双语教学实例Meteorology市公开课一等奖百校联赛特等奖课件.pptx
MeteorologyGeography Department East China Normal UniversityShu Jiong第1页The Earths Global Energy Balance Solarradiationisthedrivingpowersourceforwind,waves,weather,rivers,andoceancurrents.Theearthsenergybalance,whichincludeslandandoceansurfacesandtheatmosphere,controlstheseasonalanddailychangesintheearthssurfacetemperature.第2页Electromagnetic Radiation Wavelength describesthedistanceseparatingonewavecrestfromthenextcrest.Theunittomeasurewavelengthisthemicrometer.Radiantenergycanexistatanywavelength.第3页Radiation and Temperature Thereisaninverserelationshipbetweentheradiationthatanobjectemitsandthetemperatureoftheobject.Hotobjectsradiatemoreenergy,andatshorterwavelengths,thancoolerobjects.第4页Solar radiation TheSunisaballofconstantlychurninggasesthatareheatedbycontinuousnuclearreactions.It has a surface temperature ofabout 6000oC.Like all objects,it emitsenergy in the form of electromagneticradiation.第5页electromagnetic spectrum Shortwave radiation Ultraviolet radiation(0.2 to 0.4 m)Visible lightradiation(0.4 to 0.7m)Shortwave infrared radiation(0.7 to 3m)Longwave radiation Thermal infrared wavelengths(3m)第6页Characteristics of solar energy Thesundoesnotemitallwavelengthsofradiationequally Theintensityofsolarenergyisstrongestinvisiblewavelengths第7页Longwave radiation from the Earth Theearthssurfaceandatmospherearemuchcolderthanthesunssurface,sotheenergyfromtheEarthhaslongerwavelength第8页The global radiation balance Theearthconstantlyabsorbssolarshortwaveradiationandemitslongwaveradiation.Thesunprovidesanearlyconstantflowofshortwaveradiationtowardearth.Theatmosphere,land,andoceanalsoemitenergyintheformoflongwaveradiation.第9页Figure1GlobalEnergyBalance第10页Insolation over the GlobeInsolation(incomingsolarradiation)dependsontheangleofthesunabovethehorizon.第11页The Path of the Sun in the Sky Thesunspathintheskychangesgreatlyinpositionandheightabovehorizonfromsummertowinter.Atequinox,thesunrisesdirectlytotheeastandsetsdirectlytothewest.Thenoonsunispositionedatanangleof50oabovethehorizoninthesouthernsky.第12页Thesunisabovethehorizonforexactly12hours.Atnoonitwillbe73.5oabovethehorizon.Thesunisabovethehorizonforabout15hour第13页Daily Insolation Through the YearDailyinsolationdependsontwofactors:theangleatwhichthesunsraysstriketheearth thelengthoftimeofexposuretotheraystheequatorhastwoperiodsofmaximumdailyinsolation,theseperiodsoccurneartheequinoxes.第14页Therearealsotwominimumperiodsnear the solstices,when the subsolarpoint moves farthest north and southfromtheequator.Alllatitudesbetweenthe tropic of cancer 23.5oN and thetropic of Capricorn 23.5oS have twomaximumandminimumvalues.Seasonalpatternofdailyinsolationisdirectlyrelatedtolatitude.第15页Annual Insolation by LatitudeAnnualinsolationvariessmoothlyfromtheequatortothepoleTheannualinsolationvalueatthepoleisabout40%ofthevalueattheequator.Thetiltingoftheearthsaxisredistributesasignificantportionoftheearthsinsolationfrom the equatorial regions toward thepoles.第16页World Latitude ZonesTheequatorial zoneencompassestheequatorandcoversthelatitudebeltroughly10oNto10oSSpanningthetropicsofcancerandCapricornarethe tropical zones,rangingfromlatitudes10oto25onorthandsouth第17页Movingtowardthepolesfromeachofthetropicalzonesaretransitionalregionscalledthesubtropical zones,rangingfromlatitudes25oto35onorthandsouthThemidlatitude zonesliebetween35oand55olatitudesinthenorthernandsouthernhemispheres第18页Borderingthemidlatitudezonesonthepolewardsidearethesubarctic zoneandsubantarctic zone,55oto60onorthandsouthlatitudesAstridethearcticandAntarcticcirclesfromlatitudes60oto75oNandSliethearcticandAntarctic zones The polar zones,northandsouth,arecircularareasbetweenabout75olatitudeandthepoles第19页Composition of the Atmosphere Theearthsatmosphereconsistsofair-amixtureofvariousgasessurroundingtheearthtoaheightofmanykilometers.Almostalltheatmosphere97%lieswithin30kmoftheearthssurface.