cool dry northerly winds rushing into eastern Colorado cause an overcast sky to give way to clearing conditions. Farther south, the thunderstormspresently over the Gulf of Mexico in thesatellite image (Fig. 1.4) expanda little, then dissipate as new storms appear over waterandland areas. To the west, the hurricane over the Pacific Ocean drifts northwestward and encounters cooler water. Here, away from its warm energy source,it losesits

punch; windstaperoff, and the storm soonturnsinto an

unorganized massof cloudsandtropical moisture.

WEATHER AND CLIMATE IN OUR LIVES Weather and climate play a majorrole in ourlives. Weather,for example, often dictates the type ofclothing we wear, while

climate influences the type of clothing we buy. Climate determines whento plant crops as well as what types of crops can be planted. Weather determinesif these same crops will grow to maturity. Although weatherandclimate affect our lives in many ways, perhaps their most immediate effect is on our comfort. In order to survive

ATMOSPHERE

NOAA/National Weather Service

the cold of winter and heat of summer, we build homes,

on days when weare forced to squint, often because of

© Robert Henson

@ FIGURE 1.6 Thunderstorms developing and advancing along an approachingcold front.

@ FIGURE 1.7 The elongated frontal system in Fig. 1.5 shows up on Doppler radar as line of different colors. In this composite image, the areas shaded green andblue indicate wherelightto-moderaterain is falling. Yellow indicates heavier rainfall.

The red-shaded area represents the heaviest rainfall and the possibility of intense thunderstorms. Notice that a thunderstorm is approaching Chicago from the west.

heat them, air condition them, insulate them—only to find that when weleave ourshelter, we are at the mercy of

the weather elements.

Even when weare dressedcorrectly for the weather,

wind, humidity, and precipitation can change ourperception ofhow coldor warmit feels. On a cold, windy day the effects of wind chill tell us thatit feels much colderthan it really is, and, if we are notcorrectly dressed, we run the

risk offrostbite or even hypothermia(the rapid, progressive mental and physical collapse that accompanies the lowering ofhuman body temperature). On a hot, humid day we normally feel uncomfortably warm and blameit on the

humidity. If we become too warm, our bodies overheat

and heat exhaustion or heatstroke may result. Those most likely to suffer these maladies are the elderly with impaired circulatory systems and infants, whose heat regulatory mechanismsare notyet fully developed.

Weatheraffects how wefeel in other ways, too, not

all of them well understood. Arthritic pain is mostlikely to occur whenrising humidity is accompanied byfalling pressures. The incidenceofheart attacks showsa statistical peak after the passage ofwarm fronts, whenrain and wind are common,andafterthe passage ofcold fronts, when an

abrupt change takes place as showery precipitationis accompaniedby cold gusty winds. Headaches are common 10

CHAPTER

hazyskies or a thin,bright overcast layer of high clouds.

Somepeople wholive near mountainous regions becomeirritable or depressed when there is a warm,

dry wind blowing downslope(a chinook wind). Hot, dry downslope Santa Ana windsin Southern California can turn dry vegetation into a ragingfirestorm.

Whenthe weather turns muchcolder or warmerthan normal,it impacts directly on thelives and pocketbooks of many people. For example, the exceptional record warmth observed from January to March 2012 over the United

States saved people millionsofdollarsin heatingcosts. On the othersideof the coin, the colder-than-normal winters of2013-2014 and 2014-2015 over muchofthe northeastern UnitedStates sent heating costs soaring as demandfor heatingfuel escalated.

Major cold spells accompanied by heavy snow and ice can play havocby snarling commutertraffic, curtailing airportservices, closing schools, and downing powerlines, thereby cuttingoff electricity to thousands of customers (see @ Fig. 1.8). For example, a huge ice storm during January 1998 in northern New England and Canada left millions of people without power and causedovera billion dollars in damages; and a devastating snow storm during March 1993 buried parts of the East Coast with 14-foot snowdrifts andleft Syracuse, New York, paralyzed with a

Copyright 2018 Cengage Learning. All Rights Reserved. May not becopied, scanned, or duplicated, in whole or in part. WCN 02-200-202

sparkedby lightningor a careless human,sucha dried-up region can quickly becomea raging inferno. During the winter of 2005-2006, hundredsof thousandsof acres in

drought-stricken Oklahomaand northern Texas were ravagedbywildfires.

Every summer,scorching heat waves take manylives.

