An introduction of Three-Dimensional Precipitation Particles Imager (3D-PPI)

Abstract. A Three-Dimensional Precipitation Particles Imager (3D-PPI) is presented as a new instrument for measuring the size, fall velocity, and three-dimensional shape of the precipitation particles. The 3D-PPI consists of three high-resolution cameras with telecentric lenses and one high-speed camera with one non-telecentric lens. The former records the high- resolution images of falling particles from three angles, based on which the three-dimensional shapes of particles can be restored by using a 3D reconstruction algorithm, and the observation volume is large enough to obtain the particle size distribution (PSD). The latter records the images of the falling precipitation particles with 200 frames per second, based on which the falling velocity of particles can be calculated. The field experiment of the 3D-PPI and OTT PARSIVEL disdrometer (OTT) was conducted at Tulihe, China, more than 880,000 snowflakes were recorded during a typical snowfall case lasting for 13 hours, and the results show that the PSD obtained by the 3D-PPI and OTT a good agreement. It shows a potential application in atmospheric science, polar research, and other fields.