Laser-Based Raindrop Analyzer for Accurate Size and Distribution to Enhance Rainfall Wind Correction

Wind is the primary cause of errors in rainfall measurements, and understanding how wind affects the raindrops is critical to calculating and correcting the resulting undercatch. A range of algorithms has been developed to address undercatch, but they depend on accurate knowledge of droplet size, velocity and distribution (number of droplets over time), and wind speed. This paper introduces a cost-effective laser-based optical analyzer designed to integrate with a tipping-bucket rain gauge, capable of measuring droplets’ size, velocity, and distribution as they pass through a laser beam spanning the gauge. The analyzer setup incorporates a semiconductor laser, photodiode arrays, and analog front-end circuitry, specifically designed to detect voltage signal variations caused by passing droplets. Additionally, neural network-based algorithms were employed to predict the characteristics of the droplets, i.e., size and distribution, using the data provided by the analyzer. Experimental results demonstrate that the proposed analyzer accurately estimates droplet sizes with a minimal deviation of only 0.475% and droplet distribution with a 3% error, offering a cost-effective solution for improving rainfall wind correction.