第20页Theupperlimitoftheatmosphereisata height of approximately 10,000kmabove the earths surface,a distanceapproachingthediameteroftheearthitself.第21页Pure,dryairconsistslargelyofnitrogen,about78%byvolume,andoxygen,about21%.Othergasesaccountfortheremaining1%Watervaporisanimportantcomponentoftheatmospherethatvariesinconcentrationfromplacetoplaceandtimetotime第22页Ozone in the Upper Atmosphere Ozone(O3)isfoundmostlyintheupperpartoftheatmosphere,inalayertermedthestratosphere.Ozoneinthestratosphereabsorbsultravioletradiationfromthesunasthisradiationpassesthroughtheatmosphere第23页At both polar regions,climate and chemistry combine to deplete ozone during spring months.Dark blue indicates lowest ozone amounts.Arctic total ozone amounts seen by TOMS in March (above,left)were among the lowest ever observed in the northern hemisphere.The Antarctic ozone hole of (above,right)was the second largest ever observed.第24页Sensible Heat and Latent Heat Transfer Sensible Heat-thequantityofheatheldbyanobjectthatcanbesensedbytouchingorfeeling When two objects of unlike temperaturecontact each other,heat energy moves byconduction fromthewarmertothecooler.This type of heat flow is referred to assensible heat transfer第25页The Global Energy System InsolationlossesintheAtmosphereAlbedoCounterradiationandtheGreenhouseEffectGlobalEnergyBudgetoftheAtmosphereandSurfaceNetRadiation,Latitude,andtheEnergyBalance第26页Winds and the Pressure Gradient Force Windisairmotionwithrespecttotheearthssurface,anditisdominantlyhorizontal.Barometric pressurefallswithincreasingaltitudeabovetheearthssurface.第27页Thechangeinbarometricpressureacrossthehorizontalsurfaceofamapconstitutesapressure gradient.Thegradientisinthedirectionfromhigherpressuretolowerpressure.第28页Whereapressuregradientexists,airmoleculestendtodriftinthesamedirectionasthatgradient.Thistendencyformassmovementoftheairisreferredtoasthepressure gradient force.第29页Sea and Land Breezes Duringthedaytime,morerapidheatingofthelowerairlayeroverthelandthanovertheoceancausesapressuregradientfromseatoland.Airmovinglandwardinresponsetothisgradientfromhighertolowerpressureconstitutesthesea breeze.第30页Athigherlevels,areverseflowsetsin.Togetherwithweakrisingandsinkingairmotions,acompleteflowcircuitisformed.第31页Duringthenight,whenradiationalcoolingofthelandisrapid,thelowerairbecomescolderoverthelandthanoverthewater.Higherpressurenowdevelopsoverlandandthebarometricgradientisreversed.Airnowmovesfromlandtoseaasaland breeze.第32页Figure 2 Sea breeze and land breeze第33页Cyclones and Anticyclones A center of low pressure is called acyclone;acenterofhighpressureisananticyclone.Winds in a cyclone in the northern hemisphere show an anticlockwiseinspiral.In an anticyclone,there is aclockwiseoutspiral.第34页Thesurfacewindsspiralinwardonthecenterofthecyclone,sotheairisconvergingonthecenterandmustalsorisetobedisposedofathigherlevels.第35页Fortheanticyclone,bycontrast,surfacewindsspiraloutfromthecenter.Thismotionrepresentsadivergingofairflowandmustbeaccompaniedbyasinkingofairinthecenteroftheanticyclonetoreplacetheoutmovingair.第36页Figure 3 Surface winds in cyclones and anticyclones第37页Global Distribution of Surface Pressure Systems Overtheequatorialzoneisabeltofsomewhatlowerthannormalpressure,between1011and1008mb,whichisknownastheequatorial trough.第38页 Lowerpressureisconspicuousbycontrastwithbeltsofhigherpressurelyingtothenorthandsouthandcenteredataboutlat.30NandS.Thesearethesubtropical belts of high pressure,inwhichpressureexceed1020mb.第39页Inthesouthernhemisphere,southofthesubtropicalhigh-pressurebelt,isabroadbeltoflowpressure,extendingfromthemidlatitudezonetothearcticzone.The axis of low pressure iscenteredataboutlat.65S.Thispressuretroughiscalledthe subantactic low-pressure belt.