雙語教學(xué)實例Meteorology公開課一等獎市優(yōu)質(zhì)課賽課獲獎?wù)n件

MeteorologyGeographyDepartment

EastChinaNormalUniversity

ShuJiongTheEarth’sGlobalEnergyBalance

◆

Solarradiationisthedrivingpowersourceforwind,waves,weather,rivers,andoceancurrents.◆Theearth’senergybalance,whichincludeslandandoceansurfacesandtheatmosphere,controlstheseasonalanddailychangesintheearth’ssurfacetemperature.ElectromagneticRadiation

◆Wavelength

describesthedistanceseparatingonewavecrestfromthenextcrest.◆Theunittomeasurewavelengthisthe

micrometer.◆Radiantenergycanexistatanywavelength.RadiationandTemperature

◆

Thereisaninverserelationshipbetweentheradiationthatanobjectemitsandthetemperatureoftheobject.

◆Hotobjectsradiatemoreenergy,andatshorterwavelengths,thancoolerobjects.Solarradiation

◆TheSunisaballofconstantlychurninggasesthatareheatedbycontinuousnuclearreactions.Ithasasurfacetemperatureofabout6000oC.Likeallobjects,itemitsenergyintheformofelectromagneticradiation.electromagneticspectrum

Shortwaveradiation

◆Ultravioletradiation

(0.2to0.4μm)

◆Visiblelight

radiation(0.4to0.7μm)◆Shortwaveinfraredradiation

(0.7to3μm)

Longwaveradiation

◆Thermalinfraredwavelengths

(>3μm)

Characteristicsofsolarenergy

◆

Thesundoesnotemitallwavelengthsofradiationequally◆

TheintensityofsolarenergyisstrongestinvisiblewavelengthsLongwaveradiationfromtheEarth

◆

Theearth’ssurfaceandatmospherearemuchcolderthanthesun’ssurface,sotheenergyfromtheEarthhaslongerwavelength

Theglobalradiationbalance

◆Theearthconstantlyabsorbssolarshortwaveradiationandemitslongwaveradiation.◆Thesunprovidesanearlyconstantflowofshortwaveradiationtowardearth.◆Theatmosphere,land,andoceanalsoemitenergyintheformoflongwaveradiation.Figure1GlobalEnergyBalanceInsolationovertheGlobe

◆Insolation(incomingsolarradiation)dependsontheangleofthesunabovethehorizon.ThePathoftheSunintheSky

Thesun’spathintheskychangesgreatlyinpositionandheightabovehorizonfromsummertowinter.◆Atequinox,thesunrisesdirectlytotheeastandsetsdirectlytothewest.◆Thenoonsunispositionedatanangleof50oabovethehorizoninthesouthernsky.

◆Thesunisabovethehorizonforexactly12hours.◆Atnoonitwillbe73.5oabovethehorizon.◆Thesunisabovethehorizonforabout15hour

DailyInsolationThroughtheYear

◆

Dailyinsolationdependsontwofactors:◆

theangleatwhichthesun’sraysstriketheearth◆

thelengthoftimeofexposuretotherays◆

theequatorhastwoperiodsofmaximumdailyinsolation,theseperiodsoccurneartheequinoxes.◆Therearealsotwominimumperiodsnearthesolstices,whenthesubsolarpointmovesfarthestnorthandsouthfromtheequator.Alllatitudesbetweenthetropicofcancer23.5oNandthetropicofCapricorn23.5oShavetwomaximumandminimumvalues.◆Seasonalpatternofdailyinsolationisdirectlyrelatedtolatitude.AnnualInsolationbyLatitude

◆Annualinsolationvariessmoothlyfromtheequatortothepole◆Theannualinsolationvalueatthepoleisabout40%ofthevalueattheequator.◆Thetiltingoftheearth’saxisredistributesasignificantportionoftheearth’sinsolationfromtheequatorialregionstowardthepoles.WorldLatitudeZones

◆Theequatorialzoneencompassestheequatorandcoversthelatitudebeltroughly10oNto10oS◆SpanningthetropicsofcancerandCapricornarethe

tropicalzones,rangingfromlatitudes10oto25onorthandsouth◆Movingtowardthepolesfromeachofthetropicalzonesaretransitionalregionscalledthesubtropicalzones,rangingfromlatitudes25oto35onorthandsouth◆Themidlatitudezonesliebetween35oand55olatitudesinthenorthernandsouthernhemispheres◆Borderingthemidlatitudezonesonthepolewardsidearethesubarcticzoneand

subantarcticzone,55oto60onorthandsouthlatitudes◆AstridethearcticandAntarcticcirclesfromlatitudes60oto75oNandSliethe

arcticandAntarcticzones◆Thepolarzones,northandsouth,arecircularareasbetweenabout75olatitudeandthepolesCompositionoftheAtmosphere

◆

Theearth’satmosphereconsistsofair-amixtureofvariousgasessurroundingtheearthtoaheightofmanykilometers.