Duringthe past twenty years, an annual average of more than 300 deaths in the UnitedStates wereattributed to excessive heat exposure. In one particularly devastating heat wavethat hit Chicago,Illinois, during July 1995,high temperatures coupled with high humidity claimed the lives of more than 700 people. In California, during July 2006, more than 100 people died during a two-weekperiod as

3 g

g = = 88 S$ za e§ 2 gs = sze 58 5 & == 5s < £ 3S

air temperaturesclimbed to over 46°C (115°F). Heat waves

@ FIGURE 1.8 Utility workers in Maine clear off broken tree branches from power lines during a major ice storm on December 12, 2008.

have been especially devastating in recent years across Europe, where manycities and buildings are not designed

snow depth of 36 inches. Whenthefrigid air settles into the Deep South, many millionsof dollars worth of temperature-sensitive fruits and vegetables may beruined, the eventual consequencebeing higher produceprices for

record-breaking heat wavein Russia in 2010 killed nearly 11,000 people in Moscow.

consumers.

Prolonged drought, especially when accompanied

by high temperatures, can lead to a shortage of food and, in someplaces, widespread starvation. Parts of

Africa, for example, have periodically suffered through major droughts and famine. During the summer of 2012, muchof the United States experienced a severe

droughtwith searing summer temperatures and wilting crops, causingbillions of dollars in croplosses. California experienced a destructive multi-year drought beginning in 2011. Whentheclimate turns hot and dry, animals suffer too. In 1986, over 500,000 chickensper-

ished in Georgia during a two-day periodat the peak of a summerheat wave. Severe droughtalso has an effect on waterreserves, often forcing communities to ration

waterandrestrict its use. During periods of extended drought, vegetation often becomes tinder-dry and,

for intenseheat. In the summerof 2003, tens ofthousands died across Europe, including 14,000 in France alone. A

Each year, the violent side of weather influences

the lives of millions. Those wholive along the Gulf and Atlantic coastlines keep a close watch for hurricanes during the late summerand early autumn.These large tropical systems can be amongthenation’s most destructive weather events. More than 250,000 people lost their homes when Hurricane Andrew struck the Miami area in 1992, and nearly 2000 people along the central Gulf Coast were killed by Hurricane Katrina in 2005.

A late-season hurricanecalled Sandy took a rare path in October 2012, striking the mid-Atlantic coast from

the southeast. Although it was no longerclassified as a hurricane whenit cameashore, Sandy produced wind gusts topping 80 miles per hour in someareas. Because

of its vast size and unusual path, Sandy pushed a huge

amountofwaterinto the coast, resulting in catastrophic

storm-surge flooding and more than 100 deaths across

parts of New Jersey, New York, and New England(see

@ Fig. 1.9).

@ FIGURE 1.9 A resident of Long Beach, New York, digs sand out around his car after Hurricane Sandy, during October 2012, pushed water and sand far inland, destroying homes, commercial businesses, and approximately 10,000 cars in this area alone.

2 S S 3 a 2 3 = <=

ATMOSPHERE

Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-200-202

AP Photo/Mark Schiefelbein

AP Photo/Mark Schiefelbein

@ FIGURE 1.10 Lightning flashes inside a violent tornado that tore through Joplin, Missouri, on May 22, 2011. The tornado ripped through a hospital and destroyed entire neighborhoods.

(See tornado damagein Fig. 1.11.)

@ FIGURE 1.11 Emergency personnel walk through a neighborhoodin Joplin, Missouri, damaged bya violent tornado, with winds exceeding 174 knots (200 mi/hr), on May 22, 2011. The tornado caused hundreds of millions of dollars in damage and took 159 lives, making this single tornado the deadliest in the United States since 1947.

@ FIGURE 1.12 Residents evacuate an apartment complex in the

AP Photo/David J Phillip

Houston area on April 18, 2016, as torrential rains from severe thunderstorms producedsevere flash flooding. More than 1000 highwaterrescues took place.

It is amazing how many people whose family roots are in the Midwest knowthe story of someone who was severely injured or killed by a tornado. Tornadoes have notonly taken manylives, but annually they cause damage to buildings and property totaling in the hundreds of millions of dollars, as a single large tornadocan level an entire section of a town (see @ Fig. 1.10 and @ Fig. 1.11).

