Comparative Evaluation of the OTT PARSIVEL2 Using a Collocated Two-Dimensional Video Disdrometer

The performance of the OTT second-generation Particle Size Velocity (PARSIVEL 2 ) laser weather sensor is evaluated by comparing it with a collocated two-dimensional video disdrometer (2DVD) and rain gauges using data collected over a total of 36 rain events. A comparison of raindrop size distributions (DSDs) between the 2DVD and two PARSIVEL 2 reveals good agreement for weak rainfall rates below approximately 10 mm h −1 and for midsize drops with diameters between 0.6 and 4.0 mm irrespective of rainfall rates, whereas the PARSIVEL 2 produces overestimations of large drops with diameters above 4 mm during heavy rainfall above approximately 20 mm h −1 . The resultant DSD parameters of the PARSIVEL 2 present overestimations of the mean diameter D m in the normalized gamma function and the maximum drop diameter D max , and underestimations of the intercept parameter N w and total number of drops N T . Furthermore, how the characteristics of DSDs from the PARSIVEL 2 affect the polarimetric radar variables, such as differential reflectivity Z DR and specific differential phase K DP , is examined, as well as how these characteristics affect empirical relations required in radar hydrometeorological applications such as quantitative rainfall estimations. Based on these examinations, it can be concluded that the OTT PARSIVEL 2 still produces overestimations of large drops and underestimations of small drops during heavy rainfall, similar to older models of PARSIVEL, despite significant improvements to the PARSIVEL 2 system, and furthermore that the uses of PARSIVEL 2 measurements can act as a source of error in radar hydrometeorological applications such as radar rainfall estimations.