WEathEr - Troop 577 Wichita, Kansas · 2019-08-11 · climate is. Discuss how the weather affects farmers, sailors, aviators, and the outdoor construction industry. Tell why weather

WEathEr

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WEATHER

BOY SCOUTS OF AMERICAMERIT BADGE SERIES

Requirements1. Definemeteorology.Explainwhatweatherisandwhat

climateis.Discusshowtheweatheraffectsfarmers,sailors,aviators,andtheoutdoorconstructionindustry.Tellwhyweatherforecastsareimportanttoeachofthesegroups.

2. Namefivedangerousweather-relatedconditions.Givethesafetyrulesforeachwhenoutdoorsandexplainthedifferencebetweenasevereweatherwatchandawarning.Discussthesafetyruleswithyourfamily.

3. Explainthedifferencebetweenhighandlowpressuresystemsintheatmosphere.Tellwhichisrelatedtogoodandtopoorweather.Drawcrosssectionsofacoldfrontandawarmfront,showingthelocationandmovementsofthecoldandwarmair,thefrontalslope,thelocationandtypesofcloudsassociatedwitheachtypeoffront,andthelocationofprecipitation.

4. Tellwhatcauseswind,whyitrains,andhowlightningandhailareformed.

5. Identifyanddescribecloudsinthelow,middle,andupperlevelsoftheatmosphere.Relatethesetospecifictypesofweather.

6. Drawadiagramofthewatercycleandlabelitsmajorprocesses.Explainthewatercycletoyourcounselor.

7. Defineacidrain.Identifywhichhumanactivitiespollutetheatmosphereandtheeffectssuchpollutioncanhaveonpeople.

35964ISBN 978-0-8395-3274-3©2006 Boy Scouts of America2010 Printing

BANG/Brainerd, MN 5-2010/060102

WEATHEr 3

8.DoONEofthefollowing:

a. Makeoneofthefollowinginstruments:windvane,anemometer,raingauge,hygrometer.Keepadailyweatherlogforoneweekusinginforma-tionfromthisinstrumentaswellasfromothersourcessuchaslocalradioandtelevisionstations,NOAAWeatherRadio,andInternetsources(withyourparent’spermission).Recordthefollowinginformationatthesametimeeveryday:winddirectionandspeed,temperature,precipitation,andtypesofclouds.Besuretomakeanoteofanymorningdeworfrost.Inthelog,alsolisttheweatherforecastsfromradioortelevisionatthesametimeeachdayandshowhowtheweatherreallyturnedout.

b. VisitaNationalWeatherServiceofficeortalkwithalocalradioortelevisionweathercaster,privatemeteorologist,localagriculturalextensionserviceofficer,oruniversitymeteorologyinstructor.Findoutwhattypeofweatherismostdangerousordamagingtoyourcommunity.Determinehowsevereweatherandfloodwarningsreachthehomesinyourcommunity.

9.DoONEofthefollowing:

a. Giveatalkofatleastfiveminutestoagroup(suchasyourunitoraCubScoutpack)explainingtheoutdoorsafetyrulesintheeventoflightning,flashfloods,andtornadoes.Beforeyourtalk,shareyouroutlinewithyourcounselorforapproval.

b. Readseveralarticlesaboutacidrainandgiveapreparedtalkofatleastfiveminutestoagroup(suchasyourunitoraCubScoutpack)aboutthearticles.Beforeyourtalk,shareyouroutlinewithyourcounselorforapproval.

10. Findoutaboutaweather-relatedcareeropportunitythatinterestsyou.Discusswithandexplaintoyourcounselorwhattrainingandeducationarerequiredforsuchaposi-tion,andtheresponsibilitiesrequiredofsuchaposition.

WEATHEr 5

Contents

EarthandItsAtmosphere. . . . . . . . . . . . . . . . . . . . . . . . . . . .7

Moisture—TheWaterCycle. . . . . . . . . . . . . . . . . . . . . . . . . 15

CloudsandPrecipitation. . . . . . . . . . . . . . . . . . . . . . . . . . . 21

HazardousWeather. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

MeasuringandRecordingtheWeather. . . . . . . . . . . . . . . . . 41

WeatherandClimatePrediction. . . . . . . . . . . . . . . . . . . . . . 63

CareersinMeteorology. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

WeatherResources. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

WEATHEr 7

.Earth and Its Atmosphere

EarthandItsAtmosphereEarth’satmospherecanbethoughtofasanocean.Itisanoceanofairinsteadofwater.Theairisalmostneveratrest.Itsrestlessmovementisthesourceofeverythingpeoplecallweather.Thestudyoftheatmosphereanditsweatheristhescienceofmeteorology.

Elements of the AtmosphereTheatmosphereisamixtureofgases,sixofwhicharepresentinamountslargeenoughtobeimportantinstudyingmeteorology.Fourofthesixstaymoreorlessinconstantproportions,atleastintheatmosphere’slowest8milesorso.Themostabundantoftheseisnitrogen,makingupabout78percentoftheatmosphere.Oxygenisnext,atabout21percent,followedbyargonatabout1percent,andcarbondioxideatabout0.03percent.Nitrogen,oxygen,andcarbondioxideareessentialtolifeonEarth.Iftheirproportionsweretochangesignificantly,alllifewoulddisappear.

Theatmospherecontainstwootherimportantgases.Becausetheiramountschangefromtimetotimeandplacetoplace,theyarecalledvariable gases.Oneiswatervapor,whichcanrangefromnearlyzerotoashighasabout4percentofthetotal.Mostofthewatervaporisconcentratedinthelowestmileoftheatmosphere.Whenitcondensestoformclouds,rain,andsnow,itisthemostimportantpartoftheweather.

8 WEATHEr

Earth and Its Atmosphere.

Theothervariablegasisozone,mostofwhichisfoundmorethan6milesaboveEarth.Whileozoneatsealevelharmshumansandplantlife,itspresencehighintheatmosphereshieldsusfromthesun’sultravioletrays.

The Vertical Structure of the AtmosphereAcrosssectionoftheatmosphereshowsthatitconsistsoffourmainlayers.Thereisno“top”toEarth’satmosphere.Instead,itgraduallythinsuntilitvanishesintothevacuumofspace.

ThelowestlayerofEarth’satmosphereiscalledthetropo-sphere.Thislayervariesindepthfromabout10milesattheequatortoonly4milesovertheNorthandSouthpoles.Itiswithinthislayerthatmostweatheroccurs.Thetroposphereisconstantlystirredbythemotionsthatproduceweather,sothemixtureofgasesisnearlyconstant.Earth’ssurface,whichiswarmedbythesun,inturnwarmstheairofthelowertropo-sphere.Asaresult,temperaturesinthislayertendtodecreaseasaltitudeincreases.Onaverage,forevery1,000feetgained,theairtemperaturewilldecreasebyroughly3.5degreesFahrenheit.

Thelayerabovethetroposphereisthestratosphere.Thislayerextendstoaheightofabout30miles.Inthestratosphere,theatmosphereisquitethinandthemixtureofgasesbeginstochange.ThesmallamountofozoneinthestratosphereisvitaltolifeonEarthbecauseitabsorbsthesun’sharmfulultra-violetradiation.

Stratosphere

Mesosphere

Thermosphere

Troposphere

Sea Level

10

20

30(48 km)

(32 km)

(16 km)

50(80 km)

120(200 km)

Altitude (in miles)

MOUNT EVEREST

AIR TRAFFIC

WEATHEr 9


Theboundarybetweenthetropo-sphereandstratosphereiscalledthetropopause,alidontheweather-filledtroposphere.Temperaturebeginstoincreasewithheightabovethetropo-pausebecauseanincreasingnumberofozonemoleculesabsorbthesun’sultravioletradiation.

Abovethestratosphereisthemesosphere,whichextendsabout30to50miles.Temperaturedecreaseswithheightinthiscoldestlayeroftheatmosphere.Thenextlayeristhethermosphere.Becauseofthesun’srays,airtemperaturesinthislayercanreachmorethan1,800degrees.

The Origin of WindInprehistorictimes,humansbecameawarethattheweather—cloudyorclearskies,warmorcoldair—dependedonwinddirectionandspeed.Duringthe1600s,peoplelearnedthatairhasweight.Scientistsdiscoveredthatairbecomeslighterwhenitiswarmandheavierwhenitiscold.BecausethepressurethatanythingexertsonthesurfaceofEarthdependsonitsweight,airtemperatureaffectsairpressure.

Airtemperaturealsoisafactorinhowwindsarise.Ifairinoneplaceisheatedsothatitiswarmerthantheairaroundit,thatairtendstorise.Asitdoes,airmustflowinfromaroundtheheatedregiontoreplacetheairthatisrising.

Air has weight for the same reason you do. It is held to Earth by gravity. In fact, the air above a square inch of Earth’s surface exerts 14.7 pounds of pressure at sea level. Atmospheric pressure, or air pressure, is the amount of force the air exerts on a unit surface area (an area that has equal length and width). Why don’t you feel all that weight pressing down on you? One reason is that the air is not really pressing down but is pressing in all directions. Also, the air inside your body is pressing in all directions with equal pressure.

10 WEATHEr


Ifyoulivenearaseacoast,youmayseethisprocessoperateeveryday.Duringtheday,thelandheatsmorerapidlythantheocean.Thisheatwarmstheairoverthelandandmakesitrise.Coolerairfromtheoceanflowsintoreplaceit.Inturn,therisingairoverlandflowsouttoseaatsomelevelabovethesurfacetoreplacetheairflowinginland.Thiscreatesaseabreeze.

Atnight,theoppositehappens.Thelandcoolsmorerapidlythantheocean.Airflowsfromlandtoseaatthesurface,andthecycleisreversed.Thecirculationthatresultsisalandbreeze.Similarcirculationscandeveloparoundmountains,creatingmountainandvalleybreezes.Thewindsthatcreatetheweatherallariseinthisway,asaresultofunequalheating.However,itisnotalwaysthiseasytounderstandwhywindsbehavethewaytheydo.

The fact that sunlight does not evenly heat Earth’s surface means that temperatures vary from place to place and from time to time. This difference in air temperature (and therefore air pressure) creates a force that makes the air move from high- to low-pressure regions, trying to equalize the pressure. When the motion of the moving air is vertical or nearly so, it is called a current. When the motion is more horizontal, it is called wind.

Sea breezes

lAndOceAn

cOOleR AiR mOVes in tO tAKe WARm AiR’s PlAce.

WARmeR AiR Rising gOes bAcK Out tO seA.

WEATHEr 11


Global Wind and Pressure SystemsWarmairneartheequator,inthetropics,tendstoriseandflowtowardthepoles(poleward).Alongtheway,theaircoolsandbeginstosink.Becausetheequatorialregionsarewarm,theytendtoformabeltofrelativelylowpressure.Theregionsofsinkingairtendtobeassociatedwithrelativelyhighpressure,inwhatarecalledthe“horselatitudes,”orsubtropics.

Inasimilarfashion,airoverthepolestendstosink,beingcolderandheavier.Thissinkingsendstheairflowingintothesubpolarregions,whereitwarmsandrises,formingabeltwithrelativelylowpressureatthesurface.(Remember,warmairbringsaboutlowpressure,andcoldairbringsabouthighpressurebecauseitweighsmore.)

Themiddle latitudesliebetweenthebeltofsubpolarlowsandthesubtropichighs.MostoftheUnitedStatescanbefoundintheNorthernHemisphere’smiddlelatitudes.TheSouthernHemispherealsohasmiddlelatitudes.Airtendstoflowpole-wardatthesurfaceofEarth,andtowardtheequator(equator-ward)aloft,completingthetransitionbetweenthepolarandequatorialcirculations.

Land breezes

WARm OceAnlAnd cOOling

cOOl AiR

12 WEATHEr


Noticeonthediagramhowthesurfacewindsblowingtowardtheequatorinbothhemispherestendtoflowfromeasttowest.Similarly,thesurfacewindsblowingpolewardtendtoincludeaflowfromwesttoeast.Meteorologistsrefertowindsaccordingtothedirectionfromwhichtheyblow.Windsblow-ingfromeasttowestarecalledeasterlies,andwindsblowingfromwesttoeastarecalledwesterlies.

Ifitwerenotforthedevelopmentofeasterlyandwesterlywinds,thetendenciesforwindstoblowstraightfromhigh-tolow-pressureregionswouldbeverysimilartothelocalbreezesdescribedatthebeginningofthischapter.

POlAR high

POlAR high

lOW lOW

lOW lOW

lOW lOW

high high

high high

60°n subPOlAR lOW

midlAtitudes (PReVAiling WesteRlies)

30°n subtROPics (hORse lAtitudes)

nORtheAst tRAde Winds

0° tROPics (equAtOR)

sOutheAst tRAde Winds

subtROPics (hORse lAtitudes)30°s

midlAtitudes (PReVAiling WesteRlies)

60°s subPOlAR lOW

This global winds diagram shows wind’s basic patterns. The actual patterns of wind at any given moment are far more complicated.

