Wind Tunnel Tests of the Airborne PVM-100A Response to Large Droplets

M. Wendisch Institute for Tropospheric Research, Leipzig, Germany

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T. J. Garrett Department of Atmospheric Sciences, University of Washington, Seattle, Washington, and Meteorology Department, University of Utah, Salt Lake City, Utah

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J. W. Strapp Meteorological Service of Canada, Downsview, Ontario, Canada

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Abstract

The Gerber Scientific, Inc. Particle Volume Monitor (PVM) is widely used to measure the liquid water content (LWC) and droplet effective radius (reff) of water clouds. The LWC response of the airborne version of this instrument, the PVM-100A, was evaluated in two independent wet wind tunnel experiments under well-controlled conditions. Earlier studies predict that the PVM-100 (the ground-based version of the PVM) theoretical response to monodisperse droplets diminishes for droplet diameters larger than about 40 μm. However, results from the wind tunnel experiments presented in this paper show that the response of the PVM-100A to monodisperse droplets begins to decrease when the droplet diameter is between 20- and 30-μm diameter. For polydisperse droplet populations (such as those found in natural clouds) the efficiency of the airborne PVM-100A for sensing LWC begins to decrease when the median volume diameter (MVD) of the droplet size distribution is above 20 μm, falling to 50% efficiency for an MVD of 50 μm. Therefore, measurements of LWC obtained from the PVM-100A in natural clouds with broad droplet size distributions (and large values of MVD) should be treated with caution.

Corresponding author address: Manfred Wendisch, Institut für Troposphärenforschung e.V. (IFT), Permoserstr. 15, 04318 Leipzig, Germany. Email: wendisch@tropos.de

Abstract

The Gerber Scientific, Inc. Particle Volume Monitor (PVM) is widely used to measure the liquid water content (LWC) and droplet effective radius (reff) of water clouds. The LWC response of the airborne version of this instrument, the PVM-100A, was evaluated in two independent wet wind tunnel experiments under well-controlled conditions. Earlier studies predict that the PVM-100 (the ground-based version of the PVM) theoretical response to monodisperse droplets diminishes for droplet diameters larger than about 40 μm. However, results from the wind tunnel experiments presented in this paper show that the response of the PVM-100A to monodisperse droplets begins to decrease when the droplet diameter is between 20- and 30-μm diameter. For polydisperse droplet populations (such as those found in natural clouds) the efficiency of the airborne PVM-100A for sensing LWC begins to decrease when the median volume diameter (MVD) of the droplet size distribution is above 20 μm, falling to 50% efficiency for an MVD of 50 μm. Therefore, measurements of LWC obtained from the PVM-100A in natural clouds with broad droplet size distributions (and large values of MVD) should be treated with caution.

Corresponding author address: Manfred Wendisch, Institut für Troposphärenforschung e.V. (IFT), Permoserstr. 15, 04318 Leipzig, Germany. Email: wendisch@tropos.de

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  • Arends, B. G., Kos G. P. A. , Wobrock W. , Schell D. , Noone K. J. , Fuzzi S. , and Pahl S. , 1992: Comparison of techniques for measurements of fog liquid water content. Tellus, 44B , 604611.

    • Search Google Scholar
    • Export Citation
  • Bachalo, W. D., 1980: A method for measuring the size and velocity of spheres by dual beam scatter interferometry. Appl. Opt., 19 , 363370.

  • Blyth, A. M., Chittenden A. M. I. , and Latham J. , 1984: An optical device for the measurement of liquid water content in clouds. Quart. J. Roy. Meteor. Soc., 110 , 5364.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Bower, K. N., and Coauthors. 1999: The Great Dun Fell experiment 1995: An overview. Atmos. Res., 50 , 151184.

  • Cerni, T. A., 1983: Determination of the size and concentration of cloud drops with an FSSP. J. Climate Appl. Meteor., 22 , 13461355.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Choularton, T. W., and Coauthors. 1997: The Great Dun Fell cloud experiment 1993: An overview. Atmos. Environ., 31 , 23932405.

  • Dodge, L. G., and Rhodes D. J. , 1987: Drop-size measurement techniques for sprays—Comparison of Malvern laser-diffraction and Aerometrics phase/Doppler. Appl. Opt., 26 , 21442154.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Fuzzi, S., and Coauthors. 1992: The Po Valley fog experiment 1989—An overview. Tellus, 44B , 448468.

  • Fuzzi, S., and Coauthors. 1998: Overview of the Po Valley fog experiment 1994 (CHEMDROP). Contrib. Atmos. Phys., 71 , 319.

  • Gallagher, M. W., Beswick K. M. , and Choularton T. W. , 1992: Measurement and modelling of cloudwater deposition to a snow-covered forest canopy. Atmos. Environ., 26A , 28932903.

