Analysis of Physical Response to Cold Cloud Seeding over North China in Winter Based on Multisource Observations

The microphysical characteristics of a supercooled cloud and the physical response of cloud seeding were examined by using high-performance rain enhancement aircraft, ground-based S-band dual-polarization radar, and satellite remote sensing observations in central and southern Hebei Province on January 20, 2022. The findings revealed that, under the influence of the combination of southwest warm and humid air flow and easterly reflux, a large range of stratiform clouds formed with a cloud base of 1,400 m and a cloud top of 2,100 m, which were primarily made up of supercooled cloud droplets in central and southern Hebei Province. Radar observations demonstrated that after cloud seeding at a height of 2,100 m, the supercooled cloud droplets quickly froze into ice crystals, snow, and a few graupel particles affected by AgI nucleation. The increase in particle size led to improved radar reflectivity echoes in the cloud-seeding regions. FY-4A satellite observations revealed that clear icing cloud tracks occurred after 17–19 min of cloud seeding, which can be sustained for approximately 55 min. After cloud seeding, the supercooled cloud droplets formed ice crystal particles, which gradually grew and fell, resulting in the cloud top sinking and forming a cloud groove in the cloud top. Compared with the no-seeding regions, the reflectance at 0.65 μm and the blackbody brightness temperature at 10.8 μm increased, whereas the reflectance at 3.72 μm decreased within the cloud tracks.