[A-AS10] General Meteorology

[AAS10-13] Vertical Distribution of Supercooled-water Droplet in Snow Clouds

*Asuka Yoshimura¹, Kazuhisa Tsuboki¹ (1. Institute for Space-Earth Environmental Research, Nagoya University)

Keywords:Supercooled water droplet, Snow Clouds, Hydrometeors, Hydrometeor Videosonde

Supercooled-water droplets play a important role in precipitation formation processes, such as graupel formation and the growth of cloud particles. Clarifying the vertical distribution of supercooled-water droplets within snow clouds is meteorologically significant. Ohigashi et al. (2016) reported that Hydrometeor observations in Rikubetsu, Hokkaido, revealed the presence of supercooled-water droplets up to around 3 km near the cloud top. The objective of this study is to elucidate the distribution and quantity of supercooled-water droplets in a case observed in Niigata, where a higher altitude and a larger amount of supercooled-water droplets were recorded compared to previous studies.Observations of snow clouds using a hydrometeor Videosonde (HYVIS, Yoshimura et al. 2024) were conducted in Shiozawa, Minami-Uonuma City, Niigata, from January 15 to 16, 2025. During the observation period, cold air outbreaks occurred, and band clouds were observed over the Sea of Japan. Observations using a Micro Rain Radar showed that the echo top reached 3.5 km, with a 35 dBZ region extending up to 2 km in altitude. During the evening to early morning, when snowfall was occurring at the surface, three HYVISs were launched into stratiform clouds. All observations detected multiple layers of supercooled-water droplets distributed from 500 m above the ground to near the cloud top. The highest altitude at which supercooled-water droplets were observed was 3,854 m, at a temperature of -28.4℃. Using the method by Suzuki (2016), the liquid water content (LWC) of this layer was calculated to be 0.04 g/m³ based on the observed size and number concentration of supercooled-water droplets.The observational results of this study indicate that below the highest-altitude supercooled-water droplet layer, there were regions where ice crystals and supercooled-water droplets coexisted, as well as alternating layers of supercooled-water droplets and ice crystals. This layered structure suggests a pattern different from the seeder-feeder mechanism proposed by Browne & Cobb (1952).