Research progress in observation and shape classification of natural snow and ice crystals

Snow and ice crystals are important components of hydrometeors in clouds. Different shapes of snow and ice crystals are determined by their different physical formation and growth processes. Accurate observation of the shapes of snow and ice crystals is an important prerequisite for revealing the microphysical structure and precipitation mechanism of clouds. This paper summarizes studies and methods of observing crystals of ice and snow in the past half-century. The development of crystal measurement and shape classification technology for snow and ice is reviewed. The new progress of snow and ice crystal observation and shape classification and recognition technology is analyzed and summarized. The aim is to provide a reference of images for further studies of cloud microphysical structure and precipitation mechanism in China.