(Received 7 February 2015; accepted 11 August 2015)
Published Online: 2016
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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.
Tullis, Blake P.
Utah Water Research Laboratory, Utah State Univ., Logan, UT
Stock #: JTE20150048