    • Search Google Scholar
    • Export Citation
  • Gerber, H., 1984: Liquid water content of fogs and hazes from visible light scattering. J. Climate Appl. Meteor., 23 , 12471252.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Gerber, H., . 1991: Direct measurement of suspended particulate volume concentration and far-infrared extinction coefficient with a laser-diffraction instrument. Appl. Opt., 30 , 48244831.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Gerber, H., . 1993: Test of prototype liquid-water-content meter for aircraft use. Final Rep. ATM-9207345, National Science Foundation, Arlington, VA, 97 pp.

    • Search Google Scholar
    • Export Citation
  • Gerber, H., . 1996: Microphysics of marine stratocumulus clouds with two drizzle modes. J. Atmos. Sci., 53 , 16491662.

  • Gerber, H., . 1999: Comments on “A comparison of optical measurements of liquid water content and droplet size distribution in adiabatic regions of Florida cumuli.”. Atmos. Res., 50 , 319.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Gerber, H., . 2000: Structure of small cumulus clouds. Proc. 13th Int. Conf. on Clouds and Precipitation, Reno, NV, WMO and Cosponsors, 105–108.

    • Search Google Scholar
    • Export Citation
  • Gerber, H., Arends B. G. , and Ackerman A. S. , 1994: New microphysics sensor for aircraft use. Atmos. Res., 31 , 235252.

  • Gerber, H., Twohy C. H. , Gandrud B. , Heymsfield A. J. , McFarquhar G. M. , DeMott P. J. , and Rogers D. C. , 1998: Measurements of wave-cloud microphysical properties with two new aircraft probes. Geophys. Res. Lett., 25 , 11171120.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Gerber, H., Frick G. , and Rodi A. R. , 1999: Ground-based FSSP and PVM measurements of liquid water content. J. Atmos. Oceanic Technol., 16 , 11431149.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Hirleman, E. D., and Dodge L. G. , 1985: Performance comparison of Malvern instruments laser diffraction drop size analysers. Proc. I-Class-85, Third Int. Conf. on Liquid Atomisation and Spray Systems, London, United Kingdom, Vol. 2, Institute of Energy, IVA/311.

    • Search Google Scholar
    • Export Citation
  • Knollenberg, R. G., 1981: Techniques for probing cloud microstructure. Clouds, Their Formation, Optical Properties and Effects, P. V. Hobbs and A. Deepak, Eds., Academic Press, 15–92.

    • Search Google Scholar
    • Export Citation
  • Kowalski, A. S., Anthoni P. M. , Vong R. J. , Delany A. C. , and Maclean G. D. , 1997: Deployment and evaluation of a system for ground-based measurement of cloud liquid water turbulent fluxes. J. Atmos. Oceanic Technol., 14 , 468479.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Lawson, R. P., and Blyth A. M. , 1998: A comparison of optical measurements of liquid water content and droplet size distribution in adiabatic regions of Florida cumuli. Atmos. Res., 47/48 , 671690.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Lawson, R. P., . 1999: Reply to comments on: “A comparison of optical measurements of liquid water content and droplet size distribution in adiabatic regions of Florida cumuli.”. Atmos. Res., 50 , 7780.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Stallabrass, A., 1978: An appraisal of the single rotating cylinder method of liquid water content measurement. Rep. LTR-LT-92, NRC Canada, 26 pp.

    • Search Google Scholar
    • Export Citation
  • Swithenbank, J., Beer J. M. , Taylor D. S. , Abbot D. , and McCreath G. C. , 1977: A laser diagnostic technique for the measurement of droplet and particle size distribution. Prog. Astronaut. Aeronaut., 53 , 421447.

    • Search Google Scholar
    • Export Citation
  • Wendisch, M., 1998: A quantitative comparison of ground-based FSSP and PVM measurements. J. Atmos. Oceanic Technol., 15 , 887900.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Wendisch, M., and Keil A. , 1999: Discrepancies between measured and modeled solar and UV radiation within polluted boundary layer clouds. J. Geophys. Res., 104 , 2737327385.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Wendisch, M., and Coauthors. 1998: Droplet size distribution and LWC in Po Valley fog. Contrib. Atmos. Phys., 71 , 87100.

  • Wendisch, M., Garrett T. , Hobbs P. V. , and Strapp J. W. , 2000: PVM-100A performance tests in the NASA and NRC wind tunnels. Proc. 13th Int. Conf. on Clouds and Precipitation, Reno, NV, WMO and Cosponsors, 194–197.

    • Search Google Scholar
    • Export Citation
  • Wertheimer, A. L., and Wilcock W. L. , 1976: Light scattering measurements of particle distributions. Appl. Opt., 15 , 16161620.

  • Wobrock, W., and Coauthors. 1994: The Kleiner Feldberg cloud experiment 1990: An overview. J. Atmos. Chem., 19 , 336.

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