Comparison of a laser precipitation monitor, piezoelectric transducer and particle imaging transient visual measurement technology under simulated rainfall in laboratory conditions

Abstract

Precipitation microphysics, which describes the basic characteristics of rainfall, is important for agricultural praxis, weather prediction, aviation safety, and soil erosion prediction. In this study, three types of instruments (a laser precipitation monitor, LPM; piezoelectric transducer, PT; and particle imaging transient visual measurement technology, PIV) were employed to measure and compare the raindrop size distribution (DSD) and rainfall kinetic energy rate (KEt) under simulated rainfall conditions. Comparisons of the results indicated that under the same simulated rainfall conditions, the number of raindrops per unit area measured by LPM was larger than that measured by PIV. The DSD measured by PIV was more uniform than that of the PT and LPM under the same rainfall conditions. The raindrop size range measured by the LPM was smaller than that measured by the PT and PIV. In addition, the geometric mean diameter was a more accurate representation of raindrop size because PIV can capture the true irregular shape of raindrops. Compared to the PIV sensor, the LPM underestimates the raindrop diameter. The median raindrop diameter measured and calculated by PIV using the geometric mean diameter was approximately 1.61 times that of LPM. The KEt values measured by PIV and PT were approximately similar, while the KEt calculated by LPM was 0.51 and 0.57 times that of PIV and PT for the same rainfall conditions, respectively. A correction factor of 1.75 provided an approximate reference for the calibration of the kinetic energy calculation of the LPM instrument. The above results can provide basic insights for calibration and application of the three instruments.