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Uses and General Nature of Hydrometeor MeasurementsSurvey of InstrumentsConclusionAirborne Instruments for Measuring Concentrationsand Size Distributions of HydrometeorsAirborne Instrumentation Talk #2Al CooperEarth Observing LaboratoryNCARASP Colloquium June 2009William A CooperHydrometeor Measurements from Aircraft
Uses and General Nature of Hydrometeor MeasurementsSurvey of InstrumentsConclusionOutline1Uses and General Nature of Hydrometeor MeasurementsSome Measurements Needed for Studies of CloudsExamples of Measured Hydrometeor Size Distributions2Survey of InstrumentsCloud DropletsHydrometeor SpectrometersImaging Probes For HydrometeorsOther Measurements (e.g., LWC/IWC)3ConclusionUnmet Needs and SummaryWilliam A CooperHydrometeor Measurements from Aircraft
Uses and General Nature of Hydrometeor MeasurementsSurvey of InstrumentsConclusionNeeded MeasurementsExamples of Measured Hydrometeor Size DistributionsOutline1Uses and General Nature of Hydrometeor MeasurementsSome Measurements Needed for Studies of CloudsExamples of Measured Hydrometeor Size Distributions2Survey of InstrumentsCloud DropletsHydrometeor SpectrometersImaging Probes For HydrometeorsOther Measurements (e.g., LWC/IWC)3ConclusionUnmet Needs and SummaryWilliam A CooperHydrometeor Measurements from Aircraft
Uses and General Nature of Hydrometeor MeasurementsSurvey of InstrumentsConclusionNeeded MeasurementsExamples of Measured Hydrometeor Size DistributionsCOMMON MEASUREMENTS OF INTERESTMeasurements Often Used In ResearchDetermine concentrations of:Cloud dropletsRain and drizzle dropsIce crystalsDetermine size distributions [n(d)]Determine ice concentrations, ice n(d), habitsDetermine moments of n(d): LWC, re , Z, etc.William A CooperHydrometeor Measurements from Aircraft
Uses and General Nature of Hydrometeor MeasurementsSurvey of InstrumentsConclusionNeeded MeasurementsExamples of Measured Hydrometeor Size DistributionsCOMMON MEASUREMENTS OF INTERESTMeasurements Often Used In ResearchDetermine concentrations of:Cloud dropletsRain and drizzle dropsIce crystalsDetermine size distributions [n(d)]Determine ice concentrations, ice n(d), habitsDetermine moments of n(d): LWC, re , Z, etc.William A CooperHydrometeor Measurements from Aircraft
Uses and General Nature of Hydrometeor MeasurementsSurvey of InstrumentsConclusionNeeded MeasurementsExamples of Measured Hydrometeor Size DistributionsCOMMON MEASUREMENTS OF INTERESTMeasurements Often Used In ResearchDetermine concentrations of:Cloud dropletsRain and drizzle dropsIce crystalsDetermine size distributions [n(d)]Determine ice concentrations, ice n(d), habitsDetermine moments of n(d): LWC, re , Z, etc.William A CooperHydrometeor Measurements from Aircraft
Uses and General Nature of Hydrometeor MeasurementsSurvey of InstrumentsConclusionNeeded MeasurementsExamples of Measured Hydrometeor Size DistributionsCOMMON MEASUREMENTS OF INTERESTMeasurements Often Used In ResearchDetermine concentrations of:Cloud dropletsRain and drizzle dropsIce crystalsDetermine size distributions [n(d)]Determine ice concentrations, ice n(d), habitsDetermine moments of n(d): LWC, re , Z, etc.William A CooperHydrometeor Measurements from Aircraft
Uses and General Nature of Hydrometeor MeasurementsSurvey of InstrumentsConclusionNeeded MeasurementsExamples of Measured Hydrometeor Size DistributionsTypes of InstrumentsInstruments that measure moments of the size distribution(LWC, e ective radius)Instruments that measure portions of the size distributionInstruments that record images of the hydrometeorsInstruments that distinguish water from ice Special : e.g., holographic imaging, multiple-view imaging,instruments to measure the distance between particles,impactors, .William A CooperHydrometeor Measurements from Aircraft