Althoughthegentle rains of a typical summer thunderstorm are welcome over much of North America, the heavy downpours, high winds, andlarge hail of severe thunderstorms are not. Cloudbursts from slowly moving, intense thunderstorms can provide too much rain

too quickly, creating flash floods as small streams becomeragingrivers composed of mudandsand entangled with uprooted plants and trees. Thunderstorms dumped up to 20 inchesof rain in just a few hours overparts of the Houston area in April 2016, leading to severe flash flooding (see @ Fig. 1.12). If heavy rain coversa large area, devastating river floods can result. Record rainfall produced both types of flooding over the Southern Plains 12__

CHAPTER

in May 2015 and across South Carolina in October 2015.

Onthe average, morepeopledie in the United States from river floods andflash floods than from either lightning strikes or tornadoes. Strong downdrafts originating inside

an intense thunderstorm (a downburst) create turbulent

winds that are capable of destroying crops andinflicting damage uponsurface structures. Hundredsofpeople were killed in airline crashesattributed to turbulent wind shear (a rapid change in wind speed, winddirection, or both) from downbursts, before a safety system was implemented in the 1990s, which also has improved since that time.

Annually, hail damages crops worth millions ofdollars,

The folks of Elgin, Manitoba,literally had their “goose cooked” during April 1932, when a lightning bolt killed 52 geesethat wereflying overhead in formation. As the birds fell to the ground, they were reportedly gathered up and distributed to the townspeople for dinner.

Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-200-202

TBD

Weatherand climate have become so mucha part of our lives that the first thing manyof us do in the morning is to listen to the local weatherforecast or look it up on our smartphones. Forthis reason, many radio and mosttelevision newscasts have their own “weatherperson” to present weather information andgivedaily forecasts. More and more ofthese peopleare professionally trained in meteorology, and manystations require that the weathercaster becertified by the American Meteorological Society (AMS)or hold a seal ofapproval from the National Weather Association (NWA).

To maketheir weather presentations as up-to-the-minute as possible, weathercasters draw upon time-lapsesatellite images, Dopplerradar displays, and other waysofillustrating current weather. Many stations work with private firms that create graphics and customized forecasts,largelybased on observations and computer models from the National Weather Service (NWS). Since 1982,a staffoftrained professionals at

@ FIGURE 1.13 Estimates are that lightning strikes Earth about 40 to 50 times every second. More than 20 million lightning strikes hit the United States in a typical year. Here, lightning strikes the ground near wind turbines in Texas.

andlightning takesthe lives ofseveral dozen people in the United States andstarts fires that destroy many thousands of acres ofvaluable timber(see @ Fig. 1.13).

Upto this point, we have considered the moreviolent

side ofweather andits impact on humanity. Weather- and climate-related events can have enormous economic consequences. On average,tensofbillions of dollars in property damage occur each year in the United States alone (see @ Fig. 1.14). Yet even the quiet side of weatherhasits influence. When winds die down and humidair becomes moretranquil, fog may form. Heavy fog canrestrict visibility at airports, causingflight delays and cancellations.

Every winter, deadly fog-related auto accidents occur alongour busy highways and turnpikes. Butfog has a positive side,too, especially during a dry spell, as fog moisture collects on tree branchesanddrips to the ground, whereit

provides water for the tree’s root system.

The Weather Channel have provided weather information twenty-four hours a day oncabletelevision. (Many viewers believe the weatherperson they see on TVis a meteorologist andthat all meteorologists forecast the weather. If you are interested in learning what a meteorologist or atmospheric scientist is and what heor she mightdofora living other than forecast the weather, read Focus section 1.1.)

The National Oceanic and Atmospheric Administration

(NOAA), in cooperation with the National WeatherSer-

vice, sponsors weatherradio broadcasts at selected locations

across the United States. Known as NOAA Weather Radio (and transmitted at VHF-FM frequencies), this service provides continuous weatherinformation and regional forecasts (as well as special weatheradvisories, including watches and warnings)for over 90 percentofthe United States.

Although millions of people rely on weather broadcasts, manyuseforecasts obtained ontheir smartphones or on the internet. Websites operated by the NWSandprivate forecasting companiesprovidea wealth oflocal, national, and global data and forecasts. Smartphoneapplications

700 Numberof events

500 400

300 200.

