Large Laboratory Simulator of Natural Rainfall: From Drizzle to Storms

Rainfall simulators are versatile research tools that facilitate studying rain events and the many related physical phenomena. This work describes the development and validation of an indoor, large-scale rainfall simulator comprising a rain module installed 10.4 m from ground level, a redistribution screen at an adjustable distance below the rain module, and an ultra-filtered-water recirculation system. The droplet formers installed in the rain module were selected to achieve a wide range of rain intensities. The simulator was calibrated and validated using local natural rainfall data collected with a disdrometer over 30 months. The height of the rain module allows terminal velocity to be reached at ground level. At the same time, the redistribution screen and the droplet formers guarantee the wide variability of simulated rainfall in terms of intensity and the size of the drops. As a result, we show that the rain simulator, with proper calibration of the screen’s position, can reproduce measured natural rainfall over a broad range of intensities with high spatial and temporal uniformity and kinetic energy.