Uses and General Nature of Hydrometeor MeasurementsSurvey of InstrumentsConclusionNeeded MeasurementsExamples of Measured Hydrometeor Size DistributionsTypes of InstrumentsInstruments that measure moments of the size distribution(LWC, e ective radius)Instruments that measure portions of the size distributionInstruments that record images of the hydrometeorsInstruments that distinguish water from ice Special : e.g., holographic imaging, multiple-view imaging,instruments to measure the distance between particles,impactors, .William A CooperHydrometeor Measurements from Aircraft
Uses and General Nature of Hydrometeor MeasurementsSurvey of InstrumentsConclusionNeeded MeasurementsExamples of Measured Hydrometeor Size DistributionsTypes of InstrumentsInstruments that measure moments of the size distribution(LWC, e ective radius)Instruments that measure portions of the size distributionInstruments that record images of the hydrometeorsInstruments that distinguish water from ice Special : e.g., holographic imaging, multiple-view imaging,instruments to measure the distance between particles,impactors, .William A CooperHydrometeor Measurements from Aircraft
Uses and General Nature of Hydrometeor MeasurementsSurvey of InstrumentsConclusionNeeded MeasurementsExamples of Measured Hydrometeor Size DistributionsTypes of InstrumentsInstruments that measure moments of the size distribution(LWC, e ective radius)Instruments that measure portions of the size distributionInstruments that record images of the hydrometeorsInstruments that distinguish water from ice Special : e.g., holographic imaging, multiple-view imaging,instruments to measure the distance between particles,impactors, .William A CooperHydrometeor Measurements from Aircraft
Uses and General Nature of Hydrometeor MeasurementsSurvey of InstrumentsConclusionNeeded MeasurementsExamples of Measured Hydrometeor Size DistributionsTypes of InstrumentsInstruments that measure moments of the size distribution(LWC, e ective radius)Instruments that measure portions of the size distributionInstruments that record images of the hydrometeorsInstruments that distinguish water from ice Special : e.g., holographic imaging, multiple-view imaging,instruments to measure the distance between particles,impactors, .William A CooperHydrometeor Measurements from Aircraft
Uses and General Nature of Hydrometeor MeasurementsSurvey of InstrumentsConclusionNeeded MeasurementsExamples of Measured Hydrometeor Size DistributionsSources of Information on Instruments for Airborne ResearchWeb Sites With More InformationFacilities Assessment Database:http://www.eol.ucar.edu/fai/NSF Facilities Assessment Final Report.pdfEUFAR Database:http://www.eufar.net see instruments William A CooperHydrometeor Measurements from Aircraft
Uses and General Nature of Hydrometeor MeasurementsSurvey of InstrumentsConclusionNeeded MeasurementsExamples of Measured Hydrometeor Size DistributionsChallengesWhy These Measurements Are Di cultHydrometeors of Interest:Sizes range from 1-10000µm 6 to 103 cm 3Concentrations of 10Complex range of ice shapesMeasurements from research aircraft must be made at speeds of100 200 m/sHigh data rates: up to 100,000 hydrometeors/sShort times for detection: 10µmat 200 m/s 50 nsresponse for imaging probesWilliam A CooperHydrometeor Measurements from Aircraft
Uses and General Nature of Hydrometeor MeasurementsSurvey of InstrumentsConclusionNeeded MeasurementsExamples of Measured Hydrometeor Size DistributionsOutline1Uses and General Nature of Hydrometeor MeasurementsSome Measurements Needed for Studies of CloudsExamples of Measured Hydrometeor Size Distributions2Survey of InstrumentsCloud DropletsHydrometeor SpectrometersImaging Probes For HydrometeorsOther Measurements (e.g., LWC/IWC)3ConclusionUnmet Needs and SummaryWilliam A CooperHydrometeor Measurements from Aircraft
