Supercooled liquid droplets (SLDs) not only play important roles in precipitation formation processes but they also affect the radiation budget. Therefore, it is important to clarify the distribution and quantity of SLDs. Hydrometeor videosonde observations were performed in February 2011 at Rikubetsu in inland Hokkaido, Japan. Five hydrometeor videosondes were released in ice precipitations in stratiform clouds and SLDs were detected in three cases. The clouds in these three cases had SLDs at the cloud tops. The microphysical quantities of the SLD layers were within the ranges of those observed in Arctic mixed-phase clouds. The cloud-top SLDs had potential to cause radiative cooling, which contributed to the formation of upward motion generating ice precipitation. Small water vapor amounts above the cloud tops cannot contribute to moisture supply. Vertical profiles of temperature and moisture showed that the SLD layers were decoupled from surface moisture sources. The absence of additional moisture supply was consistent with short lifetimes, compared with persistent Arctic mixed-phase clouds.
2016 by the Meteorological Society of Japan