high resolution current profiler

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1、HIGHRESOLUTIONCURRENTPROFILERF.D.Rowe,K.L.DeinesandR.L.GordonRDInstruments9855BusinessparkAvenueSanDiego,CA92131ABSTRACTincoherentADCP's,theshort-termmeasurementprecisionofthemeanAHighResolutionCurrentProfilervelocityislimitedbythespectral(HRCP)systemhasbeendevel

2、opedwhichwidthofthebackscatteredecho.Theemploysapulse-to-pulsecoherentpredominantsourceofechospectralDopplertechniquetomeasureoceanwidthresultsfromtheacousticpulsecurrentprofileswithhighspatial,propagatingthrougha"cloud"ofmanytemporal,andvelocityresolution.Thissm

3、alldiscretewatermassscatterers.Attechniqueisconceptuallysimilartothea?yinstantoftime,thebackscatteredconventionalsinglepulseincoherentslgnalismadeupoftheaccumulatedDopplertechnique,exceptthatthereturnfromalargenumberofdiscreteDopplerfrequencyshiftiscomputed#bysca

4、tterersdistributedoveravolumeofcomparisonofsequentialpulseechoeswaterofwidthdeterminedbytheratherthanfromasinglepulse.Thistransmitterbeamwidthandoflengthmethodleadstoamuchimprovedcurrentdeterminedbythetransmittedpulsemeasurementprecision.Thelength.Astheacousticpu

5、lsedevelopmentalHRCPmeasuresverticalpropagatesthroughthewater,theprofilesofwatervelocityovera10scatteringvolumeelementconstantlymeterrange,withadepthresolutionofchanges,witheachvolumeelementhaving20cm.Velocitymeasurementprecisionadifferentbackscatteringsignature.

6、isapproximately0.5cm/secata3.3HzTheresultisabackscatteredechowithsamplingrate.anamplitudeandphasemodulationrateinverselyproportionaltothelengthofTheHRCPdevelopmenthasbeencarriedthetransmittedpulse.ForasingleoutbyRDInstrumentsundercontracttoping,theresultingstanda

7、rddeviationDetnorskeVeritas,Norway.inthemeanvelocityestimateistypi-callyontheorderof10-100cm/secforacousticpulselengths1to10BACKGROUNDmeters.Thisvelocity/space/timeresolutionleadstothefollowingOverthelastfewyearscurrentmeasurementlimitations:profilingsystemswhich

8、employthesinglepulseincoherentacousticDoppler1.Timeaveragingisrequiredtotechniquetomeasureverticalprofilesreducestatisticalerrorsinmeanofmeanwaterflowvelocityh