Uses and General Nature of Hydrometeor MeasurementsSurvey of InstrumentsConclusionNeeded MeasurementsExamples of Measured Hydrometeor Size DistributionsEXAMPLE CLOUD DROPLET SIZE DISTRIBUTIONFSSP MeasurementsWilliam A CooperHydrometeor Measurements from Aircraft
Uses and General Nature of Hydrometeor MeasurementsSurvey of InstrumentsConclusionNeeded MeasurementsExamples of Measured Hydrometeor Size DistributionsEXAMPLE DRIZZLE DROPLET SIZE DISTRIBUTION260X FSSP MeasurementsWilliam A CooperHydrometeor Measurements from Aircraft
Uses and General Nature of Hydrometeor MeasurementsSurvey of InstrumentsConclusionNeeded MeasurementsExamples of Measured Hydrometeor Size DistributionsEXAMPLE RAIN SIZE DISTRIBUTION2DC 2DPWilliam A CooperHydrometeor Measurements from Aircraft
Uses and General Nature of Hydrometeor MeasurementsSurvey of InstrumentsConclusionNeeded MeasurementsExamples of Measured Hydrometeor Size DistributionsEXAMPLE ICE IMAGES2DCWilliam A CooperHydrometeor Measurements from Aircraft
Uses and General Nature of Hydrometeor MeasurementsSurvey of InstrumentsConclusionCloud DropletsHydrometeor SpectrometersImaging Probes For HydrometeorsOther Measurements (e.g., LWC/IWC)Outline1Uses and General Nature of Hydrometeor MeasurementsSome Measurements Needed for Studies of CloudsExamples of Measured Hydrometeor Size Distributions2Survey of InstrumentsCloud DropletsHydrometeor SpectrometersImaging Probes For HydrometeorsOther Measurements (e.g., LWC/IWC)3ConclusionUnmet Needs and SummaryWilliam A CooperHydrometeor Measurements from Aircraft
Uses and General Nature of Hydrometeor MeasurementsSurvey of InstrumentsConclusionCloud DropletsHydrometeor SpectrometersImaging Probes For HydrometeorsOther Measurements (e.g., LWC/IWC)Really Old TechniquesImpactors [Formvar, soot-coated slides]issues: collection e ciency, need for short exposure,crater-to-size conversionanalysis laborious!Hot-wire sensors [ Johnson-Williams ] for LWCIcing detectors [Rosemount Icing Probe] for supercooled liquidwater contentWilliam A CooperHydrometeor Measurements from Aircraft
Uses and General Nature of Hydrometeor MeasurementsSurvey of InstrumentsConclusionCloud DropletsHydrometeor SpectrometersImaging Probes For HydrometeorsOther Measurements (e.g., LWC/IWC)The Forward Scattering Spectrometer ProbeFSSPEntered use about 1976Detects light scattered from a laser beam as a droplet passesthroughCounts and sizes individual droplets, 15 channels, 2-47µmThe standard/conventional measurement for about 3 decadesWilliam A CooperHydrometeor Measurements from Aircraft
Uses and General Nature of Hydrometeor MeasurementsSurvey of InstrumentsConclusionCloud DropletsHydrometeor SpectrometersImaging Probes For HydrometeorsOther Measurements (e.g., LWC/IWC)The FSSP-100William A CooperHydrometeor Measurements from Aircraft
Uses and General Nature of Hydrometeor MeasurementsSurvey of InstrumentsConclusionCloud DropletsHydrometeor SpectrometersImaging Probes For HydrometeorsOther Measurements (e.g., LWC/IWC)FSSP SCHEMATIC DIAGRAMWilliam A CooperHydrometeor Measurements from Aircraft
Uses and General Nature of Hydrometeor MeasurementsSurvey of InstrumentsConclusionCloud DropletsHydrometeor SpectrometersImaging Probes For HydrometeorsOther Measurements (e.g., LWC/IWC)DEFINITION OF THE SAMPLE VOLUMEFSSP Sample VolumeThe laser is focused to the center of the sampling aperture.The focal plane is focused again on a detector where the beamis split.One sensor is masked so that, in the focal plane, the scatteredlight is focused on the mask.Pulses are rejected if the light sensed by the masked detectorexceeds a xed fraction of that sensed by the unmaskeddetector.William A CooperHydrometeor Measurements from Aircraft
