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1、JOURNALOFGEOPHYSICALRESEARCH,VOL.106,NO.C8,PAGES16,729-16,745,AUGUST15,2001Directcovarianceair-seaCOzfluxesW.R.McGillisandJ.B.EdsonWoodsHoleOceanographicInstitution,WoodsHole,MassachusettsJ.E.HareCooperativeInstituteforResearchinEnvironmentalSciences,Univers
2、ityofColoradoNOAAEnvironmentalTechnologyLaboratory,Boulder,ColoradoC.W.FairallNOAAEnvironmentalTechnologyLaboratory,Boulder,ColoradoAbstract.Directcovarianceair-seaCO2fluxmeasurementsovertheopenoceanarereported.ThesemeasurementswereperformedduringJune1998int
3、heNorthAtlanticwithinasignificantCO2sink.Thesedirectestimatesareingeneralagreementwiththetraditionalgeochemicalisotopeconstraints.Thecovariance,oreddycorrelation,techniquedirectlymeasurestheair-seaCO2fluxoverhourtimescalesbycorrelatingthefluctuationsofCO2wit
4、htheturbulentverticalvelocityfluctuationsintheatmosphericsurfacelayer.ThesemeasurementsquantifythetransferofCO2betweentheatmosphereandoceanoverarangeofwindspeedsandimprovetheunderstandingoftheenvironmentalfactorscontrollingtheflux.TherelativelylargefluxofCO2
5、inthestudyregion,togetherwithimprovedanalyticaltechniques,facilitatedthemeasurements.Thehalf-hourmeanwindspeedsvariedfrom0.9to16.3rns-'overthemonth-longexperiment.ThemeanpCO2duringthestudyperiodwas-85.8ñ16.0•tatm,andthemeancovarianceCO2fluxwasestimatedat4.6m
6、olm-2yr-1.Theaverageobservedwindspeedwas7.7rns-'.Thisisincloseagreementwith3.9molm-2yr-1,theapproximateCO2fluxbasedon'4Cparameterizationsatthiswindspeed.Athighwinds,wheretherelationshipbetweengasphysicalproperties,surfaceprocesses,andair-seagasexchangeisstil
7、lelusive,directCO2fluxmeasurementsarecrucial.Themeasurementsforwindsinexcessof11rns"showageneralenhancementofgastransfervelocityoverpreviousindirectmeasurements,anditisbelievedthatthisenhancementcanbeexplainedbythefactthattheindirectmethodscannotdiscriminate
8、surfaceprocessvariabilitysuchasatmosphericstability,upperoceanmixing,waveage,wavebreaking,orsurfacefilms.1.Introductionratesareknowntovarywithwindspeed,atmosphericstability,seastate,andahostofsu