Natural Seeder‐Feeder Process Originating From Mixed‐Phase Clouds Observed With Polarization Lidar and Radiosonde at a Mid‐Latitude Plain Site
Yun He, Fan Yi, Fuchao Liu, Zhenping Yin, Yang Yi, Jun Zhou, Changming Yu, Yunpeng Zhang
Abstract
Abstract Natural seeder‐feeder processes play an essential role in the formation and enhancement of precipitation. However, the cloud‐seeding process from mixed‐phase clouds is still not well understood due to the lack of sufficient observations. Natural seeder‐feeder processes from mixed‐phase clouds (seeder clouds) to lower‐lying liquid clouds (feeder clouds) were observed on 19 occasions using ground‐based polarization lidar and radiosonde measurements from June 2018 to June 2020 at a mid‐latitude plain observatory in Wuhan (30.5°N, 114.4°E), China. Ice crystals originating from seeder clouds fell into feeder clouds located 0.2–2.2 km below. During the sedimentation between seeder and feeder clouds, ice crystals partly underwent sublimation when passing through the in‐between dry air layers. The feeder clouds inhibited those ice crystals from complete sublimation and grew them larger by riming or vapor deposition from a favorable liquid water supply. Subsequently, ice crystals were observed afresh falling from feeder clouds, forming ice virgae descending toward the surface. Owing to cloud seeding, feeder clouds with cloud‐top temperatures (CTTs) as warm as −0.2°C to −14.5°C could produce ice virgae, although these CTTs are generally considered somewhat insufficient to initiate primary ice nucleation. The observed optically thin feeder clouds prolonged the survival time/distance of falling ice crystals, indicating that denser feeder clouds may induce enhanced precipitation.