100 Flooding

Wildfires

Winter

Freeze

storms |

cyclones (hurricanes)

Drought

||

storms

Tropical

|

Severe

||

| |

National Centersfor Environmental Information (NCEI)

600

Total cost(billions of dollars)

400

@ FIGURE 1.14 The number ofbillion-dollar weatherand climate events in the United States from 1980 to 2014 (red bar). The total cost (green bar) of the 178 events during this period exceeded $1 trillon. This total is adjusted to the 2014 consumerprice index and includes insured and uninsuredlosses.

ATMOSPHERE

Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-200-202

Another random document with no related content on Scribd:

DANCE ON STILTS AT THE GIRLS’ UNYAGO, NIUCHI

Newala, too, suffers from the distance of its water-supply—at least the Newala of to-day does; there was once another Newala in a lovely valley at the foot of the plateau. I visited it and found scarcely a trace of houses, only a Christian cemetery, with the graves of several missionaries and their converts, remaining as a monument of its former glories. But the surroundings are wonderfully beautiful. A thick grove of splendid mango-trees closes in the weather-worn crosses and headstones; behind them, combining the useful and the agreeable, is a whole plantation of lemon-trees covered with ripe fruit; not the small African kind, but a much larger and also juicier imported variety, which drops into the hands of the passing traveller, without calling for any exertion on his part. Old Newala is now under the jurisdiction of the native pastor, Daudi, at Chingulungulu, who, as I am on very friendly terms with him, allows me, as a matter of course, the use of this lemon-grove during my stay at Newala.

FEET MUTILATED BY THE RAVAGES OF THE “JIGGER” (Sarcopsylla penetrans)

The water-supply of New Newala is in the bottom of the valley, some 1,600 feet lower down. The way is not only long and fatiguing, but the water, when we get it, is thoroughly bad. We are suffering not only from this, but from the fact that the arrangements at Newala are nothing short of luxurious. We have a separate kitchen—a hut built against the boma palisade on the right of the baraza, the interior of which is not visible from our usual position. Our two cooks were not long in finding this out, and they consequently do—or rather neglect to do—what they please. In any case they do not seem to be very particular about the boiling of our drinking-water—at least I can attribute to no other cause certain attacks of a dysenteric nature, from which both Knudsen and I have suffered for some time. If a man like Omari has to be left unwatched for a moment, he is capable of anything. Besides this complaint, we are inconvenienced by the state of our nails, which have become as hard as glass, and crack on the slightest provocation, and I have the additional infliction of pimples all over me. As if all this were not enough, we have also, for the last week been waging war against the jigger, who has found his Eldorado in the hot sand of the Makonde plateau. Our men are seen all day long—whenever their chronic colds and the dysentery likewise raging among them permit—occupied in removing this scourge of Africa from their feet and trying to prevent the disastrous consequences of its presence. It is quite common to see natives of this place with one or two toes missing; many have lost all their toes,

or even the whole front part of the foot, so that a well-formed leg ends in a shapeless stump. These ravages are caused by the female of Sarcopsylla penetrans, which bores its way under the skin and there develops an egg-sac the size of a pea. In all books on the subject, it is stated that one’s attention is called to the presence of this parasite by an intolerable itching. This agrees very well with my experience, so far as the softer parts of the sole, the spaces between and under the toes, and the side of the foot are concerned, but if the creature penetrates through the harder parts of the heel or ball of the foot, it may escape even the most careful search till it has reached maturity.

Then there is no time to be lost, if the horrible ulceration, of which we see cases by the dozen every day, is to be prevented. It is much easier, by the way, to discover the insect on the white skin of a European than on that of a native, on which the dark speck scarcely shows. The four or five jiggers which, in spite of the fact that I constantly wore high laced boots, chose my feet to settle in, were taken out for me by the all-accomplished Knudsen, after which I thought it advisable to wash out the cavities with corrosive sublimate. The natives have a different sort of disinfectant—they fill the hole with scraped roots. In a tiny Makua village on the slope of the plateau south of Newala, we saw an old woman who had filled all the spaces under her toe-nails with powdered roots by way of prophylactic treatment. What will be the result, if any, who can say?

The rest of the many trifling ills which trouble our existence are really more comic than serious. In the absence of anything else to smoke, Knudsen and I at last opened a box of cigars procured from the Indian store-keeper at Lindi, and tried them, with the most distressing results. Whether they contain opium or some other narcotic, neither of us can say, but after the tenth puff we were both “off,” three-quarters stupefied and unspeakably wretched. Slowly we recovered—and what happened next? Half-an-hour later we were once more smoking these poisonous concoctions—so insatiable is the craving for tobacco in the tropics.