◆Almostalltheatmosphere97%lieswithin30kmoftheearth’ssurface.

Theupperlimitoftheatmosphereisataheightofapproximately10,000kmabovetheearth’ssurface,adistanceapproachingthediameteroftheearthitself.◆Pure,dryairconsistslargelyofnitrogen,about78%byvolume,andoxygen,about21%.Othergasesaccountfortheremaining1%◆WatervaporisanimportantcomponentoftheatmospherethatvariesinconcentrationfromplacetoplaceandtimetotimeOzoneintheUpperAtmosphere

◆Ozone(O3)isfoundmostlyintheupperpartoftheatmosphere,inalayertermedthestratosphere.Ozoneinthestratosphereabsorbsultravioletradiationfromthesunasthisradiationpassesthroughtheatmosphere

Atbothpolarregions,climateandchemistrycombinetodepleteozoneduringspringmonths.Darkblueindicateslowestozoneamounts.ArctictotalozoneamountsseenbyTOMSinMarch2023(above,left)wereamongthelowesteverobservedinthenorthernhemisphere.TheAntarcticozoneholeof2023(above,right)wasthesecondlargesteverobserved.SensibleHeatandLatentHeatTransfer

◆SensibleHeat-thequantityofheatheldbyanobjectthatcanbesensedbytouchingorfeeling◆Whentwoobjectsofunliketemperaturecontacteachother,heatenergymovesbyconductionfromthewarmertothecooler.ThistypeofheatflowisreferredtoassensibleheattransferTheGlobalEnergySystem

◆

InsolationlossesintheAtmosphere◆Albedo◆CounterradiationandtheGreenhouseEffect◆GlobalEnergyBudgetoftheAtmosphereandSurface◆NetRadiation,Latitude,andtheEnergyBalanceWindsandthePressureGradientForce

◆Windisairmotionwithrespecttotheearth’ssurface,anditisdominantlyhorizontal.◆

Barometricpressurefallswithincreasingaltitudeabovetheearth’ssurface.◆

Thechangeinbarometricpressureacrossthehorizontalsurfaceofamapconstitutesapressuregradient.

Thegradientisinthedirectionfromhigherpressuretolowerpressure.◆

Whereapressuregradientexists,airmoleculestendtodriftinthesamedirectionasthatgradient.Thistendencyformassmovementoftheairisreferredtoasthepressuregradientforce.SeaandLandBreezes

◆

Duringthedaytime,morerapidheatingofthelowerairlayeroverthelandthanovertheoceancausesapressuregradientfromseatoland.Airmovinglandwardinresponsetothisgradientfromhighertolowerpressureconstitutestheseabreeze.

Athigherlevels,areverseflowsetsin.Togetherwithweakrisingandsinkingairmotions,acompleteflowcircuitisformed.◆

Duringthenight,whenradiationalcoolingofthelandisrapid,thelowerairbecomescolderoverthelandthanoverthewater.Higherpressurenowdevelopsoverlandandthebarometricgradientisreversed.Airnowmovesfromlandtoseaasa

landbreeze.Figure2SeabreezeandlandbreezeCyclonesandAnticyclones

◆Acenteroflowpressureiscalledacyclone;acenterofhighpressureisananticyclone.◆Windsinacycloneinthenorthernhemisphereshowananticlockwiseinspiral.Inananticyclone,thereisaclockwiseoutspiral.◆Thesurfacewindsspiralinwardonthecenterofthecyclone,sotheairisconvergingonthecenterandmustalsorisetobedisposedofathigherlevels.◆Fortheanticyclone,bycontrast,surfacewindsspiraloutfromthecenter.Thismotionrepresentsadivergingofairflowandmustbeaccompaniedbyasinkingofairinthecenteroftheanticyclonetoreplacetheoutmovingair.Figure3Surfacewindsincyclonesandanticyclones

GlobalDistributionofSurfacePressureSystems

◆Overtheequatorialzoneisabeltofsomewhatlowerthannormalpressure,between1011and1008mb,whichisknownastheequatorialtrough.◆Lowerpressureisconspicuousbycontrastwithbeltsofhigherpressurelyingtothenorthandsouthandcenteredataboutlat.30°NandS.Thesearethe

subtropicalbeltsofhighpressure,inwhichpressureexceed1020mb.

◆Inthesouthernhemisphere,southofthesubtropicalhigh-pressurebelt,isabroadbeltoflowpressure,extendingfromthemidlatitudezonetothearcticzone.Theaxisoflowpressureiscenteredataboutlat.65S.Thispressuretroughiscalledthe

subantacticlow-pressurebelt.◆LyingoverthecontinuousexpanseofSouthernOcean,thistroughhasaveragepressureaslowas984mb.OverthecontinentofAntarcticaisapermanentcenterofhighpressureknownasthe

polarhigh.