WEATHEr 13


The relationship Between Wind and Pressure Tounderstandwhyglobalwindshavebotheasterlyandwest-erlymovement,rememberthatEarthisrotatingaboutitspolaraxis.Itmakesonecompleteturnin24hours,whichcausesdaytoalternatewithnight.Thespeedofrotationvariesasyoumovenorthorsouth—itvarieswithlatitude.Youcanseethisonaglobe.Spintheglobeandwatchwhilepointsneartheequatormovefastwhilethepolesdonotmoveatall.ApointonEarth’sequatortravelsmorethan1,000milesperhour(about25,000milesin24hours),whilethepolesdonotmove.

ThisdifferenceinspeedproducesaninterestingeffectasseenbyanobserverwatchingthingsfromEarth.Imaginefiringacannonduesouth.Asthecannonballtravelssouth,itpassesoverpointsthataremovingmoreandmorerapidlybeneathit.Itspath,as seen on Earth(thesolidarrow),curvestotheright.Amysteriousforceappearstomakethepathofthecannonballcurve.Anobserverinspacewouldseethepathofthecannon-ballasastraightline(thedashedarrowinthediagram),butitappearscurvedtoearthboundobservers.

Thisapparentforce—calledtheCoriolis forceafterFrenchscientistGustave-GaspardCoriolis,whofirstdescribedit—isveryrealtopeoplelivingontherotatingEarth.Itmustbeaccountedforwhenfiringlong-rangeweapons.Italsoaffectsspacecraftsuchasthespaceshuttle.Fortheweather,itmakesthemovingairseemtocurvetotherightintheNorthernHemisphereandtotheleftintheSouthernHemisphere.

Much of the time,

a low-pressure

system is

related to poor

weather, and a

high-pressure

system is related

to fair weather.

The rising air of

a low-pressure

system invites

the formation

of clouds and

precipitation.

The sinking air

of a high-pressure

system makes

cloud formation

less likely.

The Coriolis ForCenORth POle nORth POle

Object tRAVeling

sOuth

Object tRAVeling

nORth

sOuth

A

A

b

b

sOuth

The origin (cannon) moves from A to B due to Earth’s rotation. The object (cannonball) follows a curved path (B to C) relative to Earth. From space, an observer would see the object follow a straight line (A to C).

c

c

WEATHEr 15

.Moisture—The Water Cycle

Moisture—TheWaterCycleThemostimportantthingabouttheweatheristhemoistureitbrings.Thewindcouldblownightanddayandthetempera-turecouldriseandfall,butifnorainfell,Earthwouldbeinrealtrouble.

Fortunately,inadditiontoawonderfulair-circulatingsystem,Earthhasawonderfulwater-circulatingsystem.ThewatervaporthatformscloudsandprecipitationcomesmostlyfromevaporationfromEarth’soceans.Asmallpartcomesfromlakes,streams,andtranspiration,thatis,thegivingoffofwaterbytheleavesofgreenplants.

Mostoftherainthatfallsoverlandevaporatesandistransportedaswatervaporbythewinds,oftenmanythousandsofmilesfromitssource.Watervaporcondenses (changesfromagastoaliquid)incloudsandfallsbacktoEarthasrain,snow,andotherformsofprecipitation.Someprecipitationformsrun-off,thewaterthatflowsinrivuletsandstreamstotherivers.Partoftheprecipitationfiltersdownintothegroundtoreplen-ishthegroundwater supply,whichalsofeedstherivers.Somegroundwateristakenupbyplantsthatrestoreittotheatmo-spherethroughtranspiration.

Someprecipitationfallsassnow.Ofthis,mosteventuallymeltsandbecomesrunofforgroundwater.However,partofthesnowfallremainsfrozen,lockedintoslow-movingriversoficecalledglaciers.AconsiderableamountofEarth’swatersupplyistiedupintheformoficeoverthepolarregionsoftheglobe,especiallyinAntarctica.Theicegraduallymovesinglacierstowardtheocean,butitmaytakehundredsorthousandsofyearsforwaterthatfallsassnowoverglacierstoreachtheocean.

16 WEATHEr

Moisture—The Water Cycle.

Asmallamountofthegroundwaterbecomestrappedintheground,formingundergroundreservoirscalledaquifers.Inmanypartsoftheworld,includingtheUnitedStates,thewaterinaquifersistappedforhumanuse,especiallyforirriga-tion.Oncetheaquifersaredrained,theymaynotfillagainforthousandsofyears.

Polaricepacks,glaciers,andundergroundaquiferstieupsomeofEarth’swatersupply,butoverall,waterthatevaporatesfromtheoceanseventuallyfindsitswaybacktotheoceans.Alloftheeventsdescribedabove—evaporation,transpiration,watervaportransport,condensation,precipitation,runoff,andstreamflow—arepartofacycleofeventsknownasthewater cycle,alsocalledthehydrologic cycle.Onthewhole,thecycleisinbalance,thatis,thetotalamountofwaterontheplanetremainsconstant.

PReciPitAtiOn (RAin)

clOud FORmAtiOn

tRAnsPiRAtiOn

eVAPORAtiOn

suRFAce RunOFF

gROund WAteR

PeRcOlAtiOn (sOAK-in)

stReAm tO OceAn

The water cycle

WEATHEr 17


Humidity and DewpointAtmospheric humiditydescribestheamountofwatervaporintheair.Airholdingthemaximumamountofwatervaporpossi-bleissaidtobesaturated.Thesaturation pointdependsontheair’stemperature.Warmaircanholdmuchmoremoisturethancoldaircan.Therefore,aircanbepushedtosaturationwhenitiscooledorwhenmorewatervaporisadded(throughevapora-tionortranspiration).

Onaclearnight,thetemperatureoftheairnearthegroundmayfalluntilsaturationisreached.Iftheaircontinuestocooltothepointthatitcannolongerholdallthewatervapor,someofthewaterwillbeforcedtocondenseontoobjectsontheground,formingdew.Undertherightconditions,fogcanform.Condensationintheatmosphereusuallyiscausedbycoolingtheairtosaturation.Onlyrarelyiscondensationintheatmospherecausedbyaddingwatertotheairthroughevaporationatthesametemperature.

Thedewpointistheairtemperatureatwhichsaturationtakesplacewhentheairpressurestaysconstant.Iftheairalreadyissaturated,theairtemperatureandthedewpointarethesame.Dewpointoftenremainsfairlyconstantduringtheday.Amorecommonmeasureofatmosphericmoistureisrelative humidity.Youprobablyhaveheardradioandtelevisionannouncersgivetherelativehumidityaspartoftheweatherreport.Relativehumidityistheactualamountofwatervaporintheairdividedbythemaximumamountofwateritcanholdatthattemperature.Itusuallyisexpressedasapercentage.Forexample,saturatedairissaidtobeat100percentrelativehumidity.Iftheaircontainsone-halfofthetotalamountofwatervaporneededtosaturateit,therelativehumidityis50percent.

However,recallthatwhentheairtemperaturerises,sodoesthetotalamountofwatervaporitcanhold.Therefore,iftheactualamountofwatervaporstaysthesame,therelativehumiditydecreaseswhenthetemperaturerisesandincreaseswhenthetemperaturefalls.That’swhyrelativehumidity

Some people refer

to dew and frost

as precipitation,

but they are

not forms of

precipitation

because they

do not actually

precipitate, or fall.

18 WEATHEr

Moisture—The Water Cycle.

reportscanbedeceiving.Inhotweather,humanssweattostaycool.Asthesweat(water)evaporatesfromourskin,ittakesheatawayfromthebody.Iftheairisnearsaturation,sweatingisnotveryeffectiveatcoolingus,sowefeeluncomfortable.

Humancomfortdependsmoreonthedewpointthanontherelativehumidity.Summerdayscanbeuncomfortablewhenthedewpointrisesabove60degrees,eventhoughtherelativehumidityatthetimeofthemaximumdaytimetempera-turecanbelow.Hereisanexample:Atatemperatureof95degreesandadewpointof65degrees,therelativehumidityisonlyabout35percent,buttheairwillfeelhotandmuggy.Ifthedewpointremainsthesameandthetemperaturedropsto70degreesafterdark,therelativehumiditywillrisetoalmost85percent.Eventhoughtherelativehumidityishigher,theairwillfeelmorecomfortablethanitdidduringtheday.

By noting changes in relative humidity as indicated on a hygrometer, you can determine whether the day will be muggy or comfortable.

WEATHEr 19


Condensation: Fog, Dew, Frost, and RimeFog is merely a cloud forming at Earth’s surface. It forms when warm, moist air comes in contact with the colder air and forms a cloud. The chilled water vapor condenses and attaches to particles in the air.

Fog occurs most frequently at night along water sources where the cooling of slow-moving air, combined with the source of moisture, pushes the air to saturation. Also, when cold air moves over warm water, the water evaporating into the cold air can increase the dewpoint temperature of the air to saturation, resulting in widespread fog. You may have noticed that there is often fog in the mountains and hills. This fog occurs when warmer air moves quickly up a slope. The air cools as it rises, and the water vapor condenses to form fog.

Dew is formed when the water vapor in the air condenses on cool objects. Dew usually forms on cool nights during warm seasons. Daytime air that is almost at its saturation point will cool down, and the air will become fully saturated with water. The extra water vapor will condense on objects cooler than the air itself, such as grass and spider webs.

In cold seasons, the same kinds of conditions

that bring about dew will form frost instead. Frost occurs when air’s dewpoint is below freezing. The condensing water vapor is deposited in feathery patterns of ice crystals instead of tiny droplets. The objects it forms upon must also be below freezing, but the air from which it condenses may be several degrees above freezing.

When the wind blows fog against objects with surface temperatures below freezing, a type of ice deposit called rime forms. The fog particles, which can remain liquid down to temperatures of about -40 degrees, freeze upon contact with the object and build up a white deposit. (A similar deposit may build up in some refrigerator freez-ers.) The white or milky appearance of rime ice is due to small regions of air that are trapped between the fog particles before they freeze.

Dew

Fog

Frost

rime

WEATHEr 21

.Clouds and Precipitation

CloudsandPrecipitationCloudsformwhenwatervaporcondensestoformicecrystalsorwaterdropletsintheair.Cloudformationgen-erallyisassociatedwithrisingair.Aircoolsasitascendsbecausepressuredecreaseswithheight.Thedropinpres-surecausestherisingairtoexpand,eventually,theairtoitsdewpoint.Thencondensa-tionorfreezingbegins.Thewatervaporcondensesaroundtinyparticlesintheair,suchasdustorsaltfromthesea.Theresultingdropletsareaboutone-millionththesizeofamediumraindrop.Thesecondensedparticlesaresominusculethatturbulentairmotionholdsthemaloft.

Learning LatinThe cloud names are derived from Latin words. If you learn the Latin meanings, you can more easily remember the cloud types. Here are the basic Latin-based words and their meanings. Cirrus: Curl or tendril of hair Stratus: A layer, like a blanket stretched out Cumulus: A heap or pile (Think of the word accumulate.) Nimbus: Rain

32,800 FeeT

ciRRus

ciRROcumulusciRROstRAtus

AltOcumulus

AltOstRAtus

cumulOnimbus

stRAtOcumulus

stRAtus

cumulus

nimbOstRAtus

19,700 FeeT

6,600 FeeT

22 WEATHEr

Clouds and Precipitation.

Cloud Formation and Types Meteorologistsusefourmaingroupingsforclouds:lowclouds,middleclouds,highclouds,andcloudsthatdevelopvertically.Meteorologistsalsoconsidertheshapesofclouds.

High CloudsThehighestcloudsaregenerallyabove20,000feetandarecalledcirrus clouds.Thesehighcloudsareoftenwispy.Cirruscloudsarecomposedentirelyoficecrystalsbecauseoftheirlowtemper-aturesandtheheightswheretheyform.

Sometimescirruscloudsarelumpy.Thosearecalledcirrocumulus.Cirrocumuluscloudscanbearrangedinpatchesoralignedinrows.

Cirrus clouds are

sometimes called

“mare’s tails”

because they

look a bit like a

horse’s tail.

Cirrus clouds

Cirrocumulus clouds

WEATHEr 23


Cirruscloudsforminginextensiveflatlayersareknownascirrostratus.Cirrostratuscloudscancoverthewholeskyoronlypartofitandcanbequitethinandnearlytransparent.Whencirruscloudsgivewaytocirrostratus,precipitationmaybeonthewaywithinthenext24hours.

Thedeep,toweringthunderheadsknownascumulonimbus cloudscanbemorethan50,000feettallandcanoccupymorethanoneheightcategory.Theirheightcertainlyqualifiesthemtobehighclouds,thoughmeteorologiststhinkofthemascloudsofverticaldevelopment.Cumulonimbuscloudsalmostalwaysflattenoutnearthetropopause.Theirflat,anvil-shapedtopisahelpinidentifyingthem.Cumulonimbuscloudswilllikelybringlightning,heavyrain,andpossiblyhail.