Uses and General Nature of Hydrometeor MeasurementsSurvey of InstrumentsConclusionCloud DropletsHydrometeor SpectrometersImaging Probes For HydrometeorsOther Measurements (e.g., LWC/IWC)ADVANTAGES OF THE FSSPProvides automated measurement of the droplet sizedistribution (15 channels)A routine and standard measurement that rapidly became theworld-wide standardContributed to many scienti c studiesWilliam A CooperHydrometeor Measurements from Aircraft
Uses and General Nature of Hydrometeor MeasurementsSurvey of InstrumentsConclusionCloud DropletsHydrometeor SpectrometersImaging Probes For HydrometeorsOther Measurements (e.g., LWC/IWC)Some Problems with the FSSPUneven laser illumination causes variations is measured sizesand degrades size resolutionCoincidence e ects on the measurements were serious at 3 )modest concentrations (700 cmSlow electronics in older versions.Pulses were undersized even at 125 m/sElongated pulses increased coincidence e ectsParticle shattering causes false countsFalse counts also obtained from ice particlesWilliam A CooperHydrometeor Measurements from Aircraft
Uses and General Nature of Hydrometeor MeasurementsSurvey of InstrumentsConclusionCloud DropletsHydrometeor SpectrometersImaging Probes For HydrometeorsOther Measurements (e.g., LWC/IWC)SOME MODIFICATIONSFSSP Fast FSSP Brenguier et al., FranceMeasures times between droplet arrivalModi ed optics to improve de nition of the sample volumeParticle Spacing MonitorRAF instrument to measure the interarrival timesWilliam A CooperHydrometeor Measurements from Aircraft
Uses and General Nature of Hydrometeor MeasurementsSurvey of InstrumentsConclusionCloud DropletsHydrometeor SpectrometersImaging Probes For HydrometeorsOther Measurements (e.g., LWC/IWC)THE DMT CLOUD DROPLET PROBEDroplet Measurement Technologies CDPSimilar to FSSP but with:fast electronics (200 m/s)more channels (20-40)Laser diode instead ofHe-NePositive optical maskNo dead-time losses3Sample rate (25 cm /s at 100m/s)William A CooperHydrometeor Measurements from Aircraft
Uses and General Nature of Hydrometeor MeasurementsSurvey of InstrumentsConclusionCloud DropletsHydrometeor SpectrometersImaging Probes For HydrometeorsOther Measurements (e.g., LWC/IWC)Phase Doppler InterferometerA fundamentally di erent way of measuring droplet size:PDI measures droplet size by reference to the wavelength ofthe light.Not subject to intensity uctuations; high stability.Schematic from Chuang et al., 2006: AST, 42, 685-703.William A CooperHydrometeor Measurements from Aircraft
Uses and General Nature of Hydrometeor MeasurementsSurvey of InstrumentsConclusionCloud DropletsHydrometeor SpectrometersImaging Probes For HydrometeorsOther Measurements (e.g., LWC/IWC)PDI Sizing by Phase ShiftDroplets pass throughinterference fringesSmall droplets scatterAlso from Chuang et al.light over a larger cone, so(2008):detectors see a smallphase di erence (top)Large droplets scatterlight in a narrower beam,so detectors see a largerphase di erence (bottom)Phase shift and the fringepattern spacing sizeand velocity.William A CooperHydrometeor Measurements from Aircraft
Uses and General Nature of Hydrometeor MeasurementsSurvey of InstrumentsConclusionCloud DropletsHydrometeor SpectrometersImaging Probes For HydrometeorsOther Measurements (e.g., LWC/IWC)Outline1Uses and General Nature of Hydrometeor MeasurementsSome Measurements Needed for Studies of CloudsExamples of Measured Hydrometeor Size Distributions2Survey of InstrumentsCloud DropletsHydrometeor SpectrometersImaging Probes For HydrometeorsOther Measurements (e.g., LWC/IWC)3ConclusionUnmet Needs and SummaryWilliam A CooperHydrometeor Measurements from Aircraft