第40页LyingoverthecontinuousexpanseofSouthernOcean,thistroughhasaveragepressureaslowas984mb.OverthecontinentofAntarcticaisapermanentcenterofhighpressureknownasthepolar high.第41页The Global Pattern of Surface WindsFromthetwosubtropicalhigh-pressurebeltsthepressuregradientisequatorward,leading down to theequatorial trough of low pressure.Airmoving from high to low pressure isdeflected by the Coriolis effect.As aresult,two belts of trade windsareproduced.第42页Meetingofthetradestakesplacewithinanarrowzonecalledtheintertropical convergence zone.Alongpartsoftheequatorialtroughoflowpressureatcertaintimesofyear,thetradesdonotcometogetherinconvergence.Instead,abeltofcalmsandvariblewinds,calledthedoldrums,forms.第43页Betweenlat.35and60NandSisthebeltofprevailing westerly winds,or westerlies.Awindsystemcalledthepolar easterliesischaracteristicofthearcticandpolarzones.第44页Figure 4 Surface winds第45页Monsoon Winds of Southeast Asia In summer southern Asia develops acycloneintowhichthereisstrongflowofair.From the Indian Ocean and thesouthwestern Pacific,warm,humid airmoves northward and northwestward intoAsia.Thisairflowconstitutesthesummer monsoon and is accompanied by heavyrainfallinsoutheasternAsia.第46页 In winter,Asia is dominated by astrong center of high pressure fromwhichthereisanoutwardflowofairreversingthatofthesummermonsoon.Blowingsouthwardandsoutheastwardtoward the equatorial oceans,thisairflowconstitutesthewinter monsoonandbringsdryweatherforaperiodofseveralmonths.第47页Mountain winds and valley windsDuringthedaylighthourstheairalongtheslopesofthemountainsisheatedmoreintenselythantheairatthesameelevationoverthevalleyfloor.Thiswarmairglidesupalongtheslopeandgeneratesavalley wind.第48页Aftersunsetthepatternisreversed.Rapidradiationheatlossalongthemountainslopesresultsincoolairdrainageintothevalleybelowandcausesthemountain wind.第49页Global Circulation The Hadley Cell CirculationInthezonebetweentheequatorandroughly30latitude,thesurfaceflowisequatorwardwhiletheflowaloftispoleward.Neartheequatorthewarmrisingairthatreleaseslatentheatduringtheformationofcumulustowersisbelievedtoprovidetheenergytodrivethiscell第50页Thecirculationbetween30and60latitudeisjustoppositethatoftheHadleycell.Thenetsurfaceflowispoleward,andbecauseoftheCorioliseffect,thewindshaveastrongwesterlycomponent.第51页 About the circulation in the highlatitudes,it is generally believed thatsubsidencenear the poles produces asurface flow that moves equatorwardandisdeflectedintothepolareasterliesofbothhemisphere.Theregionwherethe cold polar winds and the warmerwesterlyflowofthemidlatitudesclashhasbeennamedthepolarfront.第52页The global Circulation and Mans Environment Inlowlatitudes,theHadleycelloperateslikeasimpleheatenginetotransportheatfromtheequatorialzonetothesubtropicalzone.第53页Upper-airwavestakeupthetransportandmovewarmairpolewardinexchangeforcoldair.Theglobalatmosphericcirculationalsotransportsheatinthelatentformheldbywatervapor.第54页Windscarryalargeamountofwatervapor,whichisdepositedasprecipitationonthecoast.Windsalsotransportatmosphericpollutants,carryingthemtensandhundredsofkilometersfromthesourcesofpollution.第55页Air temperature Temperature is a measure of thelevel of sensible heat of matter,whetheritisgaseous,liquid,orsolid.Conduction describes the flow ofheat from a warmer substance to acolderonewhenthetwoaretouching.第56页 Evaporation,the process by whichwaterchangesfromaliquidtoagasbyabsorbing heat,tends to lower thetemperatureofawetsurface.第57页Measurement of air temperatureAirtemperaturesarenowautomaticallyrecordedbythermometersatauniformheightabovetheground.