Cumulonimbus clouds

Cirrostratus clouds

24 WEATHEr


Middle CloudsThemiddlegroupofclouds,withheightsroughlybetween10,000and20,000feet,hastheprefixalto-.Thisgroupincludesaltocumulusclouds,whichoftenlooklikeafluffyblanketcov-eringthesky.Altocumuluscloudsalsocanappearinpatchesorinrows.Theycanbedistinguishedbytheroundedcontoursofthecloudswithsmallopeningsshowingblueskyabove,andbytheirheight.Altocumuluscloudsindicatethatmoistureisrisingandthatrainmaybeontheway.

Altostratus cloudsappearflatandlayered.Altostratuscloudsoccasionallycancovernearlythewholeskybutcanbethinenoughtoletthesunshowthroughdimly.Altostratuscloudsindicateanapproachingwarmfrontandachangeofweather,suchasrainorsnow.

Fog can be

thought of as a

stratus cloud at

the surface.

Altostratus clouds

Altocumulus clouds

WEATHEr 25


Low CloudsLowcloudsappearfromnearEarth’ssurfaceuptoabout10,000feet.Stratus cloudsappearasauniformcloudlayer,withlittleornotexture.

Stratocumulus cloudstypicallyareflatandnearlyuniformattheirbasesbutpuffyandclumpedontop.Theyarelikelytoformheavyridgesthatlooklikecorrugatedroofing.Stratocumuluscloudsoftenindicateheavyprecipitation,especiallyiftheyareattheheadofacoldfront.

Nimbostratuscloudsaredark,sheetlikecloudsandindi-catethatrainorsnowisfalling.

Cumuluscloudsformbelow6,500feetbutcangrowverytall,muchtallerthantheyarewide.Meteorologistsconsiderthemcloudsofverticaldevelopment.Whenthesefluffy“cloudships”floatinthebrightbluesky,theyarecalledfair-weathercumulus,andtheyusuallymeangoodweatherisahead.

Stratus clouds

Stratocumulus clouds

Cumulus clouds

Nimbostratus clouds

26 WEATHEr


PrecipitationAcloudismadeofwatervaporthathascondensedintotinywaterdropletsoricecrystals.Asmoreandmorewatervaporcondenses,someoftheparticlescollidewitheachotherandmergetoformdropletslargeenoughtobegintofall.Astheyfall,theycontinuetogrowbysweepingupsmallerdropletsalongtheway—aprocesscalledcoalescence.Whendropletsbecomejustlargeenoughtofalltothesurface,theyarecalleddrizzle.Itmaytakeathousandormoreclouddropletstoformasingledropofdrizzle.Asthedropletscontinuetogrow,theyreachasizelargeenoughtobecalledrain.

Snowformswhencloudtemperaturesarewellbelowfreezing.Icecrystalsbecomelargerwhentheyattractwaterfromnearbysupercooledwaterdroplets.Whentheicecrystalsareheavyenoughtofall,theysticktoothericecrystalsandformsnowflakes.Snowcanformandfallevenwhentempera-turesatEarth’ssurfaceareabovefreezing.Ifsurfacetempera-turesarewarmenough,however,thefallingsnowwillmeltbeforereachingthegroundandwillfallasdrizzleorrain.Meltingsnowflakesusuallyaresmallenoughtobecomedrizzle,butsometimessnowflakesclumptogetherandformsmallwhitepelletscalledgraupel (pronouncethe“au”like“aw”in“crawl”).

Sometimesrainwillfallandhitalayerofbelow-freezingairbeforeitreachestheground.Therainthenformsicepellets,orsleet.Ifrainfallstothegroundandhitsaverycoldsurface,theresultisfreezing rain.Freezingraincancauseicyroadconditionsandcanformheavyicecoveringsonpowerlinesandvegetation.

Oneofthemostspectacularformsofprecipitationishail.Hailistheresultoficeformingintherisingcurrentsofair,orupdrafts,ofthunderstorms.Whenanupdraftisstrongenough,itholdstheicealoft.Manylayersofsupercooledwaterfreezetotheicepellets,addingtotheirsize.Theygivethehailstoneastructurelikeanonion.

The Dirt About

Snowflakes

Dirt, pollen, sand,

dust—these are

the kinds of

elements that

serve as building

blocks for ice

crystals, which

join together

to become

snowflakes. Each

delicate snowflake

has six sides

and is made up

of as many as

200 ice crystals

stuck together.

Most of the time, raindrops are not collections of smaller water droplets but are instead melted snow or graupel. If the air never becomes very warm, as in the winter, the snowflakes and graupel simply fall as snow and snow pellets.

WEATHEr 27


Thehailstonegrowsuntiltheupdraftcannolongerholditaloftoruntilitsmotionwithinthestormcarriesitoutoftheupdraft.Thenitfallstotheground,perhapsmeltingsomewhatasitnearsthesurface.Hailstonescanrangefromthesizeofsmallpeastothesizeofgrapefruits.Largehail-stonesoftenarenotsimplespheres,buttakeonirregularshapesasaresultofbeingtossedandturnedwithintheturbulentairofthethunderstorm.

VisibilityVisibility indicatesthetransparencyofair.Aircontainsparticlesthatreflectandscatterlight,sothatobjectsatadistancecannotbeseen.Smokefromfires,dustpickedupoverland,andsaltparticlesfromevaporatedoceanspraycanbecarriedgreatdis-tancesbywindandcancollectinstillareas.Waterdropletsintheformofcloudsorfogcanalsoreducevisibility,ascanrain-dropsandsnowflakesifthereareenoughofthem.

Todeterminevisibilityformeteorologicalpurposes,lookforseveralobjectswhosedistancesfromtheobservingpointareknown.Bynotingthedistanceofthefarthestobjectthatcanbeseen,youcanthenestimatevisibility.Visibilityisnor-mallyreportedinmilesorafractionofamile.Visibilityisessentialinaircraftoperationandinnavigatingalmostanykindoftransportationvehicle(cars,trucks,andespeciallyplanesandboats).Observationsofvisibilityareroutinelyreportedallovertheworld.

Hailstone

SupercoolingAn interesting phenomenon called supercooling plays a role in the formation of snow. Water that is supercooled remains in its liquid state when the temperature is below freezing. The reason the water does not freeze is that, in order for a liquid to crystallize into a solid, there needs to be something for the crystals to form around, such as a particle of dust, salt, or plant matter. If a water droplet in a cloud contains no such particle, or nucleus, it will remain liquid. However, when a nucleus is present, an ice crystal will begin to form and grow around the nucleus.

28 WEATHEr


FrontsInradioandtelevisionweatherreports,youoftenhearaboutfronts.Aweatherreportermightsaysomethinglike,“Awarmfrontiscomingupthecoast”or“AstrongcoldfrontismovingdownfromCanada.”Thesereportssoundasthoughaninva-sionwereontheway!Inasense,that’sright.Thereportsaredescribingtheinvasionofairmasses.

Air massesformwhenairremainsinplaceoveraparticularregionforseveraldays.Theairgraduallytakesonthecharacter-isticsofthesurfacebeneathit.Forexample,airovertropicaloceansbecomeswarmandmoist,whileairoversnow-coveredpolarregionsbecomesdryandcold.Whentheairmovesawayfromtheplacewhereitformed,knownasitssource region,itreplacesairofadifferenttype.Theboundariesbetweenairmassesofdifferenttypesarewhatmeteorologistscallfronts.Frontsareregionsoftransitionandoftenarewhereimportantweathereventstakeplace.

Airmassesusuallyareassociatedwithhigh-pressureregions(anticyclones)atthesurface.Low-pressureregions(cyclones)dominateontheboundariesofairmasses.Byincreasingthewindsandpushingtheairawayfromitssource,thedevelopmentofcyclonescausesairmassestomoveawayfromtheirsourceregions.

Air masses

have similar

temperature

and moisture

characteristics

based on their

source regions.

They can be

cold (polar) or

warm (tropical)

and dry

(continental) or

humid (maritime).

Watching the SkyThe movement of a frontal system often is heralded by a procession of different cloud types, each signaling a greater likelihood of an approaching storm. You might first see a clear sky of high, feathery cirrus clouds, or “mare’s tails.” These clouds will thicken until the sun is hidden behind a thin cirrostratus veil. A gray curtain of altostratus clouds comes next, followed by a moist blanket of dark stratus clouds rolling close to Earth. Finally, nimbostratus clouds bring rain.

Of course, not all clouds signal bad weather. Cirrus clouds detached from one another indicate that the weather will stay fair for a while. A scaly mackerel sky formed by cirrocumulus clouds usually promises fair weather, but it also might be a sign of inclement weather. Outdoor groups eager for dry trails welcome the sight of cumulus clouds. On hot days, however, travelers are wise to take cover if swelling cumulus clouds develop into dark cumulonimbus thunderheads, the breeders of violent storms.

WEATHEr 29


Whencoldairreplaceswarmerair,thefrontiscalledacold front.IntheUnitedStates,coldairusu-allycomesfromthenorthornorthwestofCanadaandfromthepolarregions.Becausecoldairisdenserthanwarmair,ittendstostaynearerthesurfaceandwedgesbeneaththewarmair.Thistendstomakethewarmairrise,asseeninthediagram.Therisingaircoolsbyexpansion,formingcloudsandper-hapsprecipitation.

Becausetheadvancingcoldairremainsnearthesurfacewherefrictionisafactor,themovementofthecoldairisslowedsome-whatbythefrictionofobjectsandlandformsonEarth’ssurface.Thiscreatesasteepslopealongtheleadingedgeofthefront.Theslopecanmeanthatmostoftherisingmotionalongthefrontisconfinedtoanarrowzonenearthefront.

Whenwarmairreplacescoldair,thefrontiscalledawarm front.WarmairmassesformoverthewarmtropicaloceanssouthandsoutheastoftheUnitedStatesandoverlandareastothesouthwest.Thoseformingoveroceansaremoist.Thoseformingoverlandaredry.Whenwarmairapproachesacoldairmass,ittendstorideupoveritratherthanwedgingbeneathit.Unlikecoldfronts,therefore,warmfrontstendtohavegentleslopes.Asthewarmairrisesandcools,cloudsandprecipitationmayform.Theshallowslopemeansthatrainandcloudscanprecedethepassageofawarmfrontbyadayormore.

Cross seCTioN oF CloUDs oN A ColD FroNT

FROntAl mOVement

cumulOnimbus WARm AiR

stRAtOcumulus

cOld FROnt cOld AiR

Cross seCTioN oF CloUDs oN A WArM FroNT

FROntAl mOVement

cOld AiRWARm FROnt

WARm AiR

nimbOstRAtusstRAtus

WEATHEr 31

.Hazardous Weather

HazardousWeatherPeoplereadilyadapttoroutineweatherchangesthatoccurwiththepassageofairmasses.Sometimes,however,theweathercanbecomesoviolentthatpeopleneedtotakespecialprecautions.

ForecasterswiththeNationalWeatherServiceissuewatches,warnings,andadvisoriestoalertthepublictopotentiallyviolentorhazardousweather.Thereisanimportantdifferencebetweenawatchandawarning.Awatch meansthathazardousweatherispossibleorthatconditionsarefavorableforittodevelop.Awarningisamoreurgentnoticethathazardousconditionsalreadyexistorareheadingyourway.Watchesandwarningsareissuedforeventssuchaswinterstorms,tornadoes,severethunderstorms,highwinds,andflashfloods.TheNationalWeatherServiceissuesadvisorieswhenconditionsareexpectedtocauseseriousinconveniences.Acommontypeofadvisoryalertsmotoriststohazardssuchasslipperyroadscausedbywintryweather.

Winter StormsDuringthewinter,somecyclones(low-pressureareas)developintounusuallyintensestormsthatbringheavysnow,strongwinds,andcoldtemperatures.Whenthewindisstrongenough(above35milesperhour)andvisibilityisreducedtolessthanaquartermilebysnoworblowingsnow,theeventistermedablizzard.Evenifasnowstormdoesnotquitequalifyasabliz-zard,acombinationofsnow,wind,andcoldcanbedeadlyforpeoplecaughtunprepared.

Anotherwintereventthatcanbequitesevereisfreezingrain(ordrizzle),oranice storm.Ificecoatingsbuildupenough,treebranchescanbreak,oftencrashingintopowerandtelephonelinesalreadyburdenedwithice.Roadsbecomeice-coveredandtreacherous.

32 WEATHEr

Hazardous Weather.

Evenwithoutsnoworice,extremecoldcanbedangerous.Bittercoldcanbeevenmorehazardouswhenaccompaniedbyhighwindbecausethetwoincreasetherateofheatlossfromexposedskin.Theresultcanbefrostbite,whichisdamagetoskinfromfreezing,orhypothermia,adangerousloweringofbodytemperature.

