Rain Drop Measurement Techniques: A Review

For over a century there have been many studies that describe the use of rain drop measurement techniques. Initial manual measurement methods evolved due to improved technology to include photographic and, more recently, automated disdrometer and laser measurement techniques. Despite these numerous studies, there have been few comparative reviews of the range of methodologies, and their relative performance. This review explores the raindrop measurement techniques available, and summarizes and classifies the techniques according to the method or principle involved. The requirements of a robust raindrop measurement technique are suggested, and these are reviewed against existing rain drop measurement techniques to provide a comparative guide to the use of the range of techniques available for any research study. This review revealed that while advances in technology have allowed many of the deficiencies of early techniques to be eliminated, challenges remain in relation to the precision of the measurement of the size, shape, and velocity of rain drops.