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    Volume 44, Issue 6 (November 2016)

    Comparing Raindrop Size and Velocity Measurement Accuracy Using Shadowgraphy, Disdrometery, and Pie Pan Measurement Techniques

    (Received 7 February 2015; accepted 11 August 2015)

    Published Online: 2016

    CODEN: JTEVAB

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    Abstract

    Local raindrop size and velocity data measurements are often used to quantify hyetographs for rainfall events; the accuracy of the rainfall hyetograph is dependent on the accuracy of the raindrop size and velocity measurement technique. Different raindrop size and velocity measurement techniques were evaluated using simulated raindrops of relatively uniform size in the laboratory. The measurement techniques included a high-speed photography-based imaging system (shadowgraphy), an optical disdrometer, and a pie pan method (raindrop size only). The shadowgraphy system, which had a measurement uncertainty of 2.86 %, served as the comparative standard for the other measurement techniques. The disdrometer raindrop size measurements were relatively accurate except for raindrops passing near the lateral limits of the measurement sheet; the peripheral raindrops sizes were estimated to be 97 % smaller than their actual size. The pie pan method overestimated raindrop sizes by approximately 41 %. The disdrometer raindrop velocity data underestimated actual velocities. Of the techniques evaluated, the disdrometer represents the only practical field deployable method for quantifying rainfall data.


    Author Information:

    Tullis, Blake P.
    Utah Water Research Laboratory, Utah State Univ., Logan, UT


    Stock #: JTE20150048

    ISSN:0090-3973

    DOI: 10.1520/JTE20150048

    Author
    Title Comparing Raindrop Size and Velocity Measurement Accuracy Using Shadowgraphy, Disdrometery, and Pie Pan Measurement Techniques
    Symposium ,
    Committee D18