Even my present attacks of fever scarcely deserve to be taken seriously. I have had no less than three here at Newala, all of which have run their course in an incredibly short time. In the early afternoon, I am busy with my old natives, asking questions and making notes. The strong midday coffee has stimulated my spirits to

an extraordinary degree, the brain is active and vigorous, and work progresses rapidly, while a pleasant warmth pervades the whole body. Suddenly this gives place to a violent chill, forcing me to put on my overcoat, though it is only half-past three and the afternoon sun is at its hottest. Now the brain no longer works with such acuteness and logical precision; more especially does it fail me in trying to establish the syntax of the difficult Makua language on which I have ventured, as if I had not enough to do without it. Under the circumstances it seems advisable to take my temperature, and I do so, to save trouble, without leaving my seat, and while going on with my work. On examination, I find it to be 101·48°. My tutors are abruptly dismissed and my bed set up in the baraza; a few minutes later I am in it and treating myself internally with hot water and lemon-juice.

Three hours later, the thermometer marks nearly 104°, and I make them carry me back into the tent, bed and all, as I am now perspiring heavily, and exposure to the cold wind just beginning to blow might mean a fatal chill. I lie still for a little while, and then find, to my great relief, that the temperature is not rising, but rather falling. This is about 7.30 p.m. At 8 p.m. I find, to my unbounded astonishment, that it has fallen below 98·6°, and I feel perfectly well. I read for an hour or two, and could very well enjoy a smoke, if I had the wherewithal—Indian cigars being out of the question.

Having no medical training, I am at a loss to account for this state of things. It is impossible that these transitory attacks of high fever should be malarial; it seems more probable that they are due to a kind of sunstroke. On consulting my note-book, I become more and more inclined to think this is the case, for these attacks regularly follow extreme fatigue and long exposure to strong sunshine. They at least have the advantage of being only short interruptions to my work, as on the following morning I am always quite fresh and fit.

My treasure of a cook is suffering from an enormous hydrocele which makes it difficult for him to get up, and Moritz is obliged to keep in the dark on account of his inflamed eyes. Knudsen’s cook, a raw boy from somewhere in the bush, knows still less of cooking than Omari; consequently Nils Knudsen himself has been promoted to the vacant post. Finding that we had come to the end of our supplies, he began by sending to Chingulungulu for the four sucking-pigs which we had

bought from Matola and temporarily left in his charge; and when they came up, neatly packed in a large crate, he callously slaughtered the biggest of them. The first joint we were thoughtless enough to entrust for roasting to Knudsen’s mshenzi cook, and it was consequently uneatable; but we made the rest of the animal into a jelly which we ate with great relish after weeks of underfeeding, consuming incredible helpings of it at both midday and evening meals. The only drawback is a certain want of variety in the tinned vegetables. Dr. Jäger, to whom the Geographical Commission entrusted the provisioning of the expeditions—mine as well as his own—because he had more time on his hands than the rest of us, seems to have laid in a huge stock of Teltow turnips,[46] an article of food which is all very well for occasional use, but which quickly palls when set before one every day; and we seem to have no other tins left. There is no help for it—we must put up with the turnips; but I am certain that, once I am home again, I shall not touch them for ten years to come.

Amid all these minor evils, which, after all, go to make up the genuine flavour of Africa, there is at least one cheering touch: Knudsen has, with the dexterity of a skilled mechanic, repaired my 9 × 12 cm. camera, at least so far that I can use it with a little care.

How, in the absence of finger-nails, he was able to accomplish such a ticklish piece of work, having no tool but a clumsy screw-driver for taking to pieces and putting together again the complicated mechanism of the instantaneous shutter, is still a mystery to me; but he did it successfully. The loss of his finger-nails shows him in a light contrasting curiously enough with the intelligence evinced by the above operation; though, after all, it is scarcely surprising after his ten years’ residence in the bush. One day, at Lindi, he had occasion to wash a dog, which must have been in need of very thorough cleansing, for the bottle handed to our friend for the purpose had an extremely strong smell. Having performed his task in the most conscientious manner, he perceived with some surprise that the dog did not appear much the better for it, and was further surprised by finding his own nails ulcerating away in the course of the next few days. “How was I to know that carbolic acid has to be diluted?” he mutters indignantly, from time to time, with a troubled gaze at his mutilated finger-tips.

