observational approaches to understanding cloud microphysics

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Observational approaches to understanding cloud microphysics. Microphysical measurement needs. Quantitative characterization of. Size distribution of liquid hydrometeors from CCN size (0.01 m m) to precipitation size (10000 m m) 6 orders of magnitude range of size (18 of mass!) - PowerPoint PPT Presentation

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  • Observational approachesto understanding cloud microphysics

  • Microphysical measurement needsQuantitative characterization of.

    Size distribution of liquid hydrometeors from CCN size (0.01 mm) to precipitation size (10000 mm) 6 orders of magnitude range of size (18 of mass!)

    Size/mass distributions and habits of ice-phase hydrometeors (1-10000 mm)

    Efficacy of aerosols to act as CCN and IN

    Thermodynamic and dynamic environment in which hydrometeors form, exist, grow, and evaporate

  • 1. Liquid Hydrometeors

  • Forward Scattering Spectrometer Probe (FSSP)Radius range 1-25 mNCAR

  • FSSP Scattered Energy1 10 100Diameter [microns]Scattered energy per particle [arbitrary units]1 10 100 1000

  • Phase Doppler Particle Interferometer (PDPI)Size range 1-1000 m

  • Interferometry

  • Larger particles D>>Baumgardner and Korolev, J Atmos. Ocean Tech., 1997Optical Shadow Probes (Optical Array Probes, OAPs)Size range 10-10000 mExamples:260-X2D-C2D-PHVPS

  • Comparisonof FSSP and OAPsProblems in overlap zoneBaumgardner and Korolev, J Atmos. Ocean Tech., 1997

  • 2. Ice Hydrometeors

  • Small ice the perennial problemFSSPs can be used, but.

  • Interarrival times in ice cloudsField et al., J Atmos. Ocean Tech., 2003Bursts of particles observedShattering of large ice giving impression of many small xtals

  • Small ice the perennial problemand

  • The Small Ice Detector (SID)Examines angular dependence of scatteringIrregular particlesUniversity of Hertfordshire, UK

  • Large ice crystals: OAPsField, JAS, 1999Size range 25-4000 mOAP images1000 microns [1 mm]

  • Large ice crystals: Cloud Particle Imager (CPI)SPEC Inc, BoulderSize range 10-4000 mCCD camera takes photographs of particles

  • More common crystals

  • 3. CCN/IN characterization

  • Thermal diffusion chamberSupersaturation maximizes in center of chamber and can be controlled by TSubject aerosols to known supersaturation and check for rapid growth using a droplet counterVary T and obtain a CCN spectrum

  • Thermal diffusion chambersNew designs allow for:continuous flow in chamberMultiple supersaturations simultaneouslyCan be used at between ice and water saturation to characterize heterogeneous deposition nuclei

  • IN characterizationCannot measure (in-situ):Contact freezing INImmersion freezing IN

  • 4. Characterization of thermodynamic environment TemperatureVapor contentLiquid water content

  • HumidityHigh concentrations:Optical (Lyman-alpha)Tunable diode laserDewpoint HygrometerLow concentrations:Fluorescence hygrometer

  • Liquid water contentHotwire probesNevzorov probesLyman-alpha, total water content

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