Microphysical measurements of hydrometeors using shadowgraph imaging technique

The size distributions of raindrops and precipitation particles were measured in a series of in situ experiments during various weather events in Warsaw, Poland. To perform the measurements, a shadowgraph instrument, "VisiSize D30", was set up on the roof of the Institute of Geophysics, University of Warsaw, together with an "OTT Parsivel²" laser disdrometer. The VisiSize D30, recently introduced to atmospheric research, is capable of accurately determining a wide range of particle sizes, from micrometre-scale cloud droplets to millimetre-scale precipitation particles, while directly measuring droplets by capturing shadow images of them. A comparison of the data collected by the two instruments during simultaneous measurements shows that combining the shadowgraph technique with the optical disdrometer can prevent droplet size distribution truncation and provide more accurate results.