TheGlobalPatternofSurfaceWinds

◆Fromthetwosubtropicalhigh-pressurebeltsthepressuregradientisequatorward,leadingdowntotheequatorialtroughoflowpressure.AirmovingfromhightolowpressureisdeflectedbytheCorioliseffect.Asaresult,twobeltsof

tradewinds

areproduced.◆Meetingofthetradestakesplacewithinanarrowzonecalledthe

intertropicalconvergencezone.◆Alongpartsoftheequatorialtroughoflowpressureatcertaintimesofyear,thetradesdonotcometogetherinconvergence.Instead,abeltofcalmsandvariblewinds,calledthedoldrums,forms.◆Betweenlat.35and60NandSisthebeltofprevailingwesterlywinds,orwesterlies.◆Awindsystemcalledthepolareasterliesischaracteristicofthearcticandpolarzones.Figure4Surfacewinds

MonsoonWindsof

SoutheastAsia

◆InsummersouthernAsiadevelopsacycloneintowhichthereisstrongflowofair.FromtheIndianOceanandthesouthwesternPacific,warm,humidairmovesnorthwardandnorthwestwardintoAsia.ThisairflowconstitutesthesummermonsoonandisaccompaniedbyheavyrainfallinsoutheasternAsia.◆Inwinter,Asiaisdominatedbyastrongcenterofhighpressurefromwhichthereisanoutwardflowofairreversingthatofthesummermonsoon.Blowingsouthwardandsoutheastwardtowardtheequatorialoceans,thisairflowconstitutesthewintermonsoonandbringsdryweatherforaperiodofseveralmonths.

Mountainwindsand

valleywinds

◆Duringthedaylighthourstheairalongtheslopesofthemountainsisheatedmoreintenselythantheairatthesameelevationoverthevalleyfloor.Thiswarmairglidesupalongtheslopeandgeneratesa

valleywind.◆Aftersunsetthepatternisreversed.Rapidradiationheatlossalongthemountainslopesresultsincoolairdrainageintothevalleybelowandcausesthemountainwind.

GlobalCirculation

◆TheHadleyCellCirculation

Inthezonebetweentheequatorandroughly30°latitude,thesurfaceflowisequatorwardwhiletheflowaloftispoleward.Neartheequatorthewarmrisingairthatreleaseslatentheatduringtheformationofcumulustowersisbelievedtoprovidetheenergytodrivethiscell

◆Thecirculationbetween30and60latitudeisjustoppositethatoftheHadleycell.Thenetsurfaceflowispoleward,andbecauseoftheCorioliseffect,thewindshaveastrongwesterlycomponent.◆Aboutthecirculationinthehighlatitudes,itisgenerallybelievedthatsubsidencenearthepolesproducesasurfaceflowthatmovesequatorwardandisdeflectedintothepolareasterliesofbothhemisphere.Theregionwherethecoldpolarwindsandthewarmerwesterlyflowofthemidlatitudesclashhasbeennamedthepolarfront.TheglobalCirculationandMan’sEnvironment

◆Inlowlatitudes,theHadleycelloperateslikeasimpleheatenginetotransportheatfromtheequatorialzonetothesubtropicalzone.◆Upper-airwavestakeupthetransportandmovewarmairpolewardinexchangeforcoldair.◆Theglobalatmosphericcirculationalsotransportsheatinthelatentformheldbywatervapor.

◆Windscarryalargeamountofwatervapor,whichisdepositedasprecipitationonthecoast.◆Windsalsotransportatmosphericpollutants,carryingthemtensandhundredsofkilometersfromthesourcesofpollution.

Airtemperature

◆

Temperature

isameasureofthelevelofsensibleheatofmatter,whetheritisgaseous,liquid,orsolid.◆

Conduction

describestheflowofheatfromawarmersubstancetoacolderonewhenthetwoaretouching.◆

Evaporation,theprocessbywhichwaterchangesfromaliquidtoagasbyabsorbingheat,tendstolowerthetemperatureofawetsurface.MeasurementofairtemperatureAirtemperaturesarenowautomaticallyrecordedbythermometersatauniformheightabovetheground.Thedailycycleofairtemperature◆Becausetheearthrotatesonitsaxis,incomingsolarenergyatalocationcanvarywidelythroughoutthe24-hourperiod.◆Insolationisgreatestinthemiddleofthedaylightperiod,whenthesunisatitshighestpositioninthesky,andfallstozeroatnight.Dailyinsolationandnetradiation◆Thedailycycleoftemperatureiscontrolledbythedailycycleofnetradiation.◆Attheequinox,insolationbeginsataboutsunrise(6a.m.),risestoapeakvalueatnoon,anddeclinestozeroatsunset(6p.m.).◆AttheJunesolstice,insolationbeginsabouttwohoursearlier(4a.m.)andendsabouttwohourslater(8p.m.).◆AttheDecembersolstice,insolationbeginsabouttwohourslaterthantheequinoxcurve(8a.m.)andendsabouttwohoursearlier(4p.m.).◆Whennetradiationispositive,thesurfacegainsheat,andwhennegative,itlosesheat.◆Netradiationbeginsthe24-hourdayasanegativevalue-adeficit-atmidnight.Thedeficitcontinuesintotheearlymorninghours.Netradiationshowsapositivevalue-asurplus-shortlyaftersunriseandrisessharplytoapeakatnoon.