Meteorologistsusewind chill todescribethecombinedeffectofcoldandwind.Windchilltemperaturesalwaysarethesameasorlowerthantheactualtemperature,anddecreasewithhigherwinds.Forexample,withatemperatureof30degrees,thewindchillalsois30degreesifwindsarenearlycalm,butitdropsto4degreesifwindsareblowingat20milesperhour.

Ifyouarecaughtoutdoorsinawinterstormorinextremecold,itisimportanttostaydry,coverallexposedpartsofyourbody(severallayersofclothingprovidemoreprotectionthanasingleheavycoat),andavoidoverexertion.Theseprecautions

willhelppreventfrostbiteandhypo-thermia.Ifthereisnoshelteravailable,preparealean-to,windbreak,orsnowcaveforprotectionfromthewind.Buildafireifpossible.Afirewillpro-videheatandmighthelpattracttheattentionofrescuers.Rocksplacedaroundthefirewillhelpabsorbandreflectheat.

Ifyouareoutinacar,staywiththecarandtieabrightlycoloredclothtotheantennasothatyoumightbeseenbyrescuers.Forabout10minuteseachhour,startthecarandruntheheater.Makesurethecar’sexhaustpipeisnotblocked;otherwise,deadlyexhaustfumeswillfillyourcar.Youmaymoveyourarmsandlegstokeepyourbloodcirculating,buttrynottosweatorburntoomuchoftheenergyyouneedtokeepwarm.

Always melt snow

for drinking, rather

than eating it to

quench thirst.

Using your own

body heat to

melt snow will

lower your body

temperature.

WEATHEr 33

.Hazardous WeatherW

ind

Ch

ill T

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Eq

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alen

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erat

ure

in c

oo

ling

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wer

on

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esh

Air

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per

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re (

deg

rees

Fah

ren

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t)

3530

2520

1510

50

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0-1

5-2

0-2

5-3

0

0–4

3530

2520

1510

50

-5-1

0-1

5-2

0-2

5-3

0

532

2722

1611

60

-5-1

0-1

5-2

1-2

6-3

1-3

6

1022

1610

3-3

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5-2

2-2

7-3

4-4

0-4

6-5

2-5

8

1516

92

-5-1

1-1

8-2

5-3

1-3

8-4

5-5

1-5

8-6

5-7

2

2012

4-3

-10

-17

-24

-31

-39

-46

-53

-60

-67

-74

-81

258

1-7

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-29

-36

-44

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306

-2-1

0-1

8-2

5-3

3-4

1-4

9-5

6-6

4-7

1-7

9-8

6-9

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354

-4-1

2-2

0-2

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5-4

3-5

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8-6

7-7

4-8

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illin

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ffec

t.

Wind speed (miles per hour)

34 WEATHEr

Hazardous Weather.

ThunderstormsThunderstormsaremostcommoninthetropicsandsubtropicsandduringthewarmseasoninthemiddlelatitudes,buttheycanoccurinwinterandatpolarlatitudes.Theyformwhenwarm,moistaircreatesupdraftsthatformlargeprecipitationdropsinclouds.Asthisprecipitationdevelops,positiveandnegativeelectricalchargesseparateandbuildupindifferentpartsofthecloudsandonthegroundbeneaththeclouds.Whenchargeshavebuiltupenough,theycan“jumpthegap”betweenregionsofoppositecharge,dischargingtheareas.

Thisdischargeiswhatweseeas lightning.Somelightningflashesstriketheground,butmostarefromonepartofacloudtoanother.Lightninggroundstrikes,fairlycommonintheUnitedStates,canbedeadly.IntheUnitedStatesabout90peopledieeachyearfrombeingstruckbylightning.

Thunder iscausedbythegreatheatgeneratedduringthebrieftime(lessthanasecond)thatalightningdischargeoccurs.Theheatcausestheairtoexpandrapidly,asinanexplosion.

Youhearthunderafteryouseelightningbecauseofthedifferencebetweenthespeedofsoundandthespeedoflight.Soundtravelsataspeedof1,100feetpersecond,butlighttrav-elsataspeedofabout186,000milespersecond.Therefore,youwillseealightningflashalmostinstantly,butthesoundofthunderwilltakelongertoreachyou.

Count the seconds

it takes for the

sound of the

thunder to reach

you after you see

a lightning flash.

Since a mile is

5,280 feet, it takes

thunder about

5 seconds to

travel 1 mile.

The instability of electrical charges within a cloud is heightened by collisions of ice crystals and hail and by differences in air temperature at different altitudes. When the imbalance becomes great enough between negatively charged and positively charged areas of clouds or between a cloud and the ground, electrons (negatively charged subatomic particles) form a pathway called a leader and flood from one zone to the other, resulting in a lightning strike.

WEATHEr 35

.Hazardous Weather

Staying Safe During a ThunderstormIfyouarecaughtoutdoorsinathunderstorm,donotstandinopenareasornearlightningtargetssuchastrees,powerpoles,orwirefences.Metalconductselectricity,soalsostayawayfrommetalpoles(suchastentpoles)andsuch.Removeanymetallicframepacksanddonotstaynearthem.

Wateralsoconductselectricity,soifyouareboatingorswimming,gettolandimmediatelywhenastormisapproaching.

Whenhikingnearmountaintops,whicharestruckbylightningoftenduringsummer,getdownhillbeforethelightningbegins,ifpossible.Ifastormcatchesyou,takeshelterinacaveoralowspotamongtherocks,makingsuretoavoidprominentoutcroppingsandoverhangs.Trytopickanareathatisnotlikelytoflood.

Ifyoucannotfindshelter,becomethesmallesttargetyoucan.Donotlieflatontheground,becauselyingflatmakesyouabiggertargetthancrouchingdown.Ifyoufeelyourhairstandonendoryourskingettingly,crouchdownimmediatelyandtakethefollowingpose:Squatontheballsofyourfeet,coveryourearswithyourhands,andgetyourheadclosetoyourknees.Getsmall!Thelessofyouthatistouchingtheground,thebetter.

Takeshelterinasteel-framedbuildingorhard-toppedmotorvehicle(notaconvertible)ifyoucan.Suchplacesaresafebecausethechargestayswithintheframeofthebuildingorvehicleandisconductedsafelytogroundwithoutendangeringtheoccupants.Whenyouaretakingshelterinacarduringathunderstorm,avoidtouchingthemetalparts.

Whentakingshelterinabuildingduringathunderstorm,donotusethetelephoneorholdobjectsconnectedtoelectricalpower(suchashairdryers).Stayingnearstoves,fireplaces,andplumbingisalsodangerous,becausemetalcanconductelectric-ity.Also,donottakeabathorshowerorrunwater.

100 OR mORe Feet APARt

36 WEATHEr

Hazardous Weather.

Althoughthelocationwherelightningwillstrikeisnotpredict-able,someplacesaremuchmorelikelytobestruckthanothers.Becauselightningfollowsthepathofleastresistance,objectsclosertothecloudaremorelikelytobestruck.Treesinanotherwiseopenspaceoftenaretargetsforlightning,sotreesarenotagoodplacetotakeshelterinathunderstorm.

Thunderstormscanbecomequiteviolent,producinglargehail,floodingrains,strongwinds,and

tornadoes.Theseseverethunderstormstendtooccurwheretheairmassisveryunstable.Duringwinter,asinglecyclonecanproduceblizzards,icestorms,andseverethunderstormswithtornadoes.

Whentakingsafetyprecautionsduringathunderstorm,youshouldstayalertandbereadytoreviseyourplansifamorehazardousweatherconditionoccurs,suchasaflashflood.

FloodsFloodsareanunavoidablepartoflifealongrivers.Thetorrentialrainsofthunderstormsortropicalcyclonescancauseflooding.Somefloodsoccurwhenwinterorspringrainscombinewithmeltingsnowstofillriverbasinswithtoomuchwatertooquickly.Sucheventsusuallytakeseveraldaystodevelop.Otherfloodsarisesuddenlyastheresultofheavylocalizedrainfall.Theseflash floodscanbecomeragingtorrentsveryfast,sometimesinlessthananhour,andcansweepawayeverythingintheirpath.

Areasofruggedterrainareparticularlyvulnerabletoflashfloods.Picturesquerivervalleysinthemountainscanbesweptwithoutwarningbyfloodsfromrainsfallingsomedistanceaway.Whencamping,stayclearofnaturalstreambedsduringthetimeofyearwhenrainstormsarecommon.Ifyoucamponlowground,youmightbecaughtunawares,especiallywhenasleepatnight.Incaseofafloodinruggedterrain,climbtohighgroundimmediately,evenifitmeansabandoningyourgear.Ifthefloodwatersarealreadyrising,donotgetintomotorvehiclesandattempttodriveawayfromtheflooddanger.Neverenterafloodedlowspotontheroadortrailifyoudonotknowhowdeepthewateris,especiallyifthewaterisrising.

Although lightning

can be hazardous,

it is not all bad.

It changes the

air’s nitrogen into

a form that can

be taken up by

plants. Thus, a

thunderstorm can

be a natural plant

fertilizer as well

as a waterer.

WEATHEr 37

.Hazardous Weather

Mostfatalitiesoffloodsarevictimstrappedinautomobiles.Ittakesonly2feetofwatertofloatacar,andevenlesstostallacarortruck’sengine.Ifyourvehicle’senginestalls,abandonitandclimbtohigherground.

Keepalerttosignsofwetweather—notjustinyourloca-tionbutalsoinnearbyareas.Listenfordistantthunderandwatchforlightningflashes.Fasterflowingstreamsorrisingwaterlevelscansignalrainfallupstream.Inseasonswhenheavyrainsarepossible,atleastonepersoninyourgroupshouldcarryaportableradioandstayinformedaboutweatherconditionswheninrangeofaradiostation.Whenoutofradiorange,bekeenlyobservantandalerttotheweather.

TornadoesOnrareoccasions,rapidlyrotatingcolumnsofairformwithinathunderstorm.WhentheserotatingcolumnsreachEarth’ssurface,theybecometornadoes.

TornadoescanproducethestrongestwindsonEarth,occasionallyreaching300milesperhourormore.Thetornadoisanextremeformofcyclone,withverylowpressureatitscore.Mosttornadoesproducepathsofdamagethatareonlyafewhundredyardswideorless.Becausetornadoesusuallylastonlyafewminutes,pathlengthstypicallyareamileorless.Afewtornadoes,however,aremorethanamilewideandlastforanhourormore,producingdamagepathsmorethan100mileslong.

Mosttornadocasualtiesarecausedbyflyingdebris,sothebestthingtodoifatornadothreatensistogettoaplacethatprovidesasmuchprotectionfromflyingdebrisaspossible.Avoidtakingshelterneartrees.Theybecomeasourceofdebrisduringtornadoes.Ifyouarecaughtintheopenwhenatornadoapproaches,gettoalowspot,liefacedown,andcoveryourhead.Yourgoalistobelessofatargetforflyingdebris.Therefore,lyingflatistherightposition.Aditchorotherlowspotisagoodplacetoliedown,especiallyifthereisnofloodwater.

Tornadoescanoccurwhileyouareinschoolorathome.Beawareofanyplansfortornadosafetyinyourschool.Youandyourfamilyshoulddevelopasafetyplanathome.Ifyourhomehasatornadoshelter,useit.Ifyourhomehasabase-ment,itcanbeagoodshelterifpartofitoffersprotectionfromfallingdebris.Forexample,youmighttakeshelterunderastair-wayoraheavyworkbench.

As with floods,

never attempt to

drive away from

a tornado. You

are likely to be

trapped in your

vehicle, which

is an extremely

dangerous

situation.

38 WEATHEr

Hazardous Weather.

Ifyoucannotgettoatornadoshelterorbasement,putasmanysolidwallsbetweenyouandtheoutsideaspossible.Closetsininteriorhallwaysaregoodshelters.Bathroomsoftenhavestrongerwallsthantherestofthehousebecausetheplumbingmakesakindofreinforcement.Stayawayfromwin-dows—flyingglassisextremelyhazardous.Abandonmobilehomesandseeknearbyshelter.Takealongaradioandsomesourceoffreshwater.Ifyourhomeishit,bealerttoleakinggasfrombrokenpipes.Outside,bewareoffallenpowerlines.

HurricanesAmongthemostdangerousstormsthataffecttheUnitedStatesarehurricanes.TheyoriginateinthesouthernpartofthenorthAtlanticOcean,theCaribbeanSea,theGulfofMexico,andthesoutheasternPacificOceanoffthewestcoastofMexico.Similarstormsoccurelsewhereintheworld,notablyintheoceansnearIndiaandAustralia,wheretheyarecalledcyclones,andinthewesternPacificOcean,wheretheyarecalledtyphoons.Ageneralnameforallsuchstormsistropical cyclone.