第58页The daily cycle of air temperature Because the earth rotates on its axis,incomingsolarenergyatalocationcanvarywidelythroughoutthe24-hourperiod.Insolation is greatest in the middle of thedaylightperiod,whenthesunisatitshighestpositioninthesky,andfallstozeroatnight.第59页Daily insolation and net radiation The daily cycle of temperature iscontrolled by the daily cycle of netradiation.At the equinox,insolation begins atabout sunrise(6 a.m.),rises to a peakvalueatnoon,anddeclinestozeroatsunset(6p.m.).第60页AttheJunesolstice,insolationbeginsabout two hours earlier(4 a.m.)andendsabouttwohourslater(8p.m.).AttheDecembersolstice,insolationbeginsabouttwohourslaterthantheequinoxcurve(8a.m.)andendsabouttwohoursearlier(4p.m.).第61页 When net radiation is positive,thesurfacegainsheat,andwhennegative,itlosesheat.Netradiationbeginsthe24-hourdayasa negative value-a deficit-at midnight.The deficit continues into the earlymorning hours.Net radiation shows apositive value-a surplus-shortly aftersunrise and rises sharply to a peak atnoon.第62页Daily temperatureThe minimum daily temperature usuallyoccurs about a half hourafter sunrise.Airtemperature rises sharply in the morninghours and continues to rise long after thenoonpeakofnetradiation.Airtemperaturerises as long as net radiation is positive.Temperatures are lowest just after sunriseandhighestinmidafternoon.第63页Urban and rural temperature contrastsUrbansurfaceslackmoistureandsoarewarmerthanruralsurfacesduringthe day.At night,urban materialsconductstoredheattothesurface,alsokeepingtemperatureswarmer.第64页The urban heat islandAsaresultoftheaboveeffects,airtemperaturesinthecentralregionofacity are typically several degreeswarmerthanthoseofthesurroundingsuburbsandcountryside.Thisiscalledaheatisland.第65页 The heat island persists through thenight because of the availability of aheat stored in the ground during thedaytimehours.Anotherimportantfactorinwarmingthe city is fuel consumption.Insummer,city temperatures are raisedthroughtheuseofairconditioning.第66页Temperature structure of the Atmosphere TroposphereThetroposphereisthelowestatmospheric layer,in which temperaturedecreaseswithincreasingelevation.Everyday weather phenomena,such ascloudsorstorms,occurmainlyinthislayer.第67页 The troposphere contains significantamountsofwatervaporandcountlesstinydustparticles.第68页Stratosphere Above the troposphere lies thestratosphereinwhichtheairbecomesslightlywarmerasaltitudeincreases.Thestratosphereextendstoaheightof roughly 50km above the earthssurface.第69页 It is the home of strong,persistentwindsthatblowfromwesttoeast.Oneimportantfeatureofthestratosphere is that it contains theozonelayer.第70页High-Mountain Environments At high elevations,air temperaturesaregenerallycoolerandshowagreaterday-to-nightrange.第71页Temperature Inversion and Frost In a temperature inversion,airtemperatureincreaseswithaltitude.Low-level temperature inversionsoftenoccuroversnow-coveredsurfacesinwinter.第72页 Inversions can also result when awarm air layer overlies a colder one.This type of inversion is often foundalong the west coasts of majorcontinents.第73页Frost If the temperature of the lowermostairfallsbelowthefreezingpoint,forsensitive plants during the growingseason,this temperature condition iscalledakillingfrost.第74页The annual cycle of air temperaturelTheannualcycleofnetradiation,whichresultsfromthevariationofinsolationwiththeseasons,drivestheannualcycleofairtemperatures.第75页Land and water contrastsLand-watercontrastskeepairtemperaturesat coastal locations more constant than atinteriorcontinentallocations.Oceans heat and cool more slowly thancontinents.第76页 The surface of any extensive,deepbodyofwaterheatsmoreslowlyandcoolsmoreslowlythanthesurfaceofalarge body of land when both aresubjected to the same intensity ofinsolation.第77页Daily temperature cyclelP62Figure3.15第78页Theaveragedailycycleofairtemperature f
