Validating a Method for Characterizing Rainfall Simulators Using Parsivel² Measurements and Raindrop Velocity Relationship

Rainfall simulators are widely employed in rainfall erosivity research due to their ability to reproduce precipitation events under controlled conditions. Their characterization in terms of drop size and velocity distribution requires advanced instrumentation, such as disdrometers, particularly when dealing with complex rainfall patterns. This study evaluates the applicability of a recently proposed empirical relationship to estimate drop fall velocity across various rainfall simulation systems, including drip-type, pressurized-type, and multidrippers-type configurations. Experimental results confirm that, as already well known for natural precipitations, the Parsivel² disdrometer tends to underestimate the fall velocity of raindrops even in simulated rainfall conditions. Nevertheless, by applying the empirical relationship to drop size data from the disdrometer, accurate velocity estimates can be obtained. This approach was validated across the different tested setups, and the performance of the proposed predictive model remains consistent even when terminal velocity is reached, as observed in the multidrippers simulator. These findings support the combined use of disdrometric data and the empirical relationship as a reliable approach for characterizing simulated rainfalls.