Dailytemperature

Theminimumdailytemperatureusuallyoccursaboutahalfhouraftersunrise.Airtemperaturerisessharplyinthemorninghoursandcontinuestoriselongafterthenoonpeakofnetradiation.Airtemperaturerisesaslongasnetradiationispositive.Temperaturesarelowestjustaftersunriseandhighestinmidafternoon.Urbanandruraltemperaturecontrasts◆Urbansurfaceslackmoistureandsoarewarmerthanruralsurfacesduringtheday.Atnight,urbanmaterialsconductstoredheattothesurface,alsokeepingtemperatureswarmer.

Theurbanheatisland

◆Asaresultoftheaboveeffects,airtemperaturesinthecentralregionofacityaretypicallyseveraldegreeswarmerthanthoseofthesurroundingsuburbsandcountryside.Thisiscalledaheatisland.◆Theheatislandpersiststhroughthenightbecauseoftheavailabilityofaheatstoredinthegroundduringthedaytimehours.◆Anotherimportantfactorinwarmingthecityisfuelconsumption.Insummer,citytemperaturesareraisedthroughtheuseofairconditioning.

TemperaturestructureoftheAtmosphere

Troposphere

◆Thetroposphereisthelowestatmosphericlayer,inwhichtemperaturedecreaseswithincreasingelevation.Everydayweatherphenomena,suchascloudsorstorms,occurmainlyinthislayer.◆Thetropospherecontainssignificantamountsofwatervaporandcountlesstinydustparticles.

Stratosphere◆Abovethetroposphereliesthestratosphereinwhichtheairbecomesslightlywarmerasaltitudeincreases.◆Thestratosphereextendstoaheightofroughly50kmabovetheearth’ssurface.◆Itisthehomeofstrong,persistentwindsthatblowfromwesttoeast.◆Oneimportantfeatureofthestratosphereisthatitcontainstheozonelayer.

High-MountainEnvironments

◆Athighelevations,airtemperaturesaregenerallycoolerandshowagreaterday-to-nightrange.

TemperatureInversionandFrost

◆Inatemperatureinversion,airtemperatureincreaseswithaltitude.◆Low-leveltemperatureinversionsoftenoccuroversnow-coveredsurfacesinwinter.

◆Inversionscanalsoresultwhenawarmairlayeroverliesacolderone.Thistypeofinversionisoftenfoundalongthewestcoastsofmajorcontinents.Frost◆Ifthetemperatureofthelowermostairfallsbelowthefreezingpoint,forsensitiveplantsduringthegrowingseason,thistemperatureconditioniscalledakillingfrost.

Theannualcycleofairtemperature

Theannualcycleofnetradiation,whichresultsfromthevariationofinsolationwiththeseasons,drivestheannualcycleofairtemperatures.

Landandwatercontrasts

◆Land-watercontrastskeepairtemperaturesatcoastallocationsmoreconstantthanatinteriorcontinentallocations.◆Oceansheatandcoolmoreslowlythancontinents.◆Thesurfaceofanyextensive,deepbodyofwaterheatsmoreslowlyandcoolsmoreslowlythanthesurfaceofalargebodyoflandwhenbotharesubjectedtothesameintensityofinsolation.

Dailytemperaturecycle

P62Figure3.15Theaveragedailycycleofairtemperatureforfourdifferentmonthsshowstheeffectofcontinentalandmaritimelocation.DailyandseasonalrangesaregreatatElPaso,astationinthecontinentalinterior,butonlyweaklydevelopedatNorthHead,Washington,whichisonthePacificcoast.TheseasonaleffectonoveralltemperaturesisstrongeratElPaso.

Annualtemperaturecycle

P63figure3.16Annualcyclesofinsolation(a)andmonthlymeanairtemperature(b)fortwostationsatlat.50°N:Winnipeg,Canada,andScillyIslands,England.Insolationisidenticalforthetwostations.Winnipegtemperaturesclearlyshowthelargeannualrangeandearliermaximumandminimumthatarecharacteristicofitscontinentallocation.ScillyIslandstemperaturesshowitsmaritimelocationinthe