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Oceancurrentsinawatertank

Thosewhowanttomakeaccurateweatherandclimatepredictionsmusthaveonethingaboveallelse:anunderstandingofmathematics.Becausebone-dryequationsformthebasisofallclimateprocesses.Inordertolivenuphisteaching,meteorologistDrTorgeMartinreliesonwetexperiments,withthesupportofPerLefundingforinnovativeteaching.

Colored clouds in a rotating water tank
©pur.pur

Howwilltheaddeddyesolutionmix?Willaredcloudformorratheracolumnwhenturning?

Whatwilltheweatherbeliketomorrow?Whatclimatechangesmustwefaceduringthisdecade?Thesearequestionstackledbymeteorologistsaswellasoceanographers,amongothers."However,inordertoreallyunderstandclimateprocesses,tocalculatethepathofhigh-pressureandlow-pressureareas,ortopredicttemperaturesforKielandtherestoftheworld,thestudentsmustfirstunderstandandinternalisethebasicsoftheglobalmovementofairandwatermasses,andtheirimpactontheweather,"explainedDrTorgeMartinfromtheGEOMARHelmholtzCentreforOceanResearchKiel.ThistakesplaceduringtheBachelor'sdegreeprogrammeinPhysicsoftheEarthSystemattheCAU.

Learningthebasicsmeansnothingotherthanthestudentshavingtodealwithalotofmathematicsandphysics.Forexample,howthewarmGulfStreamintheAtlanticmovesforward,howfastthewaterflows,howthecircularorswirlingmovementsofwatermassesarise,andwhatthatmeansforthetemperaturesonland-alloftheseareexplainedusingmathematicalequations.Andinthecomplexglobalcontexts,theyarenoteasytograsp."Forabetterunderstanding,eachphenomenonisbrokenupintosmallerunitsandexplained,likeforexampletheemergenceofavortex-aso-callededdy-intheGulfStream,"explainedDrMartin.Butthisdoesntchangethefactthathisexercises-withwhichhesupplementsthelecturesgivenbyProfessorArneBiastoch-areoftenverytheoretical.

Two students in a laboratory
©pur.pur

Usingthepipette,ChristianeLsel(left)andLudwigBitzanaddcolorsolutiondropbydropintotherotatingwatertank.Howtheliquidsmixdependsontherotationofthetank,asthestudentswereabletofindoutfromtheexperiments.Practicalknowledgehelpstounderstanddryfacts.

Inordertoprovideabetterunderstandingforthestudents,butalsotomakethetopicmorefunandawakencuriosity,themeteorologisttogetherwiththeoceanographerDrMirjamGlemeraredaringtotrysomethingnewthisandnextsemester:"Wewanttomakethebasicsofwatermovementstangibleandbetterunderstandable,withpracticalexperimentsinwatertanksandonthecomputer."Forthispurpose,afterinitialexperimentsinhiskitchenathome,heobtainedrotatingtraysandplacedtanksofwaterontop,measuringaround35centimetresindiameter.AsmallLEGOTechnicmotordrivesthetray,andsimulatestherotationoftheearth.Withcoloureddye,addeddropbydrop,thestudentscantesthowavortexarisesintherotatingsystem.Andhowthemixingofthedyelooks,ifthetrayisstationary.TheteachingprojectisfundedthroughtheQualityPactforTeachingoftheFederalMinistryofEducationandResearch(BMBF),throughPerLefundingforinnovativeteaching.

Thefirstlessonwasalreadyveryexciting,reportedMartin,whohimself"reallyenjoysplayingwithwateranddesigningexperiments."Insteadoffrontalinstruction,therewasinteractiveworkinsmallgroups,whotestedwithagreatdealofenthusiasmwhethertherotatingtrayscouldalsobedrivenbyhand("no,thespeedisnotconsistentenough")andwhetherpotsorvasesaresuitablefortheseexperimentsasanalternativetothetanks("no,theyareinadequate").Ifthetrayandwithitthewaterarestationary,thedyedrippedindistributesitselfinthewaterlikeacloud,"similartocreaminhottea,"saidMartin.Ontheotherhand,ifthetrayisrotatingevenly,avortexarises-similartotheeddiesintheGulfStream."Inordertoexplainthisdifference,thereisaformula,theTaylor-Proudmantheorem.Anditiseasiertounderstandwhenyouhavecreatedthevortexyourself,"hesaidwithconviction.Inanycase,thestudentsreallyenjoyedthedifferentwayofteaching.Theexerciseswillremainmostlytheoretical-"attheendoftheday,thestudentsareexpectedtopasstheirexams"-butfurtherexperimentsshouldfollow.Sothatotherstudentscanalsobenefit,thereisadigitaldocumentationoftheexperimentsintheproject'sownblog.

Author:JenniferRuske

Furtherreading:www.oceanblogs.org/teachingoceanscience