Measuring drop size distribution and kinetic energy of rainfall using a force transducer

The relatively high cost of commercially available raindrop spectrometers a nd disdrometers has inhibited detailed and intensive research on drop size distribution, kinetic energy and momentum of rainfall which are important f or understanding and modelling soil erosion caused by raindrop detachment. In this study, an approach to find the drop size distribution, momentum and kinetic energy of rainfall using a relatively inexpensive device that uses a piezoelectric force transducer for sensing raindrop impact response is i ntroduced. The instrument continuously and automatically records, on a time -scale, the amplitude of electrical pulses produced by the impact of raindr ops on the surface of the transducer. The size distribution of the raindrop s and their respective kinetic energy are calculated by analysing the numbe r and amplitude of pulses recorded, and from the measured volume of total r ainfall using a calibration curve. Simultaneous measurements of the instrum ent, a rain gauge and a dye-stain method were used to assess the performanc e of the instrument. Test results from natural and simulated rainfalls are presented. Copyright (C) 2000 John Wiley & Sons, Ltd.