On July 29, 2021, from 11:51 to 15:14, the Weather Modification Center of Hebei Province conducted warm cloud seeding experiments on the periphery cloud system of Typhoon "In-Fa" in the central and southern regions of Hebei Province, using a KingAir-350 aircraft to disperse warm cloud seeding agents (17 sticks of YF-1 warm cloud flares, including hygroscopic agents such as calcium chloride and potassium chloride, 400 g/stick). One hour after the operation, a band-shaped maximum precipitation area appeared downwind, indicating a significant increase in rainfall. The cloud physics detection equipment carried on the aircraft was used to detect the rainband on the periphery cloud system of the typhoon. The airborne detection data showed that the concentration of large particles (>50 µm) in warm clouds in the periphery cloud system of the typhoon was significantly higher than in other weather systems. The concentration of large particles had a higher correlation with water content than small particles. The water content of the warm clouds could reach 0.9 g/m3. After the warm cloud seeding agent was dispersed, the area where it was dispersed showed an increase in CIP (Cloud Imaging Probe, particle diameter >50 µm) concentration and a decrease in CDP (Cloud Droplet Probe, particle diameter <50 µm) concentration, indicating that the collision-coalescence process in the warm clouds was significantly enhanced. The rapid growth of large droplets due to collision with small droplets was related to the artificial seeding of hygroscopic agents.
 

Typhoon moving northward, aircraft, warm cloud seeding for rainfall enhancement