Unlikethelow-pressuresystemsofmiddlelatitudes,tropicalcyclonescontainnofrontsbecausetheyforminasingle,tropicalairmass.Whenwell-developed,theyarenearlycircularinshapeandvaryindiameterfromabout100to1,000miles.Inrareinstances,theirwindscanexceed200milesperhour,spiralinginwardtothelow-pressurecenter.Thecombinedeffectsofthewindsandthelowpressureacttopileupoceanwateratthecenterofthestorm,producingastorm surge.Asthestormapproachesland,thestormsurgecancombinewithnormaltidestoproduceextensiveflooding.Itisthestorm

surge,notthewind,thatcausesthemostdamageandthemostcasualtiesfromhurricanes.Mosthurricanedeathsarecausedbydrowning.

Atthecenteristheeyeofthestorm,whichcanrangefromabout5milestomorethan20milesindiameter.Withintheeye,windsarelight.Lowcloudsmightbepresent,orskiesmightactuallybeclear

Sometimes

tornadoes form

so quickly there

is no warning

from the news or

weather service.

A greenish sky,

large hail, flying

debris, and a

noise like a freight

train are all

signals that a

tornado may be

on the way.

WEATHEr 39

.Hazardous Weather

Most hurricanes

produce occa-

sional tornadoes

from the thunder-

storms in the

spiral bands.

withintheeye.Surroundingtheeyeisaringofdeepcloudscalledtheeyewall.Thestrongestwindsinthestormusuallyarefoundwithintheeyewallnexttotherelativelycalmeye.Severalcloudbandsmadeupoflinesofthunderstorms,calledspiral bands,usuallyarepresentinatropicalcyclone.Theyspiralintoandjointheeyewallfromtheouterpartsofthestorm.Torrentialrainsoftenaccompanytheeyewallandthespiralbands.

Tropicalcyclones“feed”onwarmtropicaloceanwaters.Thisishowtheyobtaintheirstrengthovertheopenwatersofthetropicsandwhytheynormallyweakenrapidlyandsoondissipateaftertheymeetland.Butevenadissipatedhurricanecanproduceextremelyheavyrainfall—sometimeswellinlandfromthepointwhereitmadelandfall.

Innearlyallcases,hurricanewatchesandwarningswillprecedeanylandfallinghurricane.Ifyouarecampingalongornearaseashorewhenhurricanewatchesareissued,strikecampandleavetheareaimmediately.Encounteringahurricaneatseaalsoisextremelydangerousandshouldbeavoidedatalltimes.

Ifofficialshavenotadvisedthatyouevac-uatethearea,stayindoors,awayfromwin-dows,andfollowtheguidelinesfortornadosafety.Aftertheeyepasses,thehurricanewindsblowintheoppositedirection,breakingtreesandotherthingsnotquitedestroyedbythefirstroundofwinds.Donotbefooledbytheeyeofthestorm.Muchdangerstillfollows.Followsafetyproceduresforfloodsaswell.

sPiRAl bAnds eYe eYeWAll

Cross section showing the structure of a typical mature tropical cyclone

WEATHEr 41

.Measuring and Recording the Weather

MeasuringandRecordingtheWeatherAccurateinformationaboutthevariousfactorsthattogetherdefinetheweatherisnecessaryinmakingreliableforecasts.Foreachofthesefactors,thereisaninstrumentthatmeasuresintensity,velocity,ordegree.

Air PressureAirpressureismeasuredusingabarometer.Ananeroid barom-eteristhetypeyouaremostlikelytohaveathomeorseeinstores.Itusesasmall,thin-metal“box”sealedwithaverageairpressureinside.Theboxcontractsunderhighpressureandexpandswhentheoutsideairpressuredrops.Anindicatorneedleisattachedtothesideoftheboxbyleversandrecordsthepressureonadial.

Scientificbarometersusedbylaboratoriesandweatherofficescontainmercury,ametallicelementthatisliquidatroomtemperature.Asimplemercury barometerconsistsofaslenderglasstubefilledwithmercuryandclosedatoneend.Theopenendofthetuberestsinabowlofmercury.Themer-curyinthetubefallstoalevelthatisabout30inchesabovethelevelofthatinthebowl.Avacuumformsatthetopofthetube.Airpressureactsonthesurfaceofthemercuryinthebowl,forcingthemercuryupintothetube.Thehighertheairpressure,thehigherthelevelofmercuryinthetube.

Mercury is very poisonous. Just a small amount can pollute a large body of water such as a lake. The United States government has placed restrictions on mercury. If you have an old barometer that uses mercury, be careful never to open it up. Liquid mercury can be absorbed through your skin. Just a small amount can also poison the air, and disposing of it improperly will cause pollution.

42 WEATHEr

Measuring and Recording the Weather.

Barometers,eithermercuryoraneroid,arereadintermsoftheheightininchesofacolumnofmer-cury.Averageairpressureatsealevelcorrespondstoacolumnofmercuryabout30inchestall.Thisiswherethebarometerreadingcomesfromonweatherreports—apressureof30.25inches,forexample.Airpressureatsealevelvariesbyonlyasmallamount.Areadingof,say,31inchesisunusuallyhigh,whileareadingbelow29inchesoccursonlyinthestrongestcyclones,suchashurricanes.

Theexactheightofthemercurycolumndependsnotonlyonairpressure,butalsoonthealtitudewherethereadingistaken.Toadjustfordifferencesinelevation,itiscommontocorrectthereadingsforaltitudesothatthemeasurementsarecomparabletothosetakenatsealevel.

Onactualweathermaps,pressuresareconvertedtomillibars,thescientificunitusedtomeasurepres-sure.Thenumbersontheisobarsonaweathermapcorrespondtopressureadjustedtosealevelinmillibars.

Downward air pressure on the mercury in a mercury barometer forces mercury up into the tube. The higher the air pressure, the higher the mercury column.

POinteRs

FAce

sPRing

chAin

leVeRs

metAl dRum(PARtiAl VAcuum)

VAcuum

760mm

meRcuRY AtmOsPheRic PRessuRe

Changes in pressure result in changes in width of an aneroid barometer’s sealed box. Levers and springs convert these changes into pressure readings.

WEATHEr 43


Therateatwhichtheairpressureischangingoftenismoreimportantthanthepressurereadingitself.Airpressurerisestypicallywiththeapproachofhighpressureanditsattendantfairweather.Soifyouhearaweatherreportersay,“Thebarometricpressureis29.65inchesandrising,”youcanbeprettysurethatgoodweatherisontheway.Likewise,theapproachofalow-pressureareacausesthereadingtofall.

Wind DirectionYouprobablyhaveseenwind vanesonhousesandbarns.Mostareintheformofanarrowthatpivotsonspecialbearingssothatitcanturnfreelyinthewind.Itisaccuratelybalancedonthebearing.Thesizeofthe“feather”partofthearrowislargersothatwindvanesalwaysswingintothewindandpointinthedirectionfromwhichthewindiscoming.

Wind SpeedWindspeedismeasuredbyaninstrumentcalledananemome-ter.Althoughthereareseveraltypesofanemometers,themostcommontypeisacupanemometer,inwhichthreeorfourcupsaremountedonhorizontalrods.Theunitisattachedtoaverticalrodsothatitcanrotateasthewindturnsit.Aswindspeedincreases,sodoesthespeedatwhichthecupsrotate.Windspeedismeasuredbythenumberofturnsthecupsmakeinasetperiodoftime.

Windspeedscanbemeasuredinmilesperhour,inknots,orinmeterspersecond.Aknotisonenautical mile perhour—anauticalmileisabout6,080feet,roughly15percentlongerthananordinarymileof5,280feet.Milesperhournormallyareusedintheweatherreportsyouhearonradioandtelevi-sion,whileknotsareusedmostlyinmarineandaviationweatherreports.Mostscientificmeasurementsareinmeterspersecond.

A professional

wind vane usually

has electrical

connections to

a scale in the

weather office

so that no one has

to go outside to

read it. Weather

reporters do know

enough to stay out

of the rain!

44 WEATHEr

Measuring and Recording the Weather.B

eau

fort

Win

d S

cale

Bea

ufo

rt

Nu

mb

erD

escr

iptio

nW

ind

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eed

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alm

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ind

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.

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e4–

7W

ind

is f

elt

on

th

e fa

ce; l

eave

s ru

stle

; ord

inar

y va

nes

are

m

oved

by

the

win

d.

3G

entle

bre

eze

8–12

Leav

es a

nd

sm

all t

wig

s ar

e in

co

nst

ant

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tion

; win

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xten

ds

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ht

flag

.

4M

od

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e b

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Du

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nd

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se p

aper

are

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; sm

all b

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leaf

beg

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nd

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ifficu

lt to

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; in

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is f

elt

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alki

ng

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8Fr

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Twig

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reak

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ly is

imp

eded

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9S

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gal

e47

–54

Slig

ht

stru

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ral d

amag

e is

rep

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ed; b

ran

ches

bre

ak.

10W

ho

le g

ale

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on

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tru

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ral d

amag

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rees

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ides

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xper

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This scale was devised by Sir Francis Beaufort in 1805. Although used mainly to estimate winds at sea, the visible effects described here relate to observations on land.

46 WEATHEr


Make a Wind VaneMaterials Needed■ Aluminum baking dish, pie tin,

or tray ■ Sturdy wooden garden stake (at

least 3 feet tall and 1 inch thick)■ 12-inch piece of wood about

1⁄2 inch thick■ Nail (2 to 3 inches long)■ Electric or hand drill■ Thick metal washer■ Hammer■ Mallet■ Glue■ Small saw■ Scissors

Step 1—Select a location for your wind vane. Then use the mallet to carefully drive the garden stake into the ground.

Step 2—Use the saw to cut a half-inch slot at each end of the 12-inch piece of wood.

Step 3—With an adult helping you, place the piece of wood on top of the stake, as shown, and drill through the wood and the stake. Use a drill bit that is slightly larger in diameter than the nail you will be using.

3

WEATHEr 47


Step 4—Place the washer on top of the stake and insert the nail through the wood and into the stake. The wood should turn easily on the axis of the nail.

Step 5—Cut the head and tail of the arrow from the aluminum tray or dish using the pattern shown as a guide. Glue the head of the arrow into one slot in the piece of wood and the tail into the other slot.

5

4

48 WEATHEr


Air TemperatureAirtemperatureisanimportantfactorinweather,especiallywhenassociatedwithotherfactorssuchashumidityandpressure.Itismeasuredwithathermometer.

Themostaccuratethermometersaretheliquid-in-glass-tubetype,containingeithermercuryoralcohol.Thealcoholversionismoreappropriateforverycoldplacesbecausealcoholfreezesatalowertemperaturethanmercury.

Athermometershouldbekeptintheshadeandawayfromwindandrain.Theweatherprofessional’sthermometerishousedinaventilatedboxraisedabovethegroundandprotectedfromtheweather.

Make a Cup AnemometerMaterials Needed■ New sharpened pencil■ 5 plastic foam cups■ Hole punch■ Straight pin■ 2 extra long plastic straws■ Felt marker■ Tape

Step 1—Mark the numeral “1” on one of the cups and set it aside.

Step 2—Set one of the unmarked cups on a work surface and punch four holes in it as shown. Be sure one set of holes is lower than the other set of holes.

Step 3—Carefully poke the pencil through the bottom of the cup.

2

3

For most of the United States, -40 degrees Fahrenheit to 110 degrees Fahrenheit is a range of temperatures wide enough to cover most temperature observations. In Death Valley, California, however, the temperature once soared to 134 degrees, while in Yellowstone National Park the temperature has been known to plummet to -66 degrees. In such places, you need a special thermometer.

WEATHEr 49


Step 4—Push the pencil down so that it is below the holes and then thread the straws through the holes in the top of the cup to make a cross shape. Tape the straws in place.

Step 5—Raise the pencil up so that the eraser comes into contact with the crossed straws. Push the straight pin through the straws and into the eraser. Do not push the pin all the way in. The unit needs to be able to turn freely.

Step 6—Punch one hole each in the side of the other three unmarked cups and the marked cup, and mount them on the straw apparatus as shown. If necessary, add tape to better secure the cups to the straws.

Step 7—To determine wind speed, count how many complete revolutions the marked cup makes in one minute.

In most of

the world,

temperatures

are measured in

degrees Celsius,

but in the United

States surface

air temperatures

are measured

and reported

in degrees

Fahrenheit.

Water freezes

at 32 degrees

Fahrenheit, which

is 0 degrees

Celsius, and boils

at 212 degrees

Fahrenheit, or

100 degrees

Celsius.