Uses and General Nature of Hydrometeor MeasurementsSurvey of InstrumentsConclusionCloud DropletsHydrometeor SpectrometersImaging Probes For HydrometeorsOther Measurements (e.g., LWC/IWC)SIZE DISTRIBUTIONS FOR LARGER HYDROMETEORSdrizzle, ice graupel, rainWilliam A CooperHydrometeor Measurements from Aircraft
Uses and General Nature of Hydrometeor MeasurementsSurvey of InstrumentsConclusionCloud DropletsHydrometeor SpectrometersImaging Probes For HydrometeorsOther Measurements (e.g., LWC/IWC)OPTICAL CONFIGURATIONOAPsWilliam A CooperHydrometeor Measurements from Aircraft
Uses and General Nature of Hydrometeor MeasurementsSurvey of InstrumentsConclusionCloud DropletsHydrometeor SpectrometersImaging Probes For HydrometeorsOther Measurements (e.g., LWC/IWC)VARIETIES OF OAPs200X (20µm200Y (300resolution)µmresolution)260X (10 or 12.5µmresolution)DMT CIP Cloud Imaging Probe (25PIP Precip. Imaging Probe (100µmµmresolution) andresolution) also 2DprobesSPEC HVPS (200µmresolution)William A CooperHydrometeor Measurements from Aircraft
Uses and General Nature of Hydrometeor MeasurementsSurvey of InstrumentsConclusionCloud DropletsHydrometeor SpectrometersImaging Probes For HydrometeorsOther Measurements (e.g., LWC/IWC)WEAKNESSES OF OAP SPECTROMETERSDepth-of- eld uncertainty:At small size, DOF is apertureAway from the focal plane, di raction distorts size, requiringcorrection to the measured sizeIn common with almost all hydrometeor probes, shattering cancontaminate the measurementsSample volumes are sometimes too small for statisticallyreliable measurementSome (probably small) errors may arise from coincidence ofparticles in the sample volumeWilliam A CooperHydrometeor Measurements from Aircraft
Uses and General Nature of Hydrometeor MeasurementsSurvey of InstrumentsConclusionCloud DropletsHydrometeor SpectrometersImaging Probes For HydrometeorsOther Measurements (e.g., LWC/IWC)Outline1Uses and General Nature of Hydrometeor MeasurementsSome Measurements Needed for Studies of CloudsExamples of Measured Hydrometeor Size Distributions2Survey of InstrumentsCloud DropletsHydrometeor SpectrometersImaging Probes For HydrometeorsOther Measurements (e.g., LWC/IWC)3ConclusionUnmet Needs and SummaryWilliam A CooperHydrometeor Measurements from Aircraft
Uses and General Nature of Hydrometeor MeasurementsSurvey of InstrumentsConclusionCloud DropletsHydrometeor SpectrometersImaging Probes For HydrometeorsOther Measurements (e.g., LWC/IWC)2D OPTICAL ARRAY PROBESOptically similar to 1D OAPsrecord images of particles:record the status of the diode array at high frequencyas the hydrometeor shadow passes over it, the images isrecordedtypically 25µmor 200µmresolutionnew versions now available with higher resolutionWeaknesses similar to 1-D OAPsImage information can help identify spurious images (e.g., streaking or fragments from shattering)Sophisticated processing algorithms are possible (circle ts torain images, pattern recognition for crystal habits, etc.)William A CooperHydrometeor Measurements from Aircraft
Uses and General Nature of Hydrometeor MeasurementsSurvey of InstrumentsConclusionCloud DropletsHydrometeor SpectrometersImaging Probes For HydrometeorsOther Measurements (e.g., LWC/IWC)CLOUD PARTICLE IMAGERSPEC CPIFrom SPEC:William A CooperHydrometeor Measurements from Aircraft
Uses and General Nature of Hydrometeor MeasurementsSurvey of InstrumentsConclusionCloud DropletsHydrometeor SpectrometersImaging Probes For HydrometeorsOther Measurements (e.g., LWC/IWC)CPI MeasurementsWilliam A CooperHydrometeor Measurements from Aircraft