Since we came to Newala we have been making excursions in all directions through the surrounding country, in accordance with old habit, and also because the akida Sefu did not get together the tribal elders from whom I wanted information so speedily as he had promised. There is, however, no harm done, as, even if seen only from the outside, the country and people are interesting enough.

The Makonde plateau is like a large rectangular table rounded off at the corners. Measured from the Indian Ocean to Newala, it is about seventy-five miles long, and between the Rovuma and the Lukuledi it averages fifty miles in breadth, so that its superficial area is about two-thirds of that of the kingdom of Saxony. The surface, however, is not level, but uniformly inclined from its south-western edge to the ocean. From the upper edge, on which Newala lies, the eye ranges for many miles east and north-east, without encountering any obstacle, over the Makonde bush. It is a green sea, from which here and there thick clouds of smoke rise, to show that it, too, is inhabited by men who carry on their tillage like so many other primitive peoples, by cutting down and burning the bush, and manuring with the ashes. Even in the radiant light of a tropical day such a fire is a grand sight.

Much less effective is the impression produced just now by the great western plain as seen from the edge of the plateau. As often as time permits, I stroll along this edge, sometimes in one direction, sometimes in another, in the hope of finding the air clear enough to let me enjoy the view; but I have always been disappointed.

Wherever one looks, clouds of smoke rise from the burning bush, and the air is full of smoke and vapour. It is a pity, for under more favourable circumstances the panorama of the whole country up to the distant Majeje hills must be truly magnificent. It is of little use taking photographs now, and an outline sketch gives a very poor idea of the scenery. In one of these excursions I went out of my way to make a personal attempt on the Makonde bush. The present edge of the plateau is the result of a far-reaching process of destruction through erosion and denudation. The Makonde strata are everywhere cut into by ravines, which, though short, are hundreds of yards in depth. In consequence of the loose stratification of these beds, not only are the walls of these ravines nearly vertical, but their upper end is closed by an equally steep escarpment, so that the

western edge of the Makonde plateau is hemmed in by a series of deep, basin-like valleys. In order to get from one side of such a ravine to the other, I cut my way through the bush with a dozen of my men.

It was a very open part, with more grass than scrub, but even so the short stretch of less than two hundred yards was very hard work; at the end of it the men’s calicoes were in rags and they themselves bleeding from hundreds of scratches, while even our strong khaki suits had not escaped scatheless.

NATIVE PATH THROUGH THE MAKONDE BUSH, NEAR MAHUTA

I see increasing reason to believe that the view formed some time back as to the origin of the Makonde bush is the correct one. I have no doubt that it is not a natural product, but the result of human occupation. Those parts of the high country where man—as a very slight amount of practice enables the eye to perceive at once—has not yet penetrated with axe and hoe, are still occupied by a splendid timber forest quite able to sustain a comparison with our mixed forests in Germany. But wherever man has once built his hut or tilled his field, this horrible bush springs up. Every phase of this process

may be seen in the course of a couple of hours’ walk along the main road. From the bush to right or left, one hears the sound of the axe— not from one spot only, but from several directions at once. A few steps further on, we can see what is taking place. The brush has been cut down and piled up in heaps to the height of a yard or more, between which the trunks of the large trees stand up like the last pillars of a magnificent ruined building. These, too, present a melancholy spectacle: the destructive Makonde have ringed them— cut a broad strip of bark all round to ensure their dying off—and also piled up pyramids of brush round them. Father and son, mother and son-in-law, are chopping away perseveringly in the background—too busy, almost, to look round at the white stranger, who usually excites so much interest. If you pass by the same place a week later, the piles of brushwood have disappeared and a thick layer of ashes has taken the place of the green forest. The large trees stretch their smouldering trunks and branches in dumb accusation to heaven—if they have not already fallen and been more or less reduced to ashes, perhaps only showing as a white stripe on the dark ground.

This work of destruction is carried out by the Makonde alike on the virgin forest and on the bush which has sprung up on sites already cultivated and deserted. In the second case they are saved the trouble of burning the large trees, these being entirely absent in the secondary bush.

After burning this piece of forest ground and loosening it with the hoe, the native sows his corn and plants his vegetables. All over the country, he goes in for bed-culture, which requires, and, in fact, receives, the most careful attention. Weeds are nowhere tolerated in the south of German East Africa. The crops may fail on the plains, where droughts are frequent, but never on the plateau with its abundant rains and heavy dews. Its fortunate inhabitants even have the satisfaction of seeing the proud Wayao and Wamakua working for them as labourers, driven by hunger to serve where they were accustomed to rule.