4

5

50 WEATHEr


Water VaporAcommoninstrumentforfindingouttheamountofwatervaporintheairisthewet-bulb hygrometer. Itisrelativelyeasytomake.Beginbypurchasingtwoidenticalliquid-in-glassalcoholthermometers.Thesecanbeboughtinhardwarestoresforareasonableprice.Mountboththermometersonamilkcartonexactlythesamedistancefromthebottom.Cutoffabout6inchesofanew,roundshoelace,trimmingoffthetip.Sliptheshoelaceoverthebulbportionofoneofthetwother-mometers.Cutaslotinthemilkcartonsothatyoucanslipthebottompartofthelaceintothecarton.Fillthecartonwithwateruptotheslot.Ifpossible,usedistilledorfilteredwaterbecauseimpuritiesinthewaterwillcauseinaccuratereadings.

Placethecartoninthebreezeofanelectricfanorinabreezyopenwindow.Makesuretheshoelaceiswetuptothethermometerbulb.Evaporationofwaterfromthelacewillcausethetemperaturemeasuredbythewet-bulbthermometertodecrease,whiletheotherthermometershouldremainattheactualairtemperature.

Usingthefollowingchart,youcanfigureouttherelativehumiditybythetemperaturedifferencebetweenthetwother-mometers.Whentheybothreadthesame,ornearlyso,expectwetweatherbecausethatmeanshigh(nearly100percent)relativehumidity.Generally,thewet-bulbtemperatureissomewherebetweentheactualairtemperatureandthedewpointtemperature.

milK cARtOn

RubbeR bAnds

shOelAce (cut in hAlF And Put OPen end OVeR bulb)

WAteRslOt

Wet-bulb hygrometer

WEATHEr 51


relative Humidity Based on Dry-Bulb (Air) and Wet-Bulb Temperatures

Using this table, compare readings on a wet-bulb thermometer with those on a dry-bulb thermometer to determine relative humidity. Check the degree difference shown on your two thermometers. Find this number in the left column of the table and read across to the column under the air (dry-bulb) temperature. The value shown is the relative humidity. Example: If the difference between dry- and wet-bulb temperature is 6 degrees and the air temperature is 70 degrees, the relative humidity is 72 percent.

Dry-bulb temperature (Fahrenheit)

Difference (dry-bulb

minus wet bulb)

30 40 50 60 70 80 90 100

1 88 92 93 94 95 96 96 –

2 77 84 87 89 90 92 92 –

3 67 76 80 84 86 87 89 –

4 57 68 74 78 81 83 85 –

6 37 53 62 68 72 76 78 80

8 17 38 50 58 64 68 71 74

10 23 39 49 56 61 65 68

12 9 28 40 48 54 59 62

14 17 31 41 48 53 57

16 7 23 34 41 47 52

18 14 27 35 42 47

20 7 20 30 37 42

22 14 24 32 38

24 7 19 27 33

26 1 14 22 29

28 9 18 25

30 4 14 21

52 WEATHEr


rainfallRainismeasuredwitharain gauge.Wemeasurerainintermsofthedepthofthelayeritwouldmakeifnonedrainedofforwasotherwiselost.IntheUnitedStates,rainfallismeasuredininchestothenearesthundredth.Anamounttoosmalltomeasureiscalledatrace.

Rainfallcanbemeasuredinmanyways,butusuallyalargefunnelandnarrowreceptacleareused.Thefigureshowsasimpletypeofraingaugethatyoucanmake.

sPlAsh guARd (tin cAn With ends RemOVed)

Funnel (meAsuRe diAmeteR OF tOP)

rainwater funnels into a narrow tube so that amounts can be read more accurately. Measure the diameters of the funnel top and the tube and calculate their ratio. Mark off the tube, then square that ratio. For example, if the funnel opening is twice as wide as the tube, then 4 inches (2 times 2) in the tube will mean 1 inch of rainfall. If the ratio is 3 to 1, then 9 inches (3 times 3) will equal 1 inch of rain, and so forth.

cleAR PlAstic OR glAss tube (meAsuRe inside diAmeteR)

54 WEATHEr


Weather Maps Thevariouselementsjustdescribed,includingtemperature,pressure,wind,andprecipitation,aremeasuredatweatherstationsallovertheworldatspecifiedtimeseachday.Observationsusuallyaremadeeverysixhoursatalllandstationsandaboardshipsatsea.

Weatherobservationsarepreparedusingashortcodeofnumbersandaretransmittedelectronicallytomajorweathercenters.Thecontentsofthesereportsareplottedonsurfaceweathermaps,mostlybycomputers.Inadditiontothesurfacereports,informationisgatheredbyballoon-borneinstrumentscalledradiosondes.Aradiosondeconsistsofinstrumentsthatmeasuretemperature,airpressure,andrelativehumidity,usuallyevery12hours.Theradiosondedataalsoareplottedonweathermapsforvariouslevelsintheatmosphere.Allthisinformationisexchangedwithsimilarreportsfromothercoun-triesandusedinpreparingweatherchartsforforecasting.

EverydayintheUnitedStates,theNationalWeatherServiceandprivateweathercompaniesprepareandtransmitmanyweathermaps.Inadditiontoshowingthedata,themapshavemanylinesdrawnonthem.Similartoterraincontours,theselinesconnectpointsofequalvaluesofweatherelements.Isobars,discussedearlier,arelinesofequalpressure.Linesofequaltemperaturearecalledisotherms.Otherfeaturesmaybeincludedonweathermaps,suchasfronts,precipitation,visibility,andcloudtypes.Theseelementsnor-mallyareindicatedbyspecialsymbols.

Theinformationtransmittedtothemajorweathercentersalsoisenteredintocomputersandusedtogeneratecomputermodelsoftheatmosphere.Thesemodelsaredifferentfromphysicalreplicas.

A radiosonde instrument package attached to a weather balloon records data about the temperature, humidity, air pressure, and winds aloft.

WEATHEr 55


Atmosphericmodelsexistonlyasdatainacomputer.Weatherobservationsareenteredintothecomputerandprocessedthroughmathematicalformulastomakewhatarecallednumericalweatherprediction(NWP)forecasts.NWPforecastinformationissentbacktotheweatherofficestobeusedbyweatherforecasters.

Byusingcurrentweatherinformationatthesurfaceandaloft,combinedwithsatelliteimagesofclouds,datafromweatherradars,andNWPforecasts,meteorologistscanmakefairlyaccuratepredictionsabouttheweathersystemsaffectinganarea.Ithasbeenshownthatevenifmeteorologistshadperfectmodelsoftheatmosphere,therearepracticallimitationsonhowwelltheycouldforecasttheweather.Weathermodelsarenotperfect,becauseitisnotpossibletotakeperfectmeasurementsateverypointwithintheentireatmosphere.Aseveryoneknows,forecastssometimesarewrong.However,weatherforecastingismuchmoreaccuratethanitusedtobebecauseofimprovementsinobservingsys-tems,computertechnology,andinthescientificunderstandingofweatherevents.

reading Weather MapsThebestwaytolearnaboutweathermapsistolookatafew.FollowingareexamplesofdailyweathermapsissuedbytheNationalWeatherService.Studythemcarefully.Theytellmuchabouttheweather.Onthem,isobarsaremarkedinmillibars.Wherethelinesarefarapart,windstendtobeweak.Wheretheyareclosetogether,windsgenerallyarestrong.

Notethesymbolsforthewindsateachstation.Thewindbarbsshowthedirectionfromwhichthewindisblowing.Theflagsandlinesshowthespeeds.Ahalflineis5knots,afulllineis10knots,andaflagis50knots.TemperaturesareshownindegreesFahrenheit.Belowthetemperaturesaredewpointtemperatures,alsoindegreesFahrenheit.

56 WEATHEr


How to Read a Weather MapThe surface weather maps on the following pages show a sampling of plotted station observations and analyses of pressure, temperature, and front locations.

Cold fronts are shown as heavy solid lines with triangles pointing in the direction in which the cold air is advancing. Warm fronts are shown as lines with solid semicircles pointing in the direction toward which the warm air is moving. Fronts with alternating triangles and semicircles pointing in opposite directions are stationary fronts. Neither the warm air nor the cold is moving very much, so these fronts are hardly moving at all. Sometimes a cold front will overtake a warm front, creating an occluded front. Occluded fronts usually extend from strong, well-developed cyclones. They are shown with alternating triangles and semicir-cles pointing in the same direction.

Contours of equal pressure, or isobars, are shown as solid lines and are labeled in millibars. Centers of high pressure (anticyclones) and low pressure (cyclones) are indicated by high and low, respectively. Note on the maps how surface winds generally spiral counterclockwise into cyclones and clockwise away from anticyclones. The tracks of well-defined cyclones are shown by a chain of arrows, with previous cyclone center locations shown by small black squares with white crosses. Thick dashed lines show elongated areas of low pressure, or low-pressure troughs.

Areas of precipitation are indicated by shading. Lines of equal temperature (isotherms) are shown for 32 degrees Fahrenheit (thin dashed line) and 0 degrees Fahrenheit (dash-dot line).

WEATHEr 57


Weather maps you access may vary in detail from the maps shown. Simpler versions usually appear in newspaper and television weather reports, while maps analyzed by weather forecasters often are much more detailed. But general features (such as fronts) are shown similarly on most maps using standard symbols like those shown here.

Surface maps and the station model below were provided by the National Oceanic and Atmospheric Administration (NOAA), National Weather Service, Climate Analysis Branch.

PPP

pp

RR

TT

T

wwV

d

Study this sample plotted station model and compare it with the actual reports on the maps to find station temperatures, winds, pressure, 6-hour rainfall, and so on.

Wind sPeed And diRectiOn

seA leVel PRessuRe

PRessuRe tendencY

PRessuRe chAnge OVeR the lAst thRee hOuRs

sKY cOnditiOndeW POint temPeRAtuRe

cuRRent WeAtheR cOnditiOns

VisibilitY

temPeRAtuRe

60 WEATHEr


Visit a Weather OfficeTheNationalWeatherServicehasmorethan120officesintheUnitedStatesanditsterritories.YoushouldbeabletoarrangeavisittoonewhileyouareworkingonyourWeathermeritbadgerequirements.Alternatively,youmightmeetwithaweatherbroadcasteratalocaltelevisionstationoraninstructorfromthemeteorologyoratmosphericsciencedepartmentatanearbyuniversityorcollege.Therealsoaremanyamateurweatherobserverswhocanshowyouthebasicmeasurements,instruments,andweathercharts.

You can find the

locations of

National Weather

Service offices by

visiting http://

www.weather.gov.

Ask an ExpertHere are a few sample questions you might ask when you talk to a meteorologist for your merit badge requirements. You can come up with your own questions as well.

• What subjects in high school are related to meteorology?

• How can high school students work as interns or student trainees?

• What books and Internet resources do you recommend for learning more about meteorology?

• What kind of degree does a person need to become a meteorologist?

• What career opportunities exist for meteorologists?

• What is the job outlook for meteorologists?

• What kinds of responsibilities do meteorologists have?

• What areas of meteorology do you foresee becoming increasingly important in the next 10 to 20 years?

WEATHEr 61


WEATHEr 61

Themostobviouswaytostudytheweatheristoobserveactualeventsandkeeparecordofwhatyousee.Dailyobservationsoftemperature,wind,pressure,clouds,andrainfallcanhelpyouunderstandhowtheatmospherebehaves.Keepadailyweatherlog,similartotheoneshown,foratleastaweek.Ifpossible,recordobservationsforamonthormore.Makeentriesatthesametimeeachday.

Youcanobtainreadingsfromyourowninstruments,fromlocaltelevisionorradio,andfromInternetsitesdevotedtometeorol-ogy.Up-to-the-minuteweatherinformationisalsoavailablefromtheNOAA.NOAAWeatherRadio,operatingonhigh-bandFMfrequencies,transmitsupdatesthatcanbereceivedbyspecialreceiversandbyAM/FMradiosequippedwithaweather-bandfeature.Bycomparingreadingsfromdaytoday,youcanseehowthevariousweatherelementschangeatyourlocationinresponsetopassingweathersystems.

Daily Weather LogObservation time: ______________

Date Observed Weather Temperature Relative

HumidityWind

(Direction/Speed) Pressure 24-Hour Rainfall

Forecast for Tomorrow

1

2

3

4

5

6

7

8

9

Make your own weather chart, using this form as a guide. Keep a 30-day record based on local weather forecasts and your own observations. Make and record observations at the same time each day.

WEATHEr 63

.Weather and Climate Prediction

WeatherandClimatePredictionThewholeoftheatmosphereisinvolvedinweatherchanges.Toforecasttheweather,ameteorologistmustknowconditionsoftemperature,pressure,humidity,andwindthroughouttheoceanofair,toptobottomandallovertheplanet.Themeteo-rologistmustknowaboutEarth’soceansaswell.Becauseitishardtoobtaininformationwheretherearenopeople,suchasovertheoceans,therearemanygapsintheknowledgeusedinweatherforecasting.