Uses and General Nature of Hydrometeor MeasurementsSurvey of InstrumentsConclusionCloud DropletsHydrometeor SpectrometersImaging Probes For HydrometeorsOther Measurements (e.g., LWC/IWC)Small Ice Detector (SID)University of HertfordshireUses multiple detectors todetect light scattered invarious directionsDiscriminates ice fromwater on the basis ofnon-uniformity in thescattering patternCounts and sizes small ice(fewµ m)William A CooperHydrometeor Measurements from Aircraft
Uses and General Nature of Hydrometeor MeasurementsSurvey of InstrumentsConclusionCloud DropletsHydrometeor SpectrometersImaging Probes For HydrometeorsOther Measurements (e.g., LWC/IWC)Outline1Uses and General Nature of Hydrometeor MeasurementsSome Measurements Needed for Studies of CloudsExamples of Measured Hydrometeor Size Distributions2Survey of InstrumentsCloud DropletsHydrometeor SpectrometersImaging Probes For HydrometeorsOther Measurements (e.g., LWC/IWC)3ConclusionUnmet Needs and SummaryWilliam A CooperHydrometeor Measurements from Aircraft
Uses and General Nature of Hydrometeor MeasurementsSurvey of InstrumentsConclusionCloud DropletsHydrometeor SpectrometersImaging Probes For HydrometeorsOther Measurements (e.g., LWC/IWC)Liquid Water ContentLWC/IWCHeated elements:King LWC: constant-temperature element heated to evaporatewaterOther collectors attempt to collect ice and measure ice watercontentCounter ow virtual impactor and other evaporators:collect the cloud water (in the CVI, by virtual impaction),evaporate the watermeasure the LWC from the resulting water vapor density.Gerber PVM:uses scattering from an ensemble of droplets at speci c angleschosen to respond to the 3rd moment of the size distributioncan also measure the 2nd moment (e ective radius)William A CooperHydrometeor Measurements from Aircraft
Uses and General Nature of Hydrometeor MeasurementsSurvey of InstrumentsConclusionUnmet Needs and SummaryOutline1Uses and General Nature of Hydrometeor MeasurementsSome Measurements Needed for Studies of CloudsExamples of Measured Hydrometeor Size Distributions2Survey of InstrumentsCloud DropletsHydrometeor SpectrometersImaging Probes For HydrometeorsOther Measurements (e.g., LWC/IWC)3ConclusionUnmet Needs and SummaryWilliam A CooperHydrometeor Measurements from Aircraft
Uses and General Nature of Hydrometeor MeasurementsSurvey of InstrumentsConclusionUnmet Needs and SummaryWeaknesses in CapabilitiesNeed standardized calibration facilities and procedures!Inadequate size resolution for cloud droplets (but promisingnew approach in the PDI).Uncertainties in sample volume for many instruments.Inadequate sample volume for some hydrometeor sizes(esp. rain)Uncertain detection of small ice crystals and drizzle (e.g.,50-100µ m)with adequate sample rates.Uncertainties in how air ow a ects the measurements.Contamination of measurements by shattering.William A CooperHydrometeor Measurements from Aircraft
Uses and General Nature of Hydrometeor MeasurementsSurvey of InstrumentsConclusionUnmet Needs and SummaryConclusionAn impressive array of automated airborne hydrometeorsensors is now available.There has been signi cant recent progress toward addressingkey uncertainties.Further progress will probably require in-depth study of thenature of the instruments and the measurements,esp. regarding sample volumes, calibration, and datainterpretation.William A CooperHydrometeor Measurements from Aircraft
Survey of Instruments Conclusion Airborne Instruments for Measuring Concentrations and Size Distributions of Hydrometeors Airborne Instrumentation alkT #2 Al Cooper Earth Observing Laboratory NCAR ASP Colloquium June 2009 William A Cooper Hydrometeor Measurements from Aircraft. Uses and General Nature of Hydrometeor Measurements
