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

Abstract. The Three-Dimensional Precipitation Particle Imager (3D-PPI) is presented as a new instrument for measuring the size, fall velocity, and three-dimensional shape of 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 captures high-resolution images of falling particles from three angles, enabling three-dimensional (3D) shape reconstruction via a 3D reconstruction algorithm, while the large observation volume facilitates particle size distribution (PSD) analysis. 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 in Tulihe, China, with more than 880 000 snowflakes recorded during a typical snowfall case lasting 13 h, and the results indicate strong agreement between the PSDs obtained by the 3D-PPI and those obtained by the OTT. This demonstrates its potential application in atmospheric science, polar research, and other fields.