Forecasting Tools and InstrumentsWeather BalloonsEarlyattemptstoobtainweatherdataaloftweremadeusingkitesorairplanesthatcarriedrecordinginstrumentscalledmeteorographs ashighasthetopofthetroposphere.Theinfor-mationrecordedonameteorographcouldnotbeuseduntiltheinstrumentwasreturnedtoaweatheroffice.

Theballoon-borneradiosondechangedallthat.Itwasresponsibleforarevolutioninunderstandingtheatmosphere.Aradiosondeisasmallboxthatcontainsabarometer,athermometer,andahygrometer.Radiosondesareattachedtoweatherballoonsthatcarrythemaloft.Bytrackingthebal-loons,itispossibletomeasurewindspeedanddirectionaloft,evenwherenocloudsarepresent.Thepracticaluseofthisabil-itydidnotbecomewidespreaduntilthedevelopmentofradiodirection-findingdevicescalledradiotheodolites.Aradiosondewithwind-measurementcapabilityisknownasarawinsonde.Rawinsondestypicallyrisetowellabovethetropopause,sotodayitiscommontohavemeasurementsofalltheneededweathervariablesuptoheightsofabout100,000feet.

64 WEATHEr

Weather and Climate Prediction.

radarAfterWorldWarII,observersnoticedthatweatherseemedtoaffectradarscopesusedfortrackingair-planes.Theydecidedthatradarmightbeagoodwaytodetectandtrackweathertargets.Theearliestweatherradarswereconvertedfrommilitaryradarsinthelate1940s.By1960,weatherradarswereinwidespreadusefortrackingprecipitation.Basically,theradarbeamissentoutfromanantennaandisbouncedbackoffobjectsthatthebeamstrikes.Thereflectedsignalisamplifiedelectronicallyanddis-playedinvariousways.Radarsignalsarecalled

echoesbecauseoftheirsimilaritytoanordinarysoundecho.Bythe1990s,weatherradarsbegantoincludeDoppler

equipment(namedfortheAustrianphysicistChristianDoppler).Dopplerradarsworklikepoliceradarstomeasurethespeedofatargetandprovideinformationaboutthespeedofprecipitationechoesalongaradarbeam.Theradargivesmeteorologistshelpfulinformationaboutmotionswithinstorms,especiallyseverethunderstormsthatmightcontaintornadoes.

Dark areas on this radar image indicate dry air and colored areas indicate the presence of water vapor. The intensity of precipitation is indicated by spectrum color, with blue meaning light precipitation and red being the heaviest.

WEATHEr 65


SatellitesThefirstweathersatellite,knownasTIROS-1,waslaunchedinthespringof1960.Itwashighlysuccessfulatgivingmeteorologiststheirfirstover-allviewofentirestormsystems.TIROSsatelliteswerepolarorbiters,whichmeanstheypassedoveranyonespotonEarthonlytwiceaday.Togetabroadviewofthewholeplanet,severalpictureshadtobepiecedtogetherintoacompositepho-tograph.Amajorbenefitfromsuchsatelliteswasthattropicalcyclonesatseacouldbespottedandtrackedlongbeforetheymadedangerouslandfalls.Beforetheageofsatellites,meteorologistshadtorelyonreportsfromshipsatseathathappeneduponcyclones.Since1960,nomajortropicalcyclonehasstruckwithoutanywarning.

Whenasatelliteislaunchedintoanorbitattherightheight(about22,000miles)overEarth’sequator,itorbitsatexactlythesamerateatwhichEarthrotatesandthusremainsfixedoverthesamespot.Suchanorbitiscalledageosynchro-nousorbit.Fromthisloftyheight,asatellitesurveysalargeregion.Thepicturestakenoveraperiodoftimefromsuchasatellitecanbedisplayedinsequencetoshowthecloudmotions.Satelliteobservationsareespeciallyimportantinareaswherelittleornootherinformationisavailable,suchasovertheoceans.

Besidessimplytakingpictures,thenewestgeosynchronoussatellites(calledGOES—geostationaryoperationalenvironmentalsatellite)canmakesophisticatedatmosphericmeasurements.Thesemeasurementsallowmeteorologiststoestimateatmo-spherictemperatureandwatervaporcontent.Itisexpectedthatthesemeasurementswillbecomeevenmoresophisticatedinthefuture.

66 WEATHEr


Weather Forecasting—Past and PresentAmericans in earlier times did not have much help from weather forecasters until the United States Weather Bureau (the predecessor to today’s National Weather Service) became well-established in the late 1800s. As often as not, farmers and sailors had to be their own forecasters. They used all kinds of natural signs as indicators. To predict short-term events, they observed cloud patterns, dew on the grass, winds, and waves. For long-term indications, they studied the hair on caterpillars, the migration patterns of birds, or the hibernation of animals.

In addition to the natural indicators, there were annual almanacs that contained weather forecasts and other informa-tion. Predictions published in these books were very general and were based mostly on past weather history. Though their true value was questionable, almanacs have served as the only forecast source for many people though the ages and are still around today.

In recent years, there has been much improvement in science-based weather forecasting. Much of this progress began with World War II. The vast wartime movements of ships, planes, and troops made it necessary for the armed services to have forecasts as accurate as possible far in advance. They set up their own meteorological groups and worked with universities and the U.S. Weather Bureau to develop new techniques. Thousands of men and women received weather training. Many stayed in meteorology after the war and helped pioneer the peacetime application of new ideas.

Advances in electronics technology have made high-speed computers an everyday working tool in many areas, including weather forecasting. The computer made it possible to solve mathematical formulas and equations of meteorology that had been unsolvable before. A completely scientific means for weather forecasting became possible in the 1950s, when the numerical weather prediction (NWP) forecasts were developed. These models are being improved continually.

WEATHEr 67


ClimateRecallthatweatheristheconditionoftheatmosphereoveraparticularareaforashorttime.Climateistheaverageoftheweatheroveraregionforalongertime,suchas30yearsormore.

ThewordclimatecomesfromtheGreekwordklima,meaning“angle.”ThisnamewasusedbecausetheangleatwhichthesunstrikesEarthlargelydeterminestheclimate.Attheequator,thesunisnearlystraightoverheadmostoftheyear,somostoftheequatorialregionishot.Inthepolarregions,theoppositeistrue.Polewardfromtheequator,theclimategraduallyshiftsfromhottocold.Inbetweenarewhatwecallthetemperate zones,whichincludetheUnitedStates.

We have seasons because Earth’s axis is tilted relative to the plane of its orbit around the sun. This tilt (about 23.5 degrees from the perpendicular) remains the same all year as seen from deep space (top) but changes relative to the sun (bottom). At the summer solstice (the first day of summer, bottom left), the North Pole tilts toward the sun, and the sun reaches its northernmost point in the sky. This is the longest day of the year in the Northern Hemisphere. The North Pole is in constant daylight, while the South Pole is in constant darkness. Everything is reversed at the winter solstice (the first day of winter, bottom, second from right). The South Pole tilts toward the sun, and the Southern Hemisphere has long days and warm weather as the sun appears at its southernmost point in the sky. In between, during the autumnal equinox and spring equinox, sunshine is evenly distributed across both hemispheres.

sun

sun

summeR sOlstice(june)

AutumnAl equinOx (sePtembeR)

WinteR sOlstice (decembeR)

sPRing equinOx (mARch)

eARth’s ORbitsPRingWinteR

summeR Autumn

68 WEATHEr


Manyotherfactorsinfluenceclimate,ofcourse.Nodefiniterulecanbemadeforapartoftheworldsimplybecauseitisacertaindistancefromtheequator.Altitudeaffectsclimate,forexample.InPeruat10,000feetto15,000feetabovesealevel,thesuncanmakeitquitewarmduringtheday,butatnightitgetsverycold.Manyhighpeaksarecoveredinsnowallyear,despitetheirlocationclosetotheequator.

Oceancurrentscanmakeamajordifferenceaswell.EnglandisasfarnorthasparttheCanadianprovinceofNewfoundlandandLabrador,butthewarmwatersoftheGulfStreammoderatethewintersinEnglandsothattheyarewarmeronaveragethanthoseinNewYorkCity,whichissignificantlysouthofEngland.

Climateinformationhelpsexpertslayoutairportrunwaysanddetermineheatingandcoolingneedsforhouses,factories,orfortheshipmentofgoods.

Human Impacts on ClimateAnimportantthingtothinkaboutistheeffectpresenthumanactivitiescanhaveonfutureclimaticconditions.Insomeareasoftheworld,humanactionshavehadaclearlynegativeimpactonthelocalclimate.

DesertificationTheworkofarchaeologistshasshownthatmanyareasthatnowaredesertsoncewerefertileandproductive.Insuchplaces,overgrazing,unsound

farmingmethods,ormininghavestrippedthelandofitspro-tectiveplantcoverandcauseddesertificationoftheland.

DesertificationhasoccurredinmanycountriesneartheMediterraneanSeaandtheArabianDesert.Forexample,theregionnorthofEgyptandEgyptitselfoncehadlushfields,orchards,andgardens,butovermanyyearshumanactivitiesresultedintheerosionoffertiletopsoilandthelossofplantcover.Acyclebeganthatproducedparchedsoil,sanddunes,andscantrainfall.SimilareventshaveoccurredintheUnitedStates,suchasduringthe“DustBowl”eraofthe1930s,butchangesinagriculturalmethodsmayhavekepttheeffectsfrombecomingpermanent.

WEATHEr 69


Acid rainAcid rainisanotherresultoftheeffecthumanactivitiescanhaveonweatherandclimate,somescientistsbelieve.Rainbecomesacidicwhenitispollutedbyacidicsubstancesemittedintotheatmospherebyvehicles,powerplants,andfactories.Pollutantsintheatmo-spherecontaminatetheprecipitationthatlaterfallsbacktotheground.Scientistssayacidraincandestroylifeinlakesandrivers,whichresultsindamagetothewatercycle,crops,for-ests,outdoorstatues,andbuildings.

Other Threats to ClimateRecently,peopleworldwidehavebecomeawareofthepossiblethreatofgreenhousegases.Themostnotablegreenhousegasiscarbondioxide,givenoffwhenfossilfuelssuchascoal,gas,andoilareburned.

Althoughmeteorologistsandclima-tologistsdonotknowexactlywhateffectthegreenhousegaseswillhave,itappearsthatexcesscarbondioxideandothergasesmighttrapmoreofthesun’sheatandcausetheclimateallovertheglobetowarmup.Somescien-tistsbelieveglobal warmingcouldhavedisastrouseffects.Forinstance,thepolaricecapsreflectthesun’sraysandareessen-tialinkeepingEarth’sclimateasitis.Iftheicecapsmelt,evenasmallamount,thesescientistssayEarth’stemperature,weath-erpatterns,andtheamountofwaterintheoceansmaychange.Manyislandsandseacoastscouldbefloodedpermanently.

Anotherconcernisthelossoftheozonelayer.Ozoneisapalebluegasthatplaysanimportantroleinthestratosphere,whereitactstoshieldallformsoflifeonEarthfromthesun’sharmfulultravioletradiation.Damagetotheozonelayerappearstobetheresultofchemicalscalledchlorofluorocarbons(CFCs),onceusedaspropellantinaerosolcans,asrefrigerantsinairconditioners,andassolventsincertainindustrialprocesses.AlthoughrecentlawshavegreatlyreducedtheuseofCFCs,somescientistsarenotcertaintheozonelayerwillrecover.

Another source of

carbon dioxide is

the clearing and

burning of trees in

the rain forests of

the world.

70 WEATHEr


Theholeintheozonelayerpermitsultravioletradiationfromthesuntoreachthesurfaceinincreasedamounts,whichmaycontributetoglobalwarmingandclimatechange.

Ingeneral,conservationofresources,suchasfossilfuelsandtheworld’sforests,canbeoflong-termbenefitbylesseningtheeffectsofhumanactivitiesontheglobalclimate.

Water conservation and careful agricultural and mining practices also can help preserve the natural balance of things.

WEATHEr 71


Weather Affects All of Us A rainy day will keep you from mowing the lawn or playing a baseball game. A serious heat wave could prevent your Scout troop from taking a hiking trip. For people in some occupations, however, the weather fore-cast is vital. Planning ahead for weather conditions can mean the differ-ence between profit and loss or even life and death.

Climate information helps experts lay out airport runways and deter-mine heating and cooling needs for houses, factories, or for the shipment of goods. Climate records may be introduced as evidence in court to clarify the causes of accidents on highways, in the air, and at sea. Climate can affect people’s health and social behavior as well as agricultural, commer-cial, and industrial pursuits the world over. Here are a few examples:

Aviators. Pilots need accurate, up-to-date forecasts to help them make deci-sions such as whether to land a plane. If a destination airport is fogged in or has icy runways, the pilot may delay departure or land at a different air-port. If there is a thunderstorm brewing along the planned route, a pilot can take an alternate route. Pilots also take advantage of good weather, letting the tailwind push the plane along to save fuel.