But the light, sandy soil is soon exhausted, and would yield no harvest the second year if cultivated twice running. This fact has been familiar to the native for ages; consequently he provides in time, and, while his crop is growing, prepares the next plot with axe and firebrand. Next year he plants this with his various crops and

lets the first piece lie fallow. For a short time it remains waste and desolate; then nature steps in to repair the destruction wrought by man; a thousand new growths spring out of the exhausted soil, and even the old stumps put forth fresh shoots. Next year the new growth is up to one’s knees, and in a few years more it is that terrible, impenetrable bush, which maintains its position till the black occupier of the land has made the round of all the available sites and come back to his starting point.

The Makonde are, body and soul, so to speak, one with this bush.

According to my Yao informants, indeed, their name means nothing else but “bush people.” Their own tradition says that they have been settled up here for a very long time, but to my surprise they laid great stress on an original immigration. Their old homes were in the south-east, near Mikindani and the mouth of the Rovuma, whence their peaceful forefathers were driven by the continual raids of the Sakalavas from Madagascar and the warlike Shirazis[47] of the coast, to take refuge on the almost inaccessible plateau. I have studied African ethnology for twenty years, but the fact that changes of population in this apparently quiet and peaceable corner of the earth could have been occasioned by outside enterprises taking place on the high seas, was completely new to me. It is, no doubt, however, correct.

The charming tribal legend of the Makonde—besides informing us of other interesting matters—explains why they have to live in the thickest of the bush and a long way from the edge of the plateau, instead of making their permanent homes beside the purling brooks and springs of the low country.

“The place where the tribe originated is Mahuta, on the southern side of the plateau towards the Rovuma, where of old time there was nothing but thick bush. Out of this bush came a man who never washed himself or shaved his head, and who ate and drank but little.

He went out and made a human figure from the wood of a tree growing in the open country, which he took home to his abode in the bush and there set it upright. In the night this image came to life and was a woman. The man and woman went down together to the Rovuma to wash themselves. Here the woman gave birth to a stillborn child. They left that place and passed over the high land into the valley of the Mbemkuru, where the woman had another child, which

was also born dead. Then they returned to the high bush country of Mahuta, where the third child was born, which lived and grew up. In course of time, the couple had many more children, and called themselves Wamatanda. These were the ancestral stock of the Makonde, also called Wamakonde,[48] i.e., aborigines. Their forefather, the man from the bush, gave his children the command to bury their dead upright, in memory of the mother of their race who was cut out of wood and awoke to life when standing upright. He also warned them against settling in the valleys and near large streams, for sickness and death dwelt there. They were to make it a rule to have their huts at least an hour’s walk from the nearest wateringplace; then their children would thrive and escape illness.”

The explanation of the name Makonde given by my informants is somewhat different from that contained in the above legend, which I extract from a little book (small, but packed with information), by Pater Adams, entitled Lindi und sein Hinterland. Otherwise, my results agree exactly with the statements of the legend. Washing?

Hapana—there is no such thing. Why should they do so? As it is, the supply of water scarcely suffices for cooking and drinking; other people do not wash, so why should the Makonde distinguish himself by such needless eccentricity? As for shaving the head, the short, woolly crop scarcely needs it,[49] so the second ancestral precept is likewise easy enough to follow. Beyond this, however, there is nothing ridiculous in the ancestor’s advice. I have obtained from various local artists a fairly large number of figures carved in wood, ranging from fifteen to twenty-three inches in height, and representing women belonging to the great group of the Mavia, Makonde, and Matambwe tribes. The carving is remarkably well done and renders the female type with great accuracy, especially the keloid ornamentation, to be described later on. As to the object and meaning of their works the sculptors either could or (more probably) would tell me nothing, and I was forced to content myself with the scanty information vouchsafed by one man, who said that the figures were merely intended to represent the nembo—the artificial deformations of pelele, ear-discs, and keloids. The legend recorded

by Pater Adams places these figures in a new light. They must surely be more than mere dolls; and we may even venture to assume that they are—though the majority of present-day Makonde are probably unaware of the fact—representations of the tribal ancestress.

