Microphysical Characteristics of A Cold Front Snowstorm Event in the West Tianshan Mountains

Based on a two-dimensional video disdrometer, combined with cloud radar, wind profile radar, microwave radiometer, GPS/MET water vapor, and other vertically-scanning instruments, the microphysical characteristics of a cold front snowstorm event in the West Tianshan Mountain on February 18 and 19, 2020, were analyzed and studied. A classification algorithm for the snowflake and graupel was designed to quantitatively study the microphysical characteristics of the snowfall. The results show that (1) in the cold front invasion and dynamic forcing stage, the precipitation particles are mainly snowflakes and the microphysical processes are deposition and aggregation; (2) in the stage of cold front control bringing wind chill, the precipitation particles are snowflakes and graupel, and the microphysical processes are aggregation and riming, with the aggregation exhibiting a positive impact on the riming; (3) in the cold front passage, less ice nucleation and enough subcooled water favor riming due to the rise of the cloud top temperature. Unlike those in Nanjing, the snowflake diameter and snow intensity in the West Tianshan Mountains are relatively small, but graupel has a greater contribution to the snow intensity. The raindrop size and Gamma distributions are fitted using two melting models, similar to the characteristics of local stratiform cloud precipitation.