Sailors. Being caught far out at sea during severe weather poses great danger to sailors. Knowing the forecast can help sailors avoid areas of high wind and other trouble. Sailors can plan alternative routes to their destinations or choose safe areas in which to work (fishing, for instance) when they have information about the weather.

Farmers. Farmers know the importance of wind, rain, and temperature on their plants and animals. An early frost can ruin a citrus crop. A bitterly cold winter or a very wet season can reduce the weight gain of livestock. Farmers plan when to sow, weed, and harvest according to the day-to-day weather forecast. They also plan what crops to grow according to the sea-sonal forecast. For instance, a rice crop that needs wet conditions while it grows and dry conditions while it ripens.

Outdoor Construction Workers. Builders and other people in the field of construction pay close attention to weather forecasts. Road-paving crews, roofers, painters, and others cannot do their work successfully in the rain. Wind can endanger those who must keep their balance high above the ground. Many building materials such as paint may be used effectively only within certain limits of humidity and temperature.

WEATHEr 73

.Careers in Meteorology

CareersinMeteorologyThemeteorologistsyouprobablyaremostfamiliarwitharetheweathernewscastersontelevision.Buttherearemanyadditionalcareeropportunitiesformeteorologists.

research and TeachingResearchersworktofurtherdevelopsatellites,computerpro-grams,mathematicalformulas,andotherinstrumentsusedinforecasting,analyzing,andcollectingdatarelatedtoclimateandweather.Suchresearchersworkforuniversities,privateindustry,andtheU.S.government.TheNationalAeronauticsandSpaceAdministration(NASA)isjustonegovernmentagencythatusesresearchers.Manyresearchersanalyzelevelsofpollutionintheoceansandatmosphere.AttheNationalCenterforAtmosphericResearch(NCAR),climateresearchisahighpriority.Atuniversities,meteorologyprofessorsteachandconductresearch.Theirresearchisusuallysupportedbygrantsfromthegovernmentorprivatefoundations.

ForecastingWeatherforecastingisformallyknownasoperationalmeteorol-ogy.ManyforecastersworkfortheNationalWeatherService(abranchoftheNOAA),whichincludestheNationalCenterforEnvironmentalPredictionaswellas124fieldofficesacrossthecountry.TheNationalWeatherServiceisagovernmentagencythatgathersinformationfromweatherballoons,satellites,andobservationstationsaroundtheworld.PeopleandcomputersattheNationalWeatherServiceanalyzeandinterpretthegathereddatatoproduceforecasts.

74 WEATHEr

Careers in Meteorology.

TheU.S.militaryalsoemploysmeteorologiststohelpplanoperationsontheground,intheair,andatsea.Weatherfore-castshelpArmytroopsknowwhentotravelandhelpAirForceaviatorsplantheirflights.Navalmeteorologyandoceanographyoftengohandinhand,astheNavyneedstopredictconditionsunderthewateraswellasaboveit.

Otherforecastersworkforprivateorganizations,suchasAccuWeather,thatinterpretdatafromNOAAandthenselltheirspecificanalysestonewspapers,radioandtelevisionstations,andindustriessuchasaviation,construction,andfarming.Privateforecastingcompaniessupplynewspaperswithfull-colorweathermapsandtheforecaststhatradiostationsbroadcast.Industriesthatpurchaseforecastsusethemtodeterminehowtheweathercouldaffectairplaneflights,outdoorpainting,andcropharvests.

QualificationsWhatknowledgeandskillsdoyouneedtoworkinmeteorologyanditsrelatedfields?Thislistgivesyousomeguidelinesforwhatittakestobecomeameteorologist.

• Youwillneedagoodfoundationinscienceandmathematics.Taketheseclassesseriouslywhileyouareinmiddleschoolandhighschool.

• Youwillneedabachelor’sdegreeinmeteorology(alsocalledatmosphericsciences)orarelatedfield,suchasphysics.Youwillneedtotakeclassesinthermodynamicsandcalculus.ThoseclassesarerequiredbytheNationalWeatherService,nomatterwhichbranchofmeteorologyyouplantopursue.

• Ifyouwouldliketobecomeatelevisionweatherreporter,youwillneedtodevelopstrongcommunicationsskills.Youalsowillprobablyhavetostartyourcareerinasmallmarket,thatis,asmallcityorcommunity.Inotherwords,forecastingforLosAngelesorNewYorkCitywillprobablynotbeyourfirstjob.

• Forecastersworkinshiftsthatoftenrequirethemtoworknightsandweekends.Duringweatheremergencies,thesemeteorologistsmayhavetoputinextrahours.

WEATHEr 77

.Weather Resources

WeatherResourcesScouting Literature

Basic Illustrated Weather Forecasting; Fieldbook;Chemistry,Emergency Preparedness,Environmental Science,andOceanographymeritbadgepamphlets

Books

Burt,ChristopherC.Extreme Weather: A Guide and Record Book.W.W.Norton,2004.

Ceban,BonnieJ.Tornadoes: Disaster and Survival.EnslowPublishers,2005.

Chaston,PeterR.Weather Maps: How to Read and Interpret All the Basic Weather Charts.ChastonScientificInc.,2002.

Cosgrove,Brian.Weather.DKPublishing,2004.

Day,John.A.,andVincentJ.Schaefer.Clouds and Weather: The Concise Field Guide to the Atmosphere.HoughtonMifflin,1998.

Elsom,DerekM.Weather Explained: A Beginner’s Guide to the Elements, Vol. 5.HenryHolt&Company,1997.

Gardner,Robert,etal.Science Projects About Weather.EnslowPublishers,1994.

Kahl,JonathanD.W.National Audubon Society First Field Guide: Weather.Scholastic,1998.

Moran,JosephM.,etal.Meteorology: The Atmosphere and Science of Weather.PrenticeHall,1996.

Petheram,Louise.Acid Rain.BridgestoneBooks,2002.

Magazines

Weatherwise: The Magazine About Weather131918thSt.,NWWashington,DC20036-1802Website:http://www.weather-wise.org

Organizations and Web Sites

Career Guide for the Atmospheric Sciences Website:http://www.ametsoc.org/atmoscareers/index.html

Earth Watch Weather on Demand Website:http://earthwatch.com

Visit the Boy Scouts of America’s official retail Web site at http://www.scoutstuff.org for a complete listing of all merit badge pamphlets and other helpful Scouting materials and supplies.

78 WEATHEr

Weather Resources.

Lightning Protection Institute P.O.Box6336St.Joseph,MO64506Toll-freetelephone:800-488-6864Website:http://www.lightning.org

Satellite Meteorology for Grades 7–12 Website:http://cimss.ssec.wisc.edu/satmet

The National Center for Atmospheric research and the UCAr Office of Programs P.O.Box3000Boulder,CO80307-3000Website:http://www.ucar.edu

The National Oceanic and Atmospheric Administration’s National Weather Service1325EastWestHighwaySilverSpring,MD20910Website:http://nws.noaa.gov

AcknowledgmentsTheBoyScoutsofAmericathanksKerryM.Jones,seniorforecasterwiththeNationalWeatherServiceinAlbuquerque,NewMexico.Mr.Jonesdiligentlyprovidedhisexpertise,time,andotherresourcesforthisnewedi-tionoftheWeathermeritbadgepam-phlet.Weappreciatehisthoroughnessandhisattentivenessduringthislengthyproject.

WeappreciatetheQuicklistConsultingCommitteeoftheAssociationforLibraryServicetoChildren,adivisionoftheAmericanLibraryAssociation,foritsassistancewithupdatingtheresourcessectionofthismeritbadgepamphlet.

WEATHEr 79

.Weather Resources

Photo and Illustration Credits

HAAPMediaLtd.,courtesy—cover(leaf, weather vane, clouds, analog barometer);pages45(both)and80

©Jupiterimages.com—page26

NASA,courtesy—cover(Earth)andpage30

NationalOceanicandAtmosphericAdministration,DepartmentofCommerce/GrantW.Goodge,courtesy—page19(bottom)

NationalOceanicandAtmosphericAdministration,DepartmentofCommerce/HistoricNWSCollection,courtesy—page38

NationalOceanicandAtmosphericAdministration,DepartmentofCommerce/RalphF.Kresge,courtesy—pages22(bottom),23(bottom),and24(top right)

NationalOceanicandAtmosphericAdministration,DepartmentofCommerce/NationalWeatherService,courtesy—page64(bottom)

NationalOceanicandAtmosphericAdministration,DepartmentofCommerce/MichaelThebrege,MaineMaritimeAcademy,courtesy—page17

NationalOceanicandAtmosphericAdministration,DepartmentofCommerce/DonWhelpey,courtesy—page25(top)

NewYorkStateDepartmentofEnvironmentalConservation,courtesy—page69

NOAAPhotoLibrary,NOAACentralLibrary;OAR/ERL/NationalSevereStormsLaboratory(NSSL),courte-sy—page27

©Photos.com—cover(penguins);pages3–4(all),6–7(both),8(inset),14,19(top, center left, center right),20,23,24(bottom),25(center, bottom),39(bottom),68,70,and76

Wikipedia.org,courtesy—pages24(top left)and78

AllotherphotosandillustrationsnotmentionedabovearethepropertyoforareprotectedbytheBoyScoutsofAmerica.

DanielGiles—pages18,40,46–47(all),51,60–61,72(both),and75(top, bottom left)

JohnMcDearmon—allillustrationsonpages10–13,16,21,29,34–35,39,42,50,52,and67

BrianPayne—pages32and36

BradRange—pages54,62,and75(center left, bottom right)

Merit badge libraryThough intended as an aid to Boy Scouts, Varsity Scouts, and qualified Venturers in meeting merit badge requirements, these pamphlets are of general interest and are made available by many schools and public libraries. The latest revision date of each pamphlet might not correspond with the copyright date shown below, because this list is corrected only once a year, in January. Any number of merit badge pamphlets may be revised throughout the year; others are simply reprinted until a revision becomes necessary.

If a Scout has already started working on a merit badge when a new edition for that pamphlet is introduced, he may continue to use the same merit badge pamphlet to earn the badge and fulfill the requirements therein. In other words, the Scout need not start all over again with the new pamphlet and possibly revised requirements.

American Business 2002American Cultures 2005American Heritage 2005American Labor 2006Animal Science 2006Archaeology 2006Archery 2004Architecture 2008Art 2006Astronomy 2004Athletics 2006Automotive Maintenance 2008Aviation 2006Backpacking 2007Basketry 2003Bird Study 2005Bugling (see Music)Camping 2005Canoeing 2004Chemistry 2004Cinematography 2008Citizenship in the

Community 2005Citizenship in the Nation 2005Citizenship in the World 2005Climbing 2006Coin Collecting 2008Collections 2008Communication 2009Composite Materials 2006Computers 2009Cooking 2007Crime Prevention 2005Cycling 2003Dentistry 2006Disabilities Awareness 2005Dog Care 2003Drafting 2008Electricity 2004Electronics 2004Emergency Preparedness 2008Energy 2005

Photography 2005Pioneering 2006Plant Science 2005Plumbing 2004Pottery 2008Public Health 2005Public Speaking 2002Pulp and Paper 2006Radio 2008Railroading 2003Reading 2003Reptile and

Amphibian Study 2005Rifle Shooting 2001Rowing 2006Safety 2006Salesmanship 2003Scholarship 2004Scuba Diving 2009Sculpture 2007Shotgun Shooting 2005Skating 2005Small-Boat Sailing 2004Snow Sports 2007Soil and Water

Conservation 2004Space Exploration 2004Sports 2006Stamp Collecting 2007Surveying 2004Swimming 2008Textile 2003Theater 2005Traffic Safety 2006Truck Transportation 2005Veterinary Medicine 2005Water Sports 2007Weather 2006Whitewater 2005Wilderness Survival 2007Wood Carving 2006Woodwork 2003

Engineering 2008Entrepreneurship 2006Environmental Science 2006Family Life 2005Farm Mechanics 2008Fingerprinting 2003Fire Safety 2004First Aid 2007Fish and Wildlife

Management 2004Fishing 2009Fly-Fishing 2009Forestry 2005Gardening 2002Genealogy 2005Geology 2005Golf 2002Graphic Arts 2006Hiking 2007Home Repairs 2009Horsemanship 2003Indian Lore 2008Insect Study 2008Journalism 2006Landscape Architecture 2008Law 2003Leatherwork 2002Lifesaving 2008Mammal Study 2003Medicine 2009Metalwork 2007Model Design and Building 2003Motorboating 2008Music and Bugling 2003Nature 2003Nuclear Science 2004Oceanography 2009Orienteering 2003Painting 2008Personal Fitness 2006Personal Management 2003Pets 2003

BOY SCOUTS OF AMERICA • SUPPLY GROUP

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WEathEr - Troop 577 Wichita, Kansas · 2019-08-11 · climate is. Discuss how the weather affects farmers, sailors, aviators, and the outdoor construction industry. Tell why weather