Correction of raindrop size distributions measured by Parsivel disdrometers, using a two-dimensional-video-disdrometer as a reference
Abstract. The raindrop size distribution (DSD) quantifies the micro-structure of rainfall and is critical to studying precipitation processes. We present a method to improve the accuracy of DSD measurements from Parsivel disdrometers, using a two-dimensional-video-disdrometer (2DVD) as a reference instrument. Parsivel disdrometers bin recorded raindrops into velocity and equivolume diameter classes, but may mis-estimate the number of drops per class. We define a filter for raw disdrometer measurements to remove particles that are unlikely to be plausible raindrops. In our correction method, drop velocities are corrected with reference to theoretical models of terminal drop velocity. Non-plausible measurements are removed. Lastly, drop concentrations are corrected such that on average the Parsivel concentrations match those recorded by a 2DVD. The correction can be trained on and applied to data from both generations of Parsivel disdrometers. The method was applied to data collected during field campaigns in Mediterranean France, for a network of first and second generation Parsivel disdrometers. We compared the moments of the resulting DSDs to those of a collocated 2DVD, and the resulting DSD-derived rain rates to collocated rain gauges. The correction vastly improved the accuracy of the moments of the Parsivel DSDs, and in the majority of cases the rain rate match with collocated rain gauges was improved.