The references in the legend to the descent from Mahuta to the Rovuma, and to a journey across the highlands into the Mbekuru valley, undoubtedly indicate the previous history of the tribe, the travels of the ancestral pair typifying the migrations of their descendants. The descent to the neighbouring Rovuma valley, with its extraordinary fertility and great abundance of game, is intelligible at a glance—but the crossing of the Lukuledi depression, the ascent to the Rondo Plateau and the descent to the Mbemkuru, also lie within the bounds of probability, for all these districts have exactly the same character as the extreme south. Now, however, comes a point of especial interest for our bacteriological age. The primitive Makonde did not enjoy their lives in the marshy river-valleys.

Disease raged among them, and many died. It was only after they had returned to their original home near Mahuta, that the health conditions of these people improved. We are very apt to think of the African as a stupid person whose ignorance of nature is only equalled by his fear of it, and who looks on all mishaps as caused by evil spirits and malignant natural powers. It is much more correct to assume in this case that the people very early learnt to distinguish districts infested with malaria from those where it is absent.

This knowledge is crystallized in the ancestral warning against settling in the valleys and near the great waters, the dwelling-places of disease and death. At the same time, for security against the hostile Mavia south of the Rovuma, it was enacted that every settlement must be not less than a certain distance from the southern edge of the plateau. Such in fact is their mode of life at the present day. It is not such a bad one, and certainly they are both safer and more comfortable than the Makua, the recent intruders from the south, who have made USUAL METHOD OF good their footing on the western edge of the CLOSING HUT-DOOR plateau, extending over a fairly wide belt of country. Neither Makua nor Makonde show in their dwellings anything of the size and comeliness of the Yao houses in the plain, especially at Masasi, Chingulungulu and Zuza’s. Jumbe Chauro, a Makonde hamlet not far from Newala, on the road to Mahuta, is the

most important settlement of the tribe I have yet seen, and has fairly spacious huts. But how slovenly is their construction compared with the palatial residences of the elephant-hunters living in the plain.

The roofs are still more untidy than in the general run of huts during the dry season, the walls show here and there the scanty beginnings or the lamentable remains of the mud plastering, and the interior is a veritable dog-kennel; dirt, dust and disorder everywhere. A few huts only show any attempt at division into rooms, and this consists merely of very roughly-made bamboo partitions. In one point alone have I noticed any indication of progress—in the method of fastening the door. Houses all over the south are secured in a simple but ingenious manner. The door consists of a set of stout pieces of wood or bamboo, tied with bark-string to two cross-pieces, and moving in two grooves round one of the door-posts, so as to open inwards. If the owner wishes to leave home, he takes two logs as thick as a man’s upper arm and about a yard long. One of these is placed obliquely against the middle of the door from the inside, so as to form an angle of from 60° to 75° with the ground. He then places the second piece horizontally across the first, pressing it downward with all his might.

It is kept in place by two strong posts planted in the ground a few inches inside the door. This fastening is absolutely safe, but of course cannot be applied to both doors at once, otherwise how could the owner leave or enter his house? I have not yet succeeded in finding out how the back door is fastened.

MAKONDE LOCK AND KEY AT JUMBE CHAURO

This is the general way of closing a house. The Makonde at Jumbe Chauro, however, have a much more complicated, solid and original one. Here, too, the door is as already described, except that there is only one post on the inside, standing by itself about six inches from one side of the doorway. Opposite this post is a hole in the wall just large enough to admit a man’s arm. The door is closed inside by a large wooden bolt passing through a hole in this post and pressing with its free end against the door. The other end has three holes into which fit three pegs running in vertical grooves inside the post. The door is opened with a wooden key about a foot long, somewhat curved and sloped off at the butt; the other end has three pegs corresponding to the holes, in the bolt, so that, when it is thrust through the hole in the wall and inserted into the rectangular opening in the post, the pegs can be lifted and the bolt drawn out.[50]

MODE OF INSERTING THE KEY

With no small pride first one householder and then a second showed me on the spot the action of this greatest invention of the Makonde Highlands. To both with an admiring exclamation of “Vizuri sana!” (“Very fine!”). I expressed the wish to take back these marvels with me to Ulaya, to show the Wazungu what clever fellows the Makonde are. Scarcely five minutes after my return to camp at Newala, the two men came up sweating under the weight of two heavy logs which they laid down at my feet, handing over at the same time the keys of the fallen fortress. Arguing, logically enough, that if the key was wanted, the lock would be wanted with it, they had taken their axes and chopped down the posts—as it never occurred to them to dig them out of the ground